WorldWideScience

Sample records for methane oxidation final

  1. Modeling the effects of vegetation on methane oxidation and emissions through soil landfill final covers across different climates.

    Science.gov (United States)

    Abichou, Tarek; Kormi, Tarek; Yuan, Lei; Johnson, Terry; Francisco, Escobar

    2015-02-01

    Plant roots are reported to enhance the aeration of soil by creating secondary macropores which improve the diffusion of oxygen into soil as well as the supply of methane to bacteria. Therefore, methane oxidation can be improved considerably by the soil structuring processes of vegetation, along with the increase of organic biomass in the soil associated with plant roots. This study consisted of using a numerical model that combines flow of water and heat with gas transport and oxidation in soils, to simulate methane emission and oxidation through simulated vegetated and non-vegetated landfill covers under different climatic conditions. Different simulations were performed using different methane loading flux (5-200 g m(-2) d(-1)) as the bottom boundary. The lowest modeled surface emissions were always obtained with vegetated soil covers for all simulated climates. The largest differences in simulated surface emissions between the vegetated and non-vegetated scenarios occur during the growing season. Higher average yearly percent oxidation was obtained in simulations with vegetated soil covers as compared to non-vegetated scenario. The modeled effects of vegetation on methane surface emissions and percent oxidation were attributed to two separate mechanisms: (1) increase in methane oxidation associated with the change of the physical properties of the upper vegetative layer and (2) increase in organic matter associated with vegetated soil layers. Finally, correlations between percent oxidation and methane loading into simulated vegetated and non-vegetated covers were proposed to allow decision makers to compare vegetated versus non-vegetated soil landfill covers. These results were obtained using a modeling study with several simplifying assumptions that do not capture the complexities of vegetated soils under field conditions.

  2. Electrochemical oxidation of methane at metal and metal oxide electrodes. Final report, December 1, 1986-December 1, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Frese, K.W.; Pound, B.G.

    1990-03-20

    An objective of the research was to gain insight into the role of surface geometry, heat of reaction, force constants and adsorption site in the activated chemisorption of methane to adsorbed hydrogen and adsorbed methyl. The model successfully calculated the activation energy for abstraction of H from CH4 by O atoms in the gas phase. The results for two crystal planes of Ni were in very good agreement with experimental findings and other calculations. For Ni(111) and Ni(110) Ea = 14 and 18 kcal/mol, respectively. The minimum electrode potential for adsorption of methane, OH, and O atoms on various metal electrodes was calculated. The open circuit decay method was employed to measure the rate of reaction between hydrocarbons including methane and adsorbed oxygen species on Pt, Pd and Rh electrodes. The rates of reaction with Pt-OH at 95C in 0.5 M H2SO4 followed the trend CH4 < C2H6 < C3H8 < H2. The faradaic efficiency for CO2 was 80% at 0.25 V vs SCE, indicating that deep oxidation occurs as desired in fuel cell applications.

  3. Biomimetic methane oxidation. Final report, October 1, 1989--June 1, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Watkins, B.E.; Satcher, J.H. Jr.; Droege, M.W.; Taylor, R.T.

    1995-07-01

    Transportation fuels are a critical energy commodity and they impact nearly every sector of this country. The need for transportation fuels is projected well into the next century. Consequently, there is a strong emphasis on the economical conversion of other domestic fossil energy resources to liquid hydrocarbons that can be used as transportation fuels. Natural gas is currently a readily available resource that has a positive future outlook considering its known and anticipated reserves. There is intense government and industrial interest in developing economic technologies to convert natural gas to liquid fuels. Methane, CH{sub 4}, is the primary hydrocarbon (85-95%) in natural gas. This document covers the following: production soluable of methane monooxygenase; production of particulate methane monooxygenase; production of methane monooxygenase in continuous culture; subunit resolution for active site identification of methylosinus trichosporium OB3b soluble methane monooxygenase; the synthesis and characterization of new copper coordination complexes contairing the asymmetric coordinating chelate ligand application to enzyme active site modeling; the synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand; further characterization of new bionuclear iron complexes.

  4. Stimulation of methane oxidation potential and effects on vegetation growth by bottom ash addition in a landfill final evapotranspiration cover

    NARCIS (Netherlands)

    Kim, G.W.; Ho, A.; Kim, P.J.; Kim, Sang Yun

    2016-01-01

    The landfilling of municipal solid waste is a significant source of atmospheric methane (CH4), contributing up to 20% of total anthropogenic CH4 emissions. The evapotranspiration (ET) cover system, an alternative final cover system in waste landfills, has been considered to be a promising way to mit

  5. Stimulation of methane oxidation potential and effects on vegetation growth by bottom ash addition in a landfill final evapotranspiration cover

    NARCIS (Netherlands)

    Kim, G.W.; Ho, A.; Kim, P.J.; Kim, Sang Yun

    2016-01-01

    The landfilling of municipal solid waste is a significant source of atmospheric methane (CH4), contributing up to 20% of total anthropogenic CH4 emissions. The evapotranspiration (ET) cover system, an alternative final cover system in waste landfills, has been considered to be a promising way to

  6. Stimulation of methane oxidation potential and effects on vegetation growth by bottom ash addition in a landfill final evapotranspiration cover

    NARCIS (Netherlands)

    Kim, G.W.; Ho, A.; Kim, P.J.; Kim, Sang Yun

    2016-01-01

    The landfilling of municipal solid waste is a significant source of atmospheric methane (CH4), contributing up to 20% of total anthropogenic CH4 emissions. The evapotranspiration (ET) cover system, an alternative final cover system in waste landfills, has been considered to be a promising way to mit

  7. The oxidative coupling of methane

    Energy Technology Data Exchange (ETDEWEB)

    Helton, T.; Anthony, R.G.; Gadalla, A.M. (Texas A and M Univ., College Park, TX (US))

    1988-01-01

    In this paper the spinel phase of cobalt oxide is evaluated as a potential coupling catalyst for converting methane to C/sub 2/+ hydrocarbons. Thermodynamic calculations indicate that the Gibbs free energies for forming higher hydrocarbons using the spinel form of cobalt oxide are similar to the free energies obtained for manganese (III) oxide. The oxidative coupling of methane was performed in an oxidation-reduction cycle.

  8. Stimulation of methane oxidation potential and effects on vegetation growth by bottom ash addition in a landfill final evapotranspiration cover.

    Science.gov (United States)

    Kim, Gil Won; Ho, Adrian; Kim, Pil Joo; Kim, Sang Yoon

    2016-09-01

    The landfilling of municipal solid waste is a significant source of atmospheric methane (CH4), contributing up to 20% of total anthropogenic CH4 emissions. The evapotranspiration (ET) cover system, an alternative final cover system in waste landfills, has been considered to be a promising way to mitigate CH4 emissions, as well as to prevent water infiltration using vegetation on landfill cover soils. In our previous studies, bottom ash from coal-fired power plants was selected among several industrial residues (blast furnace slag, bottom ash, construction waste, steel manufacture slag, stone powder sludge, and waste gypsum) as the best additive for ET cover systems, with the highest mechanical performance achieved for a 35% (wtwt(-1)) bottom ash content in soil. In this study, to evaluate the field applicability of bottom ash mixed soil as ET cover, four sets of lysimeters (height 1.2m×width 2m×length 6m) were constructed in 2007, and four different treatments were installed: (i) soil+bottom ash (35% wtwt(-1)) (SB); (ii) soil+compost (2% wtwt(-1), approximately corresponding to 40Mgha(-1) in arable field scale) (SC); (iii) soil+bottom ash+compost (SBC); and (iv) soil only as the control (S). The effects of bottom ash mixing in ET cover soil on CH4 oxidation potential and vegetation growth were evaluated in a pilot ET cover system in the 5th year after installation by pilot experiments using the treatments. Our results showed that soil properties were significantly improved by bottom ash mixing, resulting in higher plant growth. Bottom ash addition significantly increased the CH4 oxidation potential of the ET cover soil, mainly due to improved organic matter and available copper concentration, enhancing methanotrophic abundances in soil amended with bottom ash. Conclusively, bottom ash could be a good alternative as a soil additive in the ET cover system to improve vegetation growth and mitigate CH4 emission impact in the waste landfill system. Copyright © 2016

  9. Methane oxidation needs less stressed plants.

    Science.gov (United States)

    Zhou, Xiaoqi; Smaill, Simeon J; Clinton, Peter W

    2013-12-01

    Methane oxidation rates in soil are liable to be reduced by plant stress responses to climate change. Stressed plants exude ethylene into soil, which inhibits methane oxidation when present in the soil atmosphere. Here we discuss opportunities to use 1-aminocyclopropane-1-carboxylate deaminase to manage methane oxidation by regulating plant stress responses.

  10. Seasonal greenhouse gas emissions (methane, carbon dioxide, nitrous oxide) from engineered landfills: daily, intermediate, and final California cover soils.

    Science.gov (United States)

    Bogner, Jean E; Spokas, Kurt A; Chanton, Jeffrey P

    2011-01-01

    Compared with natural ecosystems and managed agricultural systems, engineered landfills represent a highly managed soil system for which there has been no systematic quantification of emissions from coexisting daily, intermediate, and final cover materials. We quantified the seasonal variability of CH, CO, and NO emissions from fresh refuse (no cover) and daily, intermediate, and final cover materials at northern and southern California landfill sites with engineered gas extraction systems. Fresh refuse fluxes (g m d [± SD]) averaged CH 0.053 (± 0.03), CO 135 (± 117), and NO 0.063 (± 0.059). Average CH emissions across all cover types and wet/dry seasons ranged over more than four orders of magnitude (types, including both final covers, averaging 200 cm) cover materials, below which methanogenesis was well established, the variability in gaseous fluxes was attributable to cover thickness, texture, density, and seasonally variable soil moisture and temperature at suboptimal conditions for CH oxidation. Thin daily covers (30 cm local soil) and fresh refuse generally had the highest CO and NO fluxes, indicating rapid onset of aerobic and semi-aerobic processes in recently buried refuse, with rates similar to soil ecosystems and windrow composting of organic waste. This study has emphasized the need for more systematic field quantification of seasonal emissions from multiple types of engineered covers.

  11. [Copper in methane oxidation: a review].

    Science.gov (United States)

    Su, Yao; Kong, Jiao-Yan; Zhang, Xuan; Xia, Fang-Fang; He, Ruo

    2014-04-01

    Methane bio-oxidation plays an important role in the global methane balance and warming mitigation, while copper has a crucial function in methane bio-oxidation. On one side, copper is known to be a key factor in regulating the expression of the genes encoding the two forms of methane monooxygenases (MMOs) and is the essential metal element of the particulate methane monooxygenase (pMMO). On the other side, the content and fractionation of copper in the environment have great effects on the distribution of methanotrophs and their metabolic capability of methane and non-methane organic compounds, as well as on the copper-specific uptake systems in methanotrophs. Thus, it is meaningful to know the role of copper in methane bio-oxidation for comprehensive understanding of this process and is valuable for guiding the application of methanotrophs in greenhouse gas removal and pollution remediation. In this paper, the roles of copper in methane oxidation were reviewed, including the effect of copper on methanotrophic community structure and activity, the expression and activity of MMOs as well as the copper uptake systems in methanotrophs. The future studies of copper and methane oxidation were also discussed.

  12. Thermophilic methane production and oxidation in compost.

    Science.gov (United States)

    Jäckel, Udo; Thummes, Kathrin; Kämpfer, Peter

    2005-04-01

    Methane cycling within compost heaps has not yet been investigated in detail. We show that thermophilic methane oxidation occurred after a lag phase of up to one day in 4-week old, 8-week old and mature (>10-week old) compost material. The potential rate of methane oxidation was between 2.6 and 4.1 micromol CH4(gdw)(-1)h(-1). Profiles of methane concentrations within heaps of different ages indicated that 46-98% of the methane produced was oxidised by methanotrophic bacteria. The population size of thermophilic methanotrophs was estimated at 10(9) cells (gdw)(-1), based on methane oxidation rates. A methanotroph (strain KTM-1) was isolated from the highest positive step of a serial dilution series. This strain belonged to the genus Methylocaldum, which contains thermotolerant and thermophilic methanotrophs. The closest relative organism on the basis of 16S rRNA gene sequence identity was M. szegediense (>99%), a species originally isolated from hot springs. The temperature optimum (45-55 degrees C) for methane oxidation within the compost material was identical to that of strain KTM-1, suggesting that this strain was well adapted to the conditions in the compost material. The temperatures measured in the upper layer (0-40 cm) of the compost heaps were also in this range, so we assume that these organisms are capable of effectively reducing the potential methane emissions from compost.

  13. Photocatalytic oxidation of methane over silver decorated zinc oxide nanocatalysts.

    Science.gov (United States)

    Chen, Xuxing; Li, Yunpeng; Pan, Xiaoyang; Cortie, David; Huang, Xintang; Yi, Zhiguo

    2016-07-20

    The search for active catalysts that efficiently oxidize methane under ambient conditions remains a challenging task for both C1 utilization and atmospheric cleansing. Here, we show that when the particle size of zinc oxide is reduced down to the nanoscale, it exhibits high activity for methane oxidation under simulated sunlight illumination, and nano silver decoration further enhances the photo-activity via the surface plasmon resonance. The high quantum yield of 8% at wavelengths oxide nanostructures shows great promise for atmospheric methane oxidation. Moreover, the nano-particulate composites can efficiently photo-oxidize other small molecular hydrocarbons such as ethane, propane and ethylene, and in particular, can dehydrogenize methane to generate ethane, ethylene and so on. On the basis of the experimental results, a two-step photocatalytic reaction process is suggested to account for the methane photo-oxidation.

  14. Biogenic Methane from Coal: The Oxidation Factor

    Science.gov (United States)

    Gallagher, L. K.; Glossner, A. W.; Landkamer, L.; Figueroa, L. A.; Mandernack, K. W.; Munakata Marr, J.

    2011-12-01

    Vast reserves of coal represent an untapped resource that can be used to produce methane gas, a cleaner energy alternative compared to standard fossil fuels. Microorganisms have demonstrated the ability to utilize coal as a carbon source, producing biogenic methane. With increasing demand for cleaner energy resources, understanding and enhancing biogenic methane production has become an area of active research. The conversion of coal to methane by microorganisms has been demonstrated experimentally by a number of research groups, but the state of the coal used as a substrate has not always been reported and may impact biogenic methane production. Microcosm experiments were designed in order to assess how the oxidation state of coal might influence methane production (e.g. as in a dewatered coal-bed natural gas system). Oxidized and un-oxidized coal samples from the Powder River Basin were incubated in microcosms inoculated with an enrichment culture that was derived from coal. Microcosms were characterized by headspace gas analysis, organic acid production, functional gene abundance (qPCR), and pyrosequencing of the 16S rRNA gene. Although the microbial consortium demonstrated the ability to utilize both oxidized and un-oxidized coal as a sole carbon source to generate methane, it was produced in higher quantities from the un-oxidized coal. This microbial community was dominated by Methanobacteriaceae (45%), epsilon-Proteobacteria (32%) and delta-Proteobacteria (13%). The results of this study provide a basis to develop strategies to enhance biogenic methane production from coal, as well as demonstrate the need for careful substrate preparation for inter-study comparisons.

  15. Partial Oxidation of Methane Over the Perovskite Oxides

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ba0.sSr0.5Co0.8Fe0.2O3-δ and Ba0.5Sr0.5Co0.8Ti0.2O3-δ oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre-treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre-treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe-site in the lattice makes the methane pre-treatment have an obvious influence on the activity of the formed BSCTO oxide.

  16. Inhibitory effects of sulfur compounds on methane oxidation by a methane-oxidizing consortium.

    Science.gov (United States)

    Lee, Eun-Hee; Moon, Kyung-Eun; Kim, Tae Gwan; Lee, Sang-Don; Cho, Kyung-Suk

    2015-12-01

    Kinetic and enzymatic inhibition experiments were performed to investigate the effects of methanethiol (MT) and hydrogen sulfide (H2S) on methane oxidation by a methane-oxidizing consortium. In the coexistence of MT and H2S, the oxidation of methane was delayed until MT and H2S were completely degraded. MT and H2S could be degraded, both with and without methane. The kinetic analysis revealed that the methane-oxidizing consortium showed a maximum methane oxidation rate (Vmax) of 3.7 mmol g-dry cell weight (DCW)(-1) h(-1) and a saturation constant (Km) of 184.1 μM. MT and H2S show competitive inhibition on methane oxidation, with inhibition values (Ki) of 1504.8 and 359.8 μM, respectively. MT was primary removed by particulate methane monooxygenases (pMMO) of the consortium, while H2S was degraded by the other microorganisms or enzymes in the consortium. DNA and mRNA transcript levels of the pmoA gene expressions were decreased to ∼10(6) and 10(3)pmoA gene copy number g-DCW(-1) after MT and H2S degradation, respectively; however, both the amount of the DNA and mRNA transcript recovered their initial levels of ∼10(7) and 10(5)pmoA gene copy number g-DCW(-1) after methane oxidation, respectively. The gene expression results indicate that the pmoA gene could be rapidly reproducible after methane oxidation. This study provides comprehensive information of kinetic interactions between methane and sulfur compounds.

  17. High-pressure oxidation of methane

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Gersen, Sander

    2016-01-01

    Methane oxidation at high pressures and intermediate temperatures was investigated in a laminar flow reactor and in a rapid compression machine (RCM). The flow-reactor experiments were conducted at 700–900 K and 100 bar for fuel-air equivalence ratios (Φ) ranging from 0.06 to 19.7, all highly...... diluted in nitrogen. It was found that under the investigated conditions, the onset temperature for methane oxidation ranged from 723 K under reducing conditions to 750 K under stoichiometric and oxidizing conditions. The RCM experiments were carried out at pressures of 15–80 bar and temperatures of 800......–1250 K under stoichiometric and fuel-lean (Φ=0.5) conditions. Ignition delays, in the range of 1–100 ms, decreased monotonically with increasing pressure and temperature. A chemical kinetic model for high-pressure methane oxidation was established, with particular emphasis on the peroxide chemistry...

  18. Microbial Methane Oxidation Rates in Guandu Wetland of northern Taiwan

    Science.gov (United States)

    Yu, Zih-Huei; Wang, Pei-Ling; Lin, Li-Hung

    2016-04-01

    Wetland is one of the major sources of atmospheric methane. The exact magnitude of methane emission is essentially controlled by microbial processes. Besides of methanogenesis, methanotrophy oxidizes methane with the reduction of various electron acceptors under oxic or anoxic conditions. The interplay of these microbial activities determines the final methane flux under different circumstances. In a tidal wetland, the cyclic flooding and recession of tide render oxygen and sulfate the dominant electron acceptors for methane oxidation. However, the details have not been fully examined, especially for the linkage between potential methane oxidation rates and in situ condition. In this study, a sub-tropical wetland in northern Taiwan, Guandu, was chosen to examine the tidal effect on microbial methane regulation. Several sediment cores were retrieved during high tide and low tide period and their geochemical profiles were characterized to demonstrate in situ microbial activities. Incubation experiments were conducted to estimate potential aerobic and anaerobic methane oxidation rates in surface and core sediments. Sediment cores collected in high tide and low tide period showed different geochemical characteristics, owning to tidal inundation. Chloride and sulfate concentration were lower during low tide period. A spike of enhanced sulfate at middle depth intervals was sandwiched by two sulfate depleted zones above and underneath. Methane was accumulated significantly with two methane depletion zones nearly mirroring the sulfate spike zone identified. During the high tide period, sulfate decreased slightly with depth with methane production inhibited at shallow depths. However, a methane consumption zone still occurred near the surface. Potential aerobic methane oxidation rates were estimated between 0.7 to 1.1 μmole/g/d, showing no difference between the samples collected at high tide or low tide period. However, a lag phase was widely observed and the lag phase

  19. Methane oxidation in anoxic lake waters

    Science.gov (United States)

    Su, Guangyi; Zopfi, Jakob; Niemann, Helge; Lehmann, Moritz

    2017-04-01

    Freshwater habitats such as lakes are important sources of methante (CH4), however, most studies in lacustrine environments so far provided evidence for aerobic methane oxidation only, and little is known about the importance of anaerobic oxidation of CH4 (AOM) in anoxic lake waters. In marine environments, sulfate reduction coupled to AOM by archaea has been recognized as important sinks of CH4. More recently, the discorvery of anaerobic methane oxidizing denitrifying bacteria represents a novel and possible alternative AOM pathway, involving reactive nitrogen species (e.g., nitrate and nitrite) as electron acceptors in the absence of oxygen. We investigate anaerobic methane oxidation in the water column of two hydrochemically contrasting sites in Lake Lugano, Switzerland. The South Basin displays seasonal stratification, the development of a benthic nepheloid layer and anoxia during summer and fall. The North Basin is permanently stratified with anoxic conditions below 115m water depth. Both Basins accumulate seasonally (South Basin) or permanently (North Basin) large amounts of CH4 in the water column below the chemocline, providing ideal conditions for methanotrophic microorganisms. Previous work revealed a high potential for aerobic methane oxidation within the anoxic water column, but no evidence for true AOM. Here, we show depth distribution data of dissolved CH4, methane oxidation rates and nutrients at both sites. In addition, we performed high resolution phylogenetic analyses of microbial community structures and conducted radio-label incubation experiments with concentrated biomass from anoxic waters and potential alternative electron acceptor additions (nitrate, nitrite and sulfate). First results from the unamended experiments revealed maximum activity of methane oxidation below the redoxcline in both basins. While the incubation experiments neither provided clear evidence for NOx- nor sulfate-dependent AOM, the phylogenetic analysis revealed the

  20. Environmental control on aerobic methane oxidation in coastal waters

    Science.gov (United States)

    Steinle, Lea; Maltby, Johanna; Engbersen, Nadine; Zopfi, Jakob; Bange, Hermann; Elvert, Marcus; Hinrichs, Kai-Uwe; Kock, Annette; Lehmann, Moritz; Treude, Tina; Niemann, Helge

    2016-04-01

    Large quantities of methane are produced in anoxic sediments of continental margins and may be liberated to the overlying water column, where some of it is consumed by aerobic methane oxidizing bacteria (MOB). Aerobic methane oxidation (MOx) in the water column is consequently the final sink for methane before its release to the atmosphere, where it acts as a potent greenhouse gas. In the context of the ocean's contribution to atmospheric methane, coastal seas are particularly important accounting >75% of global methane emission from marine systems. Coastal oceans are highly dynamic, in particular with regard to the variability of methane and oxygen concentrations as well as temperature and salinity, all of which are potential key environmental factors controlling MOx. To determine important environmental controls on the activity of MOBs in coastal seas, we conducted a two-year time-series study with measurements of physicochemical water column parameters, MOx activity and the composition of the MOB community in a coastal inlet in the Baltic Sea (Boknis Eck Time Series Station, Eckernförde Bay - E-Bay). In addition, we investigated the influence of temperature and oxygen on MOx during controlled laboratory experiments. In E-Bay, hypoxia developed in bottom waters towards the end of the stratification period. Constant methane liberation from sediments resulted in bottom water methane accumulations and supersaturation (with respect to the atmospheric equilibrium) in surface waters. Here, we will discuss the factors impacting MOx the most, which were (i) perturbations of the water column (ii) temperature and (iii) oxygen concentration. (i) Perturbations of the water column caused by storm events or seasonal mixing led to a decrease in MOx, probably caused by replacement of stagnant water with a high standing stock of MOB by 'new' waters with a lower abundance of methanotrophs. b) An increase in temperature generally led to higher MOx rates. c) Even though methane was

  1. Recent Progress in Direct Partial Oxidation of Methane to Methanol

    Institute of Scientific and Technical Information of China (English)

    Qijian Zhang; Dehua He; Qiming Zhu

    2003-01-01

    The direct conversion of methane to methanol has attracted a great deal of attention for nearly a century since it was first found possible in 1902, and it is still a challenging task. This review article describes recent advancements in the direct partial oxidation of methane to methanol. The history of direct oxidation of methane and the difficulties encountered in the partial oxidation of methane to methanol are briefly summarized. Recently reported developments in gas-phase homogeneous oxidation, heterogeneous catalytic oxidation and liquid phase homogeneous catalytic oxidation of methane are reviewed.

  2. Methane and nitrous oxide in the ice core record.

    Science.gov (United States)

    Wolff, Eric; Spahni, Renato

    2007-07-15

    Polar ice cores contain, in trapped air bubbles, an archive of the concentrations of stable atmospheric gases. Of the major non-CO2 greenhouse gases, methane is measured quite routinely, while nitrous oxide is more challenging, with some artefacts occurring in the ice and so far limited interpretation. In the recent past, the ice cores provide the only direct measure of the changes that have occurred during the industrial period; they show that the current concentration of methane in the atmosphere is far outside the range experienced in the last 650,000 years; nitrous oxide is also elevated above its natural levels. There is controversy about whether changes in the pre-industrial Holocene are natural or anthropogenic in origin. Changes in wetland emissions are generally cited as the main cause of the large glacial-interglacial change in methane. However, changing sinks must also be considered, and the impact of possible newly described sources evaluated. Recent isotopic data appear to finally rule out any major impact of clathrate releases on methane at these time-scales. Any explanation must take into account that, at the rapid Dansgaard-Oeschger warmings of the last glacial period, methane rose by around half its glacial-interglacial range in only a few decades. The recent EPICA Dome C (Antarctica) record shows that methane tracked climate over the last 650,000 years, with lower methane concentrations in glacials than interglacials, and lower concentrations in cooler interglacials than in warmer ones. Nitrous oxide also shows Dansgaard-Oeschger and glacial-interglacial periodicity, but the pattern is less clear.

  3. Trends for Methane Oxidation at Solid Oxide Fuel Cell Conditions

    DEFF Research Database (Denmark)

    Kleis, Jesper; Jones, Glenn; Abild-Pedersen, Frank;

    2009-01-01

    the Ni surfaces to other metals of interest. This allows the reactivity over the different metals to be understood in terms of two reactivity descriptors, namely, the carbon and oxygen adsorption energies. By combining a simple free-energy analysis with microkinetic modeling, activity landscapes of anode......First-principles calculations are used to predict a plausible reaction pathway for the methane oxidation reaction. In turn, this pathway is used to obtain trends in methane oxidation activity at solid oxide fuel cell (SOFC) anode materials. Reaction energetics and barriers for the elementary...

  4. Low Temperature Oxidation of Methane: The Influence of Nitrogen Oxides

    DEFF Research Database (Denmark)

    Bendtsen, Anders Broe; Glarborg, Peter; Dam-Johansen, Kim

    2000-01-01

    An experimental investigation of methane oxidation in the presence of NO and NO2 has been made in an isothermal plug-flow reactor at 750-1250K. The temperature for on-set of oxidation was lowered by 250 K in the presence of NO or NO2 at residence times of 200 ms. At shorter residence times (140 ms...

  5. [Effect of temperature on methane production and oxidation in soils].

    Science.gov (United States)

    Ding, Weixin; Cai, Zucong

    2003-04-01

    The influence of temperature and its mechanism on methane production and oxidation in soils were reviewed in this paper. Temperature can alter the soil ability to produce methane through changing types of dominant methanogens in archaeal community. Dominant methanogen is Methanosarcinaceae at higher temperature which can utilize both H2/CO2 and acetate as the precursor to produce methane, while Methanosaetaceae at lower temperature which only use acetate as the precursor and produce far less methane than do Methanosarcinaceae. Increasing soil temperature apparently raises soil ability to produce methane, which is called temperature effectiveness and expressed as Q10 with a range from 1.5 to 28 and an average of 4.1. There is an obviously positive correlation between temperature effectiveness (Q10) on methane production and substrate content. As compared to methane production, effect of temperature on methane oxidation is lower, which may be related to the strong affinity of methanotrophs for methane.

  6. Atmospheric methane removal by methane-oxidizing bacteria immobilized on porous building materials

    NARCIS (Netherlands)

    Ganendra, G; De Muynck, W; Ho, A.; Hoefman, S.; De Vos, P.; Boeckx, P.; Boon, N.

    2014-01-01

    Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six porous carrier materials have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building materials at high (similar to 20 % (v/v)) and low (similar to 100 ppmv) methane

  7. The mechanism of the partial oxidation of methane

    Science.gov (United States)

    Sinev, Mikhail Yu; Korshak, V. N.; Krylov, Oleg V.

    1989-01-01

    The principal characteristics of the homogeneous and heterogeneous-catalytic conversion of methane into condensation products (C2 and C3 hydrocarbons) and partial oxidation products (methanol and formaldehyde) are considered. Data are presented concerning the most effective catalysts and data relating to the mechanism of the activation of methane on oxide and oxide halide catalysts, the nature of the active centres, and the kinetics of the partial oxidation of methane are analysed. It is shown that the oxidative condensation of methane in the presence of the catalysts considered is a heterogeneous-homogeneous process, which imposes special requirements in its practical realisation. The bibliography includes 118 references.

  8. A marine microbial consortium apparently mediating anaerobic oxidation of methane

    DEFF Research Database (Denmark)

    Boetius, A.; Ravenschlag, K.; Schubert, CJ;

    2000-01-01

    A large fraction of globally produced methane is converted to CO2 by anaerobic oxidation in marine sediments(1). Strong geochemical evidence for net methane consumption in anoxic sediments is based on methane profiles(2), radiotracer experiments(3) and stable carbon isotope data(4). But the elusive...

  9. Biochemistry of methyl-coenzyme M reductase: the nickel metalloenzyme that catalyzes the final step in synthesis and the first step in anaerobic oxidation of the greenhouse gas methane.

    Science.gov (United States)

    Ragsdale, Stephen W

    2014-01-01

    Methane, the major component of natural gas, has been in use in human civilization since ancient times as a source of fuel and light. Methanogens are responsible for synthesis of most of the methane found on Earth. The enzyme responsible for catalyzing the chemical step of methanogenesis is methyl-coenzyme M reductase (MCR), a nickel enzyme that contains a tetrapyrrole cofactor called coenzyme F430, which can traverse the Ni(I), (II), and (III) oxidation states. MCR and methanogens are also involved in anaerobic methane oxidation. This review describes structural, kinetic, and computational studies aimed at elucidating the mechanism of MCR. Such studies are expected to impact the many ramifications of methane in our society and environment, including energy production and greenhouse gas warming.

  10. Anaerobic methane oxidation in a landfill-leachate plume.

    Science.gov (United States)

    Grossman, Ethan L; Cifuentes, Luis A; Cozzarelli, Isabelle M

    2002-06-01

    The alluvial aquifer adjacent to Norman Landfill, OK, provides an excellent natural laboratory for the study of anaerobic processes impacting landfill-leachate contaminated aquifers. We collected groundwaters from a transect of seven multilevel wells ranging in depth from 1.3 to 11 m that were oriented parallel to the flow path. The center of the leachate plume was characterized by (1) high alkalinity and elevated concentrations of total dissolved organic carbon, reduced iron, and methane, and (2) negligible oxygen, nitrate, and sulfate concentrations. Methane concentrations and stable carbon isotope (delta13C) values suggest anaerobic methane oxidation was occurring within the plume and at its margins. Methane delta13C values increased from about -54 per thousand near the source to > -10 per thousand downgradient and at the plume margins. The isotopic fractionation associated with this methane oxidation was -13.6+/-1.0 per thousand. Methane 13C enrichment indicated that 80-90% of the original landfill methane was oxidized over the 210-m transect. First-order rate constants ranged from 0.06 to 0.23 per year, and oxidation rates ranged from 18 to 230 microM/y. Overall, hydrochemical data suggest that a sulfate reducer-methanogen consortium may mediate this methane oxidation. These results demonstrate that natural attenuation through anaerobic methane oxidation can be an important sink for landfill methane in aquifer systems.

  11. Trace methane oxidation studied in several Euryarchaeota under diverse conditions

    Directory of Open Access Journals (Sweden)

    James J. Moran

    2005-01-01

    Full Text Available We used 13C-labeled methane to document the extent of trace methane oxidation by Archaeoglobus fulgidus, Archaeoglobus lithotrophicus, Archaeoglobus profundus, Methanobacterium thermoautotrophicum, Methanosarcina barkeri and Methanosarcina acetivorans. The results indicate trace methane oxidation during growth varied among different species and among methanogen cultures grown on different substrates. The extent of trace methane oxidation by Mb. thermoautotrophicum (0.05 ± 0.04%, ± 2 standard deviations of the methane produced during growth was less than that by M. barkeri (0.15 ± 0.04%, grown under similar conditions with H2 and CO2. Methanosarcina acetivorans oxidized more methane during growth on trimethylamine (0.36 ± 0.05% than during growth on methanol (0.07 ± 0.03%. This may indicate that, in M. acetivorans, either a methyltransferase related to growth on trimethylamine plays a role in methane oxidation, or that methanol is an intermediate of methane oxidation. Addition of possible electron acceptors (O2, NO3–, SO22–, SO32– or H2 to the headspace did not substantially enhance or diminish methane oxidation in M. acetivorans cultures. Separate growth experiments with FAD and NAD+ showed that inclusion of these electron carriers also did not enhance methane oxidation. Our results suggest trace methane oxidized during methanogenesis cannot be coupled to the reduction of these electron acceptors in pure cultures, and that the mechanism by which methane is oxidized in methanogens is independent of H2 concentration. In contrast to the methanogens, species of the sulfate-reducing genus Archaeoglobus did not significantly oxidize methane during growth (oxidizing 0.003 ± 0.01% of the methane provided to A. fulgidus, 0.002 ± 0.009% to A. lithotrophicus and 0.003 ± 0.02% to A. profundus. Lack of observable methane oxidation in the three Archaeoglobus species examined may indicate that methyl-coenzyme M reductase, which is not present in

  12. Quantification of methane oxidation in the rice rhizosphere using C-13-labelled methane

    NARCIS (Netherlands)

    Groot, T.T.; Bodegom, van P.M.; Harren, F.J.M.; Meijer, H.A.J.

    2003-01-01

    In this paper isotope ratio mass spectrometry is used to determine the methane (CH4) oxidation fraction in the rhizosphere of intact rice plant-soil systems. Earlier studies on quantification of the methane oxidation were based on inhibition or incubation procedures which strongly interfered with

  13. Quantification of methane oxidation in the rice rhizosphere using 13C-labelled methane

    NARCIS (Netherlands)

    Groot, T.T; van Bodegom, P.M.; Harren, F.J.M.; Meijer, H.A.J.

    In this paper isotope ratio mass spectrometry is used to determine the methane (CH4) oxidation fraction in the rhizosphere of intact rice plant-soil systems. Earlier studies on quantification of the methane oxidation were based on inhibition or incubation procedures which strongly interfered with

  14. Kinetics of methane oxidation in selected mineral soils

    Science.gov (United States)

    Walkiewicz, A.; Bulak, P.; Brzeziñska, M.; Włodarczyk, T.; Polakowski, C.

    2012-10-01

    The kinetic parameters of methane oxidation in three mineral soils were measured under laboratory conditions. Incubationswere preceded by a 24-day preincubationwith 10%vol. of methane. All soils showed potential to the consumption of added methane. None of the soils, however, consumed atmospheric CH4. Methane oxidation followed the Michaelis-Menten kinetics, with relatively low values of parameters for Eutric Cambisol, while high values for Haplic Podzol, and especially for Mollic Gleysol which showed the highest methanotrophic activity and much lower affinity to methane. The high values of parameters for methane oxidation are typical for organic soils and mineral soils from landfill cover. The possibility of the involvement of nitrifying microorganisms, which inhabit the ammonia-fertilized agricultural soils should be verified.

  15. Advances in the Partial Oxidation of Methane to Synthesis Gas

    Institute of Scientific and Technical Information of China (English)

    Quanli Zhu; Xutao Zhao; Youquan Deng

    2004-01-01

    The conversion and utilization of natural gas is of significant meaning to the national economy,even to the everyday life of people. However, it has not become a popular industrial process as expected due to the technical obstacles. In the past decades, much investigation into the conversion of methane,predominant component of natural gas, has been carried out. Among the possible routes of methane conversion, the partial oxidation of methane to synthesis gas is considered as an effective and economically feasible one. In this article, a brief review of recent studies on the mechanism of the partial oxidation of methane to synthesis gas together with catalyst development is wherein presented.

  16. Combined anaerobic ammonium and methane oxidation for nitrogen and methane removal.

    Science.gov (United States)

    Zhu, Baoli; Sánchez, Jaime; van Alen, Theo A; Sanabria, Janeth; Jetten, Mike S M; Ettwig, Katharina F; Kartal, Boran

    2011-12-01

    Anammox (anaerobic ammonium oxidation) is an environment-friendly and cost-efficient nitrogen-removal process currently applied to high-ammonium-loaded wastewaters such as anaerobic digester effluents. In these wastewaters, dissolved methane is also present and should be removed to prevent greenhouse gas emissions into the environment. Potentially, another recently discovered microbial pathway, n-damo (nitrite-dependent anaerobic methane oxidation) could be used for this purpose. In the present paper, we explore the feasibility of simultaneously removing methane and ammonium anaerobically, starting with granules from a full-scale anammox bioreactor. We describe the development of a co-culture of anammox and n-damo bacteria using a medium containing methane, ammonium and nitrite. The results are discussed in the context of other recent studies on the application of anaerobic methane- and ammonia-oxidizing bacteria for wastewater treatment.

  17. Methane oxidation linked to chlorite dismutation

    Science.gov (United States)

    Miller, Laurence G.; Baesman, Shaun M.; Carlström, Charlotte I.; Coates, John D.; Oremland, Ronald S.

    2014-01-01

    We examined the potential for CH4 oxidation to be coupled with oxygen derived from the dissimilatory reduction of perchlorate, chlorate, or via chlorite (ClO−2) dismutation. Although dissimilatory reduction of ClO−4 and ClO−3 could be inferred from the accumulation of chloride ions either in spent media or in soil slurries prepared from exposed freshwater lake sediment, neither of these oxyanions evoked methane oxidation when added to either anaerobic mixed cultures or soil enriched in methanotrophs. In contrast, ClO−2 amendment elicited such activity. Methane (0.2 kPa) was completely removed within several days from the headspace of cell suspensions of Dechloromonas agitata CKB incubated with either Methylococcus capsulatus Bath or Methylomicrobium album BG8 in the presence of 5 mM ClO−2. We also observed complete removal of 0.2 kPa CH4 in bottles containing soil enriched in methanotrophs when co-incubated with D. agitata CKB and 10 mM ClO−2. However, to be effective these experiments required physical separation of soil from D. agitata CKB to allow for the partitioning of O2 liberated from chlorite dismutation into the shared headspace. Although a link between ClO−2 and CH4 consumption was established in soils and cultures, no upstream connection with either ClO−4 or ClO−3 was discerned. This result suggests that the release of O2 during enzymatic perchlorate reduction was negligible, and that the oxygen produced was unavailable to the aerobic methanotrophs.

  18. Catalytic selective oxidation or oxidative functionalization of methane and ethane to organic oxygenates

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Selective oxidation or oxidative functionalization of methane and ethane by both homogeneous and heterogeneous catalysis is presented concerning: (1) selective oxidation of methane and ethane to organic oxygenates by hydrogen peroxide in a water medium in the presence of homogeneous osmium catalysts, (2) selective oxidation of methane to formaldehyde over highly dispersed iron and copper heterogeneous catalysts, (3) selective oxidation of ethane to acetaldehyde and formaldehyde over supported molybdenum catalysts, and (4) oxidative carbonylation of methane to methyl acetate over heterogeneous catalysts containing dual sites of rhodium and iron.

  19. Anaerobic methane oxidation in low-organic content methane seep sediments

    Science.gov (United States)

    Pohlman, John W.; Riedel, Michael; Bauer, James E.; Canuel, Elizabeth A.; Paull, Charles K.; Lapham, Laura; Grabowski, Kenneth S.; Coffin, Richard B.; Spence, George D.

    2013-01-01

    Sulfate-dependent anaerobic oxidation of methane (AOM) is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps. In this study, we investigate how the presence of low-organic content sediment influences the capacity and efficiency of AOM at Bullseye vent, a gas hydrate-bearing cold seep offshore of Vancouver Island, Canada. The upper 8 m of sediment contains 14C. A fossil origin for the DIC precludes remineralization of non-fossil OM present within the sulfate zone as a significant contributor to pore water DIC, suggesting that nearly all sulfate is available for anaerobic oxidation of fossil seep methane. Methane flux from the SMT to the sediment water interface in a diffusion-dominated flux region of Bullseye vent was, on average, 96% less than at an OM-rich seep in the Gulf of Mexico with a similar methane flux regime. Evidence for enhanced methane oxidation capacity within OM-poor sediments has implications for assessing how climate-sensitive reservoirs of sedimentary methane (e.g., gas hydrate) will respond to ocean warming, particularly along glacially-influenced mid and high latitude continental margins.

  20. Bio-tarp alternative daily cover prototypes for methane oxidation atop open landfill cells.

    Science.gov (United States)

    Adams, Bryn L; Besnard, Fabien; Bogner, Jean; Hilger, Helene

    2011-05-01

    Final landfill covers are highly engineered to prevent methane release into the atmosphere. However, methane production begins soon after waste placement and is an unaddressed source of emissions. The methane oxidation capacity of methanotrophs embedded in a "bio-tarp" was investigated as a means to mitigate methane release from open landfill cells. The bio-tarp would also serve as an alternative daily cover during routine landfill operation. Evaluations of nine synthetic geotextiles identified two that would likely be suitable bio-tarp components. Pilot tarp prototypes were tested in continuous flow systems simulating landfill gas conditions. Multilayered bio-tarp prototypes consisting of alternating layers of the two geotextiles were found to remove 16% of the methane flowing through the bio-tarp. The addition of landfill cover soil, compost, or shale amendments to the bio-tarp increased the methane removal up to 32%. With evidence of methane removal in a laboratory bioreactor, prototypes were evaluated at a local landfill using flux chambers installed atop intermediate cover at a landfill. The multilayered bio-tarp and amended bio-tarp configurations were all found to decrease landfill methane flux; however, the performance efficacy of bio-tarps was not significantly different from controls without methanotrophs. Because highly variable methane fluxes at the field site likely confounded the test results, repeat field testing is recommended under more controlled flux conditions.

  1. Electrochemical and partial oxidation of methane

    Science.gov (United States)

    Singh, Rahul

    2008-10-01

    negligible coke formation on the novel fabricated anode by electroless plating process. Hydrogen is an environmentally cleaner source of energy. The recent increase in the demand of hydrogen as fuel for all types of fuel cells and petroleum refining process has boosted the need of production of hydrogen. Methane, a major component of natural gas is the major feedstock for production of hydrogen. The route of partial oxidation of methane to produce syngas (CO + H2) offers significant advantages over commercialized steam reforming process for higher efficiency and lower energy requirements. Partial oxidation of methane was studied by pulsing O2 into a CH4 flow over Rh/Al2O3 in a sequence of in situ infrared (IR) cell and fixed bed reactor at 773 K. The results obtained from the sequence of an IR cell followed by a fixed bed reactor show that (i) adsorbed CO produced possesses a long residence time, indicating that adsorbed oxygen leading to the formation of CO is significantly different from those leading to CO2 and (ii) CO2 is not an intermediate species for the formation of CO. In situ IR of pulse reaction coupled with alternating reactor sequence is an effective approach to study the primary and secondary reactions as well as the nature of their adsorbed species. As reported earlier, hydrogen remains to be the most effective fuel for fuel cells, the production of high purity hydrogen from naturally available resources such as coal, petroleum, and natural gas requires a number of energy-intensive steps, making fuel cell processes for stationary electric power generation prohibitively uneconomic. Direct use of coal or coal gas as the feed is a promising approach for low cost electricity generation. Coal gas solid oxide fuel cell was studied by pyrolyzing Ohio #5 coal to coal gas and transporting to a Cu anode solid oxide fuel cell to generate power. The study of coal-gas solid oxide fuel cell is divided into two sections, i.e., (i) understanding the composition of coal gas by

  2. Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake

    DEFF Research Database (Denmark)

    Deutzmann, Joerg S.; Stief, Peter; Brandes, Josephin

    2014-01-01

    Anaerobic methane oxidation coupled to denitrification, also known as “nitrate/nitrite-dependent anaerobic methane oxidation” (n-damo), was discovered in 2006. Since then, only a few studies have identified this process and the associated microorganisms in natural environments. In aquatic sediments......, the close proximity of oxygen- and nitrate-consumption zones can mask n-damo as aerobic methane oxidation. We therefore investigated the vertical distribution and the abundance of denitrifying methanotrophs related to Candidatus Methylomirabilis oxyfera with cultivation-independent molecular techniques...... in the sediments of Lake Constance. Additionally, the vertical distribution of methane oxidation and nitrate consumption zones was inferred from high-resolution microsensor profiles in undisturbed sediment cores. M. oxyfera-like bacteria were virtually absent at shallow-water sites (littoral sediment) and were...

  3. Partial oxidation of methane to syngas in tubular oxygenpermeable reactor

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A dense Ba0.5Sr0.5Co0.8Fe0.2O3-δ membrane tube was prepared by the extruding method. Furthermore, a membrane reactor with this tubular membrane was successfully applied to partial oxidation of methane (POM) reaction,in which the separation of oxygen from air and the partial oxidation of methane are integrated in one process. At 875℃,94% of methane conversion, 98% of CO selectivity, 95% of H2 selectivity, and as high as 8.8 mL/(min @cm2) of oxygen flux were obtained. In POM reaction condition, the membrane tube shows a very good stability.

  4. Scrutinizing compost properties and their impact on methane oxidation efficiency.

    Science.gov (United States)

    Huber-Humer, Marion; Tintner, Johannes; Böhm, Katharina; Lechner, Peter

    2011-05-01

    Methane emissions from active or closed landfills can be reduced by means of microbial methane oxidation enhanced by properly designed landfill covers and engineered biocovers. Composts produced using different waste materials have already been proven to support methane oxidation, and may represent a low-cost alternative to other suitable substrates such as sandy or humic-rich soils, which are frequently not available in sufficient amounts or are too costly. In the present study a data set of 30 different compost materials (different age and input materials) and mixtures, as well as seven soils and mineral substrates were tested to assess methane oxidation rate under similar conditions in a laboratory column set-up. Multivariate data analysis (discriminant analysis) was applied to predict the influence of 21 different parameters (chemical, maturation and physical) on methane oxidation rate in a PLS-DA model. The results show that bulk density, total nutrient content (nitrogen and phosphorus), as well as the quantity and quality (with respect to maturity) of organic matter determined methane oxidation rate in this data set. The model explained 50% of the data variation, indicating how characterisation of oxidation rate by single, even diverse conventional parameters was limited. Thus for the first time, Fourier Transform Infrared (FTIR) spectroscopy was applied to a series of samples to better determine the characteristics of methane-oxidising materials. The initial data obtained in this study appear to be most promising. The prediction of specific methane oxidation rate of a potential biocover material from FTIR spectra and multivariate data analyses is a target to be focused on in the future. Copyright © 2010 Elsevier Ltd. All rights reserved.

  5. Selective anaerobic oxidation of methane enables direct synthesis of methanol.

    Science.gov (United States)

    Sushkevich, Vitaly L; Palagin, Dennis; Ranocchiari, Marco; van Bokhoven, Jeroen A

    2017-05-05

    Direct functionalization of methane in natural gas remains a key challenge. We present a direct stepwise method for converting methane into methanol with high selectivity (~97%) over a copper-containing zeolite, based on partial oxidation with water. The activation in helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars of methane and then water at 473 K, consistently produced 0.204 mole of CH3OH per mole of copper in zeolite. Isotopic labeling confirmed water as the source of oxygen to regenerate the zeolite active centers and renders methanol desorption energetically favorable. On the basis of in situ x-ray absorption spectroscopy, infrared spectroscopy, and density functional theory calculations, we propose a mechanism involving methane oxidation at Cu(II) oxide active centers, followed by Cu(I) reoxidation by water with concurrent formation of hydrogen. Copyright © 2017, American Association for the Advancement of Science.

  6. Platinum single crystal electrodes for the electrocatalysis of methane oxidation

    Directory of Open Access Journals (Sweden)

    Mayara Munaretto

    2011-03-01

    Full Text Available The main objective of this paper is to characterize the voltammetric profiles of platinum single crystals of low Miller indexes Pt(100 and Pt(110 and study their catalytic activities on the oxidation of methane. In this way, it was developed a metallic surface modified by presence of other metal oxide, which presents catalytic activity for this reaction. It is well known that the electrooxidation of methane (CH4 leads mainly to the formation of CO2 and H2O, however, the oxidation can also lead to the formation of CO, a reaction intermediate that has strong interaction with metal surfaces, such as platinum. This molecule tends to accumulate on the platinum surface and to passive it, due to the self-poisoning, decreasing its catalytic activity. Therefore, the main aim of this work was the development of a platinum electrode modified by deposition of titanium oxide, which presented electrocatalytic properties for the oxidation of methane.

  7. Clumped isotope effects during OH and Cl oxidation of methane

    Science.gov (United States)

    Whitehill, Andrew R.; Joelsson, Lars Magnus T.; Schmidt, Johan A.; Wang, David T.; Johnson, Matthew S.; Ono, Shuhei

    2017-01-01

    A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH was produced from the reaction of O(1D) (from O3 photolysis) with H2O, and Cl was from photolysis of Cl2. Samples were taken from the reaction cell and analyzed for methane (12CH4, 12CH3D, 13CH4, 13CH3D) isotopologue ratios using tunable infrared laser direct absorption spectroscopy. Measured kinetic isotope effects for singly substituted species were consistent with previous experimental studies. For doubly substituted methane, 13CH3D, the observed kinetic isotope effects closely follow the product of the kinetic isotope effects for the 13C and deuterium substituted species (i.e., 13,2KIE = 13KIE × 2KIE). The deviation from this relationship is 0.3‰ ± 1.2‰ and 3.5‰ ± 0.7‰ for OH and Cl oxidation, respectively. This is consistent with model calculations performed using quantum chemistry and transition state theory. The OH and Cl reactions enrich the residual methane in the clumped isotopologue in open system reactions. In a closed system, however, this effect is overtaken by the large D/H isotope effect, which causes the residual methane to become anti-clumped relative to the initial methane. Based on these results, we demonstrate that oxidation of methane by OH, the predominant oxidant for tropospheric methane, will only have a minor (∼0.3‰) impact on the clumped isotope signature (Δ13CH3D, measured as a deviation from a stochastic distribution of isotopes) of tropospheric methane. This paper shows that Δ13CH3D will provide constraints on methane source strengths, and predicts that Δ12CH2D2 can provide information on methane sink strengths.

  8. Direct iron ore reduction by methane in a fluidized bed. Final report, November 1989-December 1992

    Energy Technology Data Exchange (ETDEWEB)

    van der Vaart, D.R.; Conger, W.L.

    1993-08-01

    Novel process chemistry of methane in a fluidized bed was investigated to identify a more direct route to producing the reducing gas needed in the Direct Reduction of iron ore. A rather surprising result, however, of the study was the discovery of an inexpensive and attrition-resistant catalytic material for methane oxidative coupling. The iron oxide impregnated, non-porous silica oxide was found to be relatively active, and quite selective when steam was added to the methane/air feed.

  9. Nitrogen as a regulatory factor of methane oxidation in soils and sediments

    NARCIS (Netherlands)

    Bodelier, P.L.E.; Laanbroek, H.J.

    2004-01-01

    The oxidation of methane by methane-oxidising microorganisms is an important link in the global methane budget. Oxic soils are a net sink while wetland soils are a net source of atmospheric methane. It has generally been accepted that the consumption of methane in upland as well as lowland systems

  10. Nitrogen as a regulatory factor of methane oxidation in soils and sediments

    NARCIS (Netherlands)

    Bodelier, P.L.E.; Laanbroek, H.J.

    2004-01-01

    The oxidation of methane by methane-oxidising microorganisms is an important link in the global methane budget. Oxic soils are a net sink while wetland soils are a net source of atmospheric methane. It has generally been accepted that the consumption of methane in upland as well as lowland systems i

  11. Formation of methane and nitrous oxide in plants

    Science.gov (United States)

    Keppler, Frank; Lenhart, Katharina

    2017-04-01

    Methane, the second important anthropogenic greenhouse gas after carbon dioxide, is the most abundant reduced organic compound in the atmosphere and plays a central role in atmospheric chemistry. The global atmospheric methane budget is determined by many natural and anthropogenic terrestrial and aquatic surface sources, balanced primarily by one major sink (hydroxyl radicals) in the atmosphere. Natural sources of atmospheric methane in the biosphere have until recently been attributed to originate solely from strictly anaerobic microbial processes in wetland soils and rice paddies, the intestines of termites and ruminants, human and agricultural waste, and from biomass burning, fossil fuel mining and geological sources including mud volcanoes and seeps. However, recent studies suggested that terrestrial vegetation, fungi and mammals may also produce methane without the help of methanogens and under aerobic conditions (e.g. Keppler et al. 2009, Wang et al. 2013). These novel sources have been termed "aerobic methane production" to distinguish them from the well-known anaerobic methane production pathway. Nitrous oxide is another important greenhouse gas and major source of ozone-depleting nitric oxide. About two thirds of nitrous oxide emissions are considered to originate from anthropogenic and natural terrestrial sources, and are almost exclusively related to microbial processes in soils and sediments. However, the global nitrous oxide budget still has major uncertainties since it is unclear if all major sources have been identified but also the emission estimates of the know sources and stratospheric sink are afflicted with high uncertainties. Plants contribute, although not yet quantified, to nitrous oxide emissions either indirectly as conduits of soil derived nitrous oxide (Pihlatie et al. 2005), or directly via generation of nitrous oxide in leaves (Dean & Harper 1986) or on the leaf surface induced by UV irradiation (Bruhn et al. 2014). Moreover, lichens

  12. Ageing well: methane oxidation and methane oxidizing bacteria along a chronosequence of 2000 years.

    Science.gov (United States)

    Ho, Adrian; Lüke, Claudia; Cao, Zhihong; Frenzel, Peter

    2011-12-01

    Rice is the staple food for more than half of the world's growing population. While the area planted to wetland rice is expected to increase further, virtually nothing is known about the long-term development of the respective microbial communities, and how these might influence biogeochemistry. Focusing on methane oxidizing bacteria, we studied a chronosequence of paddy fields in China aged 50-2000 years. Potential methanotrophic activity increased substantially with age of soil. Community composition was relatively similar in all fields. However, growth and activity of one particular subgroup of methanotrophs correlated to soil age suggesting an intricate abiotic control on methanotrophs evolving with time. Our results demonstrate that continuous rice agriculture does not only shape the microbial community, but also modifies the micro-environment in a way enabling faster growth and higher activity of selected populations.

  13. Interactions between nitrogen cycling and methane oxidation in the pelagic waters of the Gulf of Mexico.

    Science.gov (United States)

    Joye, S. B.; Weber, S.; Battles, J.; Montoya, J. P.

    2014-12-01

    Methane is an important greenhouse gas that plays a critical role in climate variation. Although a variety of marine methane sources and sinks have been identified, key aspects of the fate of methane in the ocean remain poorly constrained. At cold seeps in the Gulf of Mexico and elsewhere, methane is introduced into the overlying water column via fluid escape from the seabed. We quantified the fate of methane in the water column overlying seafloor cold seeps, in a brine basin, and at several control sites. Our goals were to determine the factors that regulated methane consumption and assimilation and to explore how these controlling factors varied among and between sites. In particular, we examined the impact of nitrogen availability on methane oxidation and studied the ability of methane oxidizing bacteria to fix molecular nitrogen. Methane oxidation rates were highest in the methane rich bottom waters of natural hydrocabron seeps. At these sites, inorganic nitrogen addition stimulated methane oxidation in laboratory experiments. In vitro shipboard experiments revealed that rates of methane oxidation and nitrogen fixation were correlated strongly, suggesting that nitrogen fixation may have been mediated by methanotrophic bacteria. The highest rates of methane oxidation and nitrogen fixation were observed in the deepwater above at natural hydrocarbon seeps. Rates of methane oxidation were substantial along the chemocline of a brine basin but in these ammonium-rich brines, addition of inorganic nitrogen had little impact on methane oxidation suggesting that methanotrophy in these waters were not nitrogen limited. Control sites exhibited the lowest methane concentrations and methane oxidation rates but even these waters exhibited substantial potential for methane oxidation when methane and inorganic nitrogen concentrations were increased. Together, these data suggest that the availability of inorganic nitrogen plays a critical role in regulating methane oxidation in

  14. A Review on Complete Oxidation of Methane at Low Temperatures

    Institute of Scientific and Technical Information of China (English)

    Zhenhua Li; Gar B. Hoflund

    2003-01-01

    This paper reviews recent developments in complete oxidation of methane at low temperatures over noble metal catalysts in the past 20 years. The Pd/Al2O3 catalyst system is fully discussed. The review mainly focuses on the kinetic aspects of methane oxidation over this catalyst, and methane activation behavior over Pd and PdO phases (the form of PdO on the surface, transient behavior, the nature of the active sites, the influence of metal particle size and their structure sensitivities, and so on). Some Pd catalysts supported on other oxides besides the Al2O3 support are briefly discussed. Possible routes of non-noble metal catalysts as substitutes for the Pd catalyst are also proposed.

  15. 'Methane oxidation on supported gold catalysts'

    DEFF Research Database (Denmark)

    Walther, Guido

    2008-01-01

    Methane (CH4), a major compound of natural gas, has been suggested as a future energy carrier. However, it is also known to be a strong greenhouse gas. The use of CH4 obtained from crude oil as an associated gas is often uneconomical, and it is thus burned off. Avoiding flaring and making...

  16. Microbial methane oxidation processes and technologies for mitigation of landfill gas emissions

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Kjeldsen, Peter; Bogner, J.E.;

    2009-01-01

    utilizing oxygen that diffuses into the cover layer from the atmosphere. The methane oxidation process, which is governed by several environmental factors, can be exploited in engineered systems developed for methane emission mitigation. Mathematical models that account for methane oxidation can be used...... to predict methane emissions from landfills. Additional research and technology development is needed before methane mitigation technologies utilizing microbial methane oxidation processes can become commercially viable and widely deployed.......Landfill gas containing methane is produced by anaerobic degradation of organic waste. Methane is a strong greenhouse gas and landfills are one of the major anthropogenic sources of atmospheric methane. Landfill methane may be oxidized by methanotrophic microorganisms in soils or waste materials...

  17. Catalytic conversion of methane: Carbon dioxide reforming and oxidative coupling

    KAUST Repository

    Takanabe, Kazuhiro

    2012-01-01

    Natural gas conversion remains one of the essential technologies for current energy needs. This review focuses on the mechanistic aspects of the development of efficient and durable catalysts for two reactions, carbon dioxide reforming and the oxidative coupling of methane. These two reactions have tremendous technological significance for practical application in industry. An understanding of the fundamental aspects and reaction mechanisms of the catalytic reactions reviewed in this study would support the design of industrial catalysts. CO 2 reforming of methane utilizes CO 2, which is often stored in large quantities, to convert as a reactant. Strategies to eliminate carbon deposition, which is the major problem associated with this reaction, are discussed. The oxidative coupling of methane directly produces ethylene in one reactor through a slightly exothermic reaction, potentially minimizing the capital cost of the natural gas conversion process. The focus of discussion in this review will be on the attainable yield of C 2 products by rigorous kinetic analyses.

  18. Intensive Ammonia and Methane Oxidation in Organic Liquid Manure Crusts

    DEFF Research Database (Denmark)

    Nielsen, Daniel Aagren; Nielsen, Lars Peter; Schramm, Andreas

    of the crusts. PCR targeting the unique methane and ammonia monooxygenases were applied together with FISH to detect the presence of the two bacterial groups. Potential activity was assessed by short term slurry incubations of crust samples while monitoring NO2- production or CH4 consumption. Crusts were......Intensive agricultural practice leads to periodic accumulation of enormous amounts of liquid manure (slurry) from animal husbandry, and large quantities of environmentally hazardous ammonia and methane are emitted from the manure storages. Floating surface crusts have been suggested to harbour...... methane oxidizing bacteria (MOB) and are known to accumulate nitrite and nitrate, indicating the presence of ammonia oxidizers (AOB). We have surveyed six manure tanks with organic covers to investigate the prevalence of MOB and AOB and to link the potential activity with physical and chemical aspects...

  19. Methane oxidation and degradation of organic compounds in landfill soil covers

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Kjeldsen, Peter

    2002-01-01

    High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero-order kin......High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero...

  20. Methane oxidation in contrasting soil types

    DEFF Research Database (Denmark)

    D'Imperio, Ludovica; Nielsen, Cecilie Skov; Westergaard-Nielsen, Andreas

    2017-01-01

    Arctic ecosystems are characterized by a wide range of soil moisture conditions and thermal regimes and contribute differently to the net methane (CH4) budget. Yet, it is unclear how climate change will affect the capacity of those systems to act as a net source or sink of CH4. Here, we present...... subsequently scaled to the entire study area of 0.15 km2, a landscape also consisting of wetlands with a seasonally integrated methane release of 0.10 ± 0.01 g CH4-C m−2 (3.7 ± 1.2 g CO2-eq m−2). The result was a net landscape sink of 12.71 kg CH4-C (0.48 tonne CO2-eq) during the growing season...

  1. An attempt to selectively oxidize methane over supported gold catalysts

    NARCIS (Netherlands)

    Hereijgers, B.P.C.; Weckhuysen, B.M.

    2011-01-01

    The potential of supported gold catalysts for the selective gas-phase oxidation of methane to methanol with molecular oxygen was investigated. A broad range of supported gold-based catalyst materials was synthesized using reducible and non-reducible support materials. Although the formation of small

  2. Nitrogen oxides and methane treatment by non-thermal plasma

    Science.gov (United States)

    Alva, E.; Pacheco, M.; Colín, A.; Sánchez, V.; Pacheco, J.; Valdivia, R.; Soria, G.

    2015-03-01

    Non thermal plasma was used to treat nitrogen oxides (NOx) and methane (CH4), since they are important constituents of hydrocarbon combustion emissions processes and, both gases, play a key role in the formation of tropospheric ozone. These gases are involved in environmental problems like acid rain and some diseases such as bronchitis and pneumonia. In the case of methane is widely known its importance in the global climate change, and currently accounts for 30% of global warming. There is a growing concern for methane leaks, associated with a rapid expansion of unconventional oil and gas extraction techniques as well as a large-scale methane release from Arctic because of ice melting and the subsequent methane production of decaying organic matter. Therefore, methane mitigation is a key to avoid dangerous levels of global warming. The research, here reported, deals about the generation of non-thermal plasma with a double dielectric barrier (2DBD) at atmospheric pressure with alternating current (AC) for NOx and CH4 treatment. The degradation efficiencies and their respective power consumption for different reactor configurations (cylindrical and planar) are also reported. Qualitative and quantitative analysis of gases degradation are reported before and after treatment with cold plasma. Experimental and theoretical results are compared obtaining good removal efficiencies, superior to 90% and to 20% respectively for NOx and CH4.

  3. Biological and biochemical methane reactions. Final report, March 1986-March 1989

    Energy Technology Data Exchange (ETDEWEB)

    Dalton, H.; Pienkos, P.T.; Stirlling, D.I.

    1989-04-01

    The purpose of this project was to characterize the nature of the active site involved in methane activation by enzymes from well characterized and newly isolated methane-oxidizing bacteria. Kinetic and structural studies provided an initial picture of how the soluble methane monooxygenase (MMO) enzyme is structured and operates to selectively oxidize methane to methanol under ambient conditions. Cloning and sequencing of genes coding for some of the sMMO proteins were completed, and 72 strains of methanotrophs were isolated from extreme environments.

  4. Microreactor for the Catalytic Partial Oxidation of Methane

    Institute of Scientific and Technical Information of China (English)

    Widodo Wahyu Puwanto; Yuswan Muharam

    2006-01-01

    Fixed-bed reactors for the partial oxidation of methane to produce synthetic gas still pose hotspot problems. An alternative reactor, which is known as the shell-and-tube-typed microreactor, has been developed to resolve these problems. The microreactor consists of a 1 cm outside-diameter, 0.8 cm insidediameter and 11 cm length tube, and a 1.8 cm inside-diameter shell. The tube is made of dense alumina and the shell is made of quartz. Two different methods dip and spray coating were performed to line the tube side with the LaNixOy catalyst. Combustion and reforming reactions take place simultaneously in this reactor. Methane is oxidized in the tube side to produce flue gases (CO2 and H2O) which flow counter-currently and react with the remaining methane in the shell side to yield synthesis gas. The methane conversion using the higher-loading catalyst spray-coated tube reaches 97% at 700 ℃, whereas that using the lower-loading catalyst dip-coated tube reaches only 7.78% because of poor adhesion between the catalyst film and the alumina support. The turnover frequencies (TOFs) using the catalyst spray-and 900 ℃ provides better performance than that at 1250 ℃ because sintering reduces the surface-area. The hydrogen to carbon monoxide ratio produced by the spray-coated catalyst is greater than the stoichiometric ratio, which is caused by carbon deposition through methane cracking or the Boudouard reaction.

  5. Hydrogen production by catalytic partial oxidation of methane

    OpenAIRE

    Enger, Bjørn Christian

    2008-01-01

    Hydrogen production by catalytic partial oxidation of natural gas was investigated using tools ranging from theoretical calculations to experimental work and sophisticated characterization techniques.Catalytic partial oxidation (CPO) was carried out in a conventional continuous flow experimental apparatus using a xed-bed reactor, and operating at 1 atm and furnace temperatures in the range from ambient to 1073 K. The feed typically consisted of a mixture of methane and air, with a CH4/O2 rati...

  6. Nanocrystalline Metal Oxides for Methane Sensors: Role of Noble Metals

    Directory of Open Access Journals (Sweden)

    S. Basu

    2009-01-01

    Full Text Available Methane is an important gas for domestic and industrial applications and its source is mainly coalmines. Since methane is extremely inflammable in the coalmine atmosphere, it is essential to develop a reliable and relatively inexpensive chemical gas sensor to detect this inflammable gas below its explosion amount in air. The metal oxides have been proved to be potential materials for the development of commercial gas sensors. The functional properties of the metal oxide-based gas sensors can be improved not only by tailoring the crystal size of metal oxides but also by incorporating the noble metal catalyst on nanocrystalline metal oxide matrix. It was observed that the surface modification of nanocrystalline metal oxide thin films by noble metal sensitizers and the use of a noble metal catalytic contact as electrode reduce the operating temperatures appreciably and improve the sensing properties. This review article concentrates on the nanocrystalline metal oxide methane sensors and the role of noble metals on the sensing properties.

  7. On the relationship between methane production and oxidation by anaerobic methanotrophic communities from cold seeps of the Gulf of Mexico.

    Science.gov (United States)

    Orcutt, Beth; Samarkin, Vladimir; Boetius, Antje; Joye, Samantha

    2008-05-01

    The anaerobic oxidation of methane (AOM) in the marine subsurface is a significant sink for methane in the environment, yet our understanding of its regulation and dynamics is still incomplete. Relatively few groups of microorganisms consume methane in subsurface environments--namely the anaerobic methanotrophic archaea (ANME clades 1, 2 and 3), which are phylogenetically related to methanogenic archaea. Anaerobic oxidation of methane presumably proceeds via a 'reversed' methanogenic pathway. The ANME are generally associated with sulfate-reducing bacteria (SRB) and sulfate is the only documented final electron acceptor for AOM in marine sediments. Our comparative study explored the coupling of AOM with sulfate reduction (SR) and methane generation (MOG) in microbial communities from Gulf of Mexico cold seep sediments that were naturally enriched with methane and other hydrocarbons. These sediments harbour a variety of ANME clades and SRB. Following enrichment under an atmosphere of methane, AOM fuelled 50-100% of SR, even in sediment slurries containing petroleum-associated hydrocarbons and organic matter. In the presence of methane and sulfate, the investigated microbial communities produce methane at a small fraction ( approximately 10%) of the AOM rate. Anaerobic oxidation of methane, MOG and SR rates decreased significantly with decreasing concentration of methane, and in the presence of the SR inhibitor molybdate, but reacted differently to the MOG inhibitor 2-bromoethanesulfonate (BES). The addition of acetate, a possible breakdown product of petroleum in situ and a potential intermediate in AOM/SR syntrophy, did not suppress AOM activity; rather acetate stimulated microbial activity in oily sediment slurries.

  8. Methane and trichloroethylene oxidation by an estuarine methanotroph, Methylobacter sp. strain BB5.1.

    OpenAIRE

    Smith, K. S.; Costello, A. M.; Lidstrom, M E

    1997-01-01

    An estuarine methanotroph was isolated from sediment enrichments and designated Methylobacter sp. strain BB5.1. In cells grown on medium with added copper, oxidation of methane and trichloroethylene occurred with similar Ks values, but the Vmax for trichloroethylene oxidation was only 0.1% of the methane oxidation Vmax. Cells grown on low-copper medium did not oxidize trichloroethylene and showed a variable rate of methane oxidation.

  9. Methane Sensitivity to Perturbations in Tropospheric Oxidizing Capacity

    Science.gov (United States)

    Yegorova, Elena; Duncan, Bryan

    2011-01-01

    Methane is an important greenhouse gas and has a 25 times greater global warming potential than CO2 on a century timescale. Yet there are considerable uncertainties in the magnitude and variability of its sources and sinks. The response of the coupled non-linear methane-carbon monoxide-hydroxyl radical (OH) system is important in determining the tropospheric oxidizing capacity. Using the NASA Goddard Earth Observing System, Version 5 (GEOS-5) chemistry climate model, we study the response of methane to perturbations of OH and wetland emissions. We use a computationally-efficient option of the GEOS-5 CCM that includes an OH parameterization that accurately represents OH predicted by a full chemical mechanism. The OH parameterization allows for studying non-linear CH4-CO-OH feedbacks in computationally fast sensitivity experiments. We compare our results with surface observations (GMD) and discuss the range of uncertainty in OH and wetland emissions required to bring modeling results in better agreement with surface observations. Our results can be used to improve projections of methane emissions and methane growth.

  10. Anaerobic methane oxidation coupled to nitrite reduction can be a potential methane sink in coastal environments.

    Science.gov (United States)

    Shen, Li-Dong; Hu, Bao-Lan; Liu, Shuai; Chai, Xiao-Ping; He, Zhan-Fei; Ren, Hong-Xing; Liu, Yan; Geng, Sha; Wang, Wei; Tang, Jing-Liang; Wang, Yi-Ming; Lou, Li-Ping; Xu, Xiang-Yang; Zheng, Ping

    2016-08-01

    In the current study, we investigated nitrite-dependent anaerobic methane oxidation (N-DAMO) as a potential methane sink in the Hangzhou Bay and the adjacent Zhoushan sea area. The potential activity of the N-DAMO process was primarily observed in Hangzhou Bay by means of (13)C-labeling experiments, whereas very low or no potential N-DAMO activity could be detected in the Zhoushan sea area. The measured potential N-DAMO rates ranged from 0.2 to 1.3 nmol (13)CO2 g(-1) (dry sediment) day(-1), and the N-DAMO potentially contributed 2.0-9.4 % to the total microbial methane oxidation in the examined sediments. This indicated that the N-DAMO process may be an alternative pathway in the coastal methane cycle. Phylogenetic analyses confirmed the presence of Candidatus Methylomirabilis oxyfera-like bacteria in all the examined sediments, while the group A members (the dominant bacteria responsible for N-DAMO) were found mainly in Hangzhou Bay. Quantitative PCR showed that the 16S rRNA gene abundance of Candidatus M. oxyfera-like bacteria varied from 5.4 × 10(6) to 5.0 × 10(7) copies g(-1) (dry sediment), with a higher abundance observed in Hangzhou Bay. In addition, the overlying water NO3 (-) concentration and salinity were identified as the most important factors influencing the abundance and potential activity of Candidatus M. oxyfera-like bacteria in the examined sediments. This study showed the evidence of N-DAMO in coastal environments and indicated the importance of N-DAMO as a potential methane sink in coastal environments.

  11. Hydrogen production from methane through catalytic partial oxidation reactions

    Science.gov (United States)

    Freni, S.; Calogero, G.; Cavallaro, S.

    This paper reviews recent developments in syn-gas production processes used for partial methane oxidation with and/or without steam. In particular, we examined different process charts (fixed bed, fluidised bed, membrane, etc.), kinds of catalysts (powders, foams, monoliths, etc.) and catalytically active phases (Ni, Pt, Rh, etc.). The explanation of the various suggested technical solutions accounted for the reaction mechanism that may selectively lead to calibrated mixtures of CO and H 2 or to the unwanted formation of products of total oxidation (CO 2 and H 2O) and pyrolysis (coke). Moreover, the new classes of catalysts allow the use of small reactors to treat large amounts of methane (monoliths) or separate hydrogen in situ from the other reaction products (membrane). This leads to higher conversions and selectivity than could have been expected thermodynamically. Although catalysts based on Rh are extremely expensive, they can be used to minimise H 2O formation by maximising H 2 yield.

  12. OXIDATIVE COUPLING OF METHANE USING INORGANIC MEMBRANE REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Y.H. Ma; Dr. W.R. Moser; Dr. A.G. Dixon; Dr. A.M. Ramachandra; Dr. Y. Lu; C. Binkerd

    1998-04-01

    The objective of this research is to study the oxidative coupling of methane in catalytic inorganic membrane reactors. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and higher yields than in conventional non-porous, co-feed, fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gas phase reactions, which are believed to be a main route for the formation of CO{sub x} products. Such gas phase reactions are a cause of decreased selectivity in the oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Membrane reactor technology also offers the potential for modifying the membranes both to improve catalytic properties as well as to regulate the rate of the permeation/diffusion of reactants through the membrane to minimize by-product generation. Other benefits also exist with membrane reactors, such as the mitigation of thermal hot-spots for highly exothermic reactions such as the oxidative coupling of methane. The application of catalytically active inorganic membranes has potential for drastically increasing the yield of reactions which are currently limited by either thermodynamic equilibria, product inhibition, or kinetic selectivity.

  13. Oxidative coupling of methane using inorganic membrane reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.H.; Moser, W.R.; Dixon, A.G. [Worcester Polytechnic Institute, MA (United States)] [and others

    1995-12-31

    The goal of this research is to improve the oxidative coupling of methane in a catalytic inorganic membrane reactor. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and relatively higher yields than in fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gas phase reactions, which are believed to be a main route for formation of CO{sub x} products. Such gas phase reactions are a cause for decreased selectivity in oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Modeling work which aimed at predicting the observed experimental trends in porous membrane reactors was also undertaken in this research program.

  14. Oxidative mitigation of aquatic methane emissions in large Amazonian rivers.

    Science.gov (United States)

    Sawakuchi, Henrique O; Bastviken, David; Sawakuchi, André O; Ward, Nicholas D; Borges, Clovis D; Tsai, Siu M; Richey, Jeffrey E; Ballester, Maria Victoria R; Krusche, Alex V

    2016-03-01

    The flux of methane (CH4 ) from inland waters to the atmosphere has a profound impact on global atmospheric greenhouse gas (GHG) levels, and yet, strikingly little is known about the dynamics controlling sources and sinks of CH4 in the aquatic setting. Here, we examine the cycling and flux of CH4 in six large rivers in the Amazon basin, including the Amazon River. Based on stable isotopic mass balances of CH4 , inputs and outputs to the water column were estimated. We determined that ecosystem methane oxidation (MOX) reduced the diffusive flux of CH4 by approximately 28-96% and varied depending on hydrologic regime and general geochemical characteristics of tributaries of the Amazon River. For example, the relative amount of MOX was maximal during high water in black and white water rivers and minimal in clear water rivers during low water. The abundance of genetic markers for methane-oxidizing bacteria (pmoA) was positively correlated with enhanced signals of oxidation, providing independent support for the detected MOX patterns. The results indicate that MOX in large Amazonian rivers can consume from 0.45 to 2.07 Tg CH4 yr(-1) , representing up to 7% of the estimated global soil sink. Nevertheless, climate change and changes in hydrology, for example, due to construction of dams, can alter this balance, influencing CH4 emissions to atmosphere.

  15. Methane from landfills in Sweden. Final report; Metan fraan avfallsupplag i Sverige. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Samuelsson, Jerker [Chalmers Univ. of Technology, Goeteborg (Sweden); Galle, Bo; Boerjesson, Gunnar [Linkoeping Univ. (Sweden). Dept. of Water and Environmental Studies

    2006-01-15

    Three years of measurements has been conducted at seven Swedish landfills, quantifying methane emission, methane oxidation and methane production. The measurements reveal a large span between the sites in terms of gas recovery efficiency, 29-78% during normal operation. The fraction of the totally produced methane that is eventually leaking out to the atmosphere, was found to vary between 21-68%. Regarding methane oxidation, the study shows that of the methane going from the landfill interior towards the atmosphere, 6-43% is oxidised to CO{sub 2} in the different landfill cover soils. The highest methane oxidation was found in closed landfills during summertime, and the lowest at active landfills during wintertime, due to the strong temperature dependence of the oxidation. The equipment developed for methane emission measurements is based on time resolved concentration measurements with FTIR spectroscopy in combination with tracer gas releases from the surface of the landfill. The method has proven to be able to state the methane emission from the landfills with high accuracy, {+-}18% of the emission estimate (95% confidence interval). This is in line with what has been achieved in the literature for fugitive emission sources. The system has also proven to be useful for on site leak search. The precision for the methane production measurement was demonstrated to be high, down to {+-}4.2%. This enables trend studies and verification of improvement measures taken at the landfill sites. In terms of absolute accuracy for the production estimate, a 95%-confidence interval of down to (-6.0%, +6.2%) has been achieved. At times of strong methane oxidation the uncertainties increase, particularly if the emission is high. The gas production at the landfill site is therefore preferably measured during autumn-winter-spring when the temperature and the methane oxidation are low. The methane oxidation has been measured by carbon isotope technique, utilising the enrichment in

  16. Trace methane oxidation and the methane dependency of sulfate reduction in anaerobic granular sludge

    KAUST Repository

    Meulepas, Roel J.W.

    2010-05-01

    This study investigates the oxidation of labeled methane (CH4) and the CH4 dependence of sulfate reduction in three types of anaerobic granular sludge. In all samples, 13C-labeled CH4 was anaerobically oxidized to 13C-labeled CO2, while net endogenous CH4 production was observed. Labeled-CH4 oxidation rates followed CH4 production rates, and the presence of sulfate hampered both labeled-CH4 oxidation and methanogenesis. Labeled-CH4 oxidation was therefore linked to methanogenesis. This process is referred to as trace CH4 oxidation and has been demonstrated in methanogenic pure cultures. This study shows that the ratio between labeled-CH4 oxidation and methanogenesis is positively affected by the CH4 partial pressure and that this ratio is in methanogenic granular sludge more than 40 times higher than that in pure cultures of methanogens. The CH4 partial pressure also positively affected sulfate reduction and negatively affected methanogenesis: a repression of methanogenesis at elevated CH4 partial pressures confers an advantage to sulfate reducers that compete with methanogens for common substrates, formed from endogenous material. The oxidation of labeled CH 4 and the CH4 dependence of sulfate reduction are thus not necessarily evidence of anaerobic oxidation of CH4 coupled to sulfate reduction. © 2010 Federation of European Microbiological Societies.

  17. Methane formation by oxidation of ascorbic acid using iron minerals and hydrogen peroxide.

    Science.gov (United States)

    Althoff, Frederik; Jugold, Alke; Keppler, Frank

    2010-06-01

    The possibility of methane formation in an oxidative environment has been intensely debated, especially since the discovery of methane generation by living plants. However, recent studies with animal tissue suggested that under specific conditions aerobic methane formation is also possible. Here, we investigated the generation of methane in an abiotic model system using bioavailable substances. We show formation of methane in a highly oxidative media, using ascorbic acid, ferrihydrite and hydrogen peroxide as reagents. Methane production was shown to be related to reagent ratio, reaction volume and pH. A 2:1 ratio of hydrogen peroxide to ascorbic acid, catalytic amounts of ferrihydrite and acidic conditions (pH 3) enhanced formation of methane. We further show that gaseous oxygen has a strong influence with higher levels found to inhibit methane formation. This study is a first step towards providing an insight for the reaction mechanism of methane formation that would be applicable to aerobic environments.

  18. Effects of trace volatile organic compounds on methane oxidation

    Directory of Open Access Journals (Sweden)

    Wilai Chiemchaisri

    2001-06-01

    Full Text Available The effects of volatile organic compounds (VOCs on methane oxidation in landfill cover soils were examined. The batch experiments were conducted using single and mixed VOCs, such as, dichloromethane (DCM, trichloroethylene (TCE, tetrachloroethylene (PCE, and benzene. The results from all combinations showed a decrease in methane oxidation rate with increase in VOC concentrations. Moreover, inhibition effects of TCE and DCM were found higher than benzene and PCE. The reduction of methane oxidation by benzene and PCE could be attributed to the toxicity effect, whereas TCE and DCM were found to exhibit the competitive-inhibition effect. When the soil was mixed with DCM, no methane oxidation was found. Damage to the cell’s internal membrane was found in a methanotrophic culture exposed to VOC gases which is the attachment site of a key enzyme needed for methane oxidationOs efeitos dos compostos orgânicos voláteis (VOCs na oxidação do metano em camadas superficiais do solo. Os experimentos foram conduzidos usando somente VOCs ou mistura do mesmo, como, diclorometano (DCM, tricloroetileno (TCE, tetracloroetileno (PCE, e benzeno. Os resultados de todas as combinações mostraram uma diminuição na taxa da oxidação do metano com aumento nas concentrações de VOC. Além disso, os efeitos da inibição de TCE e de DCM foram mais elevados do que do benzeno e PCE. A redução da oxidação do metano pelo benzeno e PCE poderia ser atribuída ao efeito da toxicidade, visto que TCE e DCM exibiram o efeito de competição-inibição. Quando o solo foi misturado com o DCM, nenhuma oxidação do metano foi encontrada. Os danos à membrana interna celular foi observada em uma cultura metanotrófica exposta aos gases de VOC que é o local de ligação de uma enzima chave necessário para a oxidação do metano.

  19. Conversion of methane to higher hydrocarbons (Biomimetic catalysis of the conversion of methane to methanol). Final report

    Energy Technology Data Exchange (ETDEWEB)

    Watkins, B.E.; Taylor, R.T.; Satcher, J.H. [and others

    1993-09-01

    In addition to inorganic catalysts that react with methane, it is well-known that a select group of aerobic soil/water bacteria called methanotrophs can efficiently and selectively utilize methane as the sole source of their energy and carbon for cellular growth. The first reaction in this metabolic pathway is catalyzed by the enzyme methane monooxygenase (MMO) forming methanol. Methanol is a technology important product from this partial oxidation of methane since it can be easily converted to liquid hydrocarbon transportation fuels (gasoline), used directly as a liquid fuel or fuel additive itself, or serve as a feedstock for chemicals production. This naturally occurring biocatalyst (MMO) is accomplishing a technologically important transformation (methane directly to methanol) for which there is currently no analogous chemical (non-biological) process. The authors approach has been to use the biocatalyst, MMO, as the initial focus in the development of discrete chemical catalysts (biomimetic complexes) for methane conversion. The advantage of this approach is that it exploits a biocatalytic system already performing a desired transformation of methane. In addition, this approach generated needed new experimental information on catalyst structure and function in order to develop new catalysts rationally and systematically. The first task is a comparative mechanistic, biochemical, and spectroscopic investigation of MMO enzyme systems. This work was directed at developing a description of the structure and function of the catalytically active sites in sufficient detail to generate a biomimetic material. The second task involves the synthesis, characterization, and chemical reactions of discrete complexes that mimic the enzymatic active site. These complexes were synthesized based on their best current understanding of the MMO active site structure.

  20. Linking methane oxidation with perchlorate reduction: a microbial base for possible Martian life

    Science.gov (United States)

    Miller, L. G.; Carlstrom, C.; Baesman, S. M.; Coates, J. D.; Oremland, R. S.

    2011-12-01

    Recent observations of methane (CH4) and perchlorate (ClO4-) within the atmosphere and surface of Mars, respectively, provide impetus for establishing a metabolic linkage between these compounds whereby CH4 acts as an electron donor and perchlorate acts as an electron acceptor. Direct linkage through anaerobic oxidation of methane (AOM) has not been observed. However, indirect syntrophic oxygenase-dependent oxidation of CH4 with an aerobic methane oxidizer is feasible. The pathway for anaerobic dissimilatory perchlorate reduction includes 3 steps. The first 2 are sequential reductions of (1) perchlorate to chlorate and (2) chlorate to chlorite, mediated by perchlorate reductase. The third step is disproportionation of chlorite to chloride and molecular oxygen, mediated by chlorite dismutase. Utilization of thusly derived oxygen by hydrocarbon-degrading organisms in anoxic environments was first demonstrated by Coates et. al. (1998)1, however the link to aerobic methane oxidation was not examined at that time. Here, we systematically explore the potential for several species of aerobic methanotrophs to couple with chlorite during dissimilatory perchlorate reduction. In one experiment, 0.5 kPa CH4 was completely removed in one day from the headspace of combined cell suspensions of Dechloromonas agitata strain CKB and Methylococcus capsulatus in the presence of 5 mM chlorite. Oxidation of labeled 14CH4 to 14CO2 under similar conditions was later confirmed. Another experiment demonstrated complete removal of 0.2 kPa CH4 over several days by Methylobacter albus strain BG8 with strain CKB in the presence of 5 mM chlorite. Finally, we observed complete removal of 0.2 kPa CH4 in bottles containing natural soil (enriched in methanotrophs by CH4 additions over several weeks) and strain CKB and in the presence of 10 mM chlorite. This soil, collected from a pristine lake shoreline, demonstrated endogenous methane, perchlorate, chlorate and chlorite uptake. Other soil and

  1. Global prevalence of methane oxidation by symbiotic bacteria in peat-moss ecosystems

    Science.gov (United States)

    Kip, Nardy; van Winden, Julia F.; Pan, Yao; Bodrossy, Levente; Reichart, Gert-Jan; Smolders, Alfons J. P.; Jetten, Mike S. M.; Damsté, Jaap S. Sinninghe; Op den Camp, Huub J. M.

    2010-09-01

    Peat bogs store up to a third of all terrestrial carbon on Earth, and are one of the largest natural sources of atmospheric methane. Anaerobic degradation of submerged Sphagnum species-mosses that are prevalent in peat bogs across the globe-produces significant quantities of methane in these systems. However, a study on peat mosses in the Netherlands revealed that a large fraction of this methane is consumed by aerobic methane-oxidizing bacteria, known as methanotrophs; in return, the methanotrophs provide Sphagnum mosses with carbon. Here, we show that Sphagnum-associated methane oxidation occurs ubiquitously across the globe. We collected Sphagnum mosses from pools, lawns and hummocks in nine Sphagnum-dominated peatlands across the world, and measured their capacity to oxidize methane in a series of laboratory incubations. All mosses were capable of oxidizing methane. The rate of methane oxidation increased with temperature, and was most pronounced in submerged mosses, collected from peatland pools. According to DNA microarray analyses, the methanotrophic community responsible for methane oxidation was highly diverse. 13C labelling revealed that methane-derived carbon was incorporated into plant lipids when mosses were submerged, indicative of a mutually beneficial symbiosis between mosses and methanotrophs. Our findings suggest that the interaction between methanotrophs and Sphagnum mosses may play a role in carbon recycling in waterlogged Sphagnum vegetation, potentially reducing methane emissions.

  2. Partial oxidation of methane by pulsed corona discharges

    Science.gov (United States)

    Hoeben, W. F. L. M.; Boekhoven, W.; Beckers, F. J. C. M.; van Heesch, E. J. M.; Pemen, A. J. M.

    2014-09-01

    Pulsed corona-induced partial oxidation of methane in humid oxygen or carbon dioxide atmospheres has been investigated for future fuel synthesis applications. The obtained product spectrum is wide, i.e. saturated, unsaturated and oxygen-functional hydrocarbons. The generally observed methane conversion levels are 6-20% at a conversion efficiency of about 100-250 nmol J-1. The main products are ethane, ethylene and acetylene. Higher saturated hydrocarbons up to C6 have been detected. The observed oxygen-functional hydrocarbons are methanol, ethanol and lower concentrations of aldehydes, ketones, dimethylether and methylformate. Methanol seems to be exclusively produced with CH4/O2 mixtures at a maximum production efficiency of 0.35 nmol J-1. CH4/CO2 mixtures appear to yield higher hydrocarbons. Carboxylic acids appear to be mainly present in the aqueous reactor phase, possibly together with higher molecular weight species.

  3. Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

    Institute of Scientific and Technical Information of China (English)

    LI Kongzhai; WANG Hua; WEI Yonggang; LIU Mingchun

    2008-01-01

    The cerium iron complex oxides oxygen carder was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carrier could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carriers were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carder: the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species (bulk lattice oxygen) that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction con-dition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.

  4. Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils

    NARCIS (Netherlands)

    Cai, Yuanfeng; Yan, Zheng; Bodelier, P.L.E.; Conrad, R.; Jia, Zhongjun

    2016-01-01

    Soils serve as the biological sink of the potent greenhouse gas methane with exceptionally low concentrations of ~1.84 p.p.m.v. in the atmosphere. The as-yet-uncultivated methane-consuming bacteria have long been proposed to be responsible for this ‘high-affinity’ methane oxidation (HAMO). Here we

  5. Natural manganese oxides as catalysts for oxidative coupling of methane: a structural and degradation study

    Energy Technology Data Exchange (ETDEWEB)

    Ioffe, L.M.; Bosch, P.; Viveros, T.; Sanchez, H.; Borodko, Y.G. [Universidad Autonoma Metropolitana-Iztapalapa, Mexico (Mexico). Dept. of Chem.

    1997-12-01

    Natural manganese oxides were evaluated as oxidative coupling catalysts to convert methane into C{sub 2}-hydrocarbons. Reactions were done in a cyclic redox mode in which the oxidized catalyst was reacted with methane at 850 C in the absence of oxygen. The bulk and surface analyses (XRD, XPS, FT-IR) indicate that the catalyst deactivation in the methane atmosphere is related to reduction of manganese ions, oxygen depletion of the catalyst surface and formation of manganese carbide species. It is proposed that the XPS line of O1s electrons, Eb=528.6 eV should be assigned to the surface oxygen bound to the reduced Mn{sup 2+} cation with close oxygen vacancies, and lines ofMn2p{sub 3/2} electrons, Eb=641 eV and C1s at 282.5 eV may be assigned to the surface manganese carbide. (orig.) 27 refs.

  6. Formation and retention of methane in coal. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hucka, V.J.; Bodily, D.M.; Huang, H.

    1992-05-15

    The formation and retention of methane in coalbeds was studied for ten Utah coal samples, one Colorado coal sample and eight coal samples from the Argonne Premium Coal Sample Bank.Methane gas content of the Utah and Colorado coals varied from zero to 9 cm{sup 3}/g. The Utah coals were all high volatile bituminous coals. The Colorado coal was a gassy medium volatile bituminous coal. The Argonne coals cover a range or rank from lignite to low volatile bituminous coal and were used to determine the effect of rank in laboratory studies. The methane content of six selected Utah coal seams and the Colorado coal seam was measured in situ using a special sample collection device and a bubble desorbometer. Coal samples were collected at each measurement site for laboratory analysis. The cleat and joint system was evaluated for the coal and surrounding rocks and geological conditions were noted. Permeability measurements were performed on selected samples and all samples were analyzed for proximate and ultimate analysis, petrographic analysis, {sup 13}C NMR dipolar-dephasing spectroscopy, and density analysis. The observed methane adsorption behavior was correlated with the chemical structure and physical properties of the coals.

  7. Direct oxidation of methane to oxygenates over heteropolyanions

    Institute of Scientific and Technical Information of China (English)

    Ouarda Benlounes; Sadia Mansouri; Chérifa Rabia; Smain Hocine

    2008-01-01

    Partia]oxidation of methane to formaldehyde and methanol was studied at atmospheric pressure in the ternlperature range of 700-750℃ using heteropolycompound catalysts(NH4)6HSiMo11 FeO40,(NH4)4PMo11 FeO39,and H4PMo11VO40,which were prepared and characterized by various analysis techniques such as infrared,visible UV,XRD and DTA.O2 or N2O was used as the oxidizing agent.and the principal products of the reaction were CH3OH,CH2O,CO,CO2,and water.The conversion and the selectivity of products depend strongly on the reaction temperature,the nature of oxidizing agent,and the composition of catalyst.

  8. Adsorption and Catalytic Oxidation of Methane by Indium Oxide Sensors Doped with Platinum

    OpenAIRE

    V.V. Golovanov; B.V. Nazarchuk; V.V.  Golovanova

    2016-01-01

    Differential scanning calorimetry and X-ray photoelectron spectroscopy were used to investigate the mechanism of methane interaction with platinum-doped indium oxide surface. It was shown that sorption processes have a significant impact on the sensor response at the operating temperatures below 370 С for doped Pt/In2O3 and below 500 С for In2O3-based sensors. Above the critical temperatures the sensor response is dominated by the catalytic oxidation of methane. The operating temperature of...

  9. Nitrous oxide and methane in marine systems

    Energy Technology Data Exchange (ETDEWEB)

    De Wilde, H.P.J.

    1999-07-16

    }{sup +} concentration of the river water entering the estuary. An estimate of the N2O production during nitrification in the water column was derived from the ratio between calculated N2O loss to the atmosphere and measured nitrification activity. The differences between the present estuarine N2O distribution and the situation in 1978, as reported in literature, are discussed in the light of the gradually decreasing anthropogenic loadings of organic carbon and nutrients, and the associated increase in oxygen concentrations in the estuary. Finally, the average N2O emission from the Schelde was extrapolated to obtain an estimate of the global estuarine N2O emission. Chapter 4 describes the CH4 distribution in the Rhine estuary, its lower tributaries, and the adjacent Dutch coastal waters during 4 seasons. A CH4 budget was developed on the basis of: (1) the calculated CH4 fluxes between the tributaries, the estuary, and the coastal zone, and (2) estimated gas exchange with the atmosphere. The budget was used to assess the magnitude of in situ CH4 production in the estuary and the coastal zone, respectively. The possible origins of these in situ sources are discussed. Finally, the CH4 emission from the Rhine estuary was extrapolated to assess the global CH4 emission from estuaries to the atmosphere. Chapter 5 addresses the discrepancy between air-sea CH4 fluxes measured by the micrometeorological gradient technique on the one hand, and values calculated from air-sea concentration differences and transfer velocities on the other hand. Both techniques were applied simultaneously at a research platform in the North Sea, located 9 km off the coast of the Netherlands. In addition, the temporal distribution of CH4 saturation in the surface waters around the platform is discussed in relation to fresh water supply and hydrodynamics. Chapter 6 summarises the main results presented in thesis. In addition, the relative importance of various marine systems as sources of atmospheric N2

  10. Nickel-containing catalysts for methane oxidation to synthesis gas

    Directory of Open Access Journals (Sweden)

    Kusman Dossumov

    2014-12-01

    Full Text Available The partial oxidation of methane to synthesis gas was studied on oxides of metals of variable valence (Mn, La, Cr and Ni, supported on a carrier – ɣ-Al2O3. Among the catalysts studied, the sample of 3% Ni/ɣ-Al2O3 showed the best characteristics by yields of hydrogen and carbon monoxide in the reaction of partial oxidation of methane. The optimal conditions of the process (the reaction temperature of 850 °C, the volume rate of 4500 h-1, and the ratio CH4: O2 = 2:1 cause the increase the concentration of hydrogen and carbon monoxide to 72.2 and 75.3%, respectively. The effect of the heat-treatment temperature and textural characteristics of the Ni/ ɣ-Al2O3 catalyst on its catalytic activity was studied. The NiCe/Al2O3 catalyst developed showed a high stability during 30 hours.

  11. Ammonia, a selective agent for methane production by syntrophic acetate oxidation at mesophilic temperature.

    Science.gov (United States)

    Schnürer, A; Nordberg, A

    2008-01-01

    In biogas processes, methane production from acetate proceeds by either aceticlastic methanogenesis or through syntrophic acetate oxidation (SAO). In the present study, the pathway for methane production from acetate was analysed; i) during a gradual increase of the ammonia concentration (final concentration 7 g NH(4)(+) -N/L) in a semi-continuous lab-scale anaerobic digester (4.3 L), operating at mesophilic temperature (37 degrees C) or ii) in diluted enrichment cultures (100 ml) experiencing a gradual increase in ammonia, sodium, potassium and propionic acid. The pathway for methane formation was determined by calculating the (14)CO(2)/(14)CH(4) ratio after incubating samples with (14)C-2-acetate. In the anaerobic digester, as well as in the enrichment cultures, the (14)CO(2)/(14)CH4 ratio clearly increased with increasing ammonium-nitrogen concentration, i.e. as the ammonia concentration increased, a shift from the aceticlastic mechanism to the syntrophic pathway occurred. The shift was very distinct and occurred as the NH(4)(+) -N concentration rose above 3 g/l. No shift in pathway was seen during increasing concentrations of sodium, potassium or propionic acid. The shift to SAO in the biogas digester resulted in a twofold decrease in the specific gas and methane yield.

  12. Enzymes involved in the anaerobic oxidation of n-alkanes: from methane to long-chain paraffins

    OpenAIRE

    Callaghan, Amy V.

    2013-01-01

    Anaerobic microorganisms play key roles in the biogeochemical cycling of methane and non-methane alkanes. To date, there appear to be at least three proposed mechanisms of anaerobic methane oxidation (AOM). The first pathway is mediated by consortia of archaeal anaerobic methane oxidizers and sulfate-reducing bacteria via ‘reverse methanogenesis’ and is catalyzed by a homologue of methyl-coenzyme M reductase. The second pathway is also mediated by anaerobic methane oxidizers and sulfate-red...

  13. Methane oxidation associated to submerged brown-mosses buffers methane emissions from Siberian polygonal peatlands

    Science.gov (United States)

    Liebner, Susanne; Zeyer, Josef; Knoblauch, Christian

    2010-05-01

    Circumpolar peatlands store roughly 18 % of the globally stored carbon in soils [based on 1, 2]. Also, northern wetlands and tundra are a net source of methane (CH4), an effective greenhouse gas (GHG), with an estimated annual CH4 release of 7.2% [3] or 8.1% [4] of the global total CH4 emission. Although it is definite that Arctic tundra significantly contributes to the global methane emissions in general, regional variations in GHG fluxes are enormous. CH4 fluxes of polygonal tundra within the Siberian Lena Delta, for example, were reported to be low [5, 6], particularly at open water polygonal ponds and small lakes [7] which make up around 10 % of the delta's surface. Low methane emissions from polygonal ponds oppose that Arctic permafrost thaw ponds are generally known to emit large amounts of CH4 [8]. Combining tools of biogeochemistry and molecular microbiology, we identified sinks of CH4 in polygonal ponds from the Lena Delta that were not considered so far in GHG studies from Arctic wetlands. Pore water CH4 profiling in polygonal ponds on Samoylov, a small island in the central part of the Lena Delta, revealed a pronounced zone of CH4 oxidation near the vegetation surface in submerged layers of brown-mosses. Here, potential CH4 oxidation was an order of magnitude higher than in non-submerged mosses and in adjacent bulk soil. We could additionally show that this moss associated methane oxidation (MAMO) is hampered when exposure of light is prevented. Shading of plots with submerged Scorpidium scorpioides inhibited MAMO leading to higher CH4 concentrations and an increase in CH4 fluxes by a factor of ~13. Compared to non-submerged mosses, the submerged mosses also showed significantly lower δ13C values indicating that they use carbon dioxide derived from methane oxidation for photosynthesis. Applying stable isotope probing of DNA, type II methanotrophs were identified to be responsible for the oxidation of CH4 in the submerged Scorpidium scorpioides. Our

  14. Partial oxidation of methane (POM) assisted solid oxide co-electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Fanglin; Wang, Yao

    2017-02-21

    Methods for simultaneous syngas generation by opposite sides of a solid oxide co-electrolysis cell are provided. The method can comprise exposing a cathode side of the solid oxide co-electrolysis cell to a cathode-side feed stream; supplying electricity to the solid oxide co-electrolysis cell such that the cathode side produces a product stream comprising hydrogen gas and carbon monoxide gas while supplying oxygen ions to an anode side of the solid oxide co-electrolysis cell; and exposing the anode side of the solid oxide co-electrolysis cell to an anode-side feed stream. The cathode-side feed stream comprises water and carbon dioxide, and the anode-side feed stream comprises methane gas such that the methane gas reacts with the oxygen ions to produce hydrogen and carbon monoxide. The cathode-side feed stream can further comprise nitrogen, hydrogen, or a mixture thereof.

  15. Understanding complete oxidation of methane on spinel oxides at a molecular level

    Science.gov (United States)

    Tao, Franklin Feng; Shan, Jun-Jun; Nguyen, Luan; Wang, Ziyun; Zhang, Shiran; Zhang, Li; Wu, Zili; Huang, Weixin; Zeng, Shibi; Hu, P.

    2015-08-01

    It is crucial to develop a catalyst made of earth-abundant elements highly active for a complete oxidation of methane at a relatively low temperature. NiCo2O4 consisting of earth-abundant elements which can completely oxidize methane in the temperature range of 350-550 °C. Being a cost-effective catalyst, NiCo2O4 exhibits activity higher than precious-metal-based catalysts. Here we report that the higher catalytic activity at the relatively low temperature results from the integration of nickel cations, cobalt cations and surface lattice oxygen atoms/oxygen vacancies at the atomic scale. In situ studies of complete oxidation of methane on NiCo2O4 and theoretical simulations show that methane dissociates to methyl on nickel cations and then couple with surface lattice oxygen atoms to form -CH3O with a following dehydrogenation to -CH2O a following oxidative dehydrogenation forms CHO; CHO is transformed to product molecules through two different sub-pathways including dehydrogenation of OCHO and CO oxidation.

  16. Methane oxidation and degradation of organic compounds in landfill soil covers

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Kjeldsen, Peter

    2002-01-01

    High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero-order kin......High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero......-order kinetics and occurred in parallel with the oxidation of methane. TeCM, CFC-11, and CFC-12 were not degradable in presence of oxygen and degradation of these compounds in the oxidative zone in landfill top covers is therefore expected to be limited. However these compounds were found degradable...... in the anaerobic zone in the lower part of soil columns permeated with artificial landfill gas. The lesser-chlorinated compounds were degraded in the upper oxic zone with overlapping gradients of methane and oxygen. Methane oxidation and degradation of HOCs in the top-soils may play a very important role...

  17. Effects of Nitrogen Fertilizer,Soil Moisture and Temperature on Methane Oxidation in Paddy Soil

    Institute of Scientific and Technical Information of China (English)

    YANXIAOYUAN; CAIZUCONG

    1996-01-01

    Effects of nitrogen fertilizer,soil mosture and temperature and temperature on methane oxidation in paddy soil were investigated under laboratory conditions.Addition of 0.05 g N kg-1 soil as NH4Cl strongly inhibited methane oxidation and addition of the same rate of KCl also inhibited the oxidation but with more slight effect,suggesting that the inhibitory effect was partly caused by increase in osmotic potential in microorganism cell,Not only NH4+ but also NO3- greatly affected methane oxidation.Urea did not affect methane oxidation in paddy soil in the first two days of incubation,but strong inhibitory effect was observed afterwards.Methane was oxidized in the treated soil with an optimum moisture of 280 g kg-1 ,and air-drying inhibited methane oxidation entirely.The optimum temperature of methane oxidation was about 30℃ in paddy soil.while no methane oxidation was observed at 5℃or 50℃。

  18. Methane and fertilizer production from seaweed biomass. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Betzer, P.R.; Humm, H.J.

    1984-01-01

    It was demonstrated that several varieties of abundant benthic algae indigenous to Tampa Bay (Gracilaria, Hypnea, and Ulva) were readily degradable via anaerobic digestion to methane. The energy yield per unit weight biomass degraded was higher than any previously reported. Given the large masses of readily degradable plants which are annually produced in and around Tampa Bay, the resource is estimated to be at least equivalent to several million gallons of gasoline.

  19. Cooling of a Diesel Reformate Fuelled Solid Oxide Fuel Cell by Internal Reforming of Methane: A Modelling Study

    Institute of Scientific and Technical Information of China (English)

    HUANG Xiaowei; Alexander Kromp

    2013-01-01

    In this paper a system combining a diesel reformer using catalytic partial oxidation (CPOX) with the Solid Oxide Fuel Cell (SOFC) for Auxiliary Power Unit (APU) applications is modeled with respect to the cooling effect provided by internal reforming of methane in anode gas channel.A model mixture consisting of 80% n-hexadecane and 20% 1-methylnaphthalin is used to simulate the commercial diesel.The modelling consists of several steps.First,equilibrium gas composition at the exit of CPOX reformer is modelled in terms oxygen to carbon (O/C) ratio,fuel utilization ratio and anode gas recirculation.Second,product composition,especially methane content,is determined for the methanation process at the operating temperatures ranging from 500 ℃ to 520 ℃.Finally,the cooling power provided by internal reforming of methane in SOFC fuel channel is calculated for two concepts to increase the methane content of the diesel reformate.The results show that the first concept,operating the diesel reformer at low O/C ratio and/or recirculation ratio,is not realizable due to high probability of coke formation,whereas the second concept,combining a methanation process with CPOX,can provide a significant cooling effect in addition to the conventional cooling concept which needs higher levels of excess air.

  20. Homogeneous catalytic systems for selective oxidation of methane: state of the art

    Directory of Open Access Journals (Sweden)

    Balcer Sylwia

    2015-09-01

    Full Text Available Homogeneous catalysts for methane oxidation are of a particular interest from scientific and economic points of view. The results show a great potential for activation and functionalization of CH bonds of unreactive methane. There are still gaps in the knowledge of how to rationally design catalysts for this process. In this paper state-of-the-art. in methane oxidation homogenous catalysis is presented.

  1. Estimation of methane and nitrous oxide emissions from Indian livestock.

    Science.gov (United States)

    Patra, Amlan K

    2012-10-26

    Greenhouse gas (GHG; methane and nitrous oxide) emissions from enteric fermentation and manure management of Indian livestock were estimated from the last two Indian livestock census datasets (2003 and 2007) using IPCC Tier 2 (2006) guidelines. The total annual GHG emissions from Indian livestock increased in 2007 compared to the year 2003 with an annual growth rate of 1.52% over this period. The contributions of GHG by dairy cattle, non-dairy cattle, buffaloes, goats, sheep and other animals (yak, mithun, horse, donkeys, pigs and poultry) were 30.52, 24.0, 37.7, 4.34, 2.09 and 3.52%, respectively, in 2007. Enteric fermentation was the major source of methane, accounting for 89.2% of the total GHG emissions, followed by manure methane (9.49%). Nitrous oxide emissions accounted for 1.34%. GHG emissions (CO(2)-eq. per kg of fat and protein corrected milk (FPCM)) by female animals were considerably lower for crossbred cows (1161 g), followed by buffaloes (1332 g) and goats (2699 g), and were the highest for indigenous cattle (3261 g) in 2007. There was a decreasing trend in GHG emissions (-1.82% annual growth rate) in relation to milk production from 2003 to 2007 (1818 g and 1689 g CO(2)-eq. per kg FPCM in 2003 and 2007, respectively). This study revealed that GHG emissions (total as well as per unit of products) from dairy and other categories of livestock populations could be reduced substantially through proper dairy herd management without compromising animal production. In conclusion, although the total GHG emissions from Indian livestock increased in 2007, there was a decreasing trend in GHG production per kg of milk production or animal products.

  2. Methane combustion over lanthanum-based perovskite mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Arandiyan, Hamidreza [New South Wales Univ., Sydney (Australia). School of Chemical Engineering

    2015-11-01

    This book presents current research into the catalytic combustion of methane using perovskite-type oxides (ABO{sub 3}). Catalytic combustion has been developed as a method of promoting efficient combustion with minimum pollutant formation as compared to conventional catalytic combustion. Recent theoretical and experimental studies have recommended that noble metals supported on (ABO{sub 3}) with well-ordered porous networks show promising redox properties. Three-dimensionally ordered macroporous (3DOM) materials with interpenetrated and regular mesoporous systems have recently triggered enormous research activity due to their high surface areas, large pore volumes, uniform pore sizes, low cost, environmental benignity, and good chemical stability. These are all highly relevant in terms of the utilization of natural gas in light of recent catalytic innovations and technological advances. The book is of interest to all researchers active in utilization of natural gas with novel catalysts. The research covered comes from the most important industries and research centers in the field. The book serves not only as a text for researcher into catalytic combustion of methane, 3DOM perovskite mixed oxide, but also explores the field of green technologies by experts in academia and industry. This book will appeal to those interested in research on the environmental impact of combustion, materials and catalysis.

  3. Microbial Methane Oxidation Processes and Technologies for Mitigation of Landfill Gas Emissions

    Science.gov (United States)

    The aim of this paper is to review the present knowledge regarding the microbial methane oxidation in natural or engineered landfill environments with focus on process understanding, engineering experiences and modeling. This review includes seven sections. First, the methane oxidation is put in con...

  4. The partial catalytic oxidation of methane to give oxygen-containing compounds

    Science.gov (United States)

    Krylov, Oleg V.

    1992-11-01

    The three principal paths of the partial oxidation of methane, to give methanol, formaldehyde, and synthesis gas, have been reviewed. The kinetics and mechanism of the processes have been described. The possible oxidation of methane using different oxidising agents — oxygen and carbon dioxide — has been examined. The bibliography includes 139 references.

  5. Activation of methane and ethane and their selective oxidation to the alcohols in protic media

    Energy Technology Data Exchange (ETDEWEB)

    Sen, A.; Benvenuto, M.A.; Lin, M.; Hutson, A.C.; Basickes, N. (Pennsylvania State Univ., University Park, PA (United States))

    1994-02-09

    The selective oxidation of methane and ethane to the alcohols in solvents ranging from strong acids to neutral aqueous medium has been studied. In 98% sulfuric acid, methane is oxidized to CH[sub 3]OSO[sub 3]H by a variety of 1e[sup [minus

  6. Different Abilities of Eight Mixed Cultures of Methane-oxidizing Bacteria to Degrade TCE

    DEFF Research Database (Denmark)

    Broholm, Kim; Christensen, Thomas Højlund; Jensen, Bjørn K.

    1993-01-01

    The ability of eight mixed cultures of methane-oxidizing bacteria to degrade trichloroethylene (TCE) was examined in laboratory batch experiments. This is one of the first reported works studying TCE degradation by mixed cultures of methane-oxidizing bacteria at 10°C, a common temperature for soils...

  7. Hydrogen production by catalytic partial oxidation of methane

    Energy Technology Data Exchange (ETDEWEB)

    Enger, Bjoern Christian

    2008-12-15

    Hydrogen production by catalytic partial oxidation of natural gas was investigated using tools ranging from theoretical calculations to experimental work and sophisticated characterization techniques. Catalytic partial oxidation (CPO) was carried out in a conventional continuous flow experimental apparatus using a fixed-bed reactor, and operating at 1 atm and furnace temperatures in the range from ambient to 1073 K. The feed typically consisted of a mixture of methane and air, with a CH{sub 4}/O{sub 2} ratio of 2, and the average bed residence time was in the range 10-250 ms. Steam methane reforming (SMR) was carried out in the same apparatus at similar temperatures and pressure in a feed consisting of methane, nitrogen and water, with a steam to carbon ratio of 2.0-4.0. Temperature programmed (TP) techniques, including oxidation (TPO), reduction (TPR), reaction (TPCPO) and methane dissociation (TPMD) was used to characterize catalytic properties such as ignition temperatures, the catalyst reducibility and activation energies. Dispersions from catalyst surface area measurements were compared to X-ray diffraction (XRD) techniques and electron microscopy (SEM, TEM,STEM) to obtain information on catalyst particle sizes and dispersion. X-ray photoelectron spectroscopy (XPS) provided information on the specific catalyst surface composition, which was compared to results on the bulk structure obtained by XRD. The effect of modifying cobalt catalysts supported on alumina was investigated by adding small amounts of Ni, Fe, Cr, Re, Mn, W, Mo, V and Ta oxides. The idea behind this work was to investigate whether the cobalt crystals were decorated, covered or encircled by a modifier and to what extent this affected catalyst performance. The choice of modifiers in this study was based on the principle that in any chemical process it may be just as important to identify groups of elements that have negative effects as identifying the best promoters. It was found that the

  8. Selective oxidation of methane to ethane and ethylene over various oxide catalysts

    NARCIS (Netherlands)

    Roos, J.A.; Bakker, A.G.; Bosch, H.; van Ommen, J.G.; Ross, J.R.H.

    1987-01-01

    Preliminary results are reported for the oxidative coupling of methane to give ethane/ethylene mixtures over a series of different catalyst formulations; the temperature range studied is 650–850°C. A comparison is made of the behaviour of lead/alumina and lithium/magnesia materials. It is found that

  9. Microbial oxidation as a methane sink beneath the West Antarctic Ice Sheet

    Science.gov (United States)

    Michaud, Alexander B.; Dore, John E.; Achberger, Amanda M.; Christner, Brent C.; Mitchell, Andrew C.; Skidmore, Mark L.; Vick-Majors, Trista J.; Priscu, John C.

    2017-08-01

    Aquatic habitats beneath ice masses contain active microbial ecosystems capable of cycling important greenhouse gases, such as methane (CH4). A large methane reservoir is thought to exist beneath the West Antarctic Ice Sheet, but its quantity, source and ultimate fate are poorly understood. For instance, O2 supplied by basal melting should result in conditions favourable for aerobic methane oxidation. Here we use measurements of methane concentrations and stable isotope compositions along with genomic analyses to assess the sources and cycling of methane in Subglacial Lake Whillans (SLW) in West Antarctica. We show that sub-ice-sheet methane is produced through the biological reduction of CO2 using H2. This methane pool is subsequently consumed by aerobic, bacterial methane oxidation at the SLW sediment-water interface. Bacterial oxidation consumes >99% of the methane and represents a significant methane sink, and source of biomass carbon and metabolic energy to the surficial SLW sediments. We conclude that aerobic methanotrophy may mitigate the release of methane to the atmosphere upon subglacial water drainage to ice sheet margins and during periods of deglaciation.

  10. Comparison of the methane oxidation rate in four media

    Directory of Open Access Journals (Sweden)

    Juliana Lundgren Rose

    2012-06-01

    Full Text Available Landfill gas emissions are one of the main sources of anthropogenic methane (CH4, a major greenhouse gas. In this paper, an economically attractive alternative to minimize greenhouse gas emissions from municipal solid waste landfills was sought. This alternative consists in special biofilters as landfill covers with oxidative capacity in the presence of CH4. To improve the quality/cost ratio of the project, compost was chosen as one of the cover substrates and soil (Typic red yellow-silt-clay Podzolic as the other. The performance of four substrates was studied in laboratory experiments: municipal solid waste (MSW compost, soil, and two soil-compost at different proportions. This study aimed to evaluate the suitability and environmental compatibility as a means of CH4 oxidation in biofilters. Four biofilters were constructed in 60 cm PVC tubes with an internal diameter of 10 cm. Each filter contained 2.3 L of oxidizing substrate at the beginning of the experiment. The gas used was a mixture of CH4 and air introduced at the bottom of each biofilter, at a flow of 150 mL min-1, by a flow meter. One hundred days after the beginning of the experiment, the best biofilter was the MSW compost with an oxidation rate of 990 g m-3 day-1 , corresponding to an efficiency of 44 %. It can be concluded that the four substrates studied have satisfactory oxidative capacity, and the substrates can be used advantageously as cover substrate of MSW landfills.

  11. Experimental study of incomplete oxidation of methane in a ring channel

    Science.gov (United States)

    Kuznetsov, V. V.; Vitovsky, O. V.; Gasenko, O. A.

    2007-09-01

    Chemical transformations at incomplete methane oxidation in the air medium were studied experimentally at reaction activation on the wall of an annular microchannel. Methane was oxidized incompletely on a rhodium catalyst deposited on an inner wall of the channel. Concentrations of the products of chemical transformations were measured in the outlet gas mixture for different reactor temperatures and stay times. We have determined the range of channel wall temperatures and stay times of the mixture corresponding to an increase in the portion of hydrogen and carbon dioxide indicating transition from predominant methane combustion to cascade chemical reactions with activation of steam and carbon dioxide methane conversions. It is shown that the kinetic model of chemical transformations of methane in the air medium depends significantly on the temperature of channel walls and stay time of the mixture. The effect of outer diffusion deceleration on the rate of chemical transformations at incomplete methane oxidation under the strained conditions is determined.

  12. Temporal resilience and dynamics of anaerobic methane-oxidizing microbial communities to short-term changes in methane partial pressures

    Science.gov (United States)

    Klasek, S.; Tiantian, Y.; Torres, M. E.; Colwell, F. S.; Wang, F.; Liang, L.

    2015-12-01

    Marine sediments produce tens to hundreds of teragrams of methane annually, which is released from the seabed at thousands of cold seeps distributed globally along continental margins. Around 80-90% of this methane is consumed in shallower sediment layers before reaching the hydrosphere, in a microbially-mediated process known as anaerobic oxidation of methane (AOM) However, cold seeps appear to exhibit temporal variation in gas flux intensity, and AOM filter efficiency at cold seeps generally decreases with fluid flow rate. To our knowledge, the degree to which temporal heterogeneity in subsurface methane flux stimulates AOM community growth and adaptation to increased methane concentrations has not been investigated. Static high-pressure bioreactors were used to incubate sulfate-methane transition zone (SMTZ) and methanogenic zone sediments underlying a Mediterranean mud volcano gas flare under in situ temperature and pressure at 8 MPa methane. Sulfide production rates of 0.4 μmol/cm3/day in both sediment regimes after 4 months of incubation suggested the resilience of the marine subsurface methane filter may extend well below the SMTZ (40 cm). Similar incubations of SMTZ samples from below a gas flare off Svalbard at saturating (3.8 MPa) and 0.2 MPa methane are being sampled after 1 week, 4 weeks, and 4 months; sulfide production rates of 8-18 nmol/cm3/day were first observed after 4 weeks of incubation. Sediment samples at all specified time points for both sets of incubations were collected for nucleic acid extraction and cell fixation. Anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) are expected dominant taxa in enriched and non-enriched communities. 16S rDNA community analysis is expected to reveal additional microbial players involved in the short-term adaptation to higher methane partial pressures in the marine subsurface. Increased AOM community activity (RNA/DNA ratio) and copy numbers of methane cycling transcripts (mcr

  13. Inhibition of methane oxidation in slurry surface crust by inorganic nitrogen

    DEFF Research Database (Denmark)

    Duan, Yun-Feng; Elsgaard, Lars; Petersen, Søren O

    2013-01-01

    Livestock slurry is an important source of methane (CH4). Depending on dry matter content, a floating crust may form where methane-oxidizing bacteria (MOB) and CH4 oxidation activity have been found, suggesting that surface crusts may reduce CH4 emissions from slurry. However, it is not known how...... MOB in this environment interact with inorganic nitrogen (N). We studied inhibitory effects of ammonium (NH4+), nitrate (NO3–) and nitrite (NO2–) on potential CH4 oxidation in a cattle slurry surface crust. Methane oxidation was assayed at salt concentrations up to 500 mM at 100 and 10,000 ppmv...

  14. Methane oxidation in pig and cattle slurry storages, and effects of surface crust moisture and methane availability

    DEFF Research Database (Denmark)

    Petersen, S.O.; Ambus, P.

    2006-01-01

    Storages with liquid manure (slurry) may develop a surface crust of particulate organic matter, or an artificial crust can be established. Slurry storages are net sources of atmospheric methane (CH4), but a potential for bacterial oxidation of CH4 in surface crusts was recently suggested in a study......2 during incubation, while intact subsamples were used to characterize CH4 oxidation as a function of CH4 availability and moisture content. Methane oxidation was observed in all materials except for an expanded clay product (Leca) sampled from a pig slurry storage. Despite significant variation...... content, each time followed by determination of CH4 fluxes. Only one surface crust material showed a relationship between CH4 fluxes and moisture content that would implicate gas diffusivity in the regulation of CH4 oxidation. The occurrence of inducible CH4 oxidation activity in slurry storage surface...

  15. DOE final report: Studies on the microbial formation of methane

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, Ralph S.

    2001-04-01

    The microbial formation of methane is carried out by methanogens which are found wherever active anaerobic degradation of organic matter occurs. We developed a procedure for reliable culture of 'Methanococus jannaschii' which yields 8 g wet weight of cells per liter of medium. To initiate a study of proteomics, this organism was grown at two levels of hydrogen partial pressure, very low (650 Pa) and high (178 kPa). When cells were exposed to hydrogen excess conditions, they possessed very low or undetectable levels of four flagella-related polypeptides, whereas, when hydrogen became limiting, these proteins were synthesized. Thus, use of proteomics showed, for the first time, that this methanogen can regulate expression of proteins, and these experiments open the door for general studies of regulation in this hyperthermophile.

  16. Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils

    Science.gov (United States)

    Cai, Yuanfeng; Zheng, Yan; Bodelier, Paul L. E.; Conrad, Ralf; Jia, Zhongjun

    2016-06-01

    Soils serve as the biological sink of the potent greenhouse gas methane with exceptionally low concentrations of ~1.84 p.p.m.v. in the atmosphere. The as-yet-uncultivated methane-consuming bacteria have long been proposed to be responsible for this `high-affinity' methane oxidation (HAMO). Here we show an emerging HAMO activity arising from conventional methanotrophs in paddy soil. HAMO activity was quickly induced during the low-affinity oxidation of high-concentration methane. Activity was lost gradually over 2 weeks, but could be repeatedly regained by flush-feeding the soil with elevated methane. The induction of HAMO activity occurred only after the rapid growth of methanotrophic populations, and a metatranscriptome-wide association study suggests that the concurrent high- and low-affinity methane oxidation was catalysed by known methanotrophs rather than by the proposed novel atmospheric methane oxidizers. These results provide evidence of atmospheric methane uptake in periodically drained ecosystems that are typically considered to be a source of atmospheric methane.

  17. Fluxes of methane and nitrous oxide from an Indian mangrove

    Energy Technology Data Exchange (ETDEWEB)

    Krithika, K.; Purvaja, R.; Ramesh, R. [Anna Univ., Chennai (India). Institute for Ocean Management

    2008-01-25

    Methane and nitrous oxide are atmospheric trace gases and contribute about 15 and 6% respectively to the greenhouse effect. Both have a long atmospheric residence time of about 114 and 12 years respectively and since they are key compounds in the chemical reaction cycles of the troposphere and the stratosphere, their potential to directly or indirectly influence global climate is high. Fluxes of greenhouse gases, methane (CH{sub 4}) and nitrous oxide (N{sub 2}O), were measured from a mangrove ecosystem of the Cauvery delta (Muthupet) in South India. CH{sub 4} emissions were in the range between 18.99 and 37.53 mg/sq. m/d, with an average of 25.21 mg/sq. m/d, whereas N{sub 2}O emission ranged between 0.41 and 0.80 mg/sq. m/d (average of 0.62 mg/sq. m/d). The emission of CH{sub 4} and N{sub 2}O correlated positively with the number of pneumatophores. In addition to the flux measurements, different parts of the roots of Avicennia marina were quantified for CH{sub 4} concentration. Invariably in all the seasons, measured CH{sub 4} concentrations were high in the cable roots, with gradual decrease through the pneumatophores below water level and the above water level. This clearly indicates the transport of CH{sub 4} through the roots. We were able to establish that CH{sub 4} was released passively through the mangrove pneumatophores and is also a source to the atmosphere. We present some additional information on transport mechanisms of CH{sub 4} through the pneumatophores and bubble release from the mangrove ecosystems.

  18. Microbiology, ecology, and application of the nitrite-dependent anaerobic methane oxidation process

    OpenAIRE

    Li-Dong eShen; Bao-lan eHu

    2012-01-01

    Nitrite-dependent anaerobic methane oxidation (n-damo), which couples the anaerobic oxidation of methane to denitrification, is a recently discovered process observed in Candidatus Methylomirabilis oxyfera. M. oxyfera is affiliated with the NC10 phylum, a phylum having no members in pure culture. Based on the isotopic labeling experiments, it is hypothesized that M. oxyfera has an unusual intra-aerobic pathway for the production of oxygen via the dismutation of nitric oxide into dinitrogen ga...

  19. Scientific basis for process and catalyst design in the selective oxidation of methane to formaldehyde.

    Science.gov (United States)

    Arena, Francesco; Parmaliana, Adolfo

    2003-12-01

    The mechanism and kinetics of the gas-phase selective oxidation of methane to formaldehyde (MPO) are revised in the general context of catalytic oxidations. In agreement with ab initio calculations of the energy barrier for the activation of methane on transition metal oxide complexes, a formal Langmuir-Hinshelwood kinetic model is proposed which accounts for the "steady-state" conditions and activity-selectivity pattern of MPO catalysts, providing an original support to process design and catalyst development.

  20. Use of stable isotopes to determine methane oxidation in landfill cover soils

    Science.gov (United States)

    Liptay, K.; Chanton, J.; Czepiel, P.; Mosher, B.

    1998-04-01

    The mean isotopic composition of CH4 emitted from six New England (United States) landfills was 13C and D enriched (-48.1 to -50.4‰ and -273 to -281‰) relative to anoxic zone landfill CH4 (mean values of -55.9 to -56.2‰ and -296 to -300‰) owing to the oxidation of methane as it was transported from the landfill to the atmosphere through the soil cap. The fraction of methane oxidized f0 during its passage through the soil cap was calculated from the degree of 13C enrichment in emitted CH4 relative to anoxic zone CH4 in conjunction with values determined for the preference of soil methane oxidizing bacteria for 12CH4 over 13CH4 (α = 1.022 ± 0.008). Mean values for methane oxidation in six landfills were from 24 to 35% of the total flux through the soil during the warm season, depending upon how the data were grouped. Our results bracket recent estimates of methane oxidation of about 30% in the warm summer period produced using a model with the input terms of soil temperature, moisture, depth, and oxygen concentration. Because of variations in the response of methane oxidation to temperature at these New England sites, our study is consistent with the modeling results of Czepiel et al. [1996b] that the best estimate for the annual value for methane oxidation in the landfills considered is about 10%.

  1. Stabilisation of composite LSFCO-CGO based anodes for methane oxidation in solid oxide fuel cells

    Science.gov (United States)

    Sin, A.; Kopnin, E.; Dubitsky, Y.; Zaopo, A.; Aricò, A. S.; Gullo, L. R.; Rosa, D. La; Antonucci, V.

    A La 0.6Sr 0.4Fe 0.8Co 0.2O 3-Ce 0.8Gd 0.2O 1.9 (LSFCO-CGO) composite anode material was investigated for the direct electrochemical oxidation of methane in intermediate temperature solid oxide fuel cells (IT-SOFCs). A maximum power density of 0.17 W cm -2 at 800 °C was obtained with a methane-fed ceria electrolyte-supported SOFC. A progressive increase of performance was recorded during 140 h operation with dry methane. The anode did not show any structure degradation after the electrochemical testing. Furthermore, no formation of carbon deposits was detected by electron microscopy and elemental analysis. Alternatively, this perovskite material showed significant chemical and structural modifications after high temperature treatment in a dry methane stream in a packed-bed reactor. It is derived that the continuous supply of mobile oxygen anions from the electrolyte to the LSFCO anode, promoted by the mixed conductivity of CGO electrolyte at 800 °C, stabilises the perovskite structure near the surface under SOFC operation and open circuit conditions.

  2. Identification of Methane, Ethane, and Propane Oxidizing Bacteria at Marine Hydrocarbon Seeps by Stable Isotope Probing

    Science.gov (United States)

    Redmond, M.; Ding, H.; Friedrich, M. W.; Valentine, D. L.

    2008-12-01

    Hydrocarbon seeps emit substantial amounts of oil and natural gas into the marine environment, where they can be oxidized by microorganisms in the sediment and water column. Here, we used stable isotope probing of DNA and lipid biomarkers to identify the microorganisms actively consuming 13C-labeled natural gas compounds in seep sediment samples. Surface sediment was collected from the Coal Oil Point seep field (offshore Santa Barbara, California, USA) and incubated under aerobic conditions with 13C labeled methane, ethane, or propane for up to 37 days, with sediment sub-samples taken at 3-4 intermediate time points. DNA was extracted from sediment and separated by CsCl density gradient centrifugation. The microbial community in each fraction was profiled using T-RFLP, and bacterial 16S rRNA gene clone libraries were constructed from un-incubated hydrocarbon seep sediment and selected isotopically 'heavy' (13C) and 'light' (12C) gradient fractions from ethane incubations. All clone libraries were dominated by sequences from members of the family Rhodobacteraceae (>25% of sequences) and a diverse group of Gammaproteobacteria, including sequences related to those of methylotrophs and to those of bacteria known to consume the longer-chain alkanes present in crude oil. After 14 days of incubation, the relative abundance of Rhodobacteraceae was higher in 'heavy' fractions from the 13C-ethane incubation than in 'light' fractions, suggesting incorporation of 13C label. The Rhodobacteraceae are very diverse metabolically, but have often been observed in abundance in oil contaminated seawater. Several members of this group have been shown to oxidize longer chain alkanes (C10 or higher), but none have been previously linked to the consumption of the gaseous alkanes ethane, propane, and butane. For the final time point, 13C content of phospholipid fatty acids (PLFA) were also analyzed, showing substantial incorporation of 13C over 37 days. In the methane incubation

  3. Remarkable recovery and colonization behaviour of methane oxidizing bacteria in soil after disturbance is controlled by methane source only

    NARCIS (Netherlands)

    Pan, Y.; Abell, G.C.J.; Bodelier, P.L.E.; Meima-Franke, M.; Sessitsch, A.; Bodrossy, L.

    2014-01-01

    Little is understood about the relationship between microbial assemblage history, the composition and function of specific functional guilds and the ecosystem functions they provide. To learn more about this relationship we used methane oxidizing bacteria (MOB) as model organisms and performed soil

  4. Inhibition of methane oxidation by nitrogenous fertilizers in a paddy soil

    Directory of Open Access Journals (Sweden)

    M. Saiful Alam

    2012-07-01

    Full Text Available Nitrogenous fertilizers are generally thought to have an important role in regulating methane oxidation. In this study, the effect of ammonium on methane oxidation activity was investigated in a paddy soil using urea at concentrations of 0, 50, 100, 200 and 400 μg N per gram dry weight soil (N/g.d.w.s and ammonium sulfate at concentrations of 0, 50 and 200 μg N/g.d.w.s. The results of this study demonstrate that urea concentrations of 200 μg N/g.d.w.s. and above significantly inhibit methane oxidation activity, whereas no statistically significant difference was observed in methane oxidation activity among soil microcosms with urea concentrations of less than 200 μg N/g.d.w.s after incubation for 27 days. Similar results were obtained in a sense that methane oxidation activity was inhibited only when the ammonium sulfate concentration was 200 μg N/g.d.w.s in soil microcosms in this study. Phylogenetic analysis of pmoA genes showed that nitrogen fertilization resulted in apparent changes in the community composition of methane-oxidizing bacteria (MOB. Type I MOB displayed an increased abundance in soil microcosms amended with nitrogenous fertilizers, whereas type II MOB dominated the native soil. Furthermore, although no statistically significant relationship was observed between pmoA gene and amoA gene abundances, methane oxidation activity was significantly negatively correlated with nitrification activity in the presence of urea or ammonium sulfate. Our results indicate that the methane oxidation activity in paddy soils might be inhibited when the concentration of ammonium fertilizers is high and that the interactions between ammonia and methane oxidizers need to be further investigated.

  5. Adsorption and Catalytic Oxidation of Methane by Indium Oxide Sensors Doped with Platinum

    Directory of Open Access Journals (Sweden)

    V.V. Golovanov

    2016-11-01

    Full Text Available Differential scanning calorimetry and X-ray photoelectron spectroscopy were used to investigate the mechanism of methane interaction with platinum-doped indium oxide surface. It was shown that sorption processes have a significant impact on the sensor response at the operating temperatures below 370 С for doped Pt/In2O3 and below 500 С for In2O3-based sensors. Above the critical temperatures the sensor response is dominated by the catalytic oxidation of methane. The operating temperature of sensors was decreased on 80 С by doping of the material with Pt 0.5 wt.%. Thus formed PtxIny clusters have a significant effect on the In¬2O3 catalytic properties. The developed sensors demonstrated high sensitivity, small operating parameters range, and low consuming power together with simple production technology.

  6. Anaerobic oxidation of methane in grassland soils used for cattle husbandry

    Science.gov (United States)

    Bannert, A.; Bogen, C.; Esperschütz, J.; Koubová, A.; Buegger, F.; Fischer, D.; Radl, V.; Fuß, R.; Chroňáková, A.; Elhottová, D.; Šimek, M.; Schloter, M.

    2012-10-01

    While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore, anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using 13C-labelled methane. We were able to detect a high microbial activity utilizing CH4 as nutrient source shown by the respiration of 13CO2. Measurements of possible terminal electron acceptors for anaerobic oxidation of methane were carried out. Soil sulfate concentrations were too low to explain the oxidation of the amount of methane added, but enough nitrate and iron(III) were detected. However, only nitrate was consumed during the experiment. 13C-PLFA analyses clearly showed the utilization of CH4 as nutrient source mainly by organisms harbouring 16:1ω7 PLFAs. These lipids were also found as most 13C-enriched fatty acids by Raghoebarsing et al. (2006) after addition of 13CH4 to an enrichment culture coupling denitrification of nitrate to anaerobic oxidation of methane. This might be an indication for anaerobic oxidation of methane by relatives of "Candidatus Methylomirabilis oxyfera" in the investigated grassland soil under the conditions of the incubation experiment.

  7. Anaerobic oxidation of methane in grassland soils used for cattle husbandry

    Directory of Open Access Journals (Sweden)

    A. Bannert

    2012-04-01

    Full Text Available While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle-overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using 13C-labeled methane. We were able to detect a high microbial activity utilizing CH4 as nutrient source shown by the respiration of 13CO2. Measurements of possible terminal electron acceptors for anaerobic oxidation of methane were carried out. Soil sulfate concentrations were too low to explain the oxidation of the amount of methane added, but enough nitrate and iron(III were detected. However, only nitrate was consumed during the experiment. 13C-PLFA analyses clearly showed the utilization of CH4 as nutrient source mainly by organisms harbouring 16:1ω7 PLFAs. These lipids were found in Gram-negative microorganisms and anaerobes. The fact that these lipids are also typical for type I methanotrophs, known as aerobic methane oxidizers, might indicate a link between aerobic and anaerobic methane oxidation.

  8. Are termite mounds biofilters for methane? - Challenges and new approaches to quantify methane oxidation in termite mounds

    Science.gov (United States)

    Nauer, Philipp A.; Hutley, Lindsay B.; Bristow, Mila; Arndt, Stefan K.

    2015-04-01

    Methane emissions from termites contribute around 3% to global methane in the atmosphere, although the total source estimate for termites is the most uncertain among all sources. In tropical regions, the relative source contribution of termites can be far higher due to the high biomass and relative importance of termites in plant decomposition. Past research focused on net emission measurements and their variability, but little is known about underlying processes governing these emissions. In particular, microbial oxidation of methane (MOX) within termite mounds has rarely been investigated. In well-studied ecosystems featuring an oxic matrix above an anoxic methane-producing habitat (e.g. landfills or sediments), the fraction of oxidized methane (fox) can reach up to 90% of gross production. However, conventional mass-balance approaches to apportion production and consumption processes can be challenging to apply in the complex-structured and almost inaccessible environment of a termite mound. In effect, all field-based data on termite-mound MOX is based on one study that measured isotopic shifts in produced and emitted methane. In this study a closed-system isotope fractionation model was applied and estimated fox ranged from 10% to almost 100%. However, it is shown here that by applying an open-system isotope-pool model, the measured isotopic shifts can also be explained by physical transport of methane alone. Different field-based methods to quantify MOX in termite mounds are proposed which do not rely on assumptions of physical gas transport. A simple approach is the use of specific inhibitors for MOX, e.g. difluoromethane (CH2F2), combined with chamber-based flux measurements before and after their application. Data is presented on the suitability of different inhibitors and first results of their application in the field. Alternatively, gas-tracer methods allow the quantification of methane oxidation and reaction kinetics without knowledge of physical gas

  9. Partial oxidation of methane to synthesis gas in a dual catalyst bed system combining irreducible oxide and metallic catalysts

    NARCIS (Netherlands)

    Zhu, J.J.; Rahuman, M.S.M.M.; Ommen, van J.G.; Lefferts, L.

    2004-01-01

    Operation of partial oxidation of methane to synthesis gas over yttrium-stabilized zirconia (YSZ) at very high temperatures (¿900°C) slightly improves the selectivity to synthesis gas, which is caused by some activity of YSZ for steam and dry reforming of methane. LaCoO3 perovskite is not active in

  10. Global Change Simulations Affect Potential Methane Oxidation in Upland Soils

    Science.gov (United States)

    Blankinship, J. C.; Hungate, B. A.

    2004-12-01

    Atmospheric concentrations of methane (CH4) are higher now than they have ever been during the past 420,000 years. However, concentrations have remained stable since 1999. Emissions associated with livestock husbandry are unlikely to have changed, so some combination of reduced production in wetlands, more efficient capture by landfills, or increased consumption by biological CH4 oxidation in upland soils may be responsible. Methane oxidizing bacteria are ubiquitous in upland soils and little is known about how these bacteria respond to anthropogenic global change, and how they will influence - or already are influencing - the radiative balance of the atmosphere. Might ongoing and future global changes increase biological CH4 oxidation? Soils were sampled from two field experiments to assess changes in rates of CH4 oxidation in response to global change simulations. Potential activities of CH4 oxidizing bacterial communities were measured through laboratory incubations under optimal temperature, soil moisture, and atmospheric CH4 concentrations (~18 ppm, or 10x ambient). The ongoing 6-year multifactorial Jasper Ridge Global Change Experiment (JRGCE) simulates warming, elevated precipitation, elevated atmospheric CO2, elevated atmospheric N deposition, and increased wildfire frequency in an annual grassland in a Mediterranean-type climate in central California. The ongoing 1-year multifactorial Merriam Climate Change Experiment (MCCE) simulates warming, elevated precipitation, and reduced precipitation in four different types of ecosystems along an elevational gradient in a semi-arid climate in northern Arizona. The high desert grassland, pinyon-juniper woodland, ponderosa pine forest, and mixed conifer forest ecosystems range in annual precipitation from 100 to 1000 mm yr-1, and from productivity being strongly water limited to strongly temperature limited. Among JRGCE soils, elevated atmospheric CO2 increased potential CH4 oxidation rates (p=0.052) and wildfire

  11. Evaluating the relative contribution of methane oxidation to methane emissions from young floodplain soils under Alternative Irrigation Management

    Science.gov (United States)

    Pierreux, Sofie; Verhoeven, Elizabeth; Akter, Masuda; Sleutel, Steven; Said-Pullicino, Daniel; Romani, Marco; Boeckx, Pascal

    2016-04-01

    To keep the pace with a yearly growing demand for rice by 1-2%, future rice production must come primarily from high yielding irrigated rice, putting a pressure on fresh water reserves. In this context, water saving Alternative Irrigation Management (AIM) is progressively applied worldwide. By introducing repeated or mid-seasonal drainage, AIM suppresses emission of CH4, otherwise prevalent in continuously flooded rice. However, little is known about the effect of AIM on the balance of CH4 genesis and oxidation in paddy soils. We studied relevant soil parameters and CH4 emissions in continuously flooded (CF) and alternately wetted and dried (AWD) rice paddies. During a field campaign at the Castello d'Agogna experimental station (Pavia, Italy), we measured in situ CH4 oxidation and emission rates using the closed gas chamber technique with or without application of CH2F2 as a selective inhibitor of CH4 oxidation. In addition, we determined potential CH4 oxidation rates using incubated soil slurries originating from the same experimental plots. The dataset was supplemented with depth differentiated monitoring of redox potential, temperature, moisture content and soil solution parameters (DOC, Fe2+, Mn3+, mineral N and dissolved CH4). Peaks in dissolved CH4 manifested at 5 and 12.5cm depth, with much lower and equal levels at 25, 50 and 80cm depth. Also depth distributions of dissolved Fe and Mn followed this pattern, indicating that methanogenic activity was primarily confounded to the topsoil. Seasonal CH4 emissions were about halved by AWD compared to CF management. After a fast decline of in situ oxidation within the AWD treatment at the beginning of the season, CH4 oxidation percentages in CF and AWD increased until the booting stage (67DAS), reaching peak values of 83% and 69% of produced CH4, respectively. CH4 oxidation thereafter gradually declined to nearly 50% in both treatments after the final drainage (103 DAS). Seasonal trends of potential CH4 oxidation

  12. Anaerobic oxidation of methane in an iron-rich Danish freshwater lake sediment

    DEFF Research Database (Denmark)

    Nordi, Katrin á; Thamdrup, Bo; Schubert, Carsten J.

    2013-01-01

    Freshwater systems are identified as one of the main natural methane sources, but little is known about the importance of anaerobic oxidation of methane (AOM) in these systems. We investigated AOM in a lake sediment characterized by a high reactive iron content, normal sulfate concentrations in t...

  13. Iron oxide reduction in methane-rich deep Baltic Sea sediments

    NARCIS (Netherlands)

    Egger, M.J.; Hagens, M.; Sapart, C.J.; Dijkstra, N.; van Helmond, N.A.G.M.; Mogollón, José M.; Risgaard-Petersen, N.; van der Veen, C.; Kasten, Sabine; Riedinger, N.; Böttcher, M.E.; Röckmann, Thomas; Barker Jorgensen, B.; Slomp, C.P.

    2017-01-01

    Methane is a powerful greenhouse gas and its emission from marine sediments to the atmosphere is largely controlled by anaerobic oxidation of methane (AOM). Traditionally, sulfate is considered to be the most important electron acceptor for AOM in marine sediments. Recent evidence suggests, however,

  14. Quantitative analysis of anaerobic oxidation of methane (AOM) in marine sediments: a modeling perspective

    NARCIS (Netherlands)

    Regnier, P.; Dale, A.W.; Arndt, S.; LaRowe, D.E.; Mogollon, J.M.; Van Cappellen, P.

    2011-01-01

    Recent developments in the quantitativemodeling of methane dynamics and anaerobic oxidation of methane (AOM) in marine sediments are critically reviewed. The first part of the review begins with a comparison of alternative kinetic models for AOM. The roles of bioenergetic limitations, intermediate c

  15. Partial oxidation of methane over bimetallic copper- and nickel-actinide oxides (Th, U)

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Ana C.; Goncalves, A.P.; Gasche, T. Almeida [Instituto Tecnologico e Nuclear, Unidade de Ciencias Quimicas e Radiofarmaceuticas, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Ferraria, A.M.; Rego, A.M. Botelho do [Universidade Tecnica de Lisboa, IST, Centro de Quimica-Fisica Molecular and IN, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, M.R.; Bola, A. Margarida [I3N-Universidade de Aveiro, Department Fisica, Aveiro (Portugal); Branco, J.B., E-mail: jbranco@itn.p [Instituto Tecnologico e Nuclear, Unidade de Ciencias Quimicas e Radiofarmaceuticas, Estrada Nacional 10, 2686-953 Sacavem (Portugal)

    2010-05-14

    The study of partial oxidation of methane (POM) over bimetallic nickel- or copper-actinide oxides was undertaken. Binary intermetallic compounds of the type AnNi{sub 2} (An = Th, U) and ThCu{sub 2} were used as precursors and the products (2NiO.UO{sub 3}, 2NiO.ThO{sub 2} and 2CuO.ThO{sub 2}) characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and temperature-programmed reduction. The catalysts were active and selective for the conversion of methane to H{sub 2} and CO and stable for a period of time of {approx}18 h on stream. The nickel catalysts were more active and selective than the copper catalyst and, under the same conditions, show a catalytic behaviour comparable to that of a platinum commercial catalyst, 5 wt% Pt/Al{sub 2}O{sub 3}. The catalytic activity increases when uranium replaces thorium and the selectivity of this type of materials is clearly different from that of single metal oxides and/or mechanical mixtures. The good catalytic behaviour of the bimetallic copper- and nickel-actinide oxides was attributed to an unusual interaction between copper or nickel oxide and the actinide oxide phase as showed by H{sub 2}-TPR, XPS and Raman analysis of the catalysts before and after reaction.

  16. Field and laboratory studies of methane oxidation in an anoxic marine sediment: Evidence for a methanogen-sulfate reducer consortium

    Science.gov (United States)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christopher S.

    1994-12-01

    Field and laboratory studies of anoxic sediments from Cape Lookout Bight, North Carolina, suggest that anaerobic methane oxidation is mediated by a consortium of methanogenic and sulfate-reducing bacteria. A seasonal survey of methane oxidation and CO2 reduction rates indicates that methane production was confined to sulfate-depleted sediments at all times of year, while methane oxidation occurred in two modes. In the summer, methane oxidation was confined to sulfate-depleted sediments and occurred at rates lower than those of CO2 reduction. In the winter, net methane oxidation occurred in an interval at the base of the sulfate-containing zone. Sediment incubation experiments suggest both methanogens and sulfate reducers were responsible for the observed methane oxidation. In one incubation experiment both modes of oxidation were partially inhibited by 2-bromoethanesulfonic acid (a specific inhibitor of methanogens). This evidence, along with the apparent confinement of methane oxidation to sulfate-depleted sediments in the summer, indicates that methanogenic bacteria are involved in methane oxidation. In a second incubation experiment, net methane oxidation was induced by adding sulfate to homogenized methanogenic sediments, suggesting that sulfate reducers also play a role in the process. We hypothesize that methanogens oxidize methane and produce hydrogen via a reversal of CO2 reduction. The hydrogen is efficiently removed and maintained at low concentrations by sulfate reducers. Pore water H2 concentrations in the sediment incubation experiments (while net methane oxidation was occurring) were low enough that methanogenic bacteria could derive sufficient energy for growth from the oxidation of methane. The methanogen-sulfate reducer consortium is consistent not only with the results of this study, but may also be a feasible mechanism for previously documented anaerobic methane oxidation in both freshwater and marine environments.

  17. Oxygen vacancy promoted methane partial oxidation over iron oxide oxygen carriers in the chemical looping process.

    Science.gov (United States)

    Cheng, Zhuo; Qin, Lang; Guo, Mengqing; Xu, Mingyuan; Fan, Jonathan A; Fan, Liang-Shih

    2016-11-30

    We perform ab initio DFT+U calculations and experimental studies of the partial oxidation of methane to syngas on iron oxide oxygen carriers to elucidate the role of oxygen vacancies in oxygen carrier reactivity. In particular, we explore the effect of oxygen vacancy concentration on sequential processes of methane dehydrogenation, and oxidation with lattice oxygen. We find that when CH4 adsorbs onto Fe atop sites without neighboring oxygen vacancies, it dehydrogenates with CHx radicals remaining on the same site and evolves into CO2via the complete oxidation pathway. In the presence of oxygen vacancies, on the other hand, the formed methyl (CH3) prefers to migrate onto the vacancy site while the H from CH4 dehydrogenation remains on the original Fe atop site, and evolves into CO via the partial oxidation pathway. The oxygen vacancies created in the oxidation process can be healed by lattice oxygen diffusion from the subsurface to the surface vacancy sites, and it is found that the outward diffusion of lattice oxygen atoms is more favorable than the horizontal diffusion on the same layer. Based on the proposed mechanism and energy profile, we identify the rate-limiting steps of the partial oxidation and complete oxidation pathways. Also, we find that increasing the oxygen vacancy concentration not only lowers the barriers of CH4 dehydrogenation but also the cleavage energy of Fe-C bonds. However, the barrier of the rate-limiting step cannot further decrease when the oxygen vacancy concentration reaches 2.5%. The fundamental insight into the oxygen vacancy effect on CH4 oxidation with iron oxide oxygen carriers can help guide the design and development of more efficient oxygen carriers and CLPO processes.

  18. Influence of nanocatalyst on oxidative coupling, steam and dry reforming of methane: A short review

    DEFF Research Database (Denmark)

    Farsi, Ali; Mansouri, Seyed Soheil

    2016-01-01

    The influence of nanocatalyst on three main reactions for natural gas conversion such as steam reforming, dry reforming and oxidative coupling of methane has been reviewed with an emphasis on the literatures’ reports and results. Although literatures’ experimental results showed that the conversion...... of methane over the nanocatalysts was higher than that obtained from the ordinary catalysts, there was no correlation between the conversion of methane and the average sizes of the nanoparticles. The results of some nanocatalyst are also compared to ordinary catalysts in the literature which shows...... the improved influence of nanoscale catalyst performance on methane conversion....

  19. Influence of nanocatalyst on oxidative coupling, steam and dry reforming of methane: A short review

    Directory of Open Access Journals (Sweden)

    Ali Farsi

    2016-09-01

    Full Text Available The influence of nanocatalyst on three main reactions for natural gas conversion such as steam reforming, dry reforming and oxidative coupling of methane has been reviewed with an emphasis on the literatures’ reports and results. Although literatures’ experimental results showed that the conversion of methane over the nanocatalysts was higher than that obtained from the ordinary catalysts, there was no correlation between the conversion of methane and the average sizes of the nanoparticles. The results of some nanocatalyst are also compared to ordinary catalysts in the literature which shows the improved influence of nanoscale catalyst performance on methane conversion.

  20. Performance of alternative oxide anodes for the electrochemical oxidation of hydrogen and methane in solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tu, H.; Apfel, H.; Stimming, U. [Department of Physics E19, Technical University of Munich, James-Franck-Strasse 1, D-85748 Garching (Germany)

    2006-07-15

    The electrode performances of the alternative oxides: La{sub 0.05}Ca{sub 0.95}Cr{sub 0.05}Ti{sub 0.95}O{sub 3-{delta}}-8YSZ and Ce{sub 0.8}TM{sub 0.2}O{sub 2-{delta}}(TM=Mn, Co) for the direct electrochemical oxidation of methane are investigated to assess their potential as anode materials for efficient methane conversion in a SOFC. The electrochemical oxidation of hydrogen was also studied, for comparison. The oxides are characterised electrochemically with impedance spectroscopy in the frequency range from 10 mHz to 1MHz, using a three-electrode geometry. They are compared to a standard Ni/8YSZ anode for the electrochemical oxidation of hydrogen. It is found that La{sub 0.05}Ca{sub 0.95}Cr{sub 0.05}Ti{sub 0.95}O{sub 3-{delta}}-8YSZ demonstrates a poor electrochemical activity in both hydrogen and methane. However, the electrochemical activity of Ce{sub 0.8}Mn{sub 0.2}O{sub 2-{delta}} is promising, but the electronic conductivity needs to be increased, e.g., by adding a conducting oxide, before it can be used as an anode material in a SOFC. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  1. Ultrastructure and viral metagenome of bacteriophages from an anaerobic methane oxidizing methylomirabilis bioreactor enrichment culture

    NARCIS (Netherlands)

    Gambelli, Lavinia; Cremers, Geert; Mesman, Rob; Guerrero, Simon; Dutilh, Bas E.; Jetten, Mike S M; den Camp, Huub J M Op; van Niftrik, Laura

    2016-01-01

    With its capacity for anaerobic methane oxidation and denitrification, the bacterium Methylomirabilis oxyfera plays an important role in natural ecosystems. Its unique physiology can be exploited for more sustainable wastewater treatment technologies. However, operational stability of full-scale bio

  2. Environmental evidence for net methane production and oxidation in putative ANaerobic MEthanotrophic (ANME) archaea

    DEFF Research Database (Denmark)

    Lloyd, Karen; Teske, Andreas; Alperin, Marc J.

    2011-01-01

    Uncultured ANaerobic MEthanotrophic (ANME) archaea are often assumed to be obligate methanotrophs that are incapable of net methanogenesis, and are therefore used as proxies for anaerobic methane oxidation in many environments in spite of uncertainty regarding their metabolic capabilities...

  3. Ultrastructure and Viral Metagenome of Bacteriophages from an Anaerobic Methane Oxidizing Methylomirabilis Bioreactor Enrichment Culture

    NARCIS (Netherlands)

    Gambelli, L.; Cremers, G.; Mesman, R.; Guerrero, S.; Dutilh, B.E.; Jetten, M.S.; Camp, H.J. Op den; Niftrik, L. van

    2016-01-01

    With its capacity for anaerobic methane oxidation and denitrification, the bacterium Methylomirabilis oxyfera plays an important role in natural ecosystems. Its unique physiology can be exploited for more sustainable wastewater treatment technologies. However, operational stability of full-scale

  4. Features of non-oxidative conversion of methane into aromatic hydrocarbons over Mo-containing zeolite catalysts

    Science.gov (United States)

    Stepanov, A. A.; Korobitsyna, L. L.; Vosmerikov, A. V.

    2016-09-01

    The results of study of methane conversion under non-oxidative conditions over molybdenum containing zeolite catalysts prepared by solid-phase synthesis using nanosized molybdenum powder are presented. The kinetic mechanisms of the process behavior under different conditions of methane dehydroaromatization are determined. It is shown that nonoxidative conversion of methane can occur both in the external diffusion and kinetic regions, depending on the methane flow rate. It is found out, that the optimum temperature of the methane conversion is 750 °C. It is shown that increased methane conversion is observed at the feed space velocity of methane decreasing from 1500 to 500 h-1.

  5. Novel catalysts for methane activation. Final progress report, September 30, 1992--April 30, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Hirschon, A.S.; Du, Y.; Wu, H.J.; Malhotra, R.; Wilson, R.B.

    1996-06-11

    This final report summarizes the results of our research under Contract No. DE-AC22-92PC92112, Novel Catalysts for Methane Activation. In this research we prepared and tested fullerene soots for converting methane into higher hydrocarbons. We conducted the methane conversions using dehydrocoupling conditions, primarily in the temperature regimes of 600{degrees}-1000{degrees}C and atmospheric pressures. The research was divided into three sections. The first section focused on comparing fullerene soots with other forms of carbon such as acetylene black and Norit-A. We found that the fullerene soot was indeed more reactive than the other forms of carbon. However, due to its high reactivity, it was not selective. The second section focused on the effect of metals on the reactivity of the soots, including both transition metals and alkali metals. We found that potassium could enhance the selectivities of fullerene soot to higher hydrocarbons, but the effect was unique to fullerene soot and did not improve the performance of other forms of carbon. The third part focused on the use of co-feeds for methane activation to enhance the selectivities and lower the temperature threshold of methane activation.

  6. A basic approach to evaluate methane partial oxidation catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Parmaliana, A. (Universita degli Studi di Messina (Italy)); Frusteri, F.; Mezzapica, A.; Micelli, D.; Giordano, N. (Instituto CNR-TAE, Messina (Italy)); Scurrell, M.S. (CSIR, Pretoria (South Africa))

    1993-09-01

    The partial oxidation of methane to formaldehyde by molecular oxygen on silica and silica-supported oxide catalysts has been investigated at a pressure of 1.7 bar in the temperature range 520-650[degrees]C by using a batch reactor with external recycle. The effects of reactor diameter, recycle flow rate, catalyst weight, and methane-to-oxygen ratio on the catalyst activity have been outlined. By performing several blank tests with an empty and a quartz-filled reactor, it has been demonstrated that the gas-phase reaction does not affect the catalytic pathways. Reasons for controversial results reported previously are discussed. They lie in the lack of an adequate experimental approach and in the generally adopted rule to evaluate the catalytic activity at differential conditions in order to push the HCHO selectivity to high values. The approach presented here allows one to evaluate the catalytic activity by performing tests at quasi-zero conversion per mass but at a finite extent of conversion. The need to express the catalytic activity as space time yield (STY) to HCHO (g[center dot]kg[sub cat][sup [minus]1][center dot]h[sup [minus]1]) is presented. The reactivities of various commercial SiO[sub 2] samples obtained by precipitation, sol-gel, and pyrolysis methods have been determined. The fact that the nature and source of silica has a marked effect on STY, previously observed for reaction at 520[degrees]C, has been confirmed for operation at 550-650[degrees]C. Highest STYs are found with precipitated silica samples. In fact, at 650[degrees]C with such precipitated SiO[sub 2] a STY to HCHO of 303 g[center dot] kg[sub cat][sup [minus]1] [center dot] H[sup [minus]1] has been obtained. Incorporation of molybdena depresses the STY value for the precipitated silica but enhances the STY of bare fumed silica. In contrast, addition of vanadia to either precipitated or fumed silicas leads to higher STY values. 29 refs., 6 figs., 8 tabs.

  7. Evidence for nitrite-dependent anaerobic methane oxidation as a previously overlooked microbial methane sink in wetlands

    Science.gov (United States)

    Hu, Bao-lan; Shen, Li-dong; Lian, Xu; Zhu, Qun; Liu, Shuai; Huang, Qian; He, Zhan-fei; Geng, Sha; Cheng, Dong-qing; Lou, Li-ping; Xu, Xiang-yang; Zheng, Ping; He, Yun-feng

    2014-01-01

    The process of nitrite-dependent anaerobic methane oxidation (n-damo) was recently discovered and shown to be mediated by “Candidatus Methylomirabilis oxyfera” (M. oxyfera). Here, evidence for n-damo in three different freshwater wetlands located in southeastern China was obtained using stable isotope measurements, quantitative PCR assays, and 16S rRNA and particulate methane monooxygenase gene clone library analyses. Stable isotope experiments confirmed the occurrence of n-damo in the examined wetlands, and the potential n-damo rates ranged from 0.31 to 5.43 nmol CO2 per gram of dry soil per day at different depths of soil cores. A combined analysis of 16S rRNA and particulate methane monooxygenase genes demonstrated that M. oxyfera-like bacteria were mainly present in the deep soil with a maximum abundance of 3.2 × 107 gene copies per gram of dry soil. It is estimated that ∼0.51 g of CH4 m−2 per year could be linked to the n-damo process in the examined wetlands based on the measured potential n-damo rates. This study presents previously unidentified confirmation that the n-damo process is a previously overlooked microbial methane sink in wetlands, and n-damo has the potential to be a globally important methane sink due to increasing nitrogen pollution. PMID:24616523

  8. Fractionation of the methane isotopologues 13CH4, 12CH3D, and 13CH3D during aerobic oxidation of methane by Methylococcus capsulatus (Bath)

    Science.gov (United States)

    Wang, David T.; Welander, Paula V.; Ono, Shuhei

    2016-11-01

    Aerobic oxidation of methane plays a major role in reducing the amount of methane emitted to the atmosphere from freshwater and marine settings. We cultured an aerobic methanotroph, Methylococcus capsulatus (Bath) at 30 and 37 °C, and determined the relative abundance of 12CH4, 13CH4, 12CH3D, and 13CH3D (a doubly-substituted, or "clumped" isotopologue of methane) to characterize the clumped isotopologue effect associated with aerobic methane oxidation. In batch culture, the residual methane became enriched in 13C and D relative to starting methane, with D/H fractionation a factor of 9.14 (Dε/13ε) larger than that of 13C/12C. As oxidation progressed, the Δ13CH3D value (a measure of the excess in abundance of 13CH3D relative to a random distribution of isotopes among isotopologues) of residual methane decreased. The isotopologue fractionation factor for 13CH3D/12CH4 was found to closely approximate the product of the measured fractionation factors for 13CH4/12CH4 and 12CH3D/12CH4 (i.e., 13C/12C and D/H). The results give insight into enzymatic reversibility in the aerobic methane oxidation pathway. Based on the experimental data, a mathematical model was developed to predict isotopologue signatures expected for methane in the environment that has been partially-oxidized by aerobic methanotrophy. Measurement of methane clumped isotopologue abundances can be used to distinguish between aerobic methane oxidation and alternative methane-cycling processes.

  9. Anaerobic oxidation of methane above gas hydrates at Hydrate Ridge, NE Pacific Ocean

    DEFF Research Database (Denmark)

    Treude, T.; Boetius, A.; Knittel, K.;

    2003-01-01

    At Hydrate Ridge (HR), Cascadia convergent margin, surface sediments contain massive gas hydrates formed from methane that ascends together with fluids along faults from deeper reservoirs. Anaerobic oxidation of methane (AOM), mediated by a microbial consortium of archaea and sulfate-reducing...... bacteria, generates high concentrations of hydrogen sulfide in the surface sediments. The production of sulfide supports chemosynthetic communities that gain energy from sulfide oxidation. Depending on fluid flow, the surface communities are dominated either by the filamentous sulfur bacteria Beggiatoa...

  10. Anaerobic oxidation of methane in grassland soils used for cattle husbandry

    OpenAIRE

    2012-01-01

    While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle-overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using

  11. Anaerobic oxidation of methane in grassland soils used for cattle husbandry

    OpenAIRE

    2012-01-01

    While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore, anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using <...

  12. A unique isotopic fingerprint during sulfate-driven anaerobic oxidation of methane

    Science.gov (United States)

    Antler, G.; Turchyn, A. V.; Herut, B.; Sivan, O.

    2014-12-01

    Bacterial sulfate reduction is responsible for the majority of anaerobic methane oxidation in modern marine sediments. This sulfate-driven AOM can often metabolize all the methane produced within marine sediments, preventing any from reaching the overlying ocean. In certain areas, however, methane concentrations are high enough to form bubbles, which can reach the seafloor, only partially metabolized through sulfate-driven AOM; these areas where methane bubbles into the ocean are called cold seeps, or methane seeps. We use the sulfur and oxygen isotopes of sulfate (d34SSO4 and d18OSO4) in locations where sulfate-driven AOM is occurring both in methane seeps as well as lower flux methane transition zones to show that in methane seeps, the d34SSO4 and d18OSO4 data during the coupled sulfate reduction fall into a very narrow range and with a close to linear relationship (slope 0.37± 0.01 (R^2= 0.98, n=52, 95% confidence interval). In the studied environments, considerably different physical properties exist, excluding the possibility that this linear relationship can be attributed to physical processes such as diffusion, advection or mixing of two end-members. This unique isotopic signature emerges during bacterial sulfate reduction by methane in 'cold' seeps and differs when sulfate is reduced by either organic matter oxidation or by a slower, diffusive flux of methane within marine sediments. We show also that this unique isotope fingerprint is preserved in the rock record in authigenic build-ups of carbonates and barite associated with methane seeps, and may serve as a powerful tool for identifying catastrophic methane release in the geological record.

  13. Catalytic combustion of methane by perovskite-type oxide nanoparticles as pollution prevention strategy

    Science.gov (United States)

    Zaza, F.; Luisetto, I.; Serra, E.; Tuti, S.; Pasquali, M.

    2016-06-01

    The transition from the existing brown economy towards the desired green economy drives the research efforts to the development of advanced technologies promoting the efficient utilization of energy sources. Catalysis science offers to combustion technology significant opportunity to increase the fuel efficiency by lowering the internal temperature gradients and reduce the environmental impact by lowering local peak temperature and, consequently, thermodynamically inhibiting the nitrogen oxides formation. Alternative catalytic materials are transition metals oxide, including complex oxides with perovskite crystalline structure. The aim of this work is to synthetize lanthanum ferrite perovskites with lanthanum ions partially substituted by strontium ions in order to study the substitution effects on structural properties and redox activity of the original oxide. Lanthanum ferrite oxides partially substituted with different Strontium amount were synthesized by solution combustion method. The perovskite nanopowders obtained were characterized by XRD, SEM, TPR analyses for defining crystalline structure, morphology and redox properties. Finally, the catalytic activity for methane combustion was tested. The most performing catalysts was La0.6Sr0.4FeO3 having the highest oxygen vacancy concentration as revealed by TPR analysis.

  14. Regulation of anaerobic methane oxidation in sediments of the Black Sea

    Directory of Open Access Journals (Sweden)

    N. J. Knab

    2008-05-01

    Full Text Available Anaerobic oxidation of methane (AOM and sulfate reduction (SRR were investigated in sediments of the western Black Sea, where methane transport is controlled by diffusion. To understand the regulation and dynamics of methane production and oxidation in the Black Sea, rates of methanogenesis, AOM, and SRR were determined using radiotracers in combination with pore water chemistry and stable isotopes. On the shelf of the Danube paleo-delta and the Dnjepr Canyon, AOM did not consume methane effectively and upwards diffusing methane created an extended sulfate-methane transition zone (SMTZ that spread over more than 2.5 m and was located in formerly limnic sediment. Measurable AOM rates occurred mainly in the lower part of the SMTZ, sometimes even at depths where sulfate seemed to be unavailable. The inefficiency of methane oxidation appears to be linked to the limnic history of the sediment, since in all cores methane was completely oxidized at the limnic-marine transition. The upward tailing of methane was less pronounced in a core from the deep sea in the area of the Dnjepr Canyon, the only station with a SMTZ close to the marine deposits. Sulfate reduction rates were mostly extremely low, and in the SMTZ were even lower than AOM rates. Rates of bicarbonate-based methanogenesis were below detection limit in two of the cores, but δ13C values of methane indicate a biogenic origin. The most depleted δ13C-signal was found in the SMTZ of the core from the deep sea, most likely as a result of carbon recycling between AOM and methanogenesis.

  15. Effects of carrier and Mn loading on supported manganese oxide catalysts for catalytic combustion of methane

    Institute of Scientific and Technical Information of China (English)

    Jinyan Hu; Wei Chu; Limin Shi

    2008-01-01

    Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane cat-alytic combustion, and effects of the support (Al2O3, SiO2 and TiO2) and Mn loading were investigated. These catalysts were characterized with N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Methane conversion varied in a large range depending on supports or Mn loading. Al2O3 supported 15% Mn cata-lyst exhibited better activity toward methane catalytic oxidation. The manganese state and oxygen species played an important role in the catalytic performance.

  16. Methane-Oxidizing Enzymes: An Upstream Problem in Biological Gas-to-Liquids Conversion.

    Science.gov (United States)

    Lawton, Thomas J; Rosenzweig, Amy C

    2016-08-03

    Biological conversion of natural gas to liquids (Bio-GTL) represents an immense economic opportunity. In nature, aerobic methanotrophic bacteria and anaerobic archaea are able to selectively oxidize methane using methane monooxygenase (MMO) and methyl coenzyme M reductase (MCR) enzymes. Although significant progress has been made toward genetically manipulating these organisms for biotechnological applications, the enzymes themselves are slow, complex, and not recombinantly tractable in traditional industrial hosts. With turnover numbers of 0.16-13 s(-1), these enzymes pose a considerable upstream problem in the biological production of fuels or chemicals from methane. Methane oxidation enzymes will need to be engineered to be faster to enable high volumetric productivities; however, efforts to do so and to engineer simpler enzymes have been minimally successful. Moreover, known methane-oxidizing enzymes have different expression levels, carbon and energy efficiencies, require auxiliary systems for biosynthesis and function, and vary considerably in terms of complexity and reductant requirements. The pros and cons of using each methane-oxidizing enzyme for Bio-GTL are considered in detail. The future for these enzymes is bright, but a renewed focus on studying them will be critical to the successful development of biological processes that utilize methane as a feedstock.

  17. Evaluation of methyl fluoride and dimethyl ether as inhibitors of aerobic methane oxidation

    Science.gov (United States)

    Oremland, R.S.; Culbertson, C.W.

    1992-01-01

    Methyl fluoride (MF) and dimethyl ether (DME) were effective inhibitors of aerobic methanotrophy in a variety of soils. MF and DME blocked consumption of CH4 as well as the oxidation of 14CH4 to 14CO2, but neither MF nor DME affected the oxidation of [14C]methanol or [14C]formate to 14CO2. Cooxidation of ethane and propane by methane-oxidizing soils was also inhibited by MF. Nitrification (ammonia oxidation) in soils was inhibited by both MF and DME. Production of N2O via nitrification was inhibited by MF; however, MF did not affect N2O production associated with denitrification. Methanogenesis was partially inhibited by MF but not by DME. Methane oxidation was ~100-fold more sensitive to MF than was methanogenesis, indicating that an optimum concentration could be employed to selectively block methanotrophy. MF inhibited methane oxidation by cell suspensions of Methylococcus capsulatus; however, DME was a much less effective inhibitor.

  18. Catalytic performance for methane combustion of supported Mn-Ce mixed oxides

    Institute of Scientific and Technical Information of China (English)

    SHI Limin; CHU Wei; QU Fenfen; HU Jinyan; LI Minmin

    2008-01-01

    A series of supported Mn-Ce mixed oxide catalysts were prepared by the impregnation method and used for the oxidation of methane. The catalysts were characterized by N2 adsorption (BET), X-ray diffraction (XRD), laser Raman spectrum (LRS), and temperature programmed reduction (TPR) techniques. The XRD and LRS results confirmed the high dispersion of active components or formation of solid solution between manganese and cerium oxides in the bulk and on the surface of mixed oxide catalysts. The reducibility was remarka-bly promoted by the stronger synergistic interaction between the two oxides from H2-TPR measurements. As expected, all the experimental mixed oxide catalysts showed excellent activity for methane combustion at low temperature. Especially, for the catalyst with Mn-Ce ratio 3:7, methane conversion reached 92% at a temperature as low as 470 ℃.

  19. Advances of study on atmospheric methane oxidation (consumption) in forest soil

    Institute of Scientific and Technical Information of China (English)

    WANG Chen-rui; SHI Yi; YANG Xiao-ming; WU Jie; YUE Jin

    2003-01-01

    Next to CO2, methane (CH4) is the second important contributor to global warming in the atmosphere and global atmospheric CH4 budget depends on both CH4 sources and sinks. Unsaturated soil is known as a unique sink for atmospheric CH4 in terrestrial ecosystem. Many comparison studies proved that forest soil had the biggest capacity of oxidizing atmospheric CH4 in various unsaturated soils. However, up to now, there is not an overall review in the aspect of atmospheric CH4 oxidation (consumption) in forest soil. This paper analyzed advances of studies on the mechanism of atmospheric CH4 oxidation, and related natural factors (Soil physical and chemical characters, temperature and moisture, ambient main greenhouse gases concentrations, tree species, and forest fire) and anthropogenic factors (forest clear-cutting and thinning, fertilization, exogenous aluminum salts and atmospheric deposition, adding biocides, and switch of forest land use) in forest soils. It was believed that CH4 consumption rate by forest soil was limited by diffusion and sensitive to changes in water status and temperature of soil. CH4 oxidation was also particularly sensitive to soil C/N, Ambient CO2, CH4 and N2O concentrations, tree species and forest fire. In most cases, anthropogenic disturbances will decrease atmospheric CH4 oxidation, thus resulting in the elevating of atmospheric CH4. Finally, the author pointed out that our knowledge of atmospheric CH4 oxidation (consumption) in forest soil was insufficient. In order to evaluate the contribution of forest soils to atmospheric CH4 oxidation and the role of forest played in the process of global environmental change, and to forecast the trends of global warming exactly, more researchers need to studies further on CH4 oxidation in various forest soils of different areas.

  20. Combining oxidative coupling and reforming of methane : vision or utopia?

    NARCIS (Netherlands)

    Graf, P.O.

    2009-01-01

    Methane, which is the principal component of natural gas reserves, is currently being used for home and industrial heating and for the generation of electrical power. Methane is an ideal fuel because of its availability in most populated centres, its ease of purification and the fact that is has the

  1. Combining oxidative coupling and reforming of methane : vision or utopia?

    NARCIS (Netherlands)

    Graf, Patrick Oliver

    2009-01-01

    Methane, which is the principal component of natural gas reserves, is currently being used for home and industrial heating and for the generation of electrical power. Methane is an ideal fuel because of its availability in most populated centres, its ease of purification and the fact that is has the

  2. Oxidative Coupling of Methane over Li/MgO: Catalyst and Nanocatalyst Performance

    Science.gov (United States)

    Farsi, Ali; Moradi, Ali; Ghader, Sattar; Shadravan, Vahid

    2011-02-01

    The Li/MgO catalyst and nanocatalyst were prepared by the incipient wetness impregnation and sol-gel method, respectively. The catalytic performance of the Li/MgO catalyst and nanocatalyst on oxidative coupling of methane was compared. The catalysts prepared in two ways were characterized by X-ray powder diffraction, Brunauer-Emmett-Teller surface and transmission electron microscope. The catalyst was tested at temperature of 973-1073 K with constant total pressure of 101 kPa. Experimental results showed that Li/MgO nanocatalyst in the oxidative coupling of methane would result in higher conversion of methane, higher selectivity, and higher yield of main products (ethane and ethylene) compared to ordinary catalyst. The results show the improved influence of nanoscale Li/MgO catalyst performance on oxidative coupling of methane.

  3. Methane Oxidation and Molecular Characterization of Methanotrophs from a Former Mercury Mine Impoundment

    Directory of Open Access Journals (Sweden)

    Shaun M. Baesman

    2015-06-01

    Full Text Available The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO2 with some CH4 present. The δ13CH4 value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively 12C-enriched CO2 suggested a reworking of the ebullitive methane by methanotrophic bacteria. Therefore, we tested bottom sediments for their ability to consume methane by conducting aerobic incubations of slurried materials. Methane was removed from the headspace of live slurries, and subsequent additions of methane resulted in faster removal rates. This activity could be transferred to an artificial, acidic medium, indicating the presence of acidophilic or acid-tolerant methanotrophs, the latter reinforced by the observation of maximum activity at pH = 4.5 with incubated slurries. A successful extraction of sterol and hopanoid lipids characteristic of methanotrophs was achieved, and their abundances greatly increased with increased sediment methane consumption. DNA extracted from methane-oxidizing enrichment cultures was amplified and sequenced for pmoA genes that aligned with methanotrophic members of the Gammaproteobacteria. An enrichment culture was established that grew in an acidic (pH 4.5 medium via methane oxidation.

  4. Methane Oxidation and Molecular Characterization of Methanotrophs from a Former Mercury Mine Impoundment.

    Science.gov (United States)

    Baesman, Shaun M; Miller, Laurence G; Wei, Jeremy H; Cho, Yirang; Matys, Emily D; Summons, Roger E; Welander, Paula V; Oremland, Ronald S

    2015-06-23

    The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO₂ with some CH₄ present. The δ(13)CH₄ value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively (12)C-enriched CO₂ suggested a reworking of the ebullitive methane by methanotrophic bacteria. Therefore, we tested bottom sediments for their ability to consume methane by conducting aerobic incubations of slurried materials. Methane was removed from the headspace of live slurries, and subsequent additions of methane resulted in faster removal rates. This activity could be transferred to an artificial, acidic medium, indicating the presence of acidophilic or acid-tolerant methanotrophs, the latter reinforced by the observation of maximum activity at pH = 4.5 with incubated slurries. A successful extraction of sterol and hopanoid lipids characteristic of methanotrophs was achieved, and their abundances greatly increased with increased sediment methane consumption. DNA extracted from methane-oxidizing enrichment cultures was amplified and sequenced for pmoA genes that aligned with methanotrophic members of the Gammaproteobacteria. An enrichment culture was established that grew in an acidic (pH 4.5) medium via methane oxidation.

  5. Methane oxidation and molecular characterization of methanotrophs from a former mercury mine impoundment

    Science.gov (United States)

    Baesman, Shaun; Miller, Laurence G.; Wei, Jeremy H.; Cho, Yirang; Matys, Emily D.; Summons, Roger E.; Welander, Paula V.; Oremland, Ronald S.

    2015-01-01

    The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO2 with some CH4 present. The δ13CH4 value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively 12C-enriched CO2 suggested a reworking of the ebullitive methane by methanotrophic bacteria. Therefore, we tested bottom sediments for their ability to consume methane by conducting aerobic incubations of slurried materials. Methane was removed from the headspace of live slurries, and subsequent additions of methane resulted in faster removal rates. This activity could be transferred to an artificial, acidic medium, indicating the presence of acidophilic or acid-tolerant methanotrophs, the latter reinforced by the observation of maximum activity at pH = 4.5 with incubated slurries. A successful extraction of sterol and hopanoid lipids characteristic of methanotrophs was achieved, and their abundances greatly increased with increased sediment methane consumption. DNA extracted from methane-oxidizing enrichment cultures was amplified and sequenced for pmoA genes that aligned with methanotrophic members of the Gammaproteobacteria. An enrichment culture was established that grew in an acidic (pH 4.5) medium via methane oxidation.

  6. Fluxed of nitrous oxide and methane in a lake border ecosystem in northern Germany

    Energy Technology Data Exchange (ETDEWEB)

    Rusch, H.; Rembges, D.; Papke, H.; Rennenberg, H. [Fraunhofer Inst. for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany)

    1995-12-31

    Methane and nitrous oxide are radiatively active trace gases. This accounts for approximately 20 % of the total anticipated greenhouse effect. The atmospheric mixing ratio of both gases has increased significantly during the last decades at a rate of 0.25 % yr{sup -l} for N{sub 2}O and a rate of 1 % yr{sup -1} for CH{sub 4}. Whether this increase is caused by enhanced biogenic production of both gases or is due to decreased global sinks, has not been definitely elucidated. Soils are an important source of methane and nitrous oxide. Natural wetlands, e.g., have a similar global source strength of methane as rice paddies. On the other hand, well aerated grasslands have been shown to be a sink for atmospheric methane due to methane oxidation. Nitrous oxide is emitted by a wide range of soil types. Its rate of emission is strongly enhanced by nitrogen fertilization. In the present study, fluxes of methane and nitrous oxide were determined in a lake border ecosystem along a toposequence from reed to dry pasture. The aim of this study was to characterize the influence of soil type, land use and season on the flux rates of these greenhouse gases. (author)

  7. Assessment of methane generation, oxidation, and emission in a subtropical landfill test cell.

    Science.gov (United States)

    Moreira, João M L; Candiani, Giovano

    2016-08-01

    This paper presents results of a methane balance assessment in a test cell built in a region with a subtropical climate near São Paulo, Brazil. Measurements and calculations were carried out to obtain the total methane emission to the atmosphere, the methane oxidation rate in the cover, and the total methane generation rate in the test cell. The oxidation rate was obtained through a calculation scheme based on a vertical one-dimensional methane transport in the cover region. The measured maximum and mean methane fluxes to the atmosphere were 124.4 and 15.87 g m(-2) d(-1), respectively. The total methane generation rate obtained for the test cell was 0.0380 ± 0.0075 mol s(-1). The results yielded that 69 % of the emitted methane occurred through the central well and 31 % through the cover interface with the atmosphere. The evaluations of the methane oxidation fraction for localized conditions in the lateral embankment of the test cell yielded 0.36 ± 0.11, while for the whole test cell yielded 0.15 ± 0.10. These results conciliate localized and overall evaluations reported in the literature. The specific methane generation rate obtained for the municipal solid waste with an age of 410 days was 317 ± 62 mol year(-1) ton(-1). This result from the subtropical São Paulo region is lower than reported figures for tropical climates and higher than reported figures for temperate climates.

  8. Methane and methanol oxidation in supercritical water: Chemical kinetics and hydrothermal flame studies

    Energy Technology Data Exchange (ETDEWEB)

    Steeper, R.R.

    1996-01-01

    Supercritical water oxidation (SCWO) is an emerging technology for the treatment of wastes in the presence of a large concentration of water at conditions above water`s thermodynamic critical point. A high-pressure, optically accessible reaction cell was constructed to investigate the oxidation of methane and methanol in this environment. Experiments were conducted to examine both flame and non-flame oxidation regimes. Optical access enabled the use of normal and shadowgraphy video systems for visualization, and Raman spectroscopy for in situ measurement of species concentrations. Flame experiments were performed by steadily injecting pure oxygen into supercritical mixtures of water and methane or methanol at 270 bar and at temperatures from 390 to 510{degrees}C. The experiments mapped conditions leading to the spontaneous ignition of diffusion flames in supercritical water. Above 470{degrees}C, flames spontaneously ignite in mixtures containing only 6 mole% methane or methanol. This data is relevant to the design and operation of commercial SCWO processes that may be susceptible to inadvertent flame formation. Non-flame oxidation kinetics experiments measured rates of methane oxidation in supercritical water at 270 bar and at temperatures from 390 to 442{degrees}C. The initial methane concentration was nominally 0.15 gmol/L, a level representative of commercial SCWO processes. The observed methane concentration histories were fit to a one-step reaction rate expression indicating a reaction order close to two for methane and zero for oxygen. Experiments were also conducted with varying water concentrations (0 to 8 gmol/L) while temperature and initial reactant concentrations were held constant. The rate of methane oxidation rises steadily with water concentration up to about 5 gmol/L and then abruptly falls off at higher concentrations.

  9. Remarkable recovery and colonization behaviour of methane oxidizing bacteria in soil after disturbance is controlled by methane source only.

    Science.gov (United States)

    Pan, Yao; Abell, Guy C J; Bodelier, Paul L E; Meima-Franke, Marion; Sessitsch, Angela; Bodrossy, Levente

    2014-08-01

    Little is understood about the relationship between microbial assemblage history, the composition and function of specific functional guilds and the ecosystem functions they provide. To learn more about this relationship we used methane oxidizing bacteria (MOB) as model organisms and performed soil microcosm experiments comprised of identical soil substrates, hosting distinct overall microbial diversities(i.e., full, reduced and zero total microbial and MOB diversities). After inoculation with undisturbed soil, the recovery of MOB activity, MOB diversity and total bacterial diversity were followed over 3 months by methane oxidation potential measurements and analyses targeting pmoA and 16S rRNA genes. Measurement of methane oxidation potential demonstrated different recovery rates across the different treatments. Despite different starting microbial diversities, the recovery and succession of the MOB communities followed a similar pattern across the different treatment microcosms. In this study we found that edaphic parameters were the dominant factor shaping microbial communities over time and that the starting microbial community played only a minor role in shaping MOB microbial community.

  10. Estimating Landfill Methane Oxidation Using the Information of CO2/CH4 Fluxes Measured By the Eddy Covariance Method

    Science.gov (United States)

    Xu, L.; McDermitt, D. K.; Li, J.; Green, R. B.

    2016-12-01

    Methane plays a critical role in the radiation balance and chemistry of the atmosphere. Globally, landfill methane emission contributes about 10-19% of the anthropogenic methane burden into the atmosphere. In the United States, 18% of annual anthropogenic methane emissions come from landfills, which represent the third largest source of anthropogenic methane emissions, behind enteric fermentation and natural gas and oil production. One uncertainty in estimating landfill methane emissions is the fraction of methane oxidized when methane produced under anaerobic conditions passes through the cover soil. We developed a simple stoichiometric model to estimate the landfill methane oxidation fraction when the anaerobic CO2/CH4 production ratio is known. The model predicts a linear relationship between CO2 emission rates and CH4 emission rates, where the slope depends on anaerobic CO2/CH4 production ratio and the fraction of methane oxidized, and the intercept depends on non-methane-dependent oxidation processes. The model was tested with eddy covariance CO2 and CH4 emission rates at Bluff Road Landfill in Lincoln Nebraska. It predicted zero oxidation rate in the northern portion of this landfill where a membrane and vents were present. The zero oxidation rate was expected because there would be little opportunity for methane to encounter oxidizing conditions before leaving the vents. We also applied the model at the Turkey Run Landfill in Georgia to estimate the CH4 oxidation rate over a one year period. In contrast to Bluff Road Landfill, the Turkey Run Landfill did not have a membrane or vents. Instead, methane produced in the landfill had to diffuse through a 0.5 m soil cap before release to the atmosphere. We observed evidence for methane oxidation ranging from about 18% to above 60% depending upon the age of deposited waste material. The model will be briefly described, and results from the two contrasting landfills will be discussed in this presentation.

  11. Direct catalytic conversion of methane and light hydrocarbon gases. Final report, October 1, 1986--July 31, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, R.B. Jr.; Posin, B.M.; Chan, Yee-Wai

    1995-06-01

    This project explored conversion of methane to useful products by two techniques that do not involve oxidative coupling. The first approach was direct catalytic dehydrocoupling of methane to give hydrocarbons and hydrogen. The second approach was oxidation of methane to methanol by using heterogenized versions of catalysts that were developed as homogeneous models of cytochrome-P450, an enzyme that actively hydroxylates hydrocarbons by using molecular oxygen. Two possibilities exist for dehydrocoupling of methane to higher hydrocarbons: The first, oxidative coupling to ethane/ethylene and water, is the subject of intense current interest. Nonoxidative coupling to higher hydrocarbons and hydrogen is endothermic, but in the absence of coke formation the theoretical thermodynamic equilibrium yield of hydrocarbons varies from 25% at 827{degrees}C to 65% at 1100{degrees}C (at atmospheric pressure). In this project we synthesized novel, highly dispersed metal catalysts by attaching metal clusters to inorganic supports. The second approach mimics microbial metabolism of methane to produce methanol. The methane mono-oxygenase enzyme responsible for the oxidation of methane to methanol in biological systems has exceptional selectivity and very good rates. Enzyme mimics are systems that function as the enzymes do but overcome the problems of slow rates and poor stability. Most of that effort has focused on mimics of cytochrome P-450, which is a very active selective oxidation enzyme and has a metalloporphyrin at the active site. The interest in nonporphyrin mimics coincides with the interest in methane mono-oxygenase, whose active site has been identified as a {mu}-oxo dinuclear iron complex.We employed mimics of cytochrome P-450, heterogenized to provide additional stability. The oxidation of methane with molecular oxygen was investigated in a fixed-bed, down-flow reactor with various anchored metal phthalocyanines (PC) and porphyrins (TPP) as the catalysts.

  12. 甲烷氧化与氨氧化微生物及其耦合功能%Methane-and Ammonia-Oxidation Microorganisms and Their Coupling Functions

    Institute of Scientific and Technical Information of China (English)

    赵吉; 李靖宇; 周玉; 白玉涛; 于景丽

    2012-01-01

    to sequence the whole genome of the culturable micro- organisms and to deeply explore the similar microorganism group, such as sequencing the genome of Candidatus "Nitrosopumilus maritimus" strain SCM1 and Methylocoeeus eapsulatus. In this review, we discuss microbial mechanisms of the methane-and ammonia-oxidation processes; normally molecular methods for understanding these functional groups; the roles and significance of methane-oxidizer in the carbon cycle and controlling the greenhouse gas emission ; the roles and significance of ammonia-oxidizer in the ni- trogen cycle and controlling the greenhouse gas emission. Finally, We illuminate the common scientific problems facing in the methane-and ammonia-oxidizer studies.

  13. Evidence of sulfate-dependent anaerobic methane oxidation ...

    Science.gov (United States)

    The rapid development of unconventional gas resources has been accompanied by an increase in public awareness regarding the potential effects of drilling operations on drinking water sources. Incidents have been reported involving blowouts (e.g., Converse County, WY; Lawrence Township, PA; Aliso Canyon, CA) and home/property explosions (e.g., Bainbridge Township, OH; Dimock, PA; Huerfano County, CO) caused by methane migration in the subsurface within areas of natural gas development. We evaluated water quality characteristics in the northern Raton Basin of Colorado and documented the response of the Poison Canyon aquifer system several years after upward migration of methane gas occurred from the deeper Vermejo Formation coalbed production zone. Results show persistent secondary water quality impacts related to the biodegradation of methane. We identify four distinct characteristics of groundwater methane attenuation in the Poison Canyon aquifer: (i) consumption of methane and sulfate and production of sulfide and bicarbonate, (ii) methane loss coupled to production of higher-molecular-weight (C2+) gaseous hydrocarbons, (iii) patterns of 13C enrichment and depletion in methane and dissolved inorganic carbon, and (iv) a systematic shift in sulfur and oxygen isotope ratios of sulfate, indicative of microbial sulfate reduction. We also show that the biogeochemical response of the aquifer system has not mobilized naturally occurring trace metals, including arsenic,

  14. Closing the Gaps in the Budgets of Methane and Nitrous Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, Aslam; Rice, Andrew; Rasmussen, Reinhold

    2013-11-22

    Together methane and nitrous oxide contribute almost 40% of the estimated increase in radiative forcing caused by the buildup of greenhouse gases during the last 250 years (IPCC, 2007). These increases are attributed to human activities. Since the emissions of these gases are from biogenic sources and closely associated with living things in the major terrestrial ecosystems of the world, climate change is expected to cause feedbacks that may further increase emissions even from systems normally classified as natural. Our results support the idea that while past increases of methane were driven by direct emissions from human activities, some of these have reached their limits and that the future of methane changes may be determined by feedbacks from warming temperatures. The greatly increased current focus on the arctic and the fate of the carbon frozen in its permafrost is an example of such a feedback that could exceed the direct increases caused by future human activities (Zimov et al. 2006). Our research was aimed at three broad areas to address open questions about the global budgets of methane and nitrous oxide. These areas of inquiry were: The processes by which methane and nitrous oxide are emitted, new sources such as trees and plants, and integration of results to refine the global budgets both at present and of the past decades. For the process studies the main research was to quantify the effect of changes in the ambient temperature on the emissions of methane and nitrous oxide from rice agriculture. Additionally, the emissions of methane and nitrous oxide under present conditions were estimated using the experimental data on how fertilizer applications and water management affect emissions. Rice was chosen for detailed study because it is a prototype system of the wider terrestrial source, its role in methane emissions is well established, it is easy to cultivate and it represents a major anthropogenic source. Here we will discuss the highlights of the

  15. Closing the Gaps in the Budgets of Methane and Nitrous Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, Aslam; Rice, Andrew; Rasmussen, Reinhold

    2013-11-22

    Together methane and nitrous oxide contribute almost 40% of the estimated increase in radiative forcing caused by the buildup of greenhouse gases during the last 250 years (IPCC, 2007). These increases are attributed to human activities. Since the emissions of these gases are from biogenic sources and closely associated with living things in the major terrestrial ecosystems of the world, climate change is expected to cause feedbacks that may further increase emissions even from systems normally classified as natural. Our results support the idea that while past increases of methane were driven by direct emissions from human activities, some of these have reached their limits and that the future of methane changes may be determined by feedbacks from warming temperatures. The greatly increased current focus on the arctic and the fate of the carbon frozen in its permafrost is an example of such a feedback that could exceed the direct increases caused by future human activities (Zimov et al. 2006). Our research was aimed at three broad areas to address open questions about the global budgets of methane and nitrous oxide. These areas of inquiry were: The processes by which methane and nitrous oxide are emitted, new sources such as trees and plants, and integration of results to refine the global budgets both at present and of the past decades. For the process studies the main research was to quantify the effect of changes in the ambient temperature on the emissions of methane and nitrous oxide from rice agriculture. Additionally, the emissions of methane and nitrous oxide under present conditions were estimated using the experimental data on how fertilizer applications and water management affect emissions. Rice was chosen for detailed study because it is a prototype system of the wider terrestrial source, its role in methane emissions is well established, it is easy to cultivate and it represents a major anthropogenic source. Here we will discuss the highlights of the

  16. Perovskite-supported palladium for methane oxidation - structure-activity relationships.

    Science.gov (United States)

    Eyssler, Arnim; Lu, Ye; Matam, Santhosh Kumar; Weidenkaff, Anke; Ferri, Davide

    2012-01-01

    Palladium is the precious metal of choice for methane oxidation and perovskite-type oxides offer the possibility to stabilize it as PdO, considered crucial for catalytic activity. Pd can adopt different oxidation and coordination states when associated with perovskite-type oxides. Here, we review our work on the effect of perovskite composition on the oxidation and coordination states of Pd and its influence on catalytic activity for methane oxidation in the case of typical Mn, Fe and Co perovskite-based oxidation catalysts. Especially X-ray absorption near edge structure (XANES) spectroscopy is shown to be crucial to fingerprint the different coordination states of Pd. Pd substitutes Fe and Co in the octahedral sites but without modifying catalytic activity with respect to the Pd-free perovskite. On LaMnO(3) palladium is predominantly exposed at the surface thus bestowing catalytic activity for methane oxidation. However, the occupancy of B-cation sites of the perovskite structure by Pd can be exploited to cyclically activate Pd and to protect it from particle growth. This is explicitly demonstrated for La(Fe, Pd)O(3), where catalytic activity for methane oxidation is enhanced under oscillating redox conditions at 500 °C, therefore paving the way to the practical application in three-way catalysts for stoichiometric natural gas engines.

  17. Dissociative adsorption of methane on surface oxide structures of Pd-Pt alloys

    CERN Document Server

    Dianat, Arezoo; Ciacchi, Lucio Colombi; Pompe, Wolfgang; Cuniberti, Gianaurelio; Bobeth, Manfred; 10.1021/jp905689t

    2010-01-01

    The dissociative adsorption of methane on variously oxidized Pd, Pt and Pd-Pt surfaces is investigated using density-functional theory, as a step towards understanding the combustion of methane on these materials. For Pd-Pt alloys, models of surface oxide structures are built on the basis of known oxides on Pd and Pt. The methane adsorption energy presents large variations depending on the oxide structure and composition. Adsorption is endothermic on the bare Pd(111) metal surface as well as on stable thin layer oxide structures such as the ($\\sqrt{5}\\times\\sqrt{5}$) surface oxide on Pd(100) and the PtO$_2$-like oxide on Pt(111). Instead, large adsorption energies are obtained for the (100) surface of bulk PdO, for metastable mixed Pd$_{1-x}$Pt$_x$O$_{4/3}$ oxide layers on Pt(100), and for Pd-Pt(111) surfaces covered with one oxygen monolayer. In the latter case, we find a net thermodynamic preference for a direct conversion of methane to methanol, which remains adsorbed on the oxidized metal substrates via w...

  18. Effects of methane on the microbial populations and oxidation rates in different landfill cover soil columns.

    Science.gov (United States)

    He, Ruo; Ruan, Aidong; Shen, Dong-Sheng

    2007-05-01

    A considerable fraction of methane produced in landfills is oxidized by landfill cover soils. In this work, microbial populations and oxidation rates developed in response to the presence of methane were studied in three soil columns simulated landfill cover soil environments. The population of aerobic heterotrophic bacteria was highest in the waste soil, middle in the clay soil, and lowest in the red soil. After exposure to methane-rich environments, the populations of methanotrophic bacteria showed increases in the waste and clay soils. The population of methanotrophic bacteria increased from 30.77x10(4) to 141.77x10(4) cfu g d.w.-1 in the middle layer of the waste soil column as a function of exposure to methane for 120 days. The populations of methanotrophic bacteria were correlated with the potential methane oxidation rates in the waste and clay soils, respectively. The topsoil was observed to be dried in the three soil columns. Most of methane oxidation occurred at the depth of between 10 and 20 cm in the waste soil column, while it took place mainly at the depth of between 20 and 30 cm in the clay soil column.

  19. A Mercury-Catalyzed, High-Yield System for the Oxidation of Methane to Methanol

    Science.gov (United States)

    Periana, Roy A.; Taube, Douglas J.; Evitt, Eric R.; Loffler, Daniel G.; Wentrcek, Paul R.; Voss, George; Masuda, Toshihiko

    1993-01-01

    A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a methane conversion of 50 percent, 85 percent selectivity to methyl bisulfate (~43 percent yield; the major side product is carbon dioxide) was achieved at a molar productivity of 10-7 mole per cubic centimeter per second and Hg(II) turnover frequency of 10-3 per second. Separate hydrolysis of methyl bisulfate and reoxidation of the sulfur dioxide with air provides a potentially practical scheme for the oxidation of methane to methanol with molecular oxygen. The primary steps of the Hg(II)-catalyzed reaction were individually examined and the essential elements of the mechanism were identified. The Hg(II) ion reacts with methane by an electrophilic displacement mechanism to produce an observable species, CH_3HgOSO_3H, 1. Under the reaction conditions, 1 readily decomposes to CH_3OSO_3H and the reduced mercurous species, Hg_22+. The catalytic cycle is completed by the reoxidation of Hg_22+ with H_2SO_4 to regenerate Hg(II) and byproducts SO_2 and H_2O. Thallium(III), palladium(II), and the cations of platinum and gold also oxidize methane to methyl bisulfate in sulfuric acid.

  20. Development of vanidum-phosphate catalysts for methanol production by selective oxidation of methane. Quarterly technical progress report, 1996

    Energy Technology Data Exchange (ETDEWEB)

    McCormick, R.L.; Alptekin, G.O.

    1996-06-01

    Activities this past quarter, focused on acquisition of kinetic data for oxidation of formaldehyde and methanol on these catalysts. In the next quarter these results will be used to propose a simple reaction network and kinetic model. To date we have completed Task 1: Laboratory Setup and Task 2: Process Variable Study. Activities in the current quarter focused on finalizing these tasks and on Task 3: Promoters and Supports, this task is approximately 50% completed. Task 4: Advanced Catalysts is to be initiated in the next quarter. Specific accomplishments this quarter include: finalizing and calibrating a new reaction product analytical system with markedly improved precision and accuracy relative to older. approaches; development of procedures for accurately feeding formaldehyde to the reactor; examination of formaldehyde and methanol oxidation kinetics over vanadyl pyrophosphate at a range of temperatures; and preliminary studies of methane oxidation over a silica support.

  1. A Critical Assessment of the Direct Catalytic Oxidation of Methane to Methanol.

    Science.gov (United States)

    Ravi, Manoj; Ranocchiari, Marco; van Bokhoven, Jeroen A

    2017-06-23

    Despite the emerging number of disparate approaches for the direct selective partial oxidation of methane, none of them has translated into an industrial process. The oxidation of methane to methanol is a difficult yet intriguing and rewarding task as it has the potential to eliminate the prevalent natural gas flaring by providing novel routes to its valorisation. This review considers the synthesis of methanol and methanol derivatives from methane by homogeneous and heterogeneous pathways. In establishing the severe limitations related to the direct catalytic synthesis of methanol from methane, we highlight the vastly superior performance of systems, which produce methanol derivatives or incorporate specific measures such as the use of multi-component catalysts to stabilise methanol. We thereby identify methanol protection as being indispensable in homogeneous and heterogeneous catalysis with regard to future research on this topic. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Oxidation of methane and hydrogen on Ce1-xGdxO2-δ flourrites

    DEFF Research Database (Denmark)

    Kammer Hansen, K.; Mogensen, Mogens Bjerg

    2005-01-01

    The oxidation of methane and hydrogen was studied on cone shaped electrodes with the composition Ce1-xGdxO2-delta (x equals 0, 0.1, 0.2, 0.4). It was shown that the area specific resistance values measured at open-circuit voltage (OCV) for the oxidation of both methane and hydrogen is lowest...... for the composition Ce0.9Gd0.1O1.95. The OCV in wet methane was shown to depend on the material composition. It was shown that stable operation in wet methane could be achieved as long as the temperature was kept below 750degreesC. (C) 2004 The Electrochemical Society....

  3. Some technological aspects of methane aromatization (direct and via oxidative coupling)

    Energy Technology Data Exchange (ETDEWEB)

    Skutil, Krzysztof; Taniewski, Marian [Silesian Technical University, Chair of Chemical Organic Technology and Petrochemistry, ul. Krzywoustego 4, 44-101 Gliwice (Poland)

    2006-06-15

    The investigations on transformation of methane to benzene and naphthalene have been carried out in aim to verify and supplement earlier reported data and on this basis to estimate real industrial perspectives of the CH{sub 4} aromatization concept, the main challenges and barriers. Methane aromatization (direct and via oxidative coupling) has been studied over Mo/HZSM-5 catalyst used both for direct methane dehydroaromatization and for aromatization of methane oxidative coupling (OCM) products. The effects of Mo content in the catalyst, temperature, space velocity, the presence of CO{sub 2}, CO, H{sub 2}O, C{sub 2}H{sub 4}, C{sub 2}H{sub 6} and their mixtures in the feed have been studied. The effectiveness of the catalyst regeneration in the air was also examined. All results were confronted with the literature data and analyzed from technological point of view. It was confirmed that direct CH{sub 4} aromatization process was characterized by a low CH{sub 4} single-pass conversion, low single-pass yields of the main products (benzene, hydrogen and naphthalene) and a low catalyst stability (rapid catalyst deactivation). Various possible technological schemes were analyzed. It was concluded that real industrial chances of direct methane aromatization or aromatization via OCM would depend largely on the advancement in the cost-effective separation techniques. The methane aromatization concept was also confronted with other methane conversion processes. (author)

  4. Steam Methane Reformation Testing for Air-Independent Solid Oxide Fuel Cell Systems

    Science.gov (United States)

    Mwara, Kamwana N.

    2015-01-01

    Recently, NASA has been looking into utilizing landers that can be propelled by LOX-CH (sub 4), to be used for long duration missions. Using landers that utilize such propellants, also provides the opportunity to use solid oxide fuel cells as a power option, especially since they are able to process methane into a reactant through fuel reformation. One type of reformation, called steam methane reformation, is a process to reform methane into a hydrogen-rich product by reacting methane and steam (fuel cell exhaust) over a catalyst. A steam methane reformation system could potentially use the fuel cell's own exhaust to create a reactant stream that is hydrogen-rich, and requires less internal reforming of the incoming methane. Also, steam reformation may hold some advantages over other types of reforming, such as partial oxidation (PROX) reformation. Steam reformation does not require oxygen, while up to 25 percent can be lost in PROX reformation due to unusable CO (sub 2) reformation. NASA's Johnson Space Center has conducted various phases of steam methane reformation testing, as a viable solution for in-space reformation. This has included using two different types of catalysts, developing a custom reformer, and optimizing the test system to find the optimal performance parameters and operating conditions.

  5. Non-oxidative dehydro-oligomerization of methane to higher molecular weight hydrocarbons at low temperatures

    Institute of Scientific and Technical Information of China (English)

    王林胜; 徐奕德; 陶龙骧

    1997-01-01

    The non-oxidative dehydro-oligomerization of methane to higher molecular weight hydrocarbons such as aroma tics and C2 hydrocarbons in a low temperature range of 773-973 K with Mo/HZSM-5,Mo-Zr/HZSM-5 and Mo-W/HZSM-5 catalysts is studied.The means for enhancing the activity and stability of the Mo-containing catalysts under the reaction conditions is reported.Quite a stable methane conversion rate of over 10% with a high selectivity to the higher hydrocarbons has been obtained at a temperature of 973 K.Pure methane conversions of about 5.2% and 2.0% have been obtained at 923 and 873 K,respectively.In addition,accompanied by the C2-C3 mixture,tht- methane reaction can be initiated even at a lower temperature and the conversion rate of methane is enhanced by the presence of tne initiator of C2-C3 hydrocarbons.Compared with methane oxidative coupling to ethylene,the novel way for methane transformation is significant and reasonable for its lower reaction temperatures and high selectivity to the desired prod

  6. Anaerobic oxidation of methane in grassland soils used for cattle husbandry

    Directory of Open Access Journals (Sweden)

    A. Bannert

    2012-10-01

    Full Text Available While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore, anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using 13C-labelled methane. We were able to detect a high microbial activity utilizing CH4 as nutrient source shown by the respiration of 13CO2. Measurements of possible terminal electron acceptors for anaerobic oxidation of methane were carried out. Soil sulfate concentrations were too low to explain the oxidation of the amount of methane added, but enough nitrate and iron(III were detected. However, only nitrate was consumed during the experiment. 13C-PLFA analyses clearly showed the utilization of CH4 as nutrient source mainly by organisms harbouring 16:1ω7 PLFAs. These lipids were also found as most 13C-enriched fatty acids by Raghoebarsing et al. (2006 after addition of 13CH4 to an enrichment culture coupling denitrification of nitrate to anaerobic oxidation of methane. This might be an indication for anaerobic oxidation of methane by relatives of "Candidatus Methylomirabilis oxyfera" in the investigated grassland soil under the conditions of the incubation experiment.

  7. Environmental control on anaerobic oxidation of methane in the gassy sediments of Eckernforde Bay (German Baltic)

    DEFF Research Database (Denmark)

    Treude, T.; Kruger, M.; Boetius, A.

    2005-01-01

    We investigated the effect of seasonal environmental changes on the rate and distribution of anaerobic oxidation of methane (AOM) in Eckernforde Bay sediments (German Baltic Sea) and identified organisms that are likely to be involved in the process. Surface sediments were sampled during September...... the warm productive season and to a slightly deeper AOM zone during the cold winter season. Rising methane bubbles apparently fed AOM above the sulfate-methane transition. Methanosarcinales-related anaerobic methanotrophs (ANME-2), identified with fluorescence in situ hybridization, is suggested to mediate...

  8. Seasonal variation in methane oxidation by the rhizosphere of Phragmites australis and Scirpus lacustris

    NARCIS (Netherlands)

    Van der Nat, F.J.; Middelburg, J.J.

    1998-01-01

    Methane oxidation in the rhizosphere of two common wetland plants, reed (Phragmites australis (Cav.) Trin. Ex Steud.) and bulrush (Scirpus lacustris L.), was quantified using the methylfluoride (CH3F) inhibition and anoxic/oxic flux chamber techniques. The similarity of rhizospheric CH4 oxidation

  9. Novel high-activity catalysts for partial oxidation of methane to formaldehyde

    CSIR Research Space (South Africa)

    Parmaliana, A

    1993-05-07

    Full Text Available Vanadium oxide-silica catalysts can effect the partial oxidation of methane to formaldehyde with extremely high activities and the space time yield (STY) can reach a value in excess of 800 g kg-1cat h-1; bare silica also shows appreciable STY value...

  10. Soil fluxes of methane, nitrous oxide, and nitric oxide from aggrading forests in coastal Oregon

    Science.gov (United States)

    Erickson, Heather E.; Perakis, Steven S.

    2014-01-01

    Soil exchanges of greenhouse and other gases are poorly known for Pacific Northwest forests where gradients in nutrient availability and soil moisture may contribute to large variations in fluxes. Here we report fluxes of methane (CH4), nitrous oxide (N2O), and nitric oxide (NO) over multiple seasons from three naturally N-rich, aggrading forests of coastal Oregon, USA. Mean methane uptake rates (3.2 mg CH4 m−2 d−1) were high compared with forests globally, negatively related to water-filled pore space (WFPS), but unrelated to N availability or temperature. Emissions of NO (6.0 μg NO–N m−2 h−1) exceeded N2O (1.4 μg N2O–N m−2 h−1), except when WFPS surpassed 55%. Spatial variation in NO fluxes correlated positively with soil nitrate concentrations (which generally exceeded ammonium concentrations, indicating the overall high N status for the sites) and negatively with soil pH, and at one site increased with basal area of N2-fixing red alder. Combined NO and N2O emissions were greatest from the site with highest annual net N mineralization and lowest needle litterfall C/N. Our findings of high CH4 uptake and NO/N2O ratios generally >1 most likely reflect the high porosity of the andic soils underlying the widespread regenerating forests in this seasonally wet region.

  11. [In-situ DRIFTS study of coupling partial oxidation of methane and carbon dioxide reforming].

    Science.gov (United States)

    Ji, Hong-bing; Xu, Jian-hua; Xie, Jun-feng; Chen, Qing-lin

    2008-06-01

    8%Ru-5%Ce/gamma-Al2O3 catalyst exhibited excellent catalytic performance for low temperature activation of methane. Although the conversion rates of methane were 25.3% for exothermal partial oxidation of methane, and 0.8% for endothermal carbon dioxide reforming, whose activity was rather low, 38.8% of conversion rate of methane could be obtained for the obtained coupling reaction at 500 degrees C owing to the coupling intensification between endothermal carbon dioxide reforming reaction and exothermal partial oxidation of methane. The mechanism of coupling partial oxidation of methane and carbon dioxide reforming on supported Ru catalyst was investigated by in-situ DRIFTS. The adsorption of CO on 8%Ru-5%Ce/gamma-Al2O3 showed that two kinds of doublet peaks which were characteristic adsorption of the gaseous CO at 2167 cm(-1) (2118 cm(-1)) to form Ru(CO)2 at 2031 cm(-1) (2034 cm(-1)) to form Ce(CO)2 were observed. These CO adsorption species wee easy to be desorbed from the surface of the catalyst at high temperature. The results of in-situ DRIFTS showed that carbonate, formal (formate) and carbon monoxide formed on the surface of catalyst, and formal (formate) was intermediate for the methane partial oxidation. This intermediate was formed through the combination of the adsorption species of methane CHx and the lattice oxygen adsorption species on the surface of catalyst, and syngas was produced through the splitting of this intermediate. The DRIFTS researching on carbon dioxide reforming showed that there was no new adsorption species on the surface of the catalyst, which indicated that the mechanism for carbon dioxide reforming was through the dissociation of the adsorbed methane and carbon dioxide. During the reaction of the coupling of carbon dioxide reforming reaction and partial oxidation of methane, there was hydroxyl adsorption species on the surface of catalyst. The mechanism of coupling methane, carbon dioxide and oxygen might be composed of the above

  12. Enzymes involved in the anaerobic oxidation of n-alkanes: from methane to long-chain paraffins

    Directory of Open Access Journals (Sweden)

    Amy V. Callaghan

    2013-05-01

    Full Text Available Anaerobic microorganisms play key roles in the biogeochemical cycling of methane and non-methane alkanes. To date, there appear to be at least three proposed mechanisms of anaerobic methane oxidation (AOM. The first pathway is mediated by consortia of archaeal anaerobic methane oxidizers and sulfate-reducing bacteria via ‘reverse methanogenesis’ and is catalyzed by a homologue of methyl-coenzyme M reductase. The second pathway is also mediated by anaerobic methane oxidizers and sulfate-reducing bacteria, wherein the archaeal members catalyze both methane oxidation and sulfate reduction and zero-valent sulfur is a key intermediate. The third AOM mechanism is a nitrite-dependent, intra-aerobic pathway described for the denitrifying bacterium, ‘Candidatus Methylomirabilis oxyfera.’ It is hypothesized that AOM proceeds via reduction of nitrite to nitric oxide, followed by the conversion of two nitric oxide molecules to dinitrogen and molecular oxygen. The latter can be used to functionalize the methane via a particulate methane monooxygenase. With respect to non-methane alkanes, there also appears to be novel mechanisms of activation. The most well-described pathway is the addition of non-methane alkanes across the double bond of fumarate to form alkyl-substituted succinates via the putative glycyl radical enzyme, alkylsuccinate synthase (also known as methylalkylsuccinate synthase. Other proposed mechanisms include anaerobic hydroxylation via ethylbenzene dehydrogenase-like enzymes and an ‘intra-aerobic’ denitrification pathway similar to that described for ‘M. oxyfera.’

  13. The key nickel enzyme of methanogenesis catalyses the anaerobic oxidation of methane.

    Science.gov (United States)

    Scheller, Silvan; Goenrich, Meike; Boecher, Reinhard; Thauer, Rudolf K; Jaun, Bernhard

    2010-06-03

    Large amounts (estimates range from 70 Tg per year to 300 Tg per year) of the potent greenhouse gas methane are oxidized to carbon dioxide in marine sediments by communities of methanotrophic archaea and sulphate-reducing bacteria, and thus are prevented from escaping into the atmosphere. Indirect evidence indicates that the anaerobic oxidation of methane might proceed as the reverse of archaeal methanogenesis from carbon dioxide with the nickel-containing methyl-coenzyme M reductase (MCR) as the methane-activating enzyme. However, experiments showing that MCR can catalyse the endergonic back reaction have been lacking. Here we report that purified MCR from Methanothermobacter marburgensis converts methane into methyl-coenzyme M under equilibrium conditions with apparent V(max) (maximum rate) and K(m) (Michaelis constant) values consistent with the observed in vivo kinetics of the anaerobic oxidation of methane with sulphate. This result supports the hypothesis of 'reverse methanogenesis' and is paramount to understanding the still-unknown mechanism of the last step of methanogenesis. The ability of MCR to cleave the particularly strong C-H bond of methane without the involvement of highly reactive oxygen-derived intermediates is directly relevant to catalytic C-H activation, currently an area of great interest in chemistry.

  14. Geochemical, metagenomic and metaproteomic insights into trace metal utilization by methane-oxidizing microbial consortia in sulfidic marine sediments

    Energy Technology Data Exchange (ETDEWEB)

    Glass, DR. Jennifer [California Institute of Technology, Pasadena; Yu, DR. Hang [California Institute of Technology, Pasadena; Steele, Joshua [California Institute of Technology, Pasadena; Dawson, Katherine [California Institute of Technology, Pasadena; Sun, S [University of California, San Diego; Chourey, Karuna [ORNL; Hettich, Robert {Bob} L [ORNL; Orphan, V [California Institute of Technology, Pasadena

    2014-01-01

    Microbes have obligate requirements for trace metals in metalloenzymes that catalyze important biogeochemical reactions. In anoxic methane- and sulfide-rich environments, microbes may have unique adaptations for metal acquisition and utilization due to decreased bioavailability as a result of metal sulfide precipitation. However, micronutrient cycling is largely unexplored in cold ( 10 C) and sulfidic (>1 mM H2S) deep-sea methane seep ecosystems. We investigated trace metal geochemistry and microbial metal utilization in methane seeps offshore Oregon and California, USA, and report dissolved concentrations of nickel (0.5-270 nM), cobalt (0.5-6 nM), molybdenum (10-5,600 nM) and tungsten (0.3-8 nM) in Hydrate Ridge sediment porewaters. Despite low levels of cobalt and tungsten, metagenomic and metaproteomic data suggest that microbial consortia catalyzing anaerobic oxidation of methane utilize both scarce micronutrients in addition to nickel and molybdenum. Genetic machinery for cobalt-containing vitamin B12 biosynthesis was present in both anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). Proteins affiliated with the tungsten-containing form of formylmethanofuran dehydrogenase were expressed in ANME from two seep ecosystems, the first evidence for expression of a tungstoenzyme in psychrotolerant microorganisms. Finally, our data suggest that chemical speciation of metals in highly sulfidic porewaters may exert a stronger influence on microbial bioavailability than total concentration

  15. Effect of trichloroethylene and tetrachloroethylene on methane oxidation and community structure of methanotrophic consortium.

    Science.gov (United States)

    Choi, Sun-Ah; Lee, Eun-Hee; Cho, Kyung-Suk

    2013-01-01

    The methane oxidation rate and community structure of a methanotrophic consortium were analyzed to determine the effects of trichloroethylene (TCE) and tetrachloroethylene (PCE) on methane oxidation. The maximum methane oxidation rate (Vmax ) of the consortium was 326.8 μmol·g-dry biomass(-1)·h(-1), and it had a half-saturation constant (Km ) of 143.8 μM. The addition of TCE or PCE resulted in decreased methane oxidation rates, which were decreased from 101.73 to 5.47-24.64 μmol·g-dry biomass(-1)·h(-1) with an increase in the TCE-to-methane ratio, and to 61.95-67.43 μmol·g-dry biomass(-1)·h(-1) with an increase in the PCE-to-methane ratio. TCE and PCE were non-competitive inhibitors for methane oxidation, and their inhibition constants (Ki ) were 33.4 and 132.0 μM, respectively. When the methanotrophic community was analyzed based on pmoA using quantitative real-time PCR (qRT-PCR), the pmoA gene copy numbers were shown to decrease from 7.3 ± 0.7 × 10(8) to 2.1-5.0 × 10(7) pmoA gene copy number · g-dry biomass(-1) with an increase in the TCE-to-methane ratio and to 2.5-7.0 × 10(7) pmoA gene copy number · g-dry biomass(-1) with an increase in the PCE-to-methane ratio. Community analysis by microarray demonstrated that Methylocystis (type II methanotrophs) were the most abundant in the methanotrophic community composition in the presence of TCE. These results suggest that toxic effects caused by TCE and PCE change not only methane oxidation rates but also the community structure of the methanotrophic consortium.

  16. An experimental study on short-term changes in the anaerobic oxidation of methane in response to varying methane and sulfate fluxes

    Directory of Open Access Journals (Sweden)

    G. Wegener

    2009-05-01

    Full Text Available A major role in regulation of global methane fluxes has been attributed to the process of anaerobic oxidation of methane (AOM, which is performed by consortia of methanotrophic archaea and sulfate reducing bacteria. An important question remains how these energy limited, slow growing microorganisms with generation times of 3–7 months respond to rapid natural variations in methane fluxes at cold seeps. We used an experimental flow-through column system filled with cold seep sediments naturally enriched in methanotrophic communities, to test their responses to short-term variations in methane and sulfate fluxes. At stable methane and sulfate concentrations of ~2 mM and 28 mM, respectively, we measured constant rates of AOM and sulfate reduction (SR for up to 160 days of incubation. When percolated with methane-free medium, the anaerobic methanotrophs ceased to produce sulfide. After a starvation phase of 40 days, the addition of methane restored former AOM and SR rates immediately. At methane concentrations between 0–2.3 mM we measured a linear correlation between methane availability, AOM and SR. At constant fluid flow velocities of 30 m yr−1, ca. 50% of the methane was consumed by the anaerobic methanotrophic (ANME population at all concentrations tested. Reducing the sulfate concentration from 28 to 1 mM, a decrease in AOM and SR by 50% was observed, and 45% of the methane was consumed. Hence, the marine anaerobic methanotrophs (ANME are capable of oxidizing substantial amounts of methane over a wide and variable range of fluxes of the reaction educts.

  17. Methanation of carbon oxides. History, status quo and future perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Kaltner, W.; Rakoczy, R.A. [Clariant SE, Muenchen (Germany)

    2012-07-01

    With increasing demand in fossil sources and especially crude oil based energy carrier, proven reserves will be diminishing. Besides alternative and sustainable sources the conversion of coal into fuels which can be distributed within the existing infrastructure becomes extremely important in areas of fast growing energy demand. Driver for these technologies is mostly the lack of crude oil and availability of coal like in China or South Africa. The most common way to convert coal into chemicals and fuels is the gasification to yield a gas mixture known as synthesis gas. Synthesis gas can be converted in highly pure methane used as 'substitute natural gas' (SNG) in gas grids of major cities to produce heat at home and industry. All available SNG technologies are characterized by the difficulty to control the extreme heat release of the methanation reaction. This presentation will give an overview on available gasification and methanation technologies from recent point of view. A lot of processes are already described in literature and there are pilot and real plants for methanation and especially SNG built. Moreover, a new process to produce methane from synthesis gas without the need of recycle streams and high temperatures will be introduced. This novel process developed by Foster Wheeler - using catalysts from Clariant - is called 'VESTA Process' in accordance with the Roman goddess of hearth and fire. (orig.)

  18. Aerobic methane oxidation in a coastal environment with seasonal hypoxia - a time series study

    Science.gov (United States)

    Steinle, Lea; Bethke, Christina; Schweers, Johanna; Bange, Hermann; Kock, Annette; Lehmann, Moritz F.; Treude, Tina; Niemann, Helge

    2014-05-01

    In the coastal ocean, methane is generally produced in anoxic sediments from where it can migrate through the water column to the atmosphere. A significant amount of methane is consumed along this passage by a series of microbial filter systems. Over the last 15 years, researchers focused on the first filter in marine sediments, the anaerobic oxidation of methane (AOM). Comparably little is known about the second filter, the aerobic methane oxidation (MOx), which is mediated by bacteria and takes place in the oxic water column. MOx is particularly important in shallow coastal environments that account for more than 75 % of the global oceanic methane emissions. Key environmental factors possibly controlling MOx in these systems are subjected to strong temporal variations since coastal regions are highly dynamic systems. We will present results from a time-series study on methane cycling in the water column of a coastal inlet in the southwestern Baltic Sea (Eckernförde Bay, Boknis Eck Time Series Station, 54°31.823 N, 10°02.764 E, 28m water depth; www.bokniseck.de). Results from monthly samplings for the last 8 years revealed year-round methane seepage from the seafloor and methane supersaturation (with respect to the atmospheric equilibrium) of surface waters. Seasonal stratification during the summer months leads to intermittent oxygen depletion (hypoxic to anoxic) in bottom waters in late summer to early fall. The frequency of these low-oxygen events increased over the last 20 years. In addition to oxygen fluctuations, bottom water salinity can vary strongly (17-24 psu) due to regular inflows of salty North Sea water through the Kattegat. Over the course of one and a half years, we investigated MOx rates, the methanotrophic community, methane concentrations and physicochemical parameters of the water column on a quarterly basis. Albeit methane concentrations were high throughout the water column (20-120 nM), methane turnover showed a clear spatial pattern. That

  19. Anaerobic nitrite-dependent methane-oxidizing bacteria - novel participants in methane cycling of drained peatlands ecosystems

    Science.gov (United States)

    Kravchenko, Irina; Sukhacheva, Marina; Menko, Ekaterina; Sirin, Andrey

    2014-05-01

    Northern peatlands are one of the key sources of atmospheric methane. Process-based studies of methane dynamic are based on the hypothesis of the balance between microbial methane production and oxidation, but this doesn't explain all variations in and constraints on peatland CH4 emissions. One of the reasons for this discrepancy could be anaerobic methane oxidation (AOM) - the process which is still poorly studied and remained controversial. Very little is known about AOM in peatlands, where it could work as an important 'internal' sink for CH4. This lack of knowledge primarily originated from researchers who generally consider AOM quantitatively insignificant or even non-existent in northern peatland ecosystems. But not far ago, Smemo and Yavitt (2007) presented evidence for AOM in freshwater peatlands used indirect techniques including isotope dilution assays and selective methanogenic inhibitors. Nitrite-dependent anaerobic methane oxidation NC10 group bacteria (n-damo) were detected in a minerotrophic peatland in the Netherlands that is infiltrated by nitrate-rich ground water (Zhu et al., 2012). Present study represents the first, to our knowledge, characterization of AOM in human disturbed peatlands, including hydrological elements of artificial drainage network. The experiments were conducted with samples of peat from drained peatlands, as well as of water and bottom sediments of ditches from drained Dubnensky mire massif, Moscow region (Chistotin et al., 2006; Sirin et al., 2012). This is the key testing area of our research group in European part of Russia for the long-term greenhouse gases fluxes measurements supported by testing physicochemical parameters, intensity and genomic diversity of CH4-cycling microbial communities. Only in sediments of drainage ditches the transition anaerobic zone was found, where methane and nitrate occurred, suggested the possible ecological niche for n-damo bacteria. The NC10 group methanotrophs were analyzed by PCR

  20. Methane Oxidation to Methanol without CO2 Emission: Catalysis by Atomic Negative Ions

    CERN Document Server

    Tesfamichael, Aron; Felfli, Zineb; Msezane, Alfred Z

    2014-01-01

    The catalytic activities of the atomic Y-, Ru-, At-, In-, Pd-, Ag-, Pt-, and Os- ions have been investigated theoretically using the atomic Au- ion as the benchmark for the selective partial oxidation of methane to methanol without CO2 emission. Dispersion-corrected density-functional theory has been used for the investigation. From the energy barrier calculations and the thermodynamics of the reactions, we conclude that the catalytic effect of the atomic Ag-, At-, Ru-, and Os- ions is higher than that of the atomic Au- ion catalysis of CH4 conversion to methanol. By controlling the temperature around 290K (Os-), 300K (Ag-), 310K (At-), 320K (Ru-) and 325K (Au-) methane can be completely oxidized to methanol without the emission of CO2. We conclude by recommending the investigation of the catalytic activities of combinations of the above negative ions for significant enhancement of the selective partial oxidation of methane to methanol.

  1. Transformation of methane to synthesis gas over metal oxides without using catalyst

    Institute of Scientific and Technical Information of China (English)

    Reza Alizadeh; Esmail Jamshidi; Guangqing Zhang

    2009-01-01

    This article reviews a new developing method in the field of metal oxide reduction in chemical and metallurgical processes, which uses methane as a reducing agent. Commonly, coal is used as the reducing agent in the reduction of metal oxide and other inorganic materials; Metal producing factories are among the most intensive and concentrated source of greenhouse gases and other pollutants such as heavy metals, sulfur dioxide and fly ash. Thermodynamically, methane has a great reducing capability and can be activated to produce synthesis gas over a metal oxide as an oxygen donor. Metal oxide reduction and methane activation, two concurrent thermochemical processes, can be combined as an efficient and energy-saving process; nowadays this kind of technologies is of great importance. This new reduction process could improve energy efficiencies and significantly decrease greenhouse gas emission compared to the conventional process; furthermore, the produced gases are synthesis gas that is more valuable than methane. In this paper, thermodynamic studies and advantages of this promising method were discussed. The major aim of this article is to introduce methane as a best and environmentally friendly reducing agent at low temperature.

  2. Methane-Oxidizing Bacteria Shunt Carbon to Microbial Mats at a Marine Hydrocarbon Seep

    Science.gov (United States)

    Paul, Blair G.; Ding, Haibing; Bagby, Sarah C.; Kellermann, Matthias Y.; Redmond, Molly C.; Andersen, Gary L.; Valentine, David L.

    2017-01-01

    The marine subsurface is a reservoir of the greenhouse gas methane. While microorganisms living in water column and seafloor ecosystems are known to be a major sink limiting net methane transport from the marine subsurface to the atmosphere, few studies have assessed the flow of methane-derived carbon through the benthic mat communities that line the seafloor on the continental shelf where methane is emitted. We analyzed the abundance and isotope composition of fatty acids in microbial mats grown in the shallow Coal Oil Point seep field off Santa Barbara, CA, USA, where seep gas is a mixture of methane and CO2. We further used stable isotope probing (SIP) to track methane incorporation into mat biomass. We found evidence that multiple allochthonous substrates supported the rich growth of these mats, with notable contributions from bacterial methanotrophs and sulfur-oxidizers as well as eukaryotic phototrophs. Fatty acids characteristic of methanotrophs were shown to be abundant and 13C-enriched in SIP samples, and DNA-SIP identified members of the methanotrophic family Methylococcaceae as major 13CH4 consumers. Members of Sulfuricurvaceae, Sulfurospirillaceae, and Sulfurovumaceae are implicated in fixation of seep CO2. The mats’ autotrophs support a diverse assemblage of co-occurring bacteria and protozoa, with Methylophaga as key consumers of methane-derived organic matter. This study identifies the taxa contributing to the flow of seep-derived carbon through microbial mat biomass, revealing the bacterial and eukaryotic diversity of these remarkable ecosystems.

  3. Enrichment and characteristics of mixed methane-oxidizing bacteria from a Chinese coal mine.

    Science.gov (United States)

    Jiang, Hao; Duan, Changhong; Luo, Mingfang; Xing, Xin-Hui

    2016-12-01

    In methane-rich environments, methane-oxidizing bacteria usually occur predominantly among consortia including other types of microorganisms. In this study, artificial coal bed gas and methane gas were used to enrich mixed methanotrophic cultures from the soil of a coal mine in China, respectively. The changes in microbial community structure and function during the enrichment were examined. The microbial diversity was reduced as the enrichment proceeded, while the capacity for methane oxidation was significantly enhanced by the increased abundance of methanotrophs. The proportion of type II methanotrophs increased greatly from 7.84 % in the sampled soil to about 50 % in the enrichment cultures, due to the increase of methane concentration. After the microbial community of the cultures got stable, Methylomonas and Methylocystis became the dominant type I and type II methanotrophs, while Methylophilus was the prevailing methylotroph. The sequences affiliated with pigment-producing strains, Methylomonas rubra, Hydrogenophaga sp. AH-24, and Flavobacterium cucumis, could explain the orange appearance of the cultures. Comparing the two cultures, the multi-carbon sources in the artificial coal bed gas caused more variety of non-methanotrophic bacteria, but did not help to maintain the diversity or to increase the quantity and activity of methanotrophs. The results could help to understand the succession and interaction of microbial community in a methane-driven ecosystem.

  4. Biomarker evidence for widespread anaerobic methane oxidation in Mediterranean sediments by a consortium of methanogenic archae and bacteria

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Pancost, R.D.; Lint, S. de; Maarel, M.J.E.C. van der; Gottschal, J.C.

    2000-01-01

    Although abundant geochemical data indicate that anaerobic methane oxidation occurs in marine sediments, the linkage to specific microorganisms remains unclear. In order to examine processes of methane consumption and oxidation, sediment samples from mud volcanoes at two distinct sites on the Medite

  5. Influence of nanocatalyst on oxidative coupling, steam and dry reforming of methane: A short review

    DEFF Research Database (Denmark)

    Farsi, Ali; Mansouri, Seyed Soheil

    2012-01-01

    The influence of nanocatalyst on three main reactions for natural gas conversion such as steam reforming, dry reforming and oxidative coupling of methane has been reviewed with an emphasis on the literatures’ reports and results. Although literatures’ experimental results showed that the conversion...... of methane over the nanocatalysts was higher than that obtained from the ordinary catalysts, there was no correlation between the conversion of methane and the average sizes of the nanoparticles. The results of some nanocatalyst are also compared to ordinary catalysts in the literature which shows...... the improved influence of nanoscale catalyst performance on methane conversion. © 2011 King Saud University. Production and hosting by Elsevier B.V. All rights reserved...

  6. Crystal structure of a membrane-bound metalloenzyme that catalyses the biological oxidation of methane

    Energy Technology Data Exchange (ETDEWEB)

    Lieberman, R.L.; Rosenzweig, A.C. (NWU)

    2010-03-08

    Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that catalyses the conversion of methane to methanol. Knowledge of how pMMO performs this extremely challenging chemistry may have an impact on the use of methane as an alternative energy source by facilitating the development of new synthetic catalysts. We have determined the structure of pMMO from the methanotroph Methylococcus capsulatus (Bath) to a resolution of 2.8 {angstrom}. The enzyme is a trimer with an {alpha}{sub 3}{beta}{sub 3}{gamma}{sub 3} polypeptide arrangement. Two metal centres, modelled as mononuclear copper and dinuclear copper, are located in soluble regions of each pmoB subunit, which resembles cytochrome c oxidase subunit II. A third metal centre, occupied by zinc in the crystal, is located within the membrane. The structure provides new insight into the molecular details of biological methane oxidation.

  7. Packing materials selection for a biofilter to bio-oxidize methane in coal mine gas

    Energy Technology Data Exchange (ETDEWEB)

    Yu Hai-xia; Min Hang; Lu Zhen-mei; Li Zi-mu [Zhejiang University, Hangzhou (China). College of Life Sciences

    2008-02-15

    For bio-oxidizing methane (with the concentration 0 to 20%) in coal mine gas with a biofilter, three kinds of packing materials - small ceramic balls, vermiculite and larger sized porcelain balls - were studied. The results indicate that the small ceramic balls have the lowest capacity for biomass growth and the lowest capacity for methane removal. The biofilter with vermiculite as packing material cannot withstand the pressure of the inlet gas. The biofilter with large porcelain balls has the biggest capability to oxidise methane and to withstand the inlet gas, having a suitable specific surface area, grain diameter and density. This is the best packing material for a biofilter to oxidise methane in coal mines. 16 refs., 6 figs., 1 tab.

  8. Field-scale treatment of landfill gas with a passive methane oxidizing biofilter

    Energy Technology Data Exchange (ETDEWEB)

    Philopoulos, A. [Alberta Univ., Edmonton, AB (Canada). Dept. of Civil and Environmental Engineering; Felske, C. [Alberta Research Council, Edmonton, AB (Canada); McCartney, D. [Alberta Univ., Edmonton, AB (Canada). Dept. of Civil and Environmental Engineering, Natural Resources Engineering Facility

    2008-09-15

    Municipal solid waste (MSW) landfills produce methane (CH{sub 4}) and carbon dioxide (CO{sub 2}) as a result of the anaerobic biodegradation of organic fractions of waste. This paper provided details of field tests conducted to test 2 approaches that addressed the issue of gases produced at a landfill in Alberta. A CH{sub 4} oxidation layer was applied to replace intermediate and final landfill covers. Landfill gas (LFG) was then trapped using 3 biogenic CH{sub 4} oxidizing biofilters. Mature yard waste was used as a biofilter medium. The LFG was trapped by the liner, accumulated in a collection system, and then passed through the biofilter medium. The study was conducted over a period of 10 months. Results of the study showed that the integration of the biofilter into the landfill cover showed promising results. Low surface emissions were observed in 6 out of 8 monitoring events at 2 of the sites. Low influent LFG fluxes at the third site did not allow for full air sampling analyses to be conducted. 22 refs., 4 tabs., 8 figs.

  9. Electrochemical oxidation of methane at metal and oxide electrodes. Annual report, December 1, 1987-December 1, 1988

    Energy Technology Data Exchange (ETDEWEB)

    Summers, D.P.; Pound, B.G.; Frese, K.W.

    1989-03-01

    Electrochemical oxidation of methane at noble metal electrodes was investigated. Auger electron spectra showed no buildup of carbon on Rh electrodes after extended electroysis in 140C H/sub 3/PO/sub 4/. The surface oxidation of Rh in 140C H/sub 3/PO/sub 4/ was studied. The open-circuit potential decay method was applied to the reaction between surface oxygen species on Pt and Rh and CH/sub 4/, C/sub 2/H/sub 6/, and C/sub 3/H/sub 8/, and H/sub 2/. Methane was the least reactive hydrocarbon. The peak oxidation currents at 1 atm gas pressure were: 480 micro A cm/sq, 110 micro A cm/sq, 3.5 micro A cm/sq, for propane, ethane, and methane, respectively. Methane oxidation to CO/sub 2/ at Rh surfaces onsets at 0.3 V vs. SCE, is maximal at 0.7 to 0.8 V, and then declines at higher anodic potentials. The rising portion of the rate characteristic precedes detectible oxygen deposition, but the drop in oxidation is correlated with blocking of sites with adsorbed oxygen species.

  10. Microbiology, ecology and application of the nitrite-dependent anaerobic methane oxidation process

    Directory of Open Access Journals (Sweden)

    Li-Dong eShen

    2012-07-01

    Full Text Available Nitrite-dependent anaerobic methane oxidation (n-damo, which couples the anaerobic oxidation of methane to denitrification, is a recently discovered process observed in Candidatus Methylomirabilis oxyfera. M. oxyfera is affiliated with the NC10 phylum, a phylum having no members in pure culture. Based on the isotopic labeling experiments, it is hypothesized that M. oxyfera has an unusual intra-aerobic pathway for the production of oxygen via the dismutation of nitric oxide into dinitrogen gas and oxygen. In addition, the bacterial species has a unique ultrastructure that is distinct from that of other previously described bacterial shapes. M. oxyfera-like sequences have been recovered from different natural habitats, suggesting that the n-damo process potentially contributes to global carbon and nitrogen cycles. The n-damo process is an ecological process that can reduce the greenhouse effect, as methane is more effective in heat-trapping than carbon dioxide. The n-damo process, which uses methane instead of organic matter to drive denitrification, is also an economical nitrogen removal process because methane is a relatively inexpensive electron donor. This mini-review summarizes the peculiar microbiology of M. oxyfera and discusses the potential ecological importance and engineering application of the n-damo process.

  11. Microbiology, ecology, and application of the nitrite-dependent anaerobic methane oxidation process.

    Science.gov (United States)

    Shen, Li-Dong; He, Zhan-Fei; Zhu, Qun; Chen, Dong-Qing; Lou, Li-Ping; Xu, Xiang-Yang; Zheng, Ping; Hu, Bao-Lan

    2012-01-01

    Nitrite-dependent anaerobic methane oxidation (n-damo), which couples the anaerobic oxidation of methane to denitrification, is a recently discovered process mediated by "Candidatus Methylomirabilis oxyfera." M. oxyfera is affiliated with the "NC10" phylum, a phylum having no members in pure culture. Based on the isotopic labeling experiments, it is hypothesized that M. oxyfera has an unusual intra-aerobic pathway for the production of oxygen via the dismutation of nitric oxide into dinitrogen gas and oxygen. In addition, the bacterial species has a unique ultrastructure that is distinct from that of other previously described microorganisms. M. oxyfera-like sequences have been recovered from different natural habitats, suggesting that the n-damo process potentially contributes to global carbon and nitrogen cycles. The n-damo process is a process that can reduce the greenhouse effect, as methane is more effective in heat-trapping than carbon dioxide. The n-damo process, which uses methane instead of organic matter to drive denitrification, is also an economical nitrogen removal process because methane is a relatively inexpensive electron donor. This mini-review summarizes the peculiar microbiology of M. oxyfera and discusses the potential ecological importance and engineering application of the n-damo process.

  12. Anaerobic oxidation of methane by sulfate in hypersaline groundwater of the Dead Sea aquifer.

    Science.gov (United States)

    Avrahamov, N; Antler, G; Yechieli, Y; Gavrieli, I; Joye, S B; Saxton, M; Turchyn, A V; Sivan, O

    2014-11-01

    Geochemical and microbial evidence points to anaerobic oxidation of methane (AOM) likely coupled with bacterial sulfate reduction in the hypersaline groundwater of the Dead Sea (DS) alluvial aquifer. Groundwater was sampled from nine boreholes drilled along the Arugot alluvial fan next to the DS. The groundwater samples were highly saline (up to 6300 mm chlorine), anoxic, and contained methane. A mass balance calculation demonstrates that the very low δ(13) CDIC in this groundwater is due to anaerobic methane oxidation. Sulfate depletion coincident with isotope enrichment of sulfur and oxygen isotopes in the sulfate suggests that sulfate reduction is associated with this AOM. DNA extraction and 16S amplicon sequencing were used to explore the microbial community present and were found to be microbial composition indicative of bacterial sulfate reducers associated with anaerobic methanotrophic archaea (ANME) driving AOM. The net sulfate reduction seems to be primarily controlled by the salinity and the available methane and is substantially lower as salinity increases (2.5 mm sulfate removal at 3000 mm chlorine but only 0.5 mm sulfate removal at 6300 mm chlorine). Low overall sulfur isotope fractionation observed ((34) ε = 17 ± 3.5‰) hints at high rates of sulfate reduction, as has been previously suggested for sulfate reduction coupled with methane oxidation. The new results demonstrate the presence of sulfate-driven AOM in terrestrial hypersaline systems and expand our understanding of how microbial life is sustained under the challenging conditions of an extremely hypersaline environment.

  13. OXIDATIVE-REFORMING OF METHANE AND PARTIAL OXIDATION OF METHANE REACTIONS OVER NiO/PrO2/ZrO2 CATALYSTS: EFFECT OF NICKEL CONTENT

    Directory of Open Access Journals (Sweden)

    Y. J. O. Asencios

    Full Text Available Abstract In this work the behavior of NiO-PrO2-ZrO2 catalysts containing various nickel loadings was evaluated in the partial oxidation of methane and oxidative-reforming reactions of methane. The catalysts were characterized by X-Ray Diffraction Analysis (in situ-XRD, Temperature Programmed Reduction (H2-TPR, Scanning Electron Microscopy (SEM/EDX and Adsorption-Desorption of nitrogen (BET area. The reactions were carried out at 750 °C and 1 atm for 5 hours. The catalysts were studied with different nickel content: 0, 5, 10 and 15% (related to total weight of catalyst, wt%. In both reactions, the catalyst containing the mixture of the three oxides (NiO/PrO2/ZrO2 with 15% nickel (15NiPrZr catalyst showed the best activity for the conversion of the reactants into Syngas and showed high selectivity for H2 and CO. The results suggest that the promoter PrO2 and the Niº centers are in a good proportion in the catalyst with 15% Ni. Our results showed that low nickel concentrations in the catalyst led to high metallic dispersion; however, very low nickel concentrations did not favor the methane transformation into Syngas. The catalyst containing only NiO/ZrO2 in the mixture was not sufficient for the catalysis. The presence of the promoter PrO2 was very important for the catalysis of the POM.

  14. Synthesis gas production through redox cycles of bimetallic oxides and methane

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez, M.I.S.; Vigil, M.D.D.; Gutierrez, J.S.; Collins-Martinez, V.; Ortiz, A.L. [Centro de Investigacion en Materiales Avanzados, Chihuahua, Chih (Mexico). Dept. de Quimica de Materiales

    2009-01-15

    High-purity hydrogen is required by fuel cells to produce electricity with high efficiency and reduced emissions. Therefore, new and cost effective technologies must be developed that can produce hydrogen to supply the increased demand of the current world market. These new technologies have to overcome several challenges such as large size, weight and cost, high temperature requirements for the process and other associated obstacles such as slow start-ups, storage and transportation issues. Hydrogen production through the partial oxidation of methane (POX) is a well known technology at industrial scale. This paper examined the synthesis, characterization and evaluation of iron (Fe) cerium (Ce) zirconium (Zr) with different Fe to CeZr ratios as oxygen carrier to produce syngas through the partial oxidation of methane. The paper also examined the effect of adding nickel (Ni) to FeCeZr as a catalyst to promote the partial oxidation and the proper assessment of the carbon formation within the reaction system. The paper described the experiment with particular reference to synthesis, characterization and reaction evaluation. The results were presented using X-ray diffraction; crystallite size and BET surface area; reaction evaluation by TGA; and evaluation of the partial oxidation of methane. Experimental values showed a clear trend towards the partial oxidation of methane reaction with samples containing Ni. 28 tabs., 4 tabs., 2 figs.

  15. Competitive interactions between methane- and ammonia-oxidizing bacteria modulate carbon and nitrogen cycling in paddy soil

    Science.gov (United States)

    Zheng, Y.; Huang, R.; Wang, B. Z.; Bodelier, P. L. E.; Jia, Z. J.

    2014-06-01

    Pure culture studies have demonstrated that methanotrophs and ammonia oxidizers can both carry out the oxidation of methane and ammonia. However, the expected interactions resulting from these similarities are poorly understood, especially in complex, natural environments. Using DNA-based stable isotope probing and pyrosequencing of 16S rRNA and functional genes, we report on biogeochemical and molecular evidence for growth stimulation of methanotrophic communities by ammonium fertilization, and that methane modulates nitrogen cycling by competitive inhibition of nitrifying communities in a rice paddy soil. Pairwise comparison between microcosms amended with CH4, CH4+Urea, and Urea indicated that urea fertilization stimulated methane oxidation activity 6-fold during a 19-day incubation period, while ammonia oxidation activity was significantly suppressed in the presence of CH4. Pyrosequencing of the total 16S rRNA genes revealed that urea amendment resulted in rapid growth of Methylosarcina-like MOB, and nitrifying communities appeared to be partially inhibited by methane. High-throughput sequencing of the 13C-labeled DNA further revealed that methane amendment resulted in clear growth of Methylosarcina-related MOB while methane plus urea led to an equal increase in Methylosarcina and Methylobacter-related type Ia MOB, indicating the differential growth requirements of representatives of these genera. An increase in 13C assimilation by microorganisms related to methanol oxidizers clearly indicated carbon transfer from methane oxidation to other soil microbes, which was enhanced by urea addition. The active growth of type Ia methanotrops was significantly stimulated by urea amendment, and the pronounced growth of methanol-oxidizing bacteria occurred in CH4-treated microcosms only upon urea amendment. Methane addition partially inhibited the growth of Nitrosospira and Nitrosomonas in urea-amended microcosms, as well as growth of nitrite-oxidizing bacteria. These

  16. Growth of anaerobic methane-oxidizing archaea and sulfate-reducing bacteria in a high-pressure membrane capsule bioreactor.

    Science.gov (United States)

    Timmers, Peer H A; Gieteling, Jarno; Widjaja-Greefkes, H C Aura; Plugge, Caroline M; Stams, Alfons J M; Lens, Piet N L; Meulepas, Roel J W

    2015-02-01

    Communities of anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB) grow slowly, which limits the ability to perform physiological studies. High methane partial pressure was previously successfully applied to stimulate growth, but it is not clear how different ANME subtypes and associated SRB are affected by it. Here, we report on the growth of ANME-SRB in a membrane capsule bioreactor inoculated with Eckernförde Bay sediment that combines high-pressure incubation (10.1 MPa methane) and thorough mixing (100 rpm) with complete cell retention by a 0.2-m-pore-size membrane. The results were compared to previously obtained data from an ambient-pressure (0.101 MPa methane) bioreactor inoculated with the same sediment. The rates of oxidation of labeled methane were not higher at 10.1 MPa, likely because measurements were done at ambient pressure. The subtype ANME-2a/b was abundant in both reactors, but subtype ANME-2c was enriched only at 10.1 MPa. SRB at 10.1 MPa mainly belonged to the SEEP-SRB2 and Eel-1 groups and the Desulfuromonadales and not to the typically found SEEP-SRB1 group. The increase of ANME-2a/b occurred in parallel with the increase of SEEP-SRB2, which was previously found to be associated only with ANME-2c. Our results imply that the syntrophic association is flexible and that methane pressure and sulfide concentration influence the growth of different ANME-SRB consortia. We also studied the effect of elevated methane pressure on methane production and oxidation by a mixture of methanogenic and sulfate-reducing sludge. Here, methane oxidation rates decreased and were not coupled to sulfide production, indicating trace methane oxidation during net methanogenesis and not anaerobic methane oxidation, even at a high methane partial pressure.

  17. Effect of Ni Loading and Reaction Conditions on Partial Oxidation of Methane to Syngas

    Institute of Scientific and Technical Information of China (English)

    Haitao Wang; Zhenhua Li; Shuxun Tian

    2003-01-01

    The partial oxidation of methane to synthesis gas is studied in this paper over Ni/Al2O3 catalysts under atmospheric pressure. The effects of Ni loading on the activity and stability of catalysts with 5 mm α-Al2O3 and θ-Al2O3 pellets as supports were measured in a continuous fixed bed reactor. It is found that the optimum Ni loading is 10%. And the effect of reaction conditions on partial oxidation of methane is also studied. The methane conversion and CO selectivity increase with the increase of the reaction temperature and the space velocity on 10%Ni/α-Al2O3 catalysts. The best CH4/O2 mole ratio is 2 for CO selectivity, and the optimum space velocity is 5.4×105 h-1.

  18. Organometallic Complexes Anchored to Conductive Carbon for Electrocatalytic Oxidation of Methane at Low Temperature.

    Science.gov (United States)

    Joglekar, Madhura; Nguyen, Vinh; Pylypenko, Svitlana; Ngo, Chilan; Li, Quanning; O'Reilly, Matthew E; Gray, Tristan S; Hubbard, William A; Gunnoe, T Brent; Herring, Andrew M; Trewyn, Brian G

    2016-01-13

    Low-temperature direct methane fuel cells (DMEFCs) offer the opportunity to substantially improve the efficiency of energy production from natural gas. This study focuses on the development of well-defined platinum organometallic complexes covalently anchored to ordered mesoporous carbon (OMC) for electrochemical oxidation of methane in a proton exchange membrane fuel cell at 80 °C. A maximum normalized power of 403 μW/mg Pt was obtained, which was 5 times higher than the power obtained from a modern commercial catalyst and 2 orders of magnitude greater than that from a Pt black catalyst. The observed differences in catalytic activities for oxidation of methane are linked to the chemistry of the tethered catalysts, determined by X-ray photoelectron spectroscopy. The chemistry/activity relationships demonstrate a tangible path for the design of electrocatalytic systems for C-H bond activation that afford superior performance in DMEFC for potential commercial applications.

  19. Final Scientific/Technical Report. A closed path methane and water vapor gas analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Liukang [LI-COR Inc., Lincoln, NE (United States); McDermitt, Dayle [LI-COR Inc., Lincoln, NE (United States); Anderson, Tyler [LI-COR Inc., Lincoln, NE (United States); Riensche, Brad [LI-COR Inc., Lincoln, NE (United States); Komissarov, Anatoly [LI-COR Inc., Lincoln, NE (United States); Howe, Julie [LI-COR Inc., Lincoln, NE (United States)

    2012-02-01

    Robust, economical, low-power and reliable closed-path methane (CH4), carbon dioxide (CO2), and water vapor (H2O) analyzers suitable for long-term measurements are not readily available commercially. Such analyzers are essential for quantifying the amount of CH4 and CO2 released from various ecosystems (wetlands, rice paddies, forests, etc.) and other surface contexts (e.g. landfills, animal husbandry lots, etc.), and for understanding the dynamics of the atmospheric CH4 and CO2 budget and their impact on climate change and global warming. The purpose of this project is to develop a closed-path methane, carbon dioxide gas and water vapor analyzer capable of long-term measurements in remote areas for global climate change and environmental research. The analyzer will be capable of being deployed over a wide range of ecosystems to understand methane and carbon dioxide exchange between the atmosphere and the surface. Measurements of methane and carbon dioxide exchange need to be made all year-round with limited maintenance requirements. During this Phase II effort, we successfully completed the design of the electronics, optical bench, trace gas detection method and mechanical infrastructure. We are using the technologies of two vertical cavity surface emitting lasers, a multiple-pass Herriott optical cell, wavelength modulation spectroscopy and direct absorption to measure methane, carbon dioxide, and water vapor. We also have designed the instrument application software, Field Programmable Gate Array (FPGA), along with partial completion of the embedded software. The optical bench has been tested in a lab setting with very good results. Major sources of optical noise have been identified and through design, the optical noise floor is approaching -60dB. Both laser modules can be temperature controlled to help maximize the stability of the analyzer. Additionally, a piezo electric transducer has been

  20. Intensive Ammonia and Methane Oxidation in Organic Liquid Manure Crusts

    DEFF Research Database (Denmark)

    Nielsen, Daniel Aagren; Nielsen, Lars Peter; Schramm, Andreas;

    of the crusts. PCR targeting the unique methane and ammonia monooxygenases were applied together with FISH to detect the presence of the two bacterial groups. Potential activity was assessed by short term slurry incubations of crust samples while monitoring NO2- production or CH4 consumption. Crusts were...... also CH4 emission mitigation, an organic surface crust can be effective if populations of MOB and AOB are allowed to build up....

  1. Methane-induced Activation Mechanism of Fused Ferric Oxide-Alumina Catalysts during Methane Decomposition

    KAUST Repository

    Reddy Enakonda, Linga

    2016-06-27

    Activation of Fe2O3-Al2O3 with CH4 (instead of H2) is a meaningful method to achieve catalytic methane decomposition (CMD). This reaction of CMD is more economic and simple against commercial methane steam reforming (MSR) as it produces COx-free H2. In this study, for the first time, structure changes of the catalyst were screened during CH4 reduction with time on stream. The aim was to optimize the pretreatment conditions through understanding the activation mechanism. Based on results from various characterization techniques, reduction of Fe2O3 by CH4 proceeds in three steps: Fe2O3→Fe3O4→FeO→Fe0. Once Fe0 is formed, it decomposes CH4 with formation of Fe3C, which is the crucial initiation step in the CMD process to initiate formation of multiwall carbon nanotubes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Intrinsic kinetics of the oxidation of methane over an industrial copper II oxide catalyst on a gamma-alumina support

    NARCIS (Netherlands)

    Veldsink, J.W.; Veldsink, J.W.; Versteeg, Geert; van Swaaij, Willibrordus Petrus Maria

    1995-01-01

    The kinetic rate of the heterogeneously catalysed methane oxidation reaction was studied at temperatures ranging from 723 to 923 K and atmospheric pressure. A commercially available CuO catalyst supported by thermally stable γ-Al2O3 was used as the catalyst. This kinetic study was carried out in ord

  3. 2004 Methane and Nitrous Oxide Emissions from Manure Management in South Africa

    Directory of Open Access Journals (Sweden)

    Mokhele Edmond Moeletsi

    2015-03-01

    Full Text Available Manure management in livestock makes a significant contribution towards greenhouse gas emissions in the Agriculture; Forestry and Other Land Use category in South Africa. Methane and nitrous oxide emissions are prevalent in contrasting manure management systems; promoting anaerobic and aerobic conditions respectively. In this paper; both Tier 1 and modified Tier 2 approaches of the IPCC guidelines are utilized to estimate the emissions from South African livestock manure management. Activity data (animal population, animal weights, manure management systems, etc. were sourced from various resources for estimation of both emissions factors and emissions of methane and nitrous oxide. The results show relatively high methane emissions factors from manure management for mature female dairy cattle (40.98 kg/year/animal, sows (25.23 kg/year/animal and boars (25.23 kg/year/animal. Hence, contributions for pig farming and dairy cattle are the highest at 54.50 Gg and 32.01 Gg respectively, with total emissions of 134.97 Gg (3104 Gg CO2 Equivalent. Total nitrous oxide emissions are estimated at 7.10 Gg (2272 Gg CO2 Equivalent and the three main contributors are commercial beef cattle; poultry and small-scale beef farming at 1.80 Gg; 1.72 Gg and 1.69 Gg respectively. Mitigation options from manure management must be taken with care due to divergent conducive requirements of methane and nitrous oxide emissions requirements.

  4. Nitrous Oxide and Methane Fluxes from Smallholder Farms: A Scoping Study in the Anjeni Watershed

    Directory of Open Access Journals (Sweden)

    Haimanote K. Bayabil

    2016-12-01

    Full Text Available While agricultural practices are widely reported to contribute to anthropogenic greenhouse gas (GHG emissions, there are only limited measurements available for emission rates in the monsoon climate of the African continent. We conducted a scoping study to measure nitrous oxide (N2O-N and methane (CH4 emission rates from 24 plots constructed on smallholder agricultural farms along the slope catena of three transects in the sub-humid Anjeni watershed in the Ethiopian highlands. Greenhouse gas flux samples were collected in 2013, before, towards the end, and after the rainy monsoon phase. At each location, three plots were installed in groups: two plots grown with barley (one enriched with charcoal and the other without soil amendment and lupine was grown on the third plot without any soil amendment. Preliminary study results showed that nitrous oxide emission rates varied from −275 to 522 μg·m−2·h−1 and methane emissions ranged from −206 to 264 μg·m−2·h−1 with overall means of 51 and 5 μg·m−2·h−1 for N2O-N and CH4, respectively. Compared with the control, charcoal and lupine plots had elevated nitrous oxide emissions. Plots amended with charcoal showed on average greater methane uptake than was emitted. While this study provides insights regarding nitrous oxide and methane emission levels from smallholder farms, studies of longer durations are needed to verify the results.

  5. Partial Oxidation of Methane to Formaldehyde over Superfine Mo/ZrO2 Catalysts

    Institute of Scientific and Technical Information of China (English)

    Xin Zhang; Dehua He; Qijian Zhang; Qing Ye; Qiming Zhu

    2002-01-01

    Superfine Mo/ZrO2 catalysts were prepared for partial oxidation of methane to HCHO andcharacterized by BET, XRD, LRS, H2-TPR and XPS. Mo existed mainly in the form of Zr(MoO4)2, andthe catalytic performance and physicochemical properties of the Mo/ZrO2 catalysts were closely relatedto this species.

  6. Real time chemical imaging of a working catalytic membrane reactor during oxidative coupling of methane.

    Science.gov (United States)

    Vamvakeros, A; Jacques, S D M; Middelkoop, V; Di Michiel, M; Egan, C K; Ismagilov, I Z; Vaughan, G B M; Gallucci, F; van Sint Annaland, M; Shearing, P R; Cernik, R J; Beale, A M

    2015-08-18

    We report the results from an operando XRD-CT study of a working catalytic membrane reactor for the oxidative coupling of methane. These results reveal the importance of the evolving solid state chemistry during catalytic reaction, particularly the chemical interaction between the catalyst and the oxygen transport membrane.

  7. Learning the Fundamentals of Kinetics and Reaction Engineering with the Catalytic Oxidation of Methane

    Science.gov (United States)

    Cybulskis, Viktor J.; Smeltz, Andrew D.; Zvinevich, Yury; Gounder, Rajamani; Delgass, W. Nicholas; Ribeiro, Fabio H.

    2016-01-01

    Understanding catalytic chemistry, collecting and interpreting kinetic data, and operating chemical reactors are critical skills for chemical engineers. This laboratory experiment provides students with a hands-on supplement to a course in chemical kinetics and reaction engineering. The oxidation of methane with a palladium catalyst supported on…

  8. Spatial patterns of iron- and methane-oxidizing bacterial communities in an irregularly flooded, riparian wetland

    NARCIS (Netherlands)

    Wang, J.; Krause, S.; Muyzer, G.; Meima-Franke, M.; Laanbroek, H.J.; Bodelier, P.L.E.

    2012-01-01

    Iron- and methane-cycling are important processes in wetlands with one connected to plant growth and the other to greenhouse gas emission, respectively. In contrast to acidic habitats, there is scarce information on the ecology of microbes oxidizing ferrous iron at circumneutral pH. The latter is

  9. Five pesticides decreased oxidation of atmospheric methane in a forest soil

    DEFF Research Database (Denmark)

    Priemé, Anders; Ekelund, Flemming

    2001-01-01

    We found that five tested pesticides (the insecticide Dimethoat 40 EC, the herbicide Tolkan, and the fungicides Tilt 250 EC, Tilt Top, and Corbel) decreased the oxidation of atmospheric methane in slurries from a Danish forest soil. Dimethoat 40 EC was the most toxic with an EC50 value (i.......e. the concentration which caused a 50% inhibition of the methane oxidation) of 10 mg active ingredient (AI) l-1, followed by Tilt 250 EC (EC50=56 mg AI l-1). EC50 of Tilt Top was 350 AI mg l-1, the value of Tolkan was 410 mg AI l-1, while Corbel had a value of 1600 mg AI l-1. Dimethoat 40 EC and Tolkan inhibited...... the oxidation of atmospheric methane at concentrations expected in natural soil after application of the pesticides. Pesticides, therefore, may be partly responsible for the lowered methane oxidation rates in arable soils compared to forest soils....

  10. Conversion of Methane to Syngas by a Membrane-Based Oxidation-Reforming Process

    NARCIS (Netherlands)

    Chen, C.S.; Chen, Chusheng; Feng, Shao-Jie; Ran, S.; Zhu, Du-Chun; Liu, W.; Liu, Wei; Bouwmeester, Henricus J.M.

    2003-01-01

    Two processes in one space: Methane, the main component of natural gas, can be converted into syngas efficiently in a two-stage oxygen-permeable ceramic membrane reactor by means of integrated oxidation and reforming processes (see picture). This could be a cheaper alternative to the current steam-r

  11. Modelling the growth of methane-oxidizing bacteria in a fixed biofilm

    DEFF Research Database (Denmark)

    Bilbo, Carl Morten; Arvin, Erik; Holst, Helle

    1992-01-01

    Methane-oxidizing bacteria were grown in a fixed biofilm reactor in order to study their ability to degrade chlorinated aliphatic hydrocarbons. Focus is on the growth behaviour of the mixed culture. The growth is described by a model that includes methanotrophic bacteria in the active biomass...

  12. Spatial distribution and inhibition by ammonium of methane oxidation in intertidal freshwater marshes

    NARCIS (Netherlands)

    Van der Nat, F.J.; de Brouwer, J.F.C.; Middelburg, J.J.; Laanbroek, H.J.

    1997-01-01

    In two intertidal marshes, the vertical distribution in the sediment and inhibition by ammonium of methane oxidation were investigated by slurry incubation experiments. The two sites differ in their dominant vegetation type, i.e., reed and bulrush, and in their heights above sea level. The reed site

  13. Anaerobic oxidation of methane alters sediment records of sulfur, iron and phosphorus in the Black Sea

    NARCIS (Netherlands)

    Egger, M.J.; Kraal, P.; Jilbert, T.S.; Sulu-Gambari, F.A.; Sapart, C.J.; Roeckmann, T.; Slomp, C.P.

    2016-01-01

    The surface sediments in the Black Sea are underlain by extensive deposits of iron (Fe)-oxide-rich lake sediments that were deposited prior to the inflow of marine Mediterranean Sea waters ca. 9000 years ago. The subsequent downward diffusion of marine sulfate into the methane-bearing lake sediments

  14. Reaction scheme of partial oxidation of methane to synthesis gas over yttrium-stabilized zirconia

    NARCIS (Netherlands)

    Zhu, J.J.; van Ommen, J.G.; Lefferts, Leonardus

    2004-01-01

    The partial oxidation of methane to synthesis gas over yttrium-stabilized zirconia (YSZ) was studied with in situ FTIR and both steady-state and transient experiments. The four major products, CO, H2, CO2, and H2O, are primary products of CPOM over YSZ. Besides these major products and traces of

  15. Temperatures In Compost Landfill Covers As Result Of Methane Oxidation And Compost Respiration

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Merono, A. R.; Pedersen, Rasmus Broen

    2011-01-01

    This study investigated the influence of the temperature on methane (CH4) oxidation and respiration in compost sampled at a full scale biocover implemented at Klintholm landfill exhibiting high temperatures. Compost material was collected at Klintholm landfill and incubated with and without CH4...

  16. Emissions of methane and nitrous oxide from full-scale municipal wastewater treatment plants

    NARCIS (Netherlands)

    Daelman, M.R.J.

    2014-01-01

    Since 1750, the year that commonly marks the start of the Industrial Revolution, the atmospheric concentrations of carbon dioxide, methane and nitrous oxide have risen about 40 %, 150 % and 20 %, respectively, above the pre-industrial levels due to human activity (IPCC (2013) Climate Change 2013: Th

  17. Development of a novel reactor concept for the partial oxidation of methane to syngas

    NARCIS (Netherlands)

    Smit, J.; Sint Annaland, van M.; Kuipers, J.A.M.

    2004-01-01

    The gas-to-liquid process, consisting of the partial oxidation of methane (POM) followed by the Fischer-Tropsch reaction, is a promising alternative to conventional oil processing for the production of liquid fuels. The cost of a conventional POM process is mainly determined by cryogenic air separat

  18. Eddy covariance observations of methane and nitrous oxide emissions: Towards more accurate estimates from ecosystems

    NARCIS (Netherlands)

    Kroon-van Loon, P.S.

    2010-01-01

    About 30% of the increased greenhouse gas (GHG) emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are related to land use changes and agricultural activities. In order to select effective measures, knowledge is required about GHG emissions from these ecosystems and how these e

  19. Modelling of a reverse flow catalytic membrane reactor for the partial oxidation of methane

    NARCIS (Netherlands)

    Smit, J.; Sint Annaland, van M.; Kuipers, J.A.M.

    2003-01-01

    Gas-To-Liquid (GTL) processes have great potential as alternative to conventional oil and coal processing for the production of liquid fuels. In GTL-processes the partial oxidation of methane (POM) is combined with the Fischer-Tropsch reaction. An important part of the investment costs of a conventi

  20. Emissions of methane and nitrous oxide from full-scale municipal wastewater treatment plants

    NARCIS (Netherlands)

    Daelman, M.R.J.

    2014-01-01

    Since 1750, the year that commonly marks the start of the Industrial Revolution, the atmospheric concentrations of carbon dioxide, methane and nitrous oxide have risen about 40 %, 150 % and 20 %, respectively, above the pre-industrial levels due to human activity (IPCC (2013) Climate Change 2013:

  1. Temperature and moisture affect methane and nitrous oxide emission from bovine manure patches in tropical conditions

    NARCIS (Netherlands)

    Mazzetto, A.M.; Barneze, A.S.; Feigl, B.J.; Groenigen, van J.W.; Oenema, O.; Cerri, C.C.

    2014-01-01

    Animal production systems are important sources of greenhouse gases (GHG), especially methane (CH4) and nitrous oxide (N2O). Brazilian beef production is almost exclusively (more than 90%) pasture-based. GHG emissions from faeces deposited in pastures have been extensively studied in temperate clima

  2. Archaeal lipids in Mediterranean Cold Seeps: Molecular proxies for anaerobic methane oxidation

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Pancost, R.D.; Hopmans, E.C.

    2001-01-01

    We investigated the distributions and 13C values of biomarkers for Archaea associated with anaerobic methane oxidation in disparate settings throughout two Eastern Mediterranean mud dome fields. All major classes of archaeal lipids are present in the studied sediments, including isoprenoid glycerol

  3. Biogeochemical evidence that thermophilic Archaea mediate the anaerobic oxidation of methane

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Schouten, S.; Wakeham, S.G.; Hopmans, E.C.

    2003-01-01

    Distributions and isotopic analyses of lipids from sediment cores at a hydrothermally active site in the Guaymas Basin with a steep sedimentary temperature gradient revealed the presence of archaea that oxidize methane anaerobically. The presence of strongly 13C-depleted lipids at greater depths in

  4. Contemporary and projected biogenic fluxes of methane and nitrous oxide in North American terrestrial ecosystems

    Science.gov (United States)

    The importance of methane (CH4) and nitrous oxide (N2O) in determining global climate change has been increasingly recognized, but terrestrial CH4 and N2O budgets and the underlying mechanisms remain far from certain. Accurate estimation of terrestrial CH4 and N2O budgets would be a critical step fo...

  5. Multiple archaeal groups mediate methane oxidation in anoxic cold seep sediments.

    Science.gov (United States)

    Orphan, Victoria J; House, Christopher H; Hinrichs, Kai-Uwe; McKeegan, Kevin D; DeLong, Edward F

    2002-05-28

    No microorganism capable of anaerobic growth on methane as the sole carbon source has yet been cultivated. Consequently, information about these microbes has been inferred from geochemical and microbiological observations of field samples. Stable isotope analysis of lipid biomarkers and rRNA gene surveys have implicated specific microbes in the anaerobic oxidation of methane (AOM). Here we use combined fluorescent in situ hybridization and secondary ion mass spectrometry analyses, to identify anaerobic methanotrophs in marine methane-seep sediments. The results provide direct evidence for the involvement of at least two distinct archaeal groups (ANME-1 and ANME-2) in AOM at methane seeps. Although both archaeal groups often occurred in direct physical association with bacteria, they also were observed as monospecific aggregations and as single cells. The ANME-1 archaeal group more frequently existed in monospecific aggregations or as single filaments, apparently without a bacterial partner. Bacteria associated with both archaeal groups included, but were not limited to, close relatives of Desulfosarcina species. Isotopic analyses suggest that monospecific archaeal cells and cell aggregates were active in anaerobic methanotrophy, as were multispecies consortia. In total, the data indicate that the microbial species and biotic interactions mediating anaerobic methanotrophy are diverse and complex. The data also clearly show that highly structured ANME-2/Desulfosarcina consortia are not the sole entities responsible for AOM at marine methane seeps. Other microbial groups, including ANME-1 archaea, are capable of anaerobic methane consumption either as single cells, in monospecific aggregates, or in multispecies consortia.

  6. Electrochemical promotion of oxidative coupling of methane on platinum/polybenzimidazole catalyst

    DEFF Research Database (Denmark)

    Petrushina, Irina; Bandur, Viktor; Bjerrum, Niels

    2002-01-01

    The electrochemical promotion of catalytic methane oxidation was studied using a (CH4,O-2,Ar), Pt\\polybenzimidazole (PBI)-H3PO4\\Pt,(H-2,Ar) fuel cell at 135degreesC. It has been found that C2H2, CO2, and water are the main oxidation products. Without polarization the yield of C2H2 was 0.9% and th......The electrochemical promotion of catalytic methane oxidation was studied using a (CH4,O-2,Ar), Pt\\polybenzimidazole (PBI)-H3PO4\\Pt,(H-2,Ar) fuel cell at 135degreesC. It has been found that C2H2, CO2, and water are the main oxidation products. Without polarization the yield of C2H2 was 0...

  7. Direct partial oxidation of methane to methanol: Reaction zones and role of catalyst location

    Institute of Scientific and Technical Information of China (English)

    Qijian Zhang; Dehua He; Qiming Zhu

    2008-01-01

    Direct partial oxidation of methane to methanol was investigated in a specially designed reactor. Methanol yield of about 7%-8% was obtained in gas phase partial oxidation. It was proposed that the reactor could be divided into three reaction zones, namely pre-reaction zone, fierce reaction zone, and post-reaction zone, when the temperature was high enough to initiate a reaction. The oxidation of methane proceeded and was completed mostly in the fierce reaction zone. When the reactant mixture entered the post-reaction zone, only a small amount of produced methanol would bring about secondary reactions, because molecular oxygen had been exhausted in the fierce reaction zone. A catalyst, if necessary, should be placed either in the pre-reaction zone, to initiate a partial oxidation reaction at a lower temperature, or in the fierce reaction zone to control the homogeneous free radical reaction.

  8. Surface composition and catalytic activity of La-Fe mixed oxides for methane oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fengxiang [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China); Li, Zhanping [Analysis Center, Tsinghua University, Beijing 100084 (China); Ma, Hongwei [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China); Gao, Zhiming, E-mail: zgao@bit.edu.cn [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China)

    2015-10-01

    Graphical abstract: - Highlights: • The sample with La/Fe atomic ratio of 0.94 is single phase perovskite La{sub 0.94}FeO{sub 3−d}. • The excess ironic oxide exists on the surface of the perovskite crystallites. • La{sup 3+} ions are enriched on surface of the oxides even for the La{sub 0.68}Fe sample. - Abstract: Four La-Fe oxide samples with La/Fe atomic ratio y = 1.02 ∼ 0.68 (denoted as LayFe) were prepared by the citrate method. The samples had a decreased specific surface area with the La/Fe atomic ratio decreasing. XRD pattern proved that the sample La{sub 0.94}Fe is single phase perovskite La{sub 0.94}FeO{sub 3−d}. Phase composition of the samples was estimated by the Rietveld refinement method. XPS analyses indicate that La{sup 3+} ions are enriched on surface of crystallites for all the samples, and surface carbonate ions are relatively abundant on the samples La{sub 1.02}Fe and La{sub 0.94}Fe. Catalytic activity for methane oxidation per unit surface area of the samples is in the order of La{sub 0.68}Fe > La{sub 0.76}Fe > La{sub 0.94}Fe > La{sub 1.02}Fe both in the presence and in the absence of gaseous oxygen. A reason for this order would be the higher concentration of Fe{sup 3+} ion on the surface of the samples La{sub 0.68}Fe and La{sub 0.76}Fe.

  9. Evaluation of Methyl Fluoride and Dimethyl Ether as Inhibitors of Aerobic Methane Oxidation

    OpenAIRE

    Oremland, Ronald S.; Culbertson, Charles W.

    1992-01-01

    Methyl fluoride (MF) and dimethyl ether (DME) were effective inhibitors of aerobic methanotrophy in a variety of soils. MF and DME blocked consumption of CH4 as well as the oxidation of 14CH4 to 14CO2, but neither MF nor DME affected the oxidation of [14C]methanol or [14C]formate to 14CO2. Cooxidation of ethane and propane by methane-oxidizing soils was also inhibited by MF. Nitrification (ammonia oxidation) in soils was inhibited by both MF and DME. Production of N2O via nitrification was in...

  10. Effect of methanogenic substrates on anaerobic oxidation of methane and sulfate reduction by an anaerobic methanotrophic enrichment.

    KAUST Repository

    Meulepas, Roel J W

    2010-05-06

    Anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) is assumed to be a syntrophic process, in which methanotrophic archaea produce an interspecies electron carrier (IEC), which is subsequently utilized by sulfate-reducing bacteria. In this paper, six methanogenic substrates are tested as candidate-IECs by assessing their effect on AOM and SR by an anaerobic methanotrophic enrichment. The presence of acetate, formate or hydrogen enhanced SR, but did not inhibit AOM, nor did these substrates trigger methanogenesis. Carbon monoxide also enhanced SR but slightly inhibited AOM. Methanol did not enhance SR nor did it inhibit AOM, and methanethiol inhibited both SR and AOM completely. Subsequently, it was calculated at which candidate-IEC concentrations no more Gibbs free energy can be conserved from their production from methane at the applied conditions. These concentrations were at least 1,000 times lower can the final candidate-IEC concentration in the bulk liquid. Therefore, the tested candidate-IECs could not have been produced from methane during the incubations. Hence, acetate, formate, methanol, carbon monoxide, and hydrogen can be excluded as sole IEC in AOM coupled to SR. Methanethiol did inhibit AOM and can therefore not be excluded as IEC by this study.

  11. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    DEFF Research Database (Denmark)

    Mogensen, David; Grunwaldt, Jan-Dierk; Hendriksen, Peter Vang;

    2014-01-01

    The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC) have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were...... performed in the temperature range 600-800 degrees C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r proportional to P-CH4(0.7)). A simple model is presented which is capable of predicting the methane conversion...

  12. Oxidative Coupling of Methane over W-Mn/SiO2 Catalyst

    Institute of Scientific and Technical Information of China (English)

    李树本

    2001-01-01

    W-Mn/SiO2 catalyst has been developed in our laboratory (LICP), which is active, selective and stable for oxidative coupling of methane(OCM ) in fixed bed and fluidized bed reactors. The research resulis have been reproduced at different reaction conditions by two groups of J. H. Lunsford ( JHLL) from Texas A & M University and R. M. Lambert(RMLL) from University of Cambridge respectively.The ba sic research aspects on this catalyst systems, reaction performances, structure characterization and rcaction mechanism were reviewed. A model on two active sites related to W6+ /5+and Mn3+2+ has been suggested for activation of methane and oxygen respectively.

  13. Catalytic methanation reaction over supported nickel-rhodium oxide for purification of simulated natural gas

    Institute of Scientific and Technical Information of China (English)

    Wan Azelee Wan Abu Bakar; Rusmidah Ali; Susilawati Toemen

    2011-01-01

    In this research,new catalyst with high industrial impact is developed,which can catalyze the conversion of CO2 to methane through methanation reaction.A series of catalysts based on nickel oxide were prepared using wetness impregnation technique and ageing,followed by calcination at 400 ℃.Rh/Ni (30∶70)/Al2O3 catalyst was revealed as the most potential catalyst based on the results of catalytic activity measurementmonitored by Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography (GC).The results showed 90.1% CO2 conversion and 70.8% yield at 400 ℃.

  14. Surface Reaction Kinetics of Steam- and CO2-Reforming as Well as Oxidation of Methane over Nickel-Based Catalysts

    OpenAIRE

    Karla Herrera Delgado; Lubow Maier; Steffen Tischer; Alexander Zellner; Henning Stotz; Olaf Deutschmann

    2015-01-01

    An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented. The numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species. Reactions for the conversion of methane with oxygen, steam, and CO2 as well as methanation, water-gas shift reaction and carbon formation via Boudouard reaction are included. The mechanism is implemented i...

  15. Green chemistry perspectives of methane conversion via oxidative methylation of aromatics over zeolite catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Adebajo, M.O. [University of Queensland, St Lucia, Qld. (Australia)

    2007-06-15

    This paper provides a general overview of the recent work that we and other researchers have done on the utilisation of methane for catalytic methylation of aromatic compounds and for direct coal liquefaction for the production of liquid hydrocarbons. In particular, the paper presents a detailed description of more recent substantial experimental evidence that we have provided for the requirement of oxygen as a stoichiometry reactant for benzene methylation with methane over moderately acidic zeolite catalysts. The reaction, which has been termed 'oxidative methylation', was thus postulated to involve a two-step mechanism involving intermediate methanol formation by methane partial oxidation, followed by benzene methylation with methanol in the second step. However, strongly acidic zeolites can cause cracking of benzene to yield methylated products in the absence of oxygen. The participation of methane and oxygen, and the effective use of zeolite catalysts in this methylation reaction definitely have some positive green chemistry implications. Thus, the results of these previous studies are also discussed in this review in light of the principles and tools of green chemistry. Various metrics were used to evaluate the greenness, cost-effectiveness, and material and energy efficiency of the oxidative methylation reaction.

  16. The Apparent Involvement of ANMEs in Mineral Dependent Methane Oxidation, as an Analog for Possible Martian Methanotrophy

    Directory of Open Access Journals (Sweden)

    Victoria J. Orphan

    2011-11-01

    Full Text Available On Earth, marine anaerobic methane oxidation (AOM can be driven by the microbial reduction of sulfate, iron, and manganese. Here, we have further characterized marine sediment incubations to determine if the mineral dependent methane oxidation involves similar microorganisms to those found for sulfate-dependent methane oxidation. Through FISH and FISH-SIMS analyses using 13C and 15N labeled substrates, we find that the most active cells during manganese dependent AOM are primarily mixed and mixed-cluster aggregates of archaea and bacteria. Overall, our control experiment using sulfate showed two active bacterial clusters, two active shell aggregates, one active mixed aggregate, and an active archaeal sarcina, the last of which appeared to take up methane in the absence of a closely-associated bacterial partner. A single example of a shell aggregate appeared to be active in the manganese incubation, along with three mixed aggregates and an archaeal sarcina. These results suggest that the microorganisms (e.g., ANME-2 found active in the manganese-dependent incubations are likely capable of sulfate-dependent AOM. Similar metabolic flexibility for Martian methanotrophs would mean that the same microbial groups could inhabit a diverse set of Martian mineralogical crustal environments. The recently discovered seasonal Martian plumes of methane outgassing could be coupled to the reduction of abundant surface sulfates and extensive metal oxides, providing a feasible metabolism for present and past Mars. In an optimistic scenario Martian methanotrophy consumes much of the periodic methane released supporting on the order of 10,000 microbial cells per cm2 of Martian surface. Alternatively, most of the methane released each year could be oxidized through an abiotic process requiring biological methane oxidation to be more limited. If under this scenario, 1% of this methane flux were oxidized by biology in surface soils or in subsurface aquifers (prior to

  17. Competitive interactions between methane- and ammonia-oxidizing bacteria modulate carbon and nitrogen cycling in paddy soil

    Directory of Open Access Journals (Sweden)

    Y. Zheng

    2014-03-01

    Full Text Available Pure culture studies have demonstrated that methanotrophs and ammonia oxidizers can both carry out the oxidation of methane and ammonia. However, the expected interactions resulting from these similarities are poorly understood, especially in complex, natural environments. Using DNA-based stable isotope probing and pyrosequencing of 16S rRNA and pmoA genes, we report on biogeochemical and molecular evidence for growth stimulation of methanotrophic communities by ammonium fertilization, and that methane modulates nitrogen cycling by competitive inhibition of nitrifying communities in a rice paddy soil. Pairwise comparison between microcosms amended with CH4, CH4+Urea, and Urea indicated that urea fertilization stimulated methane oxidation activity by 6-fold during a 19 day incubation period, while ammonia oxidation activity was significantly inhibited in the presence of CH4. Pyrosequencing of the total 16S rRNA genes revealed that urea amendment resulted in rapid growth of Methylosarcina-like type Ia MOB, and nitrifying communities appeared to be suppressed by methane. High-throughput sequencing of the 13C-labeled DNA further revealed that methane amendment resulted in clear growth of Methylosarcina-related MOB while methane plus urea led to equal increase in Methylosarcina and Methylobacter-related MOB, indicating the differential growth requirements of representatives of these genera. Strikingly, type Ib MOB did not respond to methane nor to urea. Increase in 13C-assimilation by microorganisms related to methanol oxidizers clearly indicated carbon transfer from methane oxidation to other soil microbes, which was enhanced by urea addition. The active growth of type Ia methanotrops was significantly stimulated by urea amendment, and the pronounced growth of methanol-oxidizing bacteria occurred in CH4-treated microcosms only upon urea amendment. Methane addition inhibited the growth of Nitrosospira and Nitrosomonas in urea-amended microcosms, in

  18. Direct methane solid oxide fuel cells based on catalytic partial oxidation enabling complete coking tolerance of Ni-based anodes

    Science.gov (United States)

    Lee, Daehee; Myung, Jaeha; Tan, Jeiwan; Hyun, Sang-Hoon; Irvine, John T. S.; Kim, Joosun; Moon, Jooho

    2017-03-01

    Solid oxide fuel cells (SOFCs) can oxidize diverse fuels by harnessing oxygen ions. Benefited by this feature, direct utilization of hydrocarbon fuels without external reformers allows for cost-effective realization of SOFC systems. Superior hydrocarbon reforming catalysts such as nickel are required for this application. However, carbon coking on nickel-based anodes and the low efficiency associated with hydrocarbon fueling relegate these systems to immature technologies. Herein, we present methane-fueled SOFCs operated under conditions of catalytic partial oxidation (CPOX). Utilizing CPOX eliminates carbon coking on Ni and facilitates the oxidation of methane. Ni-gadolinium-doped ceria (GDC) anode-based cells exhibit exceptional power densities of 1.35 W cm-2 at 650 °C and 0.74 W cm-2 at 550 °C, with stable operation over 500 h, while the similarly prepared Ni-yttria stabilized zirconia anode-based cells exhibit a power density of 0.27 W cm-2 at 650 °C, showing gradual degradation. Chemical analyses suggest that combining GDC with the Ni anode prevents the oxidation of Ni due to the oxygen exchange ability of GDC. In addition, CPOX operation allows the usage of stainless steel current collectors. Our results demonstrate that high-performance SOFCs utilizing methane CPOX can be realized without deterioration of Ni-based anodes using cost-effective current collectors.

  19. Final report for the Iowa Livestock Industry Waste Characterization and Methane Recovery Information Dissemination Project

    Energy Technology Data Exchange (ETDEWEB)

    Garrison, M.V.; Richard, Thomas L

    2001-11-13

    This report summarizes analytical methods, characterizes Iowa livestock wastes, determines fossil fuel displacement by methane use, assesses the market potential, and offers recommendations for the implementation of methane recovery technologies.

  20. Methane drainage with horizontal boreholes in advance of longwall mining: an analysis. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Gabello, D.P.; Felts, L.L.; Hayoz, F.P.

    1981-05-01

    The US Department of Energy (DOE) Morgantown Energy Technology Center has implemented a comprehensive program to demonstrate the technical and economic viability of coalbed methane as an energy resource. The program is directed toward solution of technical and institutional problems impeding the recovery and use of large quantities of methane contained in the nation's minable and unminable coalbeds. Conducted in direct support of the DOE Methane Recovery from Coalbeds Project, this study analyzes the economic aspects of a horizontal borehole methane recovery system integrated as part of a longwall mine operation. It establishes relationships between methane selling price and annual mine production, methane production rate, and the methane drainage system capital investment. Results are encouraging, indicating that an annual coal production increase of approximately eight percent would offset all associated drainage costs over the range of methane production rates and capital investments considered.

  1. Performance comparison between partial oxidation and methane steam for SOFC micro-CHP systems

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Olesen, Anders Christian; Nielsen, Mads Pagh;

    2011-01-01

    The aim of this research work is to describe in qualitative and quantitative form the performance of a micro Combined Heat and Power system for residential application based on Solid Oxide Fuel Cell fueled by natural gas with two different types of pre-reforming systems, namely Steam Reforming...... and Partial Oxidation and recirculation of anode and cathode gas. The comparative analysis among the different configurations will lead us to conclude that maximum efficiency is achieved when cathode and anode gas recirculation are used along with steam methane reforming. Further Steam Methane Reforming...... process produces a higher electrical system efficiency compared to Partial oxidation reforming process. Efficiency is affected when running the system in part load mode mainly due to heat loss, additional natural gas supplied to the burner to satisfy the required heat demand inside the system, and ejector...

  2. Partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor

    KAUST Repository

    Zhang, Xuming

    2015-01-01

    We studied the relative importance of the reduced field intensity and the background reaction temperature in the partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor. We obtained important mechanistic insight from studying high-temperature and low-pressure conditions with similar reduced field intensities. In the tested range of background temperatures (297 < T < 773 K), we found that the conversion of methane and oxygen depended on both the electron-induced chemistry and the thermo-chemistry, whereas the chemical pathways to the products were overall controlled by the thermo-chemistry at a given temperature. We also found that the thermo-chemistry enhanced the plasma-assisted partial oxidation process. Our findings expand our understanding of the plasma-assisted partial oxidation process and may be helpful in the design of cost-effective plasma reformers. © 2014 The Combustion Institute.

  3. Predominant contribution of syntrophic acetate oxidation to thermophilic methane formation at high acetate concentrations.

    Science.gov (United States)

    Hao, Li-Ping; Lü, Fan; He, Pin-Jing; Li, Lei; Shao, Li-Ming

    2011-01-15

    To quantify the contribution of syntrophic acetate oxidation to thermophilic anaerobic methanogenesis under the stressed condition induced by acidification, the methanogenic conversion process of 100 mmol/L acetate was monitored simultaneously by using isotopic tracing and selective inhibition techniques, supplemented with the analysis of unculturable microorganisms. Both quantitative methods demonstrated that, in the presence of aceticlastic and hydrogenotrophic methanogens, a large percentage of methane (up to 89%) was initially derived from CO(2) reduction, indicating the predominant contribution of the syntrophic acetate oxidation pathway to acetate degradation at high acid concentrations. A temporal decrease of the fraction of hydrogenotrophic methanogenesis from more than 60% to less than 40% reflected the gradual prevalence of the aceticlastic methanogenesis pathway along with the reduction of acetate. This apparent discrimination of acetate methanization pathways highlighted the importance of the syntrophic acetate-oxidizing bacteria to initialize methanogenesis from high organic loadings.

  4. A silica-immobilized pt2+catalyst for the selective, aerobic oxidation of methane via an electron-transfer chain

    Institute of Scientific and Technical Information of China (English)

    Zengjian An; Xiulian Pan; Xiumei Liu; Xiuwen Han; Xinhe Bao

    2008-01-01

    The combination of Pt2+, benzoquinone and NaNO2 forms an electron-transfer chain, which leads to the oxidation of methane by O2 in CF3COOH aqueous solution. The overall turnover number per hour (TOF) of methane at 120 ℃ is 0.5 h-1, however, only about one fourth (23%) of methane is converted to the desired product of methanol in the formation of CF3COOCH3. The over-oxidation of methane to CO2, over the catalyst with the Pt2+ species immobilized via 2,2'-bipyridyl as a ligand on the silica substrate, is depressed distinctly. Under the same conditions, the conversion to methanol dominates, and no CO2 is observed, on account of the over-oxidation of methane, as confirmed by the isotope experiment.

  5. Investigation on the Performance of Supported Molybdenum Carbide for the Partial Oxidation of Methane

    Institute of Scientific and Technical Information of China (English)

    Quanli Zhu; Jian Yang; Jiaxin Wang; Shengfu Ji; Hanqing Wang

    2003-01-01

    The performance of supported and unsupported molybdenum carbide for the partial oxida-tion of methane (POM) to syngas was investigated. An evaluation of the catalysts indicates that bulkmolybdenum carbide has a higher methane conversion during the initial stage but a lower selectivity toCO and H2/CO ratio in the products. The rapid deactivation of the catalyst is also a significant problem.However, the supported molybdenum carbide catalyst shows a much higher methane conversion, increasedselectivity and significantly improved catalytic stability. The characterization by XRD and BET specificarea measurements depict an improved dispersion of molybdenum carbide when using alumina as a carrier.The bulk or the supported molybdenum carbide exists in the β-Mo2C phase, while it is transformed intomolybdenum dioxide postcatalysis which is an important cause of molybdenum carbide deactivation.

  6. Development of vanadium-phosphate catalysts for methanol production by selective oxidation of methane

    Energy Technology Data Exchange (ETDEWEB)

    McCormick, R.L. [Colorado School of Mines, Golden, CO (United States)

    1995-12-31

    The United States has vast natural gas reserves which could contribute significantly to our energy security if economical technologies for conversion to liquid fuels and chemicals were developed. Many of these reserves are small scale or in remote locations and of little value unless they can be transported to consumers. Transportation is economically performed via pipeline, but this route is usually unavailable in remote locations. Another option is to convert the methane in the gas to liquid hydrocarbons, such as methanol, which can easily and economically be transported by truck. Therefore, the conversion of methane to liquid hydrocarbons has the potential to decrease our dependence upon oil imports by opening new markets for natural gas and increasing its use in the transportation and chemical sectors of the economy. In this project, we are attempting to develop, and explore new catalysts capable of direct oxidation of methane to methanol. The specific objectives of this work are discussed.

  7. The effect of widespread early aerobic marine ecosystems on methane cycling and the Great Oxidation

    Science.gov (United States)

    Daines, Stuart J.; Lenton, Timothy M.

    2016-01-01

    The balance of evidence suggests that oxygenic photosynthesis had evolved by 3.0-2.7 Ga, several hundred million years prior to the Great Oxidation ≈2.4 Ga. Previous work has shown that if oxygenic photosynthesis spread globally prior to the Great Oxidation, this could have supported widespread aerobic ecosystems in the surface ocean, without oxidising the atmosphere. Here we use a suite of models to explore the implications for carbon cycling and the Great Oxidation. We find that recycling of oxygen and carbon within early aerobic marine ecosystems would have restricted the balanced fluxes of methane and oxygen escaping from the ocean, lowering the atmospheric concentration of methane in the Great Oxidation transition and its aftermath. This in turn would have minimised any bi-stability of atmospheric oxygen, by weakening a stabilising feedback on oxygen from hydrogen escape to space. The result would have been a more reversible and probably episodic rise of oxygen at the Great Oxidation transition, consistent with existing geochemical evidence. The resulting drop in methane levels to ≈10 ppm is consistent with climate cooling at the time but adds to the puzzle of what kept the rest of the Proterozoic warm. A key test of the scenario of abundant methanotrophy in oxygen oases before the Great Oxidation is its predicted effects on the organic carbon isotope (δ13Corg) record. Our open ocean general circulation model predicts δC13org ≈ - 30 to -45‰ consistent with most data from 2.65 to 2.45 Ga. However, values of δC13org ≈ - 50 ‰ require an extreme scenario such as concentrated methanotroph production where shelf-slope upwelling of methane-rich water met oxic shelf water.

  8. Degradation kinetics of chlorinated aliphatic hydrocarbons by methane oxidizers naturally-associated with wetland plant roots

    Science.gov (United States)

    Powell, C. L.; Goltz, M. N.; Agrawal, A.

    2014-12-01

    Chlorinated aliphatic hydrocarbons (CAHs) are common groundwater contaminants that can be removed from the environment by natural attenuation processes. CAH biodegradation can occur in wetland environments by reductive dechlorination as well as oxidation pathways. In particular, CAH oxidation may occur in vegetated wetlands, by microorganisms that are naturally associated with the roots of wetland plants. The main objective of this study was to evaluate the cometabolic degradation kinetics of the CAHs, cis-1,2-dichloroethene (cisDCE), trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1TCA), by methane-oxidizing bacteria associated with the roots of a typical wetland plant in soil-free system. Laboratory microcosms with washed live roots investigated aerobic, cometabolic degradation of CAHs by the root-associated methane-oxidizing bacteria at initial aqueous [CH4] ~ 1.9 mg L- 1, and initial aqueous [CAH] ~ 150 μg L- 1; cisDCE and TCE (in the presence of 1,1,1TCA) degraded significantly, with a removal efficiency of approximately 90% and 46%, respectively. 1,1,1TCA degradation was not observed in the presence of active methane oxidizers. The pseudo first-order degradation rate-constants of TCE and cisDCE were 0.12 ± 0.01 and 0.59 ± 0.07 d- 1, respectively, which are comparable to published values. However, their biomass-normalized degradation rate constants obtained in this study were significantly smaller than pure-culture studies, yet they were comparable to values reported for biofilm systems. The study suggests that CAH removal in wetland plant roots may be comparable to processes within biofilms. This has led us to speculate that the active biomass may be on the root surface as a biofilm. The cisDCE and TCE mass losses due to methane oxidizers in this study offer insight into the role of shallow, vegetated wetlands as an environmental sink for such xenobiotic compounds.

  9. Degradation kinetics of chlorinated aliphatic hydrocarbons by methane oxidizers naturally-associated with wetland plant roots.

    Science.gov (United States)

    Powell, C L; Goltz, M N; Agrawal, A

    2014-12-01

    Chlorinated aliphatic hydrocarbons (CAHs) are common groundwater contaminants that can be removed from the environment by natural attenuation processes. CAH biodegradation can occur in wetland environments by reductive dechlorination as well as oxidation pathways. In particular, CAH oxidation may occur in vegetated wetlands, by microorganisms that are naturally associated with the roots of wetland plants. The main objective of this study was to evaluate the cometabolic degradation kinetics of the CAHs, cis-1,2-dichloroethene (cisDCE), trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1TCA), by methane-oxidizing bacteria associated with the roots of a typical wetland plant in soil-free system. Laboratory microcosms with washed live roots investigated aerobic, cometabolic degradation of CAHs by the root-associated methane-oxidizing bacteria at initial aqueous [CH4] ~1.9mgL(-1), and initial aqueous [CAH] ~150μgL(-1); cisDCE and TCE (in the presence of 1,1,1TCA) degraded significantly, with a removal efficiency of approximately 90% and 46%, respectively. 1,1,1TCA degradation was not observed in the presence of active methane oxidizers. The pseudo first-order degradation rate-constants of TCE and cisDCE were 0.12±0.01 and 0.59±0.07d(-1), respectively, which are comparable to published values. However, their biomass-normalized degradation rate constants obtained in this study were significantly smaller than pure-culture studies, yet they were comparable to values reported for biofilm systems. The study suggests that CAH removal in wetland plant roots may be comparable to processes within biofilms. This has led us to speculate that the active biomass may be on the root surface as a biofilm. The cisDCE and TCE mass losses due to methane oxidizers in this study offer insight into the role of shallow, vegetated wetlands as an environmental sink for such xenobiotic compounds.

  10. Distribution and activity of methane-oxidizing bacteria in a polluted, stratified lake.

    Science.gov (United States)

    Fisher, M. C.; Udert, K.; Gschwend, P. M.; Cavanaugh, C. M.

    2006-12-01

    Methanotrophs are of global significance in their role as a major biological sink for methane, a greenhouse gas, and are metabolically active where methane and oxygen co-occur. Lake Mishawum in Woburn, MA, is a shallow, permanently stratified lake with a highly saline, anoxic hypolimnion rich in methane and organic pollutants, an oxic epilimnion and an interface between these layers, the metalimnion. This unique stratification is maintained because the bottom water continually receives inputs of salty, polluted groundwater while the upper layer is fed by rainwater runoff and a fast moving brook. Based upon observed decreases in methane and oxygen in metalimnion waters and geochemical modeling of the lake, methanotrophs were hypothesized to play a significant role in methane oxidation at the oxic-anoxic interface of the metalinion and to be found in greatest number at this junction between methane and oxygen. To test this hypothesis, the abundance of methanotrophs in epilimnion, metalimnion and hypolimnion of Lake Mishawum was investigated. Quantitative PCR (QPCR) studies in which the methanol dehydrogenase gene of either Type I or Type II methanotrophs was amplified showed that their populations were in fact similar in number through out the depth of the water column. Fluorescence in situ hybridization (FISH) studies confirmed the presence of methanotrophs in each layer. However, 16S rRNA hybridization studies showed that methanotrophs in the metalimnion and epilimnion have 2-3X greater rRNA content than those in the hypolimnion. These results suggest that methanotrophs are most active in the oxygenate zones of the lake, particulary in the metalimnion where the presence of methane and oxygen allows them to actively metabolize and proliferate. Furthermore, it suggests that the activity of bacteria and not necessarily the number of these populations is the more important variable in assessing the significance of these bacteria in this ecosystem.

  11. Quantitative analysis of anaerobic oxidation of methane (AOM) in marine sediments: A modeling perspective

    Science.gov (United States)

    Regnier, P.; Dale, A. W.; Arndt, S.; LaRowe, D. E.; Mogollón, J.; Van Cappellen, P.

    2011-05-01

    Recent developments in the quantitative modeling of methane dynamics and anaerobic oxidation of methane (AOM) in marine sediments are critically reviewed. The first part of the review begins with a comparison of alternative kinetic models for AOM. The roles of bioenergetic limitations, intermediate compounds and biomass growth are highlighted. Next, the key transport mechanisms in multi-phase sedimentary environments affecting AOM and methane fluxes are briefly treated, while attention is also given to additional controls on methane and sulfate turnover, including organic matter mineralization, sulfur cycling and methane phase transitions. In the second part of the review, the structure, forcing functions and parameterization of published models of AOM in sediments are analyzed. The six-orders-of-magnitude range in rate constants reported for the widely used bimolecular rate law for AOM emphasizes the limited transferability of this simple kinetic model and, hence, the need for more comprehensive descriptions of the AOM reaction system. The derivation and implementation of more complete reaction models, however, are limited by the availability of observational data. In this context, we attempt to rank the relative benefits of potential experimental measurements that should help to better constrain AOM models. The last part of the review presents a compilation of reported depth-integrated AOM rates (ΣAOM). These rates reveal the extreme variability of ΣAOM in marine sediments. The model results are further used to derive quantitative relationships between ΣAOM and the magnitude of externally impressed fluid flow, as well as between ΣAOM and the depth of the sulfate-methane transition zone (SMTZ). This review contributes to an improved understanding of the global significance of the AOM process, and helps identify outstanding questions and future directions in the modeling of methane cycling and AOM in marine sediments.

  12. Anaerobic oxidation of methane in coastal sediment from Guishan Island (Pearl River Estuary), South China Sea

    Indian Academy of Sciences (India)

    Zijun Wu; Huaiyang Zhou; Xiaotong Peng; Nan Jia; Yuhong Wang; Linxi Yuan

    2008-12-01

    The concentrations of CH4, SO$^{2−}_{4}$, CO2 and the carbon isotope compositions of CO2 and CH4 in the pore-water of the GS sedimentary core collected from Guishan Island (Pearl River Estuary), South China Sea,were determined. The methane concentration in the pore-water shows dramatic changes and sulfate concentration gradients are linear at the base of the sulfate reduction zone for the station. The carbon isotope of methane becomes heavier at the sulfate-methane transition (SMT)likely because of the Raleigh distillation effect; 12CH4 was oxidized faster than 13CH4 and this caused the enrichment of residual methane 13C and 13C- CO2 minimum. The geochemical profiles of the pore-water support the existence of anaerobic oxidation of methane (AOM), which is mainly controlled by the quality and quantity of the sedimentary organic matter. As inferred from the index of 13C-TOC value and TOC/TN ratio, the organic matter is a mix of mainly refractory terrestrial component plus some labile alga marine-derived in the study area. A large amount of labile organic matter (mainly labile alga marine-derived) is consumed via the process of sedimentary organic matter diagenesis, and this reduces the amount of labile organic matter incorporated into the base of the sulfate reduction zone. Due to the scarcity of labile organic matter, the sulfate will in turn be consumed by its reaction with methane and therefore AOM takes place.Based on a diffussion model, the portion of pore-water sulfate reduction via AOM is 58.6%,and the percentage of CO2 in the pore-water derived from AOM is 41.4%. Thus, AOM plays an important role in the carbon and sulfur cycling in the marine sediments of Pearl River Estuary.

  13. Differential methane oxidation activity and microbial community composition at cold seeps in the Arctic off western Svalbard

    Science.gov (United States)

    Gründger, Friederike; Svenning, Mette M.; Niemann, Helge; Silyakova, Anna; Serov, Pavel; Li Hong, Wei; Wegener, Gunter; Panieri, Giuliana; Carroll, JoLynn

    2016-04-01

    Most models considering climate change related bottom water warming suggest that gas hydrates may become destabilized, leading to the mobilization of methane into seabed and water column ecosystems, and, eventually, into the atmosphere. However, the capacity of methanotrophic microbes retaining methane in sediments and the hydrosphere is not well constrained. Here, we investigate the microbial utilization of methane in sediments and the water column, focusing on cold seeps discovered at the arctic continental margin of western Svalbard. We measured ex situ rates of methane oxidation and sulfate reduction in two active gas flare sites with different geological settings at the Vestnesa Ridge (1204 m water depth) and within a pingolike feature area southwest off Svalbard (PLF; 380 m water depth). Our results show contrarily situations at our two sampling sites: At Vestnesa Ridge we find high methane oxidation rates with values up to 2055 nmol cm-3 d-1 at the sediment surface where the sediments are oversaturated with methane. Whereas, methane concentration and oxidation rates are low in the overlying water column (2 pmol cm-3 d-1). In contrast, at the sediment surface at PLF methane concentration and oxidation rates are considerably lower (up to 1.8 nmol cm-3 d-1). While the overlying bottom water contains high concentration of methane and shows oxidation rates with values of up to 3.8 nmol cm-3 d-1. The data on methane oxidation and sulfate reduction activity are compared to the sediment geochemistry and to data from metagenomic analysis identifying the methanotrophic community composition. These results provide unique insight into the dynamic responses of the seabed biological filter at cold seeps in the Arctic off western Svalbard. This study is part of the Centre for Arctic Gas Hydrate, Environment and Climate and was supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259.

  14. Microbial diversity and community structure of a highly active anaerobic methane-oxidizing sulfate-reducing enrichment

    NARCIS (Netherlands)

    Jagersma, C.G.; Meulepas, R.J.W.; Heikamp-de Jong, G.A.M.; Gieteling, J.; Klimiuk, A.; Schouten, S.; Sinninghe Damsté, J.S.; Lens, P.N.L.; Stams, A.J.M.

    2009-01-01

    Summary Anaerobic oxidation of methane (AOM) is an important methane sink in the ocean but the microbes responsible for AOM are as yet resilient to cultivation. Here we describe the microbial analysis of an enrichment obtained in a novel submerged-membrane bioreactor system and capable of high-rate

  15. Anaerobic oxidation of methane alters sediment records of sulfur, iron and phosphorus in the Black Sea

    Science.gov (United States)

    Egger, Matthias; Kraal, Peter; Jilbert, Tom; Sulu-Gambari, Fatimah; Sapart, Célia J.; Röckmann, Thomas; Slomp, Caroline P.

    2016-09-01

    The surface sediments in the Black Sea are underlain by extensive deposits of iron (Fe)-oxide-rich lake sediments that were deposited prior to the inflow of marine Mediterranean Sea waters ca. 9000 years ago. The subsequent downward diffusion of marine sulfate into the methane-bearing lake sediments has led to a multitude of diagenetic reactions in the sulfate-methane transition zone (SMTZ), including anaerobic oxidation of methane (AOM) with sulfate. While the sedimentary cycles of sulfur (S), methane and Fe in the SMTZ have been extensively studied, relatively little is known about the diagenetic alterations of the sediment record occurring below the SMTZ.Here we combine detailed geochemical analyses of the sediment and porewater with multicomponent diagenetic modeling to study the diagenetic alterations below the SMTZ at two sites in the western Black Sea. We focus on the dynamics of Fe, S and phosphorus (P), and demonstrate that diagenesis has strongly overprinted the sedimentary burial records of these elements. In line with previous studies in the Black Sea, we show that sulfate-mediated AOM substantially enhances the downward diffusive flux of sulfide into the deep limnic deposits. During this downward sulfidization, Fe oxides, Fe carbonates and Fe phosphates (e.g., vivianite) are converted to sulfide phases, leading to an enrichment in solid-phase S and the release of phosphate to the porewater. Below the sulfidization front, high concentrations of dissolved ferrous Fe (Fe2+) lead to sequestration of downward-diffusing phosphate as authigenic vivianite, resulting in a transient accumulation of total P directly below the sulfidization front.Our model results further demonstrate that downward-migrating sulfide becomes partly re-oxidized to sulfate due to reactions with oxidized Fe minerals, fueling a cryptic S cycle and thus stimulating slow rates of sulfate-driven AOM ( ˜ 1-100 pmol cm-3 d-1) in the sulfate-depleted limnic deposits. However, this process is

  16. Rule of 100: An inherent limitation or performance measure in oxidative coupling of methane?

    Institute of Scientific and Technical Information of China (English)

    Saeed Sahebdelfar; Maryam Takht Ravanchi; Mahtab Gharibi; Marzieh Hamidzadeh

    2012-01-01

    The oxidative coupling of methane over La2O3/CaO type-catalyst in a fixed-bed reactor is studied under a wide range of operating conditions (973<T< 1103 K,55< Ptotal <220 kPa,and 3.7< mcat/VSTP <50 kg·s/m3).A ten-step kinetic model incorporating all main products was used to predict the behavior of the system.Methane conversions and C2 selectivities were calculated by varying methane to oxygen ratios in the feed under different operating conditions which were also compared with the rule of 100.The results show that deviation from this rule depends on the operating conditions.Within the range studied,an increase in pressure,temperature and contact time results in smaller deviation from the rule.This rule is best approximated when the catalyst operates near its optimal performance.For negative deviations,common to the most catalysts,it is found that the optimal performance should occur at methane conversion levels lower than 50%.A plot of selectivity versus conversion for high-yield reported performance data of a large variety of catalysts shows that data points concentrated roughly in 20%-50% methane conversion region,confirning the generality and prediction of modeling.

  17. Ce-Fe-O mixed oxide as oxygen carrier for the direct partial oxidation of methane to syngas

    Institute of Scientific and Technical Information of China (English)

    魏永刚; 王华; 李孔斋

    2010-01-01

    The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...

  18. Response of Atmospheric-Methane Oxidation to Methane-Flux Manipulation in a Laboratory Soil-Column Experiment

    Science.gov (United States)

    Schroth, M. H.; Mignola, I.; Henneberger, R.

    2015-12-01

    Upland soils are an important sink for atmospheric methane (CH4). Uptake of atmospheric CH4 in soils is generally diffusion limited, and is mediated by aerobic CH4 oxidizing bacteria (MOB) that possess a high-affinity form of a key enzyme, allowing CH4 consumption at near-atmospheric concentrations (≤ 1.9 µL/L). As cultivation attempts for these high-affinity MOB have shown little success, there remains much speculation regarding their functioning in different environments. For example, it is frequently assumed that they are highly sensitive to physical disturbance, but their response in activity and abundance to changes in substrate availability remains largely unknown. We present results of a laboratory column experiment conducted to investigate the response in activity and abundance of high-affinity MOB to an increase in CH4 flux. Intact soil cores, collected at a field site where atmospheric CH4 oxidation activity is frequently quantified, were transferred into two 1-m-long, 12-cm-dia. columns. The columns were operated at constant temperature in the dark, their headspace being continuously flushed with air. Diffusive gas-transport conditions were maintained in the reference column, whereas CH4 flux was increased in several steps in the treatment column by inducing advective gas flow using a diaphragm pump. Soil-gas samples periodically collected from ports installed along the length of the columns were analyzed for CH4 content. Together with measurements of soil-water content, atmospheric CH4 oxidation was quantified using the soil-profile method. First results indicate that atmospheric CH4 oxidation activity comparable with the field was maintained in the reference column throughout the experiment. Moreover, high-affinity MOB quickly adjusted to an increase in CH4 flux in the treatment column, efficiently consuming CH4. Quantification of MOB abundance is currently ongoing. Our data provide new insights into controls on atmospheric CH4 oxidation in soils.

  19. Catalytic Reaction Synthesis for the Partial Oxidation of Methane to Formaldehyde.

    Science.gov (United States)

    Cardenas-Galindo, Maria-Guadalupe

    Catalytic reaction synthesis for the partial oxidation of methane to formaldehyde has been studied by combining microkinetic analysis with molecular orbital calculations. This strategy is used to establish microscopic correlations between the structure and composition of the active site and the kinetic parameters of the reaction mechanism. Using atom clusters to represent the active site of transition metal oxide catalysts, the relationship was probed between coordination number, oxidation state, and ionization potential of the active cation and the reaction steps of methane activation and surface reactions leading to formaldehyde formation. The analysis suggests that in transition metal oxide catalysts, the d-band orbitals of the metal cation should be empty, since otherwise CO_2 formation from CO oxidation will be excessive. Furthermore, the transition metal oxide d-band must be located at sufficiently low energy that it may accept electrons during methane activation. Oxygen O- species, representing vacancies in the 2p cluster band, will favor methane activation. However, clusters with fully occupied 2p bands (O^ {2-}^ecies) will favor formaldehyde production. Such inferences illustrate how experimental and theoretical information already incorporated into an existing microkinetic model for the reaction over V _2O_5 and MoO _3 catalysts can be extended to describe the reaction over new materials in the search for more active and selective catalysts. Using parameters estimated from the molecular orbital calculations, microkinetic reaction simulations were also shown to be useful to identify reactor operating conditions that may favor the production of formaldehyde. The simulation can be used to identify key experiments necessary to test the performance of postulated catalytic materials. The economic evaluation of the process design sets important target goals for methane conversion and formaldehyde selectivity that a catalytic material must satisfy to create a new

  20. A novel thermophilic methane-oxidizing bacteria from thermal springs of Uzon volcano caldera, Kamchatka

    Science.gov (United States)

    Dvorianchikova, E.; Kizilova, A.; Kravchenko, I.; Galchenko, V.

    2012-04-01

    Methane is a radiatively active trace gas, contributing significantly to the greenhouse effect. It is 26 times more efficient in absorbing and re-emitting infrared radiation than carbon dioxide. Methanotrophs play an essential role in the global carbon cycle by oxidizing 50-75% of the biologically produced methane in situ, before it reaches the atmosphere. Methane-oxidizing bacteria are isolated from the various ecosystems and described at present. Their biology, processes of methane oxidation in fresh-water, marsh, soil and marine habitats are investigated quite well. Processes of methane oxidation in places with extreme physical and chemical conditions (high or low , salinity and temperature values) are studied in much smaller degree. Such ecosystems occupy a considerable part of the Earth's surface. The existence of aerobic methanotrophs inhabiting extreme environments has been verified so far by cultivation experiments and direct detection of methane monooxygenase genes specific to almost all aerobic methanotrophs. Thermophilic and thermotolerant methanotrophs have been isolated from such extreme environments and consist of the gammaproteobacterial (type I) genera Methylothermus, Methylocaldum, Methylococcus and the verrucomicrobial genus Methylacidiphilum. Uzon volcano caldera is a unique area, where volcanic processes still happen today. Hydrothermal springs of the area are extreme ecosystems which microbial communities represent considerable scientific interest of fundamental and applied character. A thermophilic aerobic methane-oxidising bacterium was isolated from a sediment sample from a hot spring (56.1; 5.3) of Uzon caldera. Strain S21 was isolated using mineral low salt medium. The headspace gas was composed of CH4, Ar, CO2, and O2 (40:40:15:5). The temperature of cultivation was 50, pH 5.5. Cells of strain S21 in exponential and early-stationary phase were coccoid bacilli, about 1 μm in diameter, and motile with a single polar flagellum. PCR and

  1. Ecological and genomic profiling of anaerobic methane-oxidizing archaea in a deep granitic environment.

    Science.gov (United States)

    Ino, Kohei; Hernsdorf, Alex W; Konno, Uta; Kouduka, Mariko; Yanagawa, Katsunori; Kato, Shingo; Sunamura, Michinari; Hirota, Akinari; Togo, Yoko S; Ito, Kazumasa; Fukuda, Akari; Iwatsuki, Teruki; Mizuno, Takashi; Komatsu, Daisuke D; Tsunogai, Urumu; Ishimura, Toyoho; Amano, Yuki; Thomas, Brian C; Banfield, Jillian F; Suzuki, Yohey

    2017-09-08

    Recent single-gene-based surveys of deep continental aquifers demonstrated the widespread occurrence of archaea related to Candidatus Methanoperedens nitroreducens (ANME-2d) known to mediate anaerobic oxidation of methane (AOM). However, it is unclear whether ANME-2d mediates AOM in the deep continental biosphere. In this study, we found the dominance of ANME-2d in groundwater enriched in sulfate and methane from a 300-m deep underground borehole in granitic rock. A near-complete genome of one representative species of the ANME-2d obtained from the underground borehole has most of functional genes required for AOM and assimilatory sulfate reduction. The genome of the subsurface ANME-2d is different from those of other members of ANME-2d by lacking functional genes encoding nitrate and nitrite reductases and multiheme cytochromes. In addition, the subsurface ANME-2d genome contains a membrane-bound NiFe hydrogenase gene putatively involved in respiratory H2 oxidation, which is different from those of other methanotrophic archaea. Short-term incubation of microbial cells collected from the granitic groundwater with (13)C-labeled methane also demonstrates that AOM is linked to microbial sulfate reduction. Given the prominence of granitic continental crust and sulfate and methane in terrestrial subsurface fluids, we conclude that AOM may be widespread in the deep continental biosphere.The ISME Journal advance online publication, 8 September 2017; doi:10.1038/ismej.2017.140.

  2. Temperature response of methane oxidation and production potentials in peatland ecosystems across Finland

    Science.gov (United States)

    Welti, Nina; Korrensalo, Aino; Kerttula, Johanna; Maljanen, Marja; Uljas, Salli; Lohila, Annalea; Laine, Anna; Vesala, Timo; Elliott, David; Tuittila, Eeva-Stiina

    2016-04-01

    It has been suggested that the ecosystems located in the high latitudes are especially sensitive to warming. Therefore, we compared 14 peatland systems throughout Finland along a latitudinal gradient from 69°N to 61°N to examine the response of methane production and methane oxidation with warming climate. Peat samples were taken at the height of the growing season in 2015 from 0 - 10cm below the water table depth. The plant communities in sampling locations were described by estimating cover of each plant species and pH of water was measured. Upon return to the lab, we made two parallel treatments, under anoxic and oxic conditions in order to calculate the CH4 production and consumption potentials of the peat and used three temperatures, 4°C, 17.5°C, and 30°C to examine the temperature effect on the potentials. We hypothesized that there will be an observable response curve in CH4 production and oxidation relative to temperature with a greater response with increasing latitude. In general, increasing temperature increased the potential for CH4 production and oxidation, at some sites, the potential was highest at 17.5°C, indicating that there is an optimum temperature threshold for the in situ methane producing and oxidizing microbial communities. Above this threshold, the peat microbial communities are not able to cope with increasing temperature. This is especially noticeable for methane oxidation at sites above 62°N. As countries are being expected to adequately account for their greenhouse gas budgets with increasing temperature models, knowing where the temperature threshold exists is of critical importance.

  3. Improved enrichment culture technique for methane-oxidizing bacteria from marine ecosystems: the effect of adhesion material and gas composition.

    Science.gov (United States)

    Vekeman, Bram; Dumolin, Charles; De Vos, Paul; Heylen, Kim

    2017-02-01

    Cultivation of microbial representatives of specific functional guilds from environmental samples depends largely on the suitability of the applied growth conditions. Especially the cultivation of marine methanotrophs has received little attention, resulting in only a limited number of ex situ cultures available. In this study we investigated the effect of adhesion material and headspace composition on the methane oxidation activity in methanotrophic enrichments obtained from marine sediment. Addition of sterilized natural sediment or alternatively the addition of acid-washed silicon dioxide significantly increased methane oxidation. This positive effect was attributed to bacterial adhesion on the particles via extracellular compounds, with a minimum amount of particles required for effect. As a result, the particles were immobilized, thus creating a stratified environment in which a limited diffusive gas gradients could build up and various microniches were formed. Such diffusive gas gradient might necessitate high headspace concentrations of CH4 and CO2 for sufficient concentrations to reach the methane-oxidizing bacteria in the enrichment culture technique. Therefore, high concentrations of methane and carbon dioxide, in addition to the addition of adhesion material, were tested and indeed further stimulated methane oxidation. Use of adhesion material in combination with high concentrations of methane and carbon dioxide might thus facilitate the cultivation and subsequent enrichment of environmentally important members of this functional guild. The exact mechanism of the observed positive effects on methane oxidation and the differential effect on methanotrophic diversity still needs to be explored.

  4. Does dissolved organic carbon regulate biological methane oxidation in semiarid soils?

    Science.gov (United States)

    Sullivan, Benjamin W; Selmants, Paul C; Hart, Stephen C

    2013-07-01

    In humid ecosystems, the rate of methane (CH4 ) oxidation by soil-dwelling methane-oxidizing bacteria (MOB) is controlled by soil texture and soil water holding capacity, both of which limit the diffusion of atmospheric CH4 into the soil. However, it remains unclear whether these same mechanisms control CH4 oxidation in more arid soils. This study was designed to measure the proximate controls of potential CH4 oxidation in semiarid soils during different seasons. Using a unique and well-constrained 3-million-year-old semiarid substrate age gradient, we were able to hold state factors constant while exploring the relationship between seasonal potential CH4 oxidation rates and soil texture, soil water holding capacity, and dissolved organic carbon (DOC). We measured unexpectedly higher rates of potential CH4 oxidation in the wet season than the dry season. Although other studies have attributed low CH4 oxidation rates in dry soils to desiccation of MOB, we present several lines of evidence that this may be inaccurate. We found that soil DOC concentration explained CH4 oxidation rates better than soil physical factors that regulate the diffusion of CH4 from the atmosphere into the soil. We show evidence that MOB facultatively incorporated isotopically labeled glucose into their cells, and MOB utilized glucose in a pattern among our study sites that was similar to wet-season CH4 oxidation rates. This evidence suggests that DOC, which is utilized by MOB in other environments with varying effects on CH4 oxidation rates, may be an important regulator of CH4 oxidation rates in semiarid soils. Our collective understanding of the facultative use of DOC by MOB is still in its infancy, but our results suggest it may be an important factor controlling CH4 oxidation in soils from dry ecosystems.

  5. Oscillatory Behavior during the Catalytic Partial Oxidation of Methane: Following Dynamic Structural Changes of Palladium Using the QEXAFS Technique

    DEFF Research Database (Denmark)

    Stoetzel, Jan; Frahm, Ronald; Kimmerle, Bertram

    2012-01-01

    as a combination of total oxidation and reforming in the catalytic capillary reactor was observed. This change in catalytic performance was directly linked to changes in the oxidation state of the Pd/Al2O3 catalysts at different positions along the catalytic reactor. During the ignition of the catalytic partial......Pd/Al2O3 catalysts oscillate between ignition and extinction of the catalytic partial oxidation of methane when they are exposed to a 2:1 reaction mixture of methane and oxygen. The oscillations of the catalytic performance and the structure of Pd/Al2O3 catalysts in a fixed-bed reactor were...... investigated using spatially and time-resolved in situ quick scanning X-ray absorption spectroscopy with online mass spectrometry. The dynamic methane conversion oscillated between an inactive state, where only combustion occurred, and an active state, after ignition, where partial oxidation of methane...

  6. Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide (Final Report)

    Science.gov (United States)

    EPA has finalized its Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide. This assessment addresses the potential carcinogenicity from long-term inhalation exposure to ethylene oxide. Now final, this assessment updates the carcinogenicity information in EPA’s 1985 Hea...

  7. Deposition of Biogenic Iron Minerals in a Methane Oxidizing Microbial Mat

    Directory of Open Access Journals (Sweden)

    Christoph Wrede

    2013-01-01

    Full Text Available The syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates.

  8. Partial oxidation of methane to syngas in a mixed-conducting oxygen permeable membrane reactor

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Mixed-conducting oxygen permeable membranes represent a class of novel ceramic membranes, which exhibit mixed oxygen ionic and electronic conductivities. At high temperatures, oxygen can permeate through the membrane from the high to low oxygen pressure side under an oxygen concentration gradient. Theoretically, the permselectivity of oxygen is 100%. Recently, a novel mixed-conducting membrane--Ba0.5Sr0.5Co0.8Fe0.2O3-δ has been developed, which shows extremely high oxygen permeability and promising stability. Furthermore, the reactor made with such membranes was successfully applied to the partial oxidation of methane to syngas reaction using air as the oxygen source, which realized the coupling of the separation of oxygen from air and the partial oxidation of membrane reaction in one process. At 850℃, methane conversion >88%, CO selectivity >97% and oxygen permeation rate of about 7.8 mL/(cm2.min) were obtained.

  9. Deposition of biogenic iron minerals in a methane oxidizing microbial mat.

    Science.gov (United States)

    Wrede, Christoph; Kokoschka, Sebastian; Dreier, Anne; Heller, Christina; Reitner, Joachim; Hoppert, Michael

    2013-01-01

    The syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates.

  10. Determination of emissions of methane and nitrous oxide in rice plantations in Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Jorge Herrera

    2013-12-01

    Full Text Available Methane and nitrous oxide emissions fluxes were measured in 10 rice plantations located in Liberia, Guanacaste, working at least with 04 varieties of rice and two types of soil in the period August 2012 - April 2013. For the determination of flows static camera technique were used taking four air gas samples located in the headspace of the chamber using a plastic syringe of 12 ml at 0, 10, 20 and 30 min after camera location. The gas samples were analyzed with a gas chromatograph, equipped with FID and ECD. Averages of flow methane and nitrous oxide were recorded between 0,12 to 1,9 kg ha-1d-1 and 0,11 - 1,1 mg ha-1d-1, respectively, and no significant difference was found (p < 0,05 in the values between different rice varieties and soil types subject experimental design.

  11. Methane oxidation at low temperatures in soil exposed to landfill gas

    DEFF Research Database (Denmark)

    Christophersen, Mette; Linderød, L.; Jensen, Pernille Erland

    2000-01-01

    to gas recovery at smaller and older landfills in northern Europe. Equations have been developed that describe the dependency of temperature and soil moisture content for each soil. The oxidation rates depended significantly on the soils (and thereby organic matter content), temperature, and soil...... moisture content. Soil moisture was the most important factor. However, high Q(10) values indicate that temperature also was important. The four soils tested had optimum soil moisture content between 11 and 32%. At increasing organic matter content, both the optimal soil moisture content and the maximum...... cannot be extrapolated to soils exposed to high methane concentrations. Four sandy soils with different organic matter content (1-9% w/w) from two landfills in Denmark were investigated in batch experiments in the laboratory to determine the response of methane oxidation at low temperatures and different...

  12. Methane oxidation and abundance of methane oxidizers in tropical agricultural soil (vertisol) in response to CuO and ZnO nanoparticles contamination.

    Science.gov (United States)

    Mohanty, Santosh Ranjan; Rajput, Parul; Kollah, Bharati; Chourasiya, Dipanti; Tiwari, Archana; Singh, Muneshwar; Rao, A Subba

    2014-06-01

    There is worldwide concern over the increase use of nanoparticles (NPs) and their ecotoxicological effect. It is not known if the annual production of tons of industrial nanoparticles (NPs) has the potential to impact terrestrial microbial communities, which are so necessary for ecosystem functioning. Here, we have examined the consequences of adding the NPs particularly the metal oxide (CuO, ZnO) on CH4 oxidation activity in vertisol and the abundance of heterotrophs, methane oxidizers, and ammonium oxidizers. Soil samples collected from the agricultural field located at Madhya Pradesh, India, were incubated with either CuO and ZnO NPs or ionic heavy metals (CuCl2, ZnCl2) separately at 0, 10, and 20 μg g(-1) soil. CH4 oxidation activity in the soil samples was estimated at 60 and 100 % moisture holding capacity (MHC) in order to link soil moisture regime with impact of NPs. NPs amended to soil were highly toxic for the microbial-mediated CH4 oxidation, compared with the ionic form. The trend of inhibition was Zn 20 > Zn 10 > Cu 20 > Cu 10. NPs delayed the lag phase of CH4 oxidation to a maximum of 4-fold and also decreased the apparent rate constant k up to 50 % over control. ANOVA and Pearson correlation analysis (α = 0.01) revealed significant impact of NPs on the CH4 oxidation activity and microbial abundance (p Biplot indicated negative impact of NPs on CH4 oxidation and microbial abundance. Our result also confirmed that higher soil moisture regime alleviates toxicity of NPs and opens new avenues of research to manage ecotoxicity and environmental hazard of NPs.

  13. Methane catalytic combustion on Pd9/gamma-Al2O3 with different degrees of Pd oxidation.

    Science.gov (United States)

    Czekaj, Izabela; Kacprzak, Katarzyna A; Mantzaras, John

    2013-01-01

    This research is focused on the analysis of adsorbed CH4 intermediates at oxidized Pd9 nanoparticles supported on gamma-alumina. From first-principle density functional theory (DFT) calculations, several configurations, charge transfer and electronic density of states have been analyzed in order to determine feasible paths for the oxidation process. Furthermore methane oxidation cycles have been investigated on Pd nanoparticles with different degrees of oxidation. In case of low oxidized Pd nanoparticles, activation of methane is observed, whereby hydrogen from methane is adsorbed at one oxygen atom. This reaction is exothermic. In a subsequent step, two water molecules desorb. Additionally, a very interesting structural effect becomes evident; Pd-carbide formation, which is also an exothermic reaction. Furthermore, oxidation of such carbidized Pd-nanoparticles leads to CO2 formation, which is an endothermic reaction. One important result is that the support is involved in the CO2 formation. A different mechanism of methane oxidation was discovered for highly oxidized Pd nanoparticles. When the Pd nanoparticle is more strongly exposed to oxidative conditions, adsorption of methane is also possible, but it leads to carbonic acid production at the interface between the Pd nanoparticles and support. This process is endothermic.

  14. Visualizing a Catalyst at Work during the Ignition of the Catalytic Partial Oxidation of Methane

    DEFF Research Database (Denmark)

    Kimmerle, Bertram; Grunwaldt, Jan-Dierk; Baiker, Alfons

    2009-01-01

    We present a spatiotemporal operando X-ray absorption study of a highly dynamic process, the ignition of the noble metal catalyzed partial oxidation of methane. Evolvement and propagation of the platinum component's structural changes are investigated with a high-speed X-ray camera, which in comb...... in combination with temperature profiling by IR-thermography and catalytic activity measurements by online mass spectrometry gives insight into the first stages of the ignition of the reaction toward hydrogen and carbon monoxide....

  15. Thermodynamic Study on the Catalytic Partial Oxidation of Methane to Syngas

    Institute of Scientific and Technical Information of China (English)

    XUJian; WEIWeisheng; 等

    2002-01-01

    The catalytic partial oxidation of methane to syngas (CO+H2) has been simulated thermodynamically with the advanced process simulator PRO/Ⅱ. The influences of temperature,pressure,CH4/O2 ratio and steam addition in feed gas on the conversion of CH4 selectively to syngas and heat duty required were investigated, and their effects on carbon formation were also discussed. The simulation results were in good agreement with the literature data taken from a spouted bed reactor.

  16. Plant physiological and soil characteristics associated with methane and nitrous oxide emission from rice paddy

    OpenAIRE

    Baruah, K.K.; Gogoi, Boby; Gogoi, P.

    2010-01-01

    Methane (CH4) and nitrous oxide (N2O) are important greenhouse gases causing global warming and climate change. Efforts were made to analyze the CH4 and N2O flux in relation to plant and soil factors from rice (Oryza sativa L.) paddy. Ten popularly grown rice varieties namely Rashmisali, Bogajoha, Basmuthi, Lalkalamdani, Choimora (traditional varieties); Mahsuri, Moniram, Kushal, Gitesh and Profulla (high yielding varieties = HYV) were grown during monsoon season of July 2006. The CH4 and N2O...

  17. Microbial methane oxidation at the redoxcline of the Gotland Deep (Central Baltic Sea

    Directory of Open Access Journals (Sweden)

    O. Schmale

    2012-07-01

    Full Text Available Methane concentrations in the stratified water column of the Gotland Deep (Central Baltic Sea show a strong gradient from high values in the saline deep water (max. 504nM to low concentrations in the less dense, brackish surface water (about 4 nM. The steepest gradient is present within the redoxcline (between 115 and 135 m water depth that separates the anoxic deep part from the oxygenated surface water, implying a methane consumption rate of 0.28 nM d−1. The process of microbial methane oxidation within the redoxcline is mirrored by a shift of the stable carbon isotope ratio of methane between the bottom water (δ13C CH4 = −82.4‰ and the suboxic depth interval (δ13C CH4 = −38.7‰. A water column sample from 100 m water depth was studied to identify the microorganisms responsible for the methane turnover at the redoxcline. Notably, methane monoxygenase gene expression analyses for the specific water depth demonstrated that accordant methanotrophic activity was due to only one microbial phylotype. An imprint of these organisms on the particular organic matter was revealed by distinctive lipid biomarkers showing bacteriohopanepolyols and lipid fatty acids characteristic for aerobic type I methanotrophic bacteria (e.g. 35-aminobacteriohopane-30,31,32,33,34-pentol. In conjunction with earlier findings, our results support the idea that biogeochemical cycles in Central Baltic Sea redoxclines are mainly driven by only a few microbial key species.

  18. Catalytic partial oxidation of methane to synthesis gas over a ruthenium catalyst: the role of the oxidation state.

    Science.gov (United States)

    Rabe, Stefan; Nachtegaal, Maarten; Vogel, Frédéric

    2007-03-28

    The catalytic partial oxidation of methane to synthesis gas over ruthenium catalysts was investigated by thermogravimetry coupled with infrared spectroscopy (TGA-FTIR) and in situ X-ray absorption spectroscopy (XAS). It was found that the oxidation state of the catalyst influences the product formation. On oxidized ruthenium sites, carbon dioxide was formed. The reduced catalyst yielded carbon monoxide as a product. The influence of the temperature was also investigated. At temperatures below the ignition point of the reaction, the catalyst was in an oxidized state. At temperatures above the ignition point, the catalyst was reduced. This was also confirmed by the in situ XAS spectroscopy. The results indicate that both a direct reaction mechanism as well as a combustion-reforming mechanism can occur. The importance of knowing the oxidation state of the surface is discussed and a method to determine it under reaction conditions is presented.

  19. Numerical modelling of methane oxidation efficiency and coupled water-gas-heat reactive transfer in a sloping landfill cover.

    Science.gov (United States)

    Feng, S; Ng, C W W; Leung, A K; Liu, H W

    2017-10-01

    Microbial aerobic methane oxidation in unsaturated landfill cover involves coupled water, gas and heat reactive transfer. The coupled process is complex and its influence on methane oxidation efficiency is not clear, especially in steep covers where spatial variations of water, gas and heat are significant. In this study, two-dimensional finite element numerical simulations were carried out to evaluate the performance of unsaturated sloping cover. The numerical model was calibrated using a set of flume model test data, and was then subsequently used for parametric study. A new method that considers transient changes of methane concentration during the estimation of the methane oxidation efficiency was proposed and compared against existing methods. It was found that a steeper cover had a lower oxidation efficiency due to enhanced downslope water flow, during which desaturation of soil promoted gas transport and hence landfill gas emission. This effect was magnified as the cover angle and landfill gas generation rate at the bottom of the cover increased. Assuming the steady-state methane concentration in a cover would result in a non-conservative overestimation of oxidation efficiency, especially when a steep cover was subjected to rainfall infiltration. By considering the transient methane concentration, the newly-modified method can give a more accurate oxidation efficiency. Copyright © 2017. Published by Elsevier Ltd.

  20. Methane oxidation and formation of EPS in compost: effect of oxygen concentration

    Energy Technology Data Exchange (ETDEWEB)

    Wilshusen, J.H.; Hettiaratchi, J.P.A.; Visscher, A. de; Saint-Fort, R

    2004-05-01

    Oxygen concentration plays an important role in the regulation of methane oxidation and the microbial ecology of methanotrophs. However, this effect is still poorly quantified in soil and compost ecosystems. The effect of oxygen on the formation of exopolymeric substances (EPS) is as yet unknown. We studied the effect of oxygen on the evolution of methanotrophic activity. At both high and low oxygen concentrations, peak activity was observed twice within a period of 6 months. Phospholipid fatty acid analysis showed that there was a shift from type I to type II methanotrophs during this period. At high oxygen concentration, EPS production was about 250% of the amount at low oxygen concentration. It is hypothesized that EPS serves as a carbon cycling mechanism for type I methanotrophs when inorganic nitrogen is limiting. Simultaneously, EPS stimulates nitrogenase activity in type II methanotrophs by creating oxygen-depleted zones. The kinetic results were incorporated in a simulation model for gas transport and methane oxidation in a passively aerated biofilter. Comparison between the model and experimental data showed that, besides acting as a micro-scale diffusion barrier, EPS can act as a barrier to macro-scale diffusion, reducing the performance of such biofilters. - 1.5% oxygen resulted in a slightly higher and more stable methane oxidation activity.

  1. Kinetics of oxidative coupling of methane: Bridging the gap between comprehension and description

    Institute of Scientific and Technical Information of China (English)

    M. Yu. Sinev; Z.T. Fattakhova; V.I. Lomonosov; Yu. A. Gordienko

    2009-01-01

    The development of notions about the mechanism of the oxidative coupling of methane (OCM) over oxide catalysts and corresponding progress in its kinetic description are reviewed and discussed. The latter becomes essential at the stage of scaling up and optimization of the process in pilot and industrial reactors. It is demonstrated that the main achievements in the development of kinetic models can be reached by combining the approaches conventionally used in homo-geneous gas-phase kinetics and in heterogeneous catalysis. In partic-ular,some important features of the OCM process can be described if several elementary reactions of free radical species (formation and transformation) with surface active sites are included into the detailed scheme of methane oxidation in gas. However,some important fea-tures,such as a non-additive character of the reciprocal influence of methane and ethane in the case of their simultaneous presence in the reaction mixture,cannot yet be described and comprehended in the framework of schemes developed so far. Possible ways towards an advanced kinetic model,accounting the main principles of catalyst functioning (redox nature of active sites) and pathways of product formation (via free radicals) are traced.

  2. Experimental Investigation of Flow Resistance in a Coal Mine Ventilation Air Methane Preheated Catalytic Oxidation Reactor

    Directory of Open Access Journals (Sweden)

    Bin Zheng

    2015-01-01

    Full Text Available This paper reports the results of experimental investigation of flow resistance in a coal mine ventilation air methane preheated catalytic oxidation reactor. The experimental system was installed at the Energy Research Institute of Shandong University of Technology. The system has been used to investigate the effects of flow rate (200 Nm3/h to 1000 Nm3/h and catalytic oxidation bed average temperature (20°C to 560°C within the preheated catalytic oxidation reactor. The pressure drop and resistance proportion of catalytic oxidation bed, the heat exchanger preheating section, and the heat exchanger flue gas section were measured. In addition, based on a large number of experimental data, the empirical equations of flow resistance are obtained by the least square method. It can also be used in deriving much needed data for preheated catalytic oxidation designs when employed in industry.

  3. A Long-Term Cultivation of an Anaerobic Methane-Oxidizing Microbial Community from Deep-Sea Methane-Seep Sediment Using a Continuous-Flow Bioreactor

    Science.gov (United States)

    Aoki, Masataka; Ehara, Masayuki; Saito, Yumi; Yoshioka, Hideyoshi; Miyazaki, Masayuki; Saito, Yayoi; Miyashita, Ai; Kawakami, Shuji; Yamaguchi, Takashi; Ohashi, Akiyoshi; Nunoura, Takuro; Takai, Ken; Imachi, Hiroyuki

    2014-01-01

    Anaerobic oxidation of methane (AOM) in marine sediments is an important global methane sink, but the physiological characteristics of AOM-associated microorganisms remain poorly understood. Here we report the cultivation of an AOM microbial community from deep-sea methane-seep sediment using a continuous-flow bioreactor with polyurethane sponges, called the down-flow hanging sponge (DHS) bioreactor. We anaerobically incubated deep-sea methane-seep sediment collected from the Nankai Trough, Japan, for 2,013 days in the bioreactor at 10°C. Following incubation, an active AOM activity was confirmed by a tracer experiment using 13C-labeled methane. Phylogenetic analyses demonstrated that phylogenetically diverse Archaea and Bacteria grew in the bioreactor. After 2,013 days of incubation, the predominant archaeal components were anaerobic methanotroph (ANME)-2a, Deep-Sea Archaeal Group, and Marine Benthic Group-D, and Gammaproteobacteria was the dominant bacterial lineage. Fluorescence in situ hybridization analysis showed that ANME-1 and -2a, and most ANME-2c cells occurred without close physical interaction with potential bacterial partners. Our data demonstrate that the DHS bioreactor system is a useful system for cultivating fastidious methane-seep-associated sedimentary microorganisms. PMID:25141130

  4. Effect of heat transfer on the oscillatory behavior in partial oxidation of methane over nickel catalyst

    Institute of Scientific and Technical Information of China (English)

    Xiubin Ren; Xiangyun Guo

    2011-01-01

    Monte Carlo method was applied to simulate the oscillatory behavior during partial oxidation of methane under non-isothermal condition.The simulation was performed to examine the influences of heat transfer constant and particle size on the kinetic oscillation.The oscillatory period and amplitude were observed to increase with the increase of heat transfer constant.The increase of catalyst particle size was found to result in short oscillatory period and more or less regular oscillations combined with the formation of oxide down to L =100.

  5. First-principles investigations for the catalytic dissociation and oxidation of methane on the Cu surfaces

    Science.gov (United States)

    Li, Ying; Mahadevan, Jagan; Wang, Sanwu

    2010-03-01

    The catalytic reactions of dissociation and oxidation of methane on the copper surfaces play a key role in, for example, the development of high-performance solid oxide fuel cells. We used first-principles quantum theory and large-scale parallel calculations to investigate the atomic-scale mechanism of the catalytic chemical reactions. We report the calculated results, which provide fundamental information and understanding about the atomic-scale dynamics and electronic structures pertinent to the reactions and specifically the catalytic role of the Cu(100) and Cu(111) surfaces. We also report comparison of our results with available experimental data and previous theoretical investigations.

  6. The potential for biologically catalyzed anaerobic methane oxidation on ancient Mars.

    Science.gov (United States)

    Marlow, Jeffrey J; Larowe, Douglas E; Ehlmann, Bethany L; Amend, Jan P; Orphan, Victoria J

    2014-04-01

    This study examines the potential for the biologically mediated anaerobic oxidation of methane (AOM) coupled to sulfate reduction on ancient Mars. Seven distinct fluids representative of putative martian groundwater were used to calculate Gibbs energy values in the presence of dissolved methane under a range of atmospheric CO2 partial pressures. In all scenarios, AOM is exergonic, ranging from -31 to -135 kJ/mol CH4. A reaction transport model was constructed to examine how environmentally relevant parameters such as advection velocity, reactant concentrations, and biomass production rate affect the spatial and temporal dependences of AOM reaction rates. Two geologically supported models for ancient martian AOM are presented: a sulfate-rich groundwater with methane produced from serpentinization by-products, and acid-sulfate fluids with methane from basalt alteration. The simulations presented in this study indicate that AOM could have been a feasible metabolism on ancient Mars, and fossil or isotopic evidence of this metabolic pathway may persist beneath the surface and in surface exposures of eroded ancient terrains.

  7. Atmospheric observations and emissions estimates of methane and nitrous oxide from regional to global scale

    Science.gov (United States)

    Kort, Eric Adam

    2011-12-01

    Methane (CH4) and Nitrous Oxide (N2O) are the two most significant anthropogenic, long-lived, non-CO2 greenhouse gases, together perturbing the earth's energy balance by an amount comparable to that of CO2. This dissertation will focus on the use of atmospheric observations to quantify emissions of CH4 and N2O. First top-down emissions constraints on the regional scale, covering large areas of the U.S and southern Canada, are derived from airborne observations made in Spring of 2003. Using a receptor-oriented Lagrangian particle dispersion model provides robust validation of bottom-up emission estimates from EDGAR 32FT2000 and GEIA inventories. It is found that EDGAR CH4 emission rates are slightly low by a factor of 1.08 +/- 0.15 (2 sigma), while both EDGAR and GEIA N2O emissions are significantly too low, by factors of 2.62 +/- 0.50 and 3.05 +/- 0.61 respectively. This analysis is then extended over a full calendar year in 2004 with observations from NOAA's tall tower and aircraft profile network. EDGAR 32FT2000 CH 4 emissions are found to be consistent with observations, though the newer EDGAR v4.0 reduces CH4 emissions by 30%, and this reduction is not consistent with this study. Scaling factors found for N2O in May/June of 2003 (2.62 & 3.05) are found to hold for February-May of 2004, suggesting inventories are significantly too low in primary growing season coincident with significant fertilizer inputs. A new instrument for airborne observation of CO2, CH 4, N2O, and CO is introduced, and its operation and in-field performance are highlighted (demonstrated 1-sec precisions of 20 ppb, 0.5 ppb, 0.09 ppb, and 0.15 ppb respectively). Finally, global N2O observations collected with this sensor on the HIPPO (Hlaper Pole to Pole Observations) campaign are assessed. Comparison with a global model and subsequent inversion indicates strong, episodic inputs of nitrous oxide from tropical regions are necessary to bring observations and model in agreement. Findings

  8. Methane Conversion to C2 Hydrocarbons in Solid State Oxide Electrolyte Membrane Reactor

    Institute of Scientific and Technical Information of China (English)

    LI Jun; ZHAO Ling; ZHU Zhong-nan; XI Dan-li

    2005-01-01

    Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0<x<1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examined in a fixed-bed reactor. The former group presented higher activity in the OCM, but the main product was carbon dioxide. While the later group showed lower activity but much higher selectivity to C2 hydrocarbons compared with the former. Electrochemical measurements were conducted in a solid oxide membrane reactor with La0.8 Na0.2CoO3 as catalyst. The results showed that methane was oxidized to carbon dioxide and ethane by two parallel reactions. Ethane was oxidized to ethene and carbon dioxide. A fraction of ethene was oxidized deeply to carbon dioxide. The total selectivity to C2 hydrocarbons exceeded 70%. Based on the experimental results, a kinetic model was suggested to describe the reaction results.

  9. Utilization of fuel cells to beneficially use coal mine methane. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Brown, J.T.; O`Brien, D.G.; Miller, A.R.; Atkins, R.; Sanders, M.

    1996-03-01

    DOE has been given the responsibility to encourage industry to recover and use methane that is currently being released to the atmosphere. At this time the only method being employed at the Left Fork Mine to remove methane is the mine ventilation system. The methane content was measured at one one-hundredth of a percent. To prevent this methane from being vented to the atmosphere, degasification wells are proposed. To use the coal mine methane, it is proposed to use phosphoric-acid fuel cells to convert methane to electric power. These fuel cells contain (1) a steam reformer to convert the methane to hydrogen (and carbon dioxide), (2) the fuel cell stack, and (3) a power conditioner that provides 200 kW of 60 Hz alternating current output. The environmental impacts and benefits of using this technology ware summarized in the report. The study indicates the methane emission reduction that could be achieved on a national and Global level. The important point being that this technology is economically viable as is demonstrated in the report.

  10. Methane Oxidation to Synthesis Gas Using Lattice Oxygen of La1-xSrxMO3-λ(M = Fe, Mn) Perovskite Oxides Instead of Molecular Oxygen

    Institute of Scientific and Technical Information of China (English)

    LiRanjia; YuChangchun; ZhuGuangrong; ShenShikong

    2005-01-01

    In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1-xSrxMO3-λ(M=Fe,Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2, with a selectivity of over 90.7% using the lattice oxygen of La1-xSrxFeO3-λ(x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1-xSrxFeO3-λ(x≤0.2) perovskite oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.

  11. Catalytic Oxidation of Methane into Methanol over Copper-Exchanged Zeolites with Oxygen at Low Temperature.

    Science.gov (United States)

    Narsimhan, Karthik; Iyoki, Kenta; Dinh, Kimberly; Román-Leshkov, Yuriy

    2016-06-22

    The direct catalytic conversion of methane to liquid oxygenated compounds, such as methanol or dimethyl ether, at low temperature using molecular oxygen is a grand challenge in C-H activation that has never been met with synthetic, heterogeneous catalysts. We report the first demonstration of direct, catalytic oxidation of methane into methanol with molecular oxygen over copper-exchanged zeolites at low reaction temperatures (483-498 K). Reaction kinetics studies show sustained catalytic activity and high selectivity for a variety of commercially available zeolite topologies under mild conditions (e.g., 483 K and atmospheric pressure). Transient and steady state measurements with isotopically labeled molecules confirm catalytic turnover. The catalytic rates and apparent activation energies are affected by the zeolite topology, with caged-based zeolites (e.g., Cu-SSZ-13) showing the highest rates. Although the reaction rates are low, the discovery of catalytic sites in copper-exchanged zeolites will accelerate the development of strategies to directly oxidize methane into methanol under mild conditions.

  12. Cultivation of nitrite-dependent anaerobic methane-oxidizing bacteria: impact of reactor configuration.

    Science.gov (United States)

    Hu, Baolan; He, Zhanfei; Geng, Sha; Cai, Chen; Lou, Liping; Zheng, Ping; Xu, Xinhua

    2014-09-01

    Nitrite-dependent anaerobic methane oxidation (n-damo) is mediated by bacteria that anaerobically oxidize methane coupled with nitrite reduction and is a potential bioprocess for wastewater treatment. In this work, the effect of reactor configuration on n-damo bacterial cultivation was investigated. A magnetically stirred gas lift reactor (MSGLR), a sequencing batch reactor (SBR), and a continuously stirred tank reactor (CSTR) were selected to cultivate the bacteria. Microbial community was monitored by using quantitative PCR, 16S rRNA gene sequencing, pmoA gene sequencing, and fluorescence in situ hybridization (FISH). The effects of substrate inhibition, methane mass transfer, and biomass washout in the three reactors were focused on. The results indicated that the MSGLR had the best performance among the three reactor systems, with the highest total and specific n-damo activities. Its maximum volumetric nitrogen removal rate was up to 76.9 mg N L(-1) day(-1), which was higher than previously reported values (5.1-37.8 mg N L(-1) d(-1)).

  13. Diversity and enrichment of nitrite-dependent anaerobic methane oxidizing bacteria from wastewater sludge.

    Science.gov (United States)

    Luesken, Francisca A; van Alen, Theo A; van der Biezen, Erwin; Frijters, Carla; Toonen, Ger; Kampman, Christel; Hendrickx, Tim L G; Zeeman, Grietje; Temmink, Hardy; Strous, Marc; Op den Camp, Huub J M; Jetten, Mike S M

    2011-11-01

    Recently discovered microorganisms affiliated to the bacterial phylum NC10, named "Candidatus Methylomirabilis oxyfera", perform nitrite-dependent anaerobic methane oxidation. These microorganisms could be important players in a novel way of anaerobic wastewater treatment where ammonium and residual dissolved methane might be removed at the expense of nitrate or nitrite. To find suitable inocula for reactor startup, ten selected wastewater treatment plants (WWTPs) located in The Netherlands were screened for the endogenous presence of M. oxyfera using molecular diagnostic methods. We could identify NC10 bacteria with 98% similarity to M. oxyfera in nine out of ten WWTPs tested. Sludge from one selected WWTP was used to start a new enrichment culture of NC10 bacteria. This enrichment was monitored using specific pmoA primers and M. oxyfera cells were visualized with fluorescence oligonucleotide probes. After 112 days, the enrichment consumed up to 0.4 mM NO(2)(-) per day. The results of this study show that appropriate sources of biomass, enrichment strategies, and diagnostic tools existed to start and monitor pilot scale tests for the implementation of nitrite-dependent methane oxidation in wastewater treatment at ambient temperature.

  14. Emissions of greenhouse gases (methane and nitrous oxide) from cattle slurry storage in Northern Europe

    Science.gov (United States)

    Rodhe, L.; Ascue, J.; Nordberg, Å.

    2009-11-01

    Total greenhouse gas (GHG) emissions from stored manure corresponded to 14% of overall GHG emissions from Swedish agriculture in 2006 according to calculations using standard values for a cool climate. The present study identified storage conditions for cattle slurry in different regions of Sweden, developed methodology for measuring GHGs from slurry stored under similar conditions to full-scale storage, and determined annual GHG emissions (methane and nitrous oxide) from stored cattle slurry under Swedish conditions. Temperature measurements in full-scale storage of cattle slurry on farms showed a mean annual slurry temperature of 9.7°C in south-west Sweden and 5.6°C in the north. The closed chamber methodology and equipment developed for measuring GHG emissions were implemented for one year in a pilot-scale plant with similar conditions to full-scale storage as regards slurry temperature, climate and filling/emptying routines. During winter (Oct-April), methane emissions from stored cattle slurry were 3.6 g CH4-C per kg VS, while during summer (May-Sept) they were 6.5 g CH4-C per kg VS. This corresponded to an annual methane conversion factor (MCF) of 2.7%. Losses of nitrous oxide were close to zero.

  15. Methane oxidation in permeable sediments at hydrocarbon seeps in the Santa Barbara Channel, California

    Science.gov (United States)

    Treude, T.; Ziebis, W.

    2010-03-01

    A shallow-water area in the Santa Barbara Channel (California), known collectively as the Coal Oil Point seep field, is one the largest natural submarine oil and gas emission areas in the world. Both gas and oil are seeping constantly through a predominantly sandy seabed into the ocean. This study focused on the methanotrophic activity within the surface sediments (0-15 cm) of the permeable seabed in the so-called Brian Seep area at a water depth ~10 m. Detailed investigations of biogeochemical parameters in the sediment surrounding active gas vents indicated that methane seepage through the permeable seabed induces a convective transport of fluids within the surface sediment layer, which results in a deeper penetration of oxidants (oxygen, sulfate) into the sediment, as well as in a faster removal of potentially inhibiting reduced end products (e.g. hydrogen sulfide). Methanotrophic activity was often found close to the sediment-water interface, indicating the involvement of aerobic bacteria. However, biogeochemical data suggests that the majority of methane is consumed by anaerobic oxidation of methane (AOM) coupled to sulfate reduction below the surface layer (>15 cm), where sulfate is still available in high concentrations. This subsurface maximum of AOM activity in permeable sands is in contrast to known deep-sea seep habitats, where upward fluid advection through more fine-grained sediments leads to an accumulation of AOM activity within the top 10 cm of the sediments, because sulfate is rapidly depleted.

  16. Catalytic combustion of methane over alumina-supported palladium: Relationships between the oxidation state, particle size, morphology and activity

    Science.gov (United States)

    Lyubovsky, Maxim R.

    Supported palladium was studied as a catalyst for combustion of natural gas. The influence of variations in temperature and oxygen concentration, of addition of CO and water and of in situ hydrogen reduction on catalyst activity was studied experimentally. The activation energy for methane oxidation over crystalline PdO is about 17.5 kcal/mole and over metallic Pd - 40--45 kcal/mole. The difference in the activation energy is compensated by the preexponential coefficient that is 5--6 orders of magnitude higher for Pd than for PdO. In this work the activity variations under the different reaction conditions were correlated with the corresponding changes in the catalyst oxidation state, particle size and morphology. Formation of metallic hexagonal crystallites 100--200 nm in size was observed by TEM after PdO reduction, which resulted in an increase in the catalyst activity. Redispersion of these metallic crystallites into PdO clusters of 3--5 nm in size occurred during the Pd reoxidation, which resulted in a reversible increase of the catalyst activity on the cooling cycle, known as "negative activation." Activation of the methane molecule is the limiting step of the reaction over both the Pd and the PdO states. We propose that on the Pd surface the reaction occurs through the Langmuir-Hinshelwood mechanism. Under conditions of catalytic combustion the surface is completely covered with oxygen and competitive dissociative adsorption of methane is the limiting step of the process. The high heat of oxygen adsorption explains the high activation energy for the overall process. On the PdO surface the reaction occurs through a redox mechanism. A methane molecule interacts with a surface Pd-O dimer resulting in adsorbed CH3 and OH species. The activation energy of this interaction is about 15 kcal/mole and the probability is low due to the different multiplicity of the initial and final states of the transition complex. Oscillations in the reaction rate under fuel

  17. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    Directory of Open Access Journals (Sweden)

    D. Mogensen

    2014-01-01

    Full Text Available The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were performed in the temperature range 600–800°C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r ∝PCH40.7. A simple model is presented which is capable of predicting the methane conversion in a stack configuration from intrinsic kinetics of the anode support material. The predictions are compared with the stack measurements presented here, and good agreement is observed.

  18. Optimization of dry reforming of methane over Ni/YSZ anodes for solid oxide fuel cells

    Science.gov (United States)

    Guerra, Cosimo; Lanzini, Andrea; Leone, Pierluigi; Santarelli, Massimo; Brandon, Nigel P.

    2014-01-01

    This work investigates the catalytic properties of Ni/YSZ anodes as electrodes of Solid Oxide Fuel Cells (SOFCs) to be operated under direct dry reforming of methane. The experimental test rig consists of a micro-reactor, where anode samples are characterized. The gas composition at the reactor outlet is monitored using a mass spectrometer. The kinetics of the reactions occurring over the anode is investigated by means of Isotherm reactions and Temperature-programmed reactions. The effect of the variation of temperature, gas residence time and inlet carbon dioxide-methane volumetric ratio is analyzed. At 800 °C, the best catalytic performance (in the carbon safe region) is obtained for 1.5 dry reforming and cracking reactions, respectively. In other ranges, dry reforming and reverse water gas shift are the dominant reactions and the inlet feed reaches almost the equilibrium condition provided that a sufficient gas residence time is obtained.

  19. Coupled models of free methane gas and anaerobic oxidation of methane : from core to regional scales. Geologica Ultraiectina (339)

    NARCIS (Netherlands)

    Mogollón, J.M.

    2011-01-01

    Methane is a potent greenhouse gas that is produced in marine sediments containing high amounts of degrading organic carbon. It is therefore not surprising that marine sediments contain vast amounts of methane (500-5000 gigatons) present in dissolved (aqueous), free gas (gaseous), and solid

  20. Anaerobic oxidation of methane (AOM) in marine sediments from the Skagerrak (Denmark): II. Reaction-transport modeling

    DEFF Research Database (Denmark)

    Dale, A.W.; Regnier, P.; Knab, N.J.;

    2008-01-01

    A steady-state reaction-transport model is applied to sediments retrieved by gravity core from two stations (S10 and S13) in the Skagerrak to determine the main kinetic and thermodynamic controls on anaerobic oxidation of methane (AOM). The model considers an extended biomass-implicit reaction...... for limitation by the in situ catabolic energy yields. The fraction of total sulfate reduction due to AOM in the sulfate-methane transition zone (SMTZ) at each site is calculated. The model provides an explanation for the methane tailing phenomenon which is observed here and in other marine sediments, whereby...... methane diffuses up from the SMTZ to the top of the core without being consumed. The tailing is due to bioenergetic limitation of AOM in the sulfate reduction zone, because the methane concentration is too low to engender favorable thermodynamic drive. AOM is also bioenergetically inhibited below the SMTZ...

  1. Landfill gas distribution at the base of passive methane oxidation biosystems: Transient state analysis of several configurations.

    Science.gov (United States)

    Ahoughalandari, Bahar; Cabral, Alexandre R

    2017-08-18

    The design process of passive methane oxidation biosystems needs to include design criteria that account for the effect of unsaturated hydraulic behavior on landfill gas migration, in particular, restrictions to landfill gas flow due to the capillary barrier effect, which can greatly affect methane oxidation rates. This paper reports the results of numerical simulations performed to assess the landfill gas flow behavior of several passive methane oxidation biosystems. The concepts of these biosystems were inspired by selected configurations found in the technical literature. We adopted the length of unrestricted gas migration (LUGM) as the main design criterion in this assessment. LUGM is defined as the length along the interface between the methane oxidation and gas distribution layers, where the pores of the methane oxidation layer material can be considered blocked for all practical purposes. High values of LUGM indicate that landfill gas can flow easily across this interface. Low values of LUGM indicate greater chances of having preferential upward flow and, consequently, finding hotspots on the surface. Deficient designs may result in the occurrence of hotspots. One of the designs evaluated included an alternative to a concept recently proposed where the interface between the methane oxidation and gas distribution layers was jagged (in the form of a see-saw). The idea behind this ingenious concept is to prevent blockage of air-filled pores in the upper areas of the jagged segments. The results of the simulations revealed the extent of the capability of the different scenarios to provide unrestricted and conveniently distributed upward landfill gas flow. They also stress the importance of incorporating an appropriate design criterion in the selection of the methane oxidation layer materials and the geometrical form of passive biosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. The role of paraffin oil on the interaction between denitrifying anaerobic methane oxidation and Anammox processes.

    Science.gov (United States)

    Fu, Liang; Ding, Zhao-Wei; Ding, Jing; Zhang, Fang; Zeng, Raymond J

    2015-10-01

    Methane is sparingly soluble in water, resulting in a slow reaction rate in the denitrifying anaerobic methane oxidation (DAMO) process. The slow rate limits the feasibility of research to examine the interaction between the DAMO and the anaerobic ammonium oxidation (Anammox) process. In this study, optimized 5 % (v/v) paraffin oil was added as a second liquid phase to improve methane solubility in a reactor containing DAMO and Anammox microbes. After just addition, methane solubility was found to increase by 25 % and DAMO activity was enhanced. After a 100-day cultivation, the paraffin reactor showed almost two times higher consumption rates of NO3 (-) (0.2268 mmol/day) and NH4 (+) (0.1403 mmol/day), compared to the control reactor without paraffin oil. The microbes tended to distribute in the oil-water interface. The quantitative (q) PCR result showed the abundance of gene copies of DAMO archaea, DAMO bacteria, and Anammox bacteria in the paraffin reactor were higher than those in the control reactor after 1 month. Fluorescence in situ hybridization revealed that the percentages of the three microbes were 55.5 and 77.6 % in the control and paraffin reactors after 100 days, respectively. A simple model of mass balance was developed to describe the interactions between DAMO and Anammox microbes and validate the activity results. A mechanism was proposed to describe the possible way that paraffin oil enhanced DAMO activity. It is quite clear that paraffin oil enhances not only DAMO activity but also Anammox activity via the interaction between them; both NO3 (-) and NH4 (+) consumption rates were about two times those of the control.

  3. Calcium-doped ceria materials for anode of solid oxide fuel cells running on methane fuel

    Science.gov (United States)

    Zhao, Kai; Du, Yanhai

    2017-04-01

    A calcium-doped ceria with nominal compositions of Ce1-xCaxO2-δ (0.00 ≤ x ≤ 0.30) has been developed as an anode component for solid oxide fuel cells running on methane fuel. Crystal phases of Ce1-xCaxO2-δ are investigated with respect to the amount of calcium dopant. The Ce1-xCaxO2-δ shows single fluorite phase when the calcium is within 15 mol.%, and higher calcium doping levels lead to the appearance of a secondary phase (CaO). Conductivities of Ce1-xCaxO2-δ ceramics are studied by a four-probe method in air and the composition of Ce0.9Ca0.1O2-δ (x = 0.10) is found exhibiting the highest conductivity among the samples investigated in this work. Electrocatalytic properties of Ce0.9Ca0.1O2-δ are evaluated based on Ni-Ce1-xCaxO2-δ anode supported single cell running on methane fuel. At 800 °C, the single cell with Ni-Ce0.9Ca0.1O2-δ (x = 0.10) anode exhibits an optimum maximum powder density (618 mW cm-2) and good performance stability during 30 h operation in methane fuel. The promising findings substantiate the good performance of Ni-Ce0.9Ca0.1O2-δ anode for electrochemical oxidation of methane fuel.

  4. Changes in methane oxidation activity and methanotrophic community composition in saline alkaline soils.

    Science.gov (United States)

    Serrano-Silva, Nancy; Valenzuela-Encinas, César; Marsch, Rodolfo; Dendooven, Luc; Alcántara-Hernández, Rocio J

    2014-05-01

    The soil of the former Lake Texcoco is a saline alkaline environment where anthropogenic drainage in some areas has reduced salt content and pH. Potential methane (CH4) consumption rates were measured in three soils of the former Lake Texcoco with different electrolytic conductivity (EC) and pH, i.e. Tex-S1 a >18 years drained soil (EC 0.7 dS m(-1), pH 8.5), Tex-S2 drained for ~10 years (EC 9.0 dS m(-1), pH 10.3) and the undrained Tex-S3 (EC 84.8 dS m(-1), pH 10.3). An arable soil from Alcholoya (EC 0.7 dS m(-1), pH 6.7), located nearby Lake Texcoco was used as control. Methane oxidation in the soil Tex-S1 (lowest EC and pH) was similar to that in the arable soil from Alcholoya (32.5 and 34.7 mg CH4 kg(-1) dry soil day(-1), respectively). Meanwhile, in soils Tex-S2 and Tex-S3, the potential CH4 oxidation rates were only 15.0 and 12.8 mg CH4 kg(-1) dry soil day(-1), respectively. Differences in CH4 oxidation were also related to changes in the methane-oxidizing communities in these soils. Sequence analysis of pmoA gene showed that soils differed in the identity and number of methanotrophic phylotypes. The Alcholoya soil and Tex-S1 contained phylotypes grouped within the upland soil cluster gamma and the Jasper Ridge, California JR-2 clade. In soil Tex-S3, a phylotype related to Methylomicrobium alcaliphilum was detected.

  5. The effect of coal bed dewatering and partial oxidation on biogenic methane potential

    Science.gov (United States)

    Jones, Elizabeth J.P.; Harris, Steve H.; Barnhart, Elliott P.; Orem, William H.; Clark, Arthur C.; Corum, Margo D.; Kirshtein, Julie D.; Varonka, Matthew S.; Voytek, Mary A.

    2013-01-01

    Coal formation dewatering at a site in the Powder River Basin was associated with enhanced potential for secondary biogenic methane determined by using a bioassay. We hypothesized that dewatering can stimulate microbial activity and increase the bioavailability of coal. We analyzed one dewatered and two water-saturated coals to examine possible ways in which dewatering influences coal bed natural gas biogenesis by looking at differences with respect to the native coal microbial community, coal-methane organic intermediates, and residual coal oxidation potential. Microbial biomass did not increase in response to dewatering. Small Subunit rRNA sequences retrieved from all coals sampled represented members from genera known to be aerobic, anaerobic and facultatively anaerobic. A Bray Curtis similarity analysis indicated that the microbial communities in water-saturated coals were more similar to each other than to the dewatered coal, suggesting an effect of dewatering. There was a higher incidence of long chain and volatile fatty acid intermediates in incubations of the dewatered coal compared to the water-saturated coals, and this could either be due to differences in microbial enzymatic activities or to chemical oxidation of the coal associated with O2 exposure. Dilute H2O2 treatment of two fractions of structural coal (kerogen and bitumen + kerogen) was used as a proxy for chemical oxidation by O2. The dewatered coal had a low residual oxidation potential compared to the water-saturated coals. Oxidation with 5% H2O2 did increase the bioavailability of structural coal, and the increase in residual oxidation potential in the water saturated coals was approximately equivalent to the higher methanogenic potential measured in the dewatered coal. Evidence from this study supports the idea that coal bed dewatering could stimulate biogenic methanogenesis through partial oxidation of the structural organics in coal once anaerobic conditions are restored.

  6. The Leeuwenhoek Lecture 2000 the natural and unnatural history of methane-oxidizing bacteria.

    Science.gov (United States)

    Dalton, Howard

    2005-06-29

    Methane gas is produced from many natural and anthropogenic sources. As such, methane gas plays a significant role in the Earth's climate, being 25 times more effective as a greenhouse gas than carbon dioxide. As with nearly all other naturally produced organic molecules on Earth, there are also micro-organisms capable of using methane as their sole source of carbon and energy. The microbes responsible (methanotrophs) are ubiquitous and, for the most part, aerobic. Although anaerobic methanotrophs are believed to exist, so far, none have been isolated in pure culture. Methanotrophs have been known to exist for over 100 years; however, it is only in the last 30 years that we have begun to understand their physiology and biochemistry. Their unique ability to use methane for growth is attributed to the presence of a multicomponent enzyme system-methane monooxygenase (MMO)-which has two distinct forms: soluble (sMMO) and membrane-associated (pMMO); however, both convert methane into the readily assimilable product, methanol. Our understanding of how bacteria are capable of effecting one of the most difficult reactions in chemistry-namely, the controlled oxidation of methane to methanol-has been made possible by the isolation, in pure form, of the enzyme components.The mechanism by which methane is activated by sMMO involves abstraction of a hydrogen atom from methane by a high-valence iron species (FeIV or possibly FeV) in the hydroxylase component of the MMO complex to form a methyl radical. The radical combines with a captive oxygen atom from dioxygen to form the reaction product, methanol, which is further metabolized by the cell to produce multicarbon intermediates. Regulation of the sMMO system relies on the remarkable properties of an effector protein, protein B. This protein is capable of facilitating component interactions in the presence of substrate, modifying the redox potential of the diiron species at the active site. These interactions permit access of

  7. Effect of calcination temperature and reaction conditions on methane partial oxidation using lanthanum-based perovskite as oxygen donor

    Institute of Scientific and Technical Information of China (English)

    DAI Xiaoping; YU Changchun; LI Ranjia; WU Qiong; SHI Kaijiao; HAO Zhengping

    2008-01-01

    We investigated the effect of calcination temperature, reaction temperature, and different amounts of replenished lattice oxygen on the partial oxidation of methane (POM) to synthesis gas using perovskite-type LaFeO3 oxide as oxygen donor instead of gaseous oxygen, which was prepared by the sol-gel method, and the oxides were characterized by XRD, TG/DTA, and BET. The results indicated that the particle size increased with the calcination temperature increasing, while BET and CH4 conversion declined with the calcination temperature increasing using LaFeO3 oxide as oxygen donor in the absence of gaseous oxygen. CO selectivity remained at a high level such as above 92%, and increased slightly as the calcination temperature increased. Exposure of LaFeO3 oxides to methane atmosphere enhanced the oxygen migration of in the bulk with time online owing to the loss of lattice oxygen and reduction of the oxidative stated Fe ion simultaneously. The high reaction temperature was favorable to the migration of oxygen species from the bulk toward the surface for the synthesis gas production with high CO selectivity. The product distribution and evolution for POM by sequential redox reaction was determined by amounts of replenished lattice oxygen with gaseous oxygen. The optimal process should decline the total oxidation of methane, and increase the selectivity of partial oxidation of methane.

  8. Competitive interactions between methane- and ammonia-oxidizing bacteria modulate carbon and nitrogen cycling in paddy soil

    NARCIS (Netherlands)

    Zheng, Yan; Huang, Rong; Wang, B.; Bodelier, P.L.E.; Jia, Z.

    2014-01-01

    Pure culture studies have demonstrated that methanotrophs and ammonia oxidizers can both carry out the oxidation of methane and ammonia. However, the expected interactions resulting from these similarities are poorly understood, especially in complex, natural environments. Using DNA-based stable iso

  9. Partial oxidation of methane to formaldehyde on Mo03, Fe203 and ferromolybdenum catalysts

    Directory of Open Access Journals (Sweden)

    José Daniel Del Río

    2010-04-01

    Full Text Available One of the main challenges for catalysis has been direct methane conversion to useful products such as methanol and formaldehyde. Formaldehyde is currently produced by a three-step industrial process with syngas and metha- nol as intermediate products. MoO , Fe O and Fe (MoO catalysts were used with four different Mo/Fe molar 3\t2 3 2 4 3 ratios (0.5, 1, 1.5, 2 in this work. The ferromolybdenum catalyst was prepared by coprecipitation. Pure oxides are more active; however they are not formaldehyde selective, but carbon oxide (CO, CO selective. The ferro- molybdenum catalysts showed better HCHO selectivity at low conversions; the molybdenum oxide content did not show increased in catalytic activity. Increased reaction temperature did not increase formaldehyde selectivity.

  10. Monte Carlo simulation of the oscillatory behavior in partial oxidation of methane on nickel catalyst

    Science.gov (United States)

    Ren, Xiu-Bin; Li, Huan-Ying; Guo, Xiang-Yun

    The Monte Carlo method is employed to study the kinetics of catalytic partial oxidation of methane to syngas on nickel catalyst. Using the Langmuir-Hinshelwood mechanism, self-sustained reaction rate oscillations can be observed under suitable conditions. Further analysis reveals that the rate oscillations are caused by the repetitive oxidation and reduction cycles of nickel surface, which result in a transformation of the formation mechanism of carbon monoxide from the reaction between C and O to the direct reduction of nickel oxide. The conditions for generating the self-sustained oscillations are investigated, and the regular oscillations are found for the diffusion parameter Ndif > 50 and the lattice size L ⩾ 90.

  11. Seasonal Production and Emission of Methane from Rice Fields, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, M. Aslam K.; Rasmussen,Reinhold A.

    2002-12-03

    B 139 - Methane (CH4) is a greenhouse gas regarded second only to carbon dioxide in its ability to cause global warming. Methane is important because of its relatively fast increase, and also because it is, per molecule, some 60 times more effective than carbon dioxide in causing global warming. The largest present anthropogenic sources of methane are rice fields, cattle and biomass burning. The global emissions from these sources are still not well known. In the middle 1980s there were few available data on methane emissions from rice fields leading to estimates of a global source between 100-280 Tg/yr. Extensive worldwide research during the last decade has shown that the global emissions from rice fields are more likely to be in the range of 30-80Tg/yr. While this work has led to a substantial reduction in the estimated emissions, the uncertainty is still quite large, and seriously affects our ability to include methane in integrated assessments for future climate change and environmental management.China dominated estimates of methane emissions from rice fields because it was, and is, the largest producer of rice, and major increases in rice production had taken place in the country over the last several decades. This report summarizes the work in Sichuan Province, China, in each of the following areas: the design of the experiment; the main results on methane emissions from rice fields, delineating the factors controlling emissions; production of methane in the soil; a survey of water management practices in sample of counties in Sichuan province; and results of ambient measurements including data from the background continental site. B139

  12. Enhanced Emission Performance and Fuel Efficiency for HD Methane Engines. Literature Study. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Broman, R.; Staalhammar, P.; Erlandsson, L.

    2010-05-15

    A literature survey has been conducted in order to define state-of-the-art for methane fuelled engines to be used in heavy duty vehicles. Use of methane can be favourable to increase security of supply and mitigate CO2 emissions, especially when the methane origins from biomass. Furthermore, methane used as a fuel in heavy duty engines has a potential to reduce toxic exhaust emissions. Historically, use of methane in heavy duty engines has often been hampered by poor efficiency, i.e. high fuel consumption when using the Otto-cycle. However, current generation technology engines might be within 5-10 % of the efficiency of Diesel engine technology. In this context it is worth mentioning that compliance-driven changes for meeting future emission regulations for Diesel engines may have a negative impact on fuel efficiency, thereby narrowing the gap. This may present an opportunity for heavy methane fuelled engines. The reliability and durability of the exhaust aftertreatment devices for methane fuelled engines has also given rise to some concerns. Some concepts are performing acceptable while others do not meet expectations. This is partly due to difficulties in handling methane in the aftertreatment device and partly to issues in the design of the ignition system. Methane is a fuel used worldwide and has a potential to be an important complement to Diesel oil. There are two categories of HD methane engines available to end-users: Retrofitted engines, which often include computer controlled retrofit systems developed as 'bolt-on' technologies that can be removed if necessary, to resell the vehicle with a normal diesel engine, and those developed specifically for and in conjunction with engine manufacturers and delivered to customers as factory-built engines or vehicles (OEM). Additionally, both these categories can include engines that use the Otto- or Diesel combustion cycles. When adapting a HD Diesel engine to run on methane there are two options, either

  13. Mechanistic Variants in Gas-Phase Metal-Oxide Mediated Activation of Methane at Ambient Conditions.

    Science.gov (United States)

    Li, Jilai; Zhou, Shaodong; Zhang, Jun; Schlangen, Maria; Usharani, Dandamudi; Shaik, Sason; Schwarz, Helmut

    2016-09-07

    The C-H bond activation of methane mediated by a prototypical heteronuclear metal-oxide cluster, [Al2Mg2O5](•+), was investigated by using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in conjunction with high-level quantum mechanical calculations. Experimentally, hydrogen-atom abstraction from methane by the cluster ion [Al2Mg2O5](•+) takes place at ambient conditions. As to the mechanism, according to our computational findings, both the proton-coupled electron transfer (PCET) and the conventional hydrogen-atom transfer (HAT) are feasible and compete with each other. This is in distinct contrast to the [XYO2](+) (X, Y = Mg, Al, Si) cluster oxide ions which activate methane exclusively via the PCET route (Li, J.; Zhou, S.; Zhang, J.; Schlangen, M.; Weiske, T.; Usharani, D.; Shaik, S.; Schwarz, H. J. Am. Chem. Soc. 2016, 138, 7973-7981). The electronic origins of the mechanistically rather complex reactivity scenarios of the [Al2Mg2O5](•+)/CH4 couple were elucidated. For the PCET mechanism, in which the Lewis acid-base pair [Al(+)-O(-)] of the cluster acts as the active site, a clear correlation has been established between the nature of the transition state, the corresponding barrier height, the Lewis acidity-basicity of the [M(+)-O(-)] unit, as well as the bond order of the M(+)-O(-) bond. Also addressed is the role of the spin and charge distributions of a terminal oxygen radical site in the direct HAT route. The knowledge of the factors that control the reactivity of PCET and HAT pathways not only deepens our mechanistic understanding of metal-oxide mediated C-H bond activation but may also provide guidance for the rational design of catalysts.

  14. Butachlor inhibits production and oxidation of methane in tropical rice soils under flooded condition.

    Science.gov (United States)

    Mohanty, S R; Nayak, D R; Babu, Y J; Adhya, T K

    2004-01-01

    In laboratory incubation experiments, application of a commercial formulation of the herbicide butachlor (N-butoxymethyl-2-chloro-2',6'-diethyl acetanilide) to three tropical rice soils, widely differing in their physicochemical characteristics, under flooded condition inhibited methane (CH4) production. The inhibitory effect was concentration dependent and most remarkable in the alluvial soil. Thus, following application of butachlor at 5, 10, 50 and 100 microg g(-1) soil, respectively, cumulative CH4 production in the alluvial soil was inhibited by 15%, 31%, 91% and 98% over unamended control. Since CH4 production was less pronounced in the sandy loam and acid sulfate soil, the impact of amendment with butchalor, albeit inhibitory, was less extensive than the alluvial soil. Inhibition of CH4 production in butachlor-amended alluvial soil was related to the prevention in the drop in redox potential as well as low methanogenic bacterial population especially at high concentrations of butachlor. CH4 oxidation was also inhibited in butachlor-amended alluvial soil with the inhibitory effect being more prevalent under flooded condition. Inhibition in CH4 oxidation was related to a reduction in the population of soluble methane monooxygenase producing methanotrophs. Results demonstrate that butachlor, a commonly used herbicide in rice cultivation, even at very low concentrations can affect CH4 production and its oxidation, thereby influencing the biogeochemical cycle of CH4 in flooded rice soils.

  15. Immunological detection of enzymes for sulfate reduction in anaerobic methane-oxidizing consortia.

    Science.gov (United States)

    Milucka, Jana; Widdel, Friedrich; Shima, Seigo

    2013-05-01

    Anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) at marine gas seeps is performed by archaeal-bacterial consortia that have so far not been cultivated in axenic binary or pure cultures. Knowledge about possible biochemical reactions in AOM consortia is based on metagenomic retrieval of genes related to those in archaeal methanogenesis and bacterial sulfate reduction, and identification of a few catabolic enzymes in protein extracts. Whereas the possible enzyme for methane activation (a variant of methyl-coenzyme M reductase, Mcr) was shown to be harboured by the archaea, enzymes for sulfate activation and reduction have not been localized so far. We adopted a novel approach of fluorescent immunolabelling on semi-thin (0.3-0.5 μm) cryosections to localize two enzymes of the SR pathway, adenylyl : sulfate transferase (Sat; ATP sulfurylase) and dissimilatory sulfite reductase (Dsr) in microbial consortia from Black Sea methane seeps. Both Sat and Dsr were exclusively found in an abundant microbial morphotype (c. 50% of all cells), which was tentatively identified as Desulfosarcina/Desulfococcus-related bacteria. These results show that ANME-2 archaea in the Black Sea AOM consortia did not express bacterial enzymes of the canonical sulfate reduction pathway and thus, in contrast to previous suggestions, most likely cannot perform canonical sulfate reduction. Moreover, our results show that fluorescent immunolabelling on semi-thin cryosections which to our knowledge has been so far only applied on cell tissues, is a powerful tool for intracellular protein detection in natural microbial associations.

  16. The kinetic studies of direct methane oxidation to methanol in the plasma process

    Institute of Scientific and Technical Information of China (English)

    INDARTO Antonius; CHOI Jae-Wook; LEE Hwaung; SONG Hyung Keun

    2008-01-01

    The research outlined here includes a study of methanol production from direct methane conversion by means of thermal and plasma method. The kinetic study, derived from thermal-based approach, was carried out to investigate thoroughly the possible intermediate species likely to be presented in the process. A set of plasma experiments was undertaken by using dielectric barrier discharge (DBD), classified as non-thermal plasma, done at atmospheric pressure and room temperature. Plasma proc-ess yields more methanol than thermal process at the same methane conversion rates and methane to oxygen feed ratios. Oxidation reaction of thermal process resulted CO and CO2 as the most dominant products and the selectivity reached 19% and 68%, respectively. Moreover, more CO and less CO2 were produced in plasma process than in thermal process. The selectivity of CO and CO2 by plasma was 47% and 20%, respectively. Ethane (C2H6) was detected as the only higher hydrocarbon with a signifi-cant concentration. The concentration of ethane reached 9% of the total products in plasma process and 17% in thermal process. The maximum selectivity of methanol, the target material of this research, was 12% obtained by plasma method and less than 5% by thermal process. In some certain points, the kinetic model closely matched with the experimental results.

  17. Methane assisted solid oxide co-electrolysis process for syngas production

    Science.gov (United States)

    Wang, Yao; Liu, Tong; Lei, Libin; Chen, Fanglin

    2017-03-01

    In this study, methane assisted high temperature steam/CO2 co-electrolysis process is performed on symmetrical cells with a configuration of SFM-SDC/LSGM/SFM-SDC to produce high-quality synthesis gas (syngas, a mixture of H2 and CO). The Nernst potential has been evaluated for solid oxide cells in the methane assisted mode, which is reduced by nearly one order of magnitude through substituting the anode atmosphere from air to methane. The open circuit voltage (OCV) is -0.06 V at 800 °C, and an electrolysis current density of -242 mAcm-2 has been obtained at 850 °C and 0.3 V. Effects of operating conditions on products composition have been revealed by using the chemical equilibrium co-electrolysis model and HSC software. High-quality syngas with high conversion rate of CO2 to CO as well as ideal H2/CO molar ratio of 2 could be achieved in both electrode sides by adjusting appropriate operating conditions. The short-term cell voltage is slightly fluctuant less than 0.05 V at 850 °C and -120 mAcm-2, in which condition carbon deposition has been observed in the SFM-SDC anode due to the low O2-/CH4 ratio.

  18. Estimation of methane and nitrous oxide emissions from rice field with rice straw management in Cambodia.

    Science.gov (United States)

    Vibol, S; Towprayoon, S

    2010-02-01

    To estimate the greenhouse gas emissions from paddy fields of Cambodia, the methodology of the Intergovernmental Panel on Climate Change (IPCC) guidelines, IPCC coefficients, and emission factors from the experiment in Thailand and another country were used. Total area under rice cultivation during the years 2005-2006 was 2,048,360 ha in the first crop season and 298,529 ha in the second crop season. The emission of methane from stubble incorporation with manure plus fertilizer application areas in the first crop season was estimated to be 192,783.74 ton higher than stubble with manure, stubble with fertilizer, and stubble without fertilizer areas. The fields with stubble burning emitted the highest emission of methane (75,771.29 ton) followed by stubble burning with manure (22,251.08 ton), stubble burning with fertilizer (13,213.27 ton), and stubble burning with fertilizer application areas (3,222.22 ton). The total emission of methane from rice field in Cambodia for the years 2005-2006 was approximately 342,649.26 ton (342.65 Gg) in the first crop season and 36,838.88 ton (36.84 Gg) in the second crop season. During the first crop season in the years 2005-2006, Battambang province emitted the highest amount of CH(4) (38,764.48 ton) and, in the second crop season during the years 2005-2006, the highest emission (8,262.34 ton) was found in Takeo province (8,262.34 ton). Nitrous oxide emission was between 2.70 and 1,047.92 ton in the first crop season and it ranged from 0 to 244.90 ton in the second crop season. Total nitrous oxide emission from paddy rice field was estimated to be 9,026.28 ton in the first crop season and 1,091.93 ton in the second crop season. Larger area under cultivation is responsible for higher emission of methane and nitrous oxide. Total emission of nitrous oxide by using IPCC default emission coefficient was approximately 2,328.85 ton. The total global warming potential of Cambodian paddy rice soil is 11,723,217.03 ton (11,723 Gg

  19. Methane oxidation over Fe-, Co-, Ni- and V-containing mixed conductors

    Energy Technology Data Exchange (ETDEWEB)

    Kharton, V.V.; Yaremchenko, A.A.; Tsipis, E.V.; Shaula, A.L.; Frade, J.R. [Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Valente, A.A.; Rocha, J. [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Sobyanin, V.A.; Belyaev, V.D.; Semin, G.L.; Veniaminov, S.A. [Boreskov Institute of Catalysis SB RAS, 5 pr. Akademika Lavrentieva, Novosibirsk 630090 (Russian Federation)

    2005-02-28

    The catalytic oxidation of methane over mixed conducting ceramics, including perovskite-type SrFe{sub 0.7}Al{sub 0.3}O{sub 3-{delta}} and La{sub 0.3}Sr{sub 0.7}Co{sub 0.8}Ga{sub 0.2}O{sub 3-{delta}}, dual-phase composite (SrCo){sub 0.5}(Sr{sub 2}Fe{sub 3}){sub 0.5}O{sub 4.75+}/-{sub {delta}}, La{sub 2}Ni{sub 0.9}Co{sub 0.1}O{sub 4+{delta}} with K{sub 2}NiF{sub 4}-type structure and zircon-type CeVO{sub 4+{delta}}, is primarily governed by bonding energy between oxygen and transition metal cations, which leads to general correlations between the catalytic activity, oxygen desorption, oxygen ionic transport, thermal expansion, and, often, phase stability. The steady-state conversion of dry CH{sub 4} either by oxygen permeating through dense oxide ceramics in a membrane reactor or by atmospheric O{sub 2} (methane/air ratio of 30:70) in a fixed bed reactor with membrane material as catalyst results in high CO{sub 2} selectivity, increasing when the oxygen permeability of mixed conductors increases. The prevailing mechanism of total methane combustion makes it necessary to incorporate reforming catalysts in the membrane reactors for natural gas conversion to Synthesis gas (syngas). Dominant CO{sub 2} formation is also observed for the oxidation of CH{sub 4} pulses supplied in helium flow over the mixed conductor powders, except for SrFe{sub 0.7}Al{sub 0.3}O{sub 3-{delta}} yielding synthesis gas with the H{sub 2}/CO ratio close to 2, characteristic of the partial oxidation process. For a model reactor comprising one disk-shaped membrane and a catalyst both made of SrFe{sub 0.7}Al{sub 0.3}O{sub 3-{delta}}, the methane conversion and CO selectivity at 1223 K achieved 65% and 48%, respectively.

  20. Yttria promoted metallic nickel catalysts for the partial oxidation of methane to synthesis gas

    Institute of Scientific and Technical Information of China (English)

    Yaquan Wang; Xuebin Hong; Bingbing Li; Wenju Wang; Dalin Wang

    2008-01-01

    A metallic Ni catalyst was prepared with nickel sponge, followed by acid treatment. It was further promoted with yttria by an impregnation method. The catalysts were characterized by SEM, BET, XRD, TPR, XPS, etc., and studied in the partial oxidation of methane to syngas. The characterization results showed that the yttria promoted metallic Ni catalysts had high specific surface area and more NiO. The reaction results showed that the yttria promoter increased the CH4 conversion and the selectivity for H2 and CO.

  1. Lanthanum Modified Ni/γ-Al2O3 Catalysts for Partial Oxidation of Methane

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    La modified Ni/γ-Al2O3 catalysts prepared by co-precipitation method using NaOH-Na2CO3 as a precipitator show high activity and selectivity for the partial oxidation of methane (POM). Meanwhile, the addition of La is beneficial for the formation of an active component and stability of support. We investigated some factors including calcining temperature, nickel content, and space velocity, which turned out to have a strong influence on catalytic activity and selectivity. By XRD and TPR, it is concluded that Ni0 reduced from amorphous NiAl2O4 is the major active component for POM.

  2. Enhanced Emission Performance and Fuel Efficiency for HD Methane Engines. Literature Study. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Broman, R.; Staalhammar, P.; Erlandsson, L.

    2010-05-15

    A literature survey has been conducted in order to define state-of-the-art for methane fuelled engines to be used in heavy duty vehicles. Use of methane can be favourable to increase security of supply and mitigate CO2 emissions, especially when the methane origins from biomass. Furthermore, methane used as a fuel in heavy duty engines has a potential to reduce toxic exhaust emissions. Historically, use of methane in heavy duty engines has often been hampered by poor efficiency, i.e. high fuel consumption when using the Otto-cycle. However, current generation technology engines might be within 5-10 % of the efficiency of Diesel engine technology. In this context it is worth mentioning that compliance-driven changes for meeting future emission regulations for Diesel engines may have a negative impact on fuel efficiency, thereby narrowing the gap. This may present an opportunity for heavy methane fuelled engines. The reliability and durability of the exhaust aftertreatment devices for methane fuelled engines has also given rise to some concerns. Some concepts are performing acceptable while others do not meet expectations. This is partly due to difficulties in handling methane in the aftertreatment device and partly to issues in the design of the ignition system. Methane is a fuel used worldwide and has a potential to be an important complement to Diesel oil. There are two categories of HD methane engines available to end-users: Retrofitted engines, which often include computer controlled retrofit systems developed as 'bolt-on' technologies that can be removed if necessary, to resell the vehicle with a normal diesel engine, and those developed specifically for and in conjunction with engine manufacturers and delivered to customers as factory-built engines or vehicles (OEM). Additionally, both these categories can include engines that use the Otto- or Diesel combustion cycles. When adapting a HD Diesel engine to run on methane there are two options, either

  3. Metabolic capabilities of microorganisms involved in and associated with the anaerobic oxidation of methane

    Directory of Open Access Journals (Sweden)

    Gunter eWegener

    2016-02-01

    Full Text Available In marine sediments the anaerobic oxidation of methane with sulfate as electron acceptor (AOM is responsible for the removal of a major part of the greenhouse gas methane. AOM is performed by consortia of anaerobic methane-oxidizing archaea (ANME and their specific partner bacteria. The physiology of these organisms is poorly understood, which is due to their slow growth with doubling times in the order of months and the phylogenetic diversity in natural and in vitro AOM enrichments. Here we study sediment-free long-term AOM enrichments that were cultivated from seep sediments sampled off the Italian Island Elba (20°C; hereon called E20 and from hot vents of the Guaymas Basin, Gulf of California, cultivated at 37°C (G37 or at 50°C (G50. These enrichments were dominated by consortia of ANME-2 archaea and Seep-SRB2 partner bacteria (E20 or by ANME-1, forming consortia with Seep-SRB2 bacteria (G37 or with bacteria of the HotSeep-1 cluster (G50. We investigate lipid membrane compositions as possible factors for the different temperature affinities of the different ANME clades and show autotrophy as characteristic feature for both ANME clades and their partner bacteria. Although in the absence of additional substrates methane formation was not observed, methanogenesis from methylated substrates (methanol and methylamine could be quickly stimulated in the E20 and the G37 enrichment. Responsible for methanogenesis are archaea from the genus Methanohalophilus and Methanococcoides, which are minor community members during AOM (1 to 7‰ of archaeal 16S rRNA gene amplicons. In the same two cultures also sulfur disproportionation could be quickly stimulated by addition of zero-valent colloidal sulfur. The isolated partner bacteria are likewise minor community members (1 to 9‰ of bacterial 16S rRNA gene amplicons, whereas the dominant partner bacteria (Seep-SRB1a, Seep-SRB2 or HotSeep-1 did not grow on elemental sulfur. Our results support a

  4. Methane-free biogas for direct feeding of solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Leone, P.; Lanzini, A.; Santarelli, M.; Cali, M. [Dipartimento di Energetica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy); Sagnelli, F.; Boulanger, A.; Scaletta, A.; Zitella, P. [BioEnergy Lab, Environment Park S.p.A., Via Livorno 60, 10144 Turin (Italy)

    2010-01-01

    This paper deals with the experimental analysis of the performance and degradation issues of a Ni-based anode-supported solid oxide fuel cell fed by a methane-free biogas from dark-anaerobic digestion of wastes by pastry and fruit shops. The biogas is produced by means of an innovative process where the biomass is fermented with a pre-treated bacteria inoculum (Clostridia) able to completely inhibit the methanization step during the fermentation process and to produce a H{sub 2}/CO{sub 2} mixture instead of conventional CH{sub 4}/CO{sub 2} anaerobic digested gas (bio-methane). The proposed biogas production route leads to a biogas composition which avoids the need of introducing a reformer agent into or before the SOFC anode in order to reformate it. In order to analyse the complete behaviour of a SOFC with the bio-hydrogen fuel, an experimental session with several H{sub 2}/CO{sub 2} synthetic mixtures was performed on an anode-supported solid oxide fuel cell with a Ni-based anode. It was found that side reactions occur with such mixtures in the typical thermodynamic conditions of SOFCs (650-800 C), which have an effect especially at high currents, due to the shift to a mixture consisting of hydrogen, carbon monoxide, carbon dioxide and water. However, cells operated with acceptable performance and carbon deposits (typical of a traditional hydrocarbon-containing biogas) were avoided after 50 h of cell operation even at 650 C. Experiments were also performed with traditional bio-methane from anaerobic digestion with 60/40 vol% of composition. It was found that the cell performance dropped after few hours of operation due to the formation of carbon deposits. A short-term test with the real as-produced biogas was also successfully performed. The cell showed an acceptable power output (at 800 C, 0.35 W cm{sup -2} with biogas, versus 0.55 W cm{sup -2} with H{sub 2}) although a huge quantity of sulphur was present in the feeding fuel (hydrogen sulphide at 103 ppm and

  5. Methane-free biogas for direct feeding of solid oxide fuel cells

    Science.gov (United States)

    Leone, P.; Lanzini, A.; Santarelli, M.; Calì, M.; Sagnelli, F.; Boulanger, A.; Scaletta, A.; Zitella, P.

    This paper deals with the experimental analysis of the performance and degradation issues of a Ni-based anode-supported solid oxide fuel cell fed by a methane-free biogas from dark-anaerobic digestion of wastes by pastry and fruit shops. The biogas is produced by means of an innovative process where the biomass is fermented with a pre-treated bacteria inoculum (Clostridia) able to completely inhibit the methanization step during the fermentation process and to produce a H 2/CO 2 mixture instead of conventional CH 4/CO 2 anaerobic digested gas (bio-methane). The proposed biogas production route leads to a biogas composition which avoids the need of introducing a reformer agent into or before the SOFC anode in order to reformate it. In order to analyse the complete behaviour of a SOFC with the bio-hydrogen fuel, an experimental session with several H 2/CO 2 synthetic mixtures was performed on an anode-supported solid oxide fuel cell with a Ni-based anode. It was found that side reactions occur with such mixtures in the typical thermodynamic conditions of SOFCs (650-800 °C), which have an effect especially at high currents, due to the shift to a mixture consisting of hydrogen, carbon monoxide, carbon dioxide and water. However, cells operated with acceptable performance and carbon deposits (typical of a traditional hydrocarbon-containing biogas) were avoided after 50 h of cell operation even at 650 °C. Experiments were also performed with traditional bio-methane from anaerobic digestion with 60/40 vol% of composition. It was found that the cell performance dropped after few hours of operation due to the formation of carbon deposits. A short-term test with the real as-produced biogas was also successfully performed. The cell showed an acceptable power output (at 800 °C, 0.35 W cm -2 with biogas, versus 0.55 W cm -2 with H 2) although a huge quantity of sulphur was present in the feeding fuel (hydrogen sulphide at 103 ppm and mercaptans up to 10 ppm). Therefore, it

  6. Macroscopic biofilms in fracture-dominated sediment that anaerobically oxidize methane

    Science.gov (United States)

    Briggs, B.R.; Pohlman, J.W.; Torres, M.; Riedel, M.; Brodie, E.L.; Colwell, F.S.

    2011-01-01

    Methane release from seafloor sediments is moderated, in part, by the anaerobic oxidation of methane (AOM) performed by consortia of archaea and bacteria. These consortia occur as isolated cells and aggregates within the sulfate-methane transition (SMT) of diffusion and seep-dominant environments. Here we report on a new SMT setting where the AOM consortium occurs as macroscopic pink to orange biofilms within subseafloor fractures. Biofilm samples recovered from the Indian and northeast Pacific Oceans had a cellular abundance of 10 7 to 10 8 cells cm -3. This cell density is 2 to 3 orders of magnitude greater than that in the surrounding sediments. Sequencing of bacterial 16S rRNA genes indicated that the bacterial component is dominated by Deltaproteobacteria, candidate division WS3, and Chloroflexi, representing 46%, 15%, and 10% of clones, respectively. In addition, major archaeal taxa found in the biofilm were related to the ANME-1 clade, Thermoplasmatales, and Desulfurococcales, representing 73%, 11%, and 10% of archaeal clones, respectively. The sequences of all major taxa were similar to sequences previously reported from cold seep environments. PhyloChip microarray analysis detected all bacterial phyla identified by the clone library plus an additional 44 phyla. However, sequencing detected more archaea than the PhyloChip within the phyla of Methanosarcinales and Desulfurococcales. The stable carbon isotope composition of the biofilm from the SMT (-35 to-43%) suggests that the production of the biofilm is associated with AOM. These biofilms are a novel, but apparently widespread, aggregation of cells represented by the ANME-1 clade that occur in methane-rich marine sediments. ?? 2011, American Society for Microbiology.

  7. Towards Biogeochemical Modeling of Anaerobic Oxidation of Methane: Characterization of Microbial Communities in Methane-bearing North American Continental Margin Sediments

    Science.gov (United States)

    Graw, M. F.; Solomon, E. A.; Chrisler, W.; Krause, S.; Treude, T.; Ruppel, C. D.; Pohlman, J.; Colwell, F. S.

    2015-12-01

    Methane advecting through continental margin sediments may enter the water column and potentially contribute to ocean acidification and increase atmospheric methane concentrations. Anaerobic oxidation of methane (AOM), mediated by syntrophic consortia of anaerobic methanotrophic archaea and sulfate-reducing bacteria (ANME-SRB), consumes nearly all dissolved methane in methane-bearing sediments before it reaches the sediment-water interface. Despite the significant role ANME-SRB play in carbon cycling, our knowledge of these organisms and their surrounding microbial communities is limited. Our objective is to develop a metabolic model of ANME-SRB within methane-bearing sediments and to couple this to a geochemical reaction-transport model for these margins. As a first step towards this goal, we undertook fluorescent microscopic imaging, 16S rRNA gene deep-sequencing, and shotgun metagenomic sequencing of sediments from the US Pacific (Washington) and northern Atlantic margins where ANME-SRB are present. A successful Illumina MiSeq sequencing run yielded 106,257 bacterial and 857,834 archaeal 16S rRNA gene sequences from 12 communities from the Washington Margin using both universal prokaryotic and archaeal-specific primer sets. Fluorescent microscopy confirmed the presence of cells of the ANME-2c lineage in the sequenced communities. Microbial community characterization was coupled with measurements of sediment physical and geochemical properties and, for samples from the US Atlantic margin, 14C-based measurements of AOM rates and 35S-based measurements of sulfate reduction rates. These findings have the potential to increase understanding of ANME-SRB, their surrounding microbial communities, and their role in carbon cycling within continental margins. In addition, they pave the way for future efforts at developing a metabolic model of ANME-SRB and coupling it to geochemical models of the US Washington and Atlantic margins.

  8. A global model of tropospheric chlorine chemistry: Organic versus inorganic sources and impact on methane oxidation

    Science.gov (United States)

    Hossaini, Ryan; Chipperfield, Martyn P.; Saiz-Lopez, Alfonso; Fernandez, Rafael; Monks, Sarah; Feng, Wuhu; Brauer, Peter; Glasow, Roland

    2016-12-01

    Chlorine atoms (Cl) are highly reactive toward hydrocarbons in the Earth's troposphere, including the greenhouse gas methane (CH4). However, the regional and global CH4 sink from Cl is poorly quantified as tropospheric Cl concentrations ([Cl]) are uncertain by 2 orders of magnitude. Here we describe the addition of a detailed tropospheric chlorine scheme to the TOMCAT chemical transport model. The model includes several sources of tropospheric inorganic chlorine (Cly), including (i) the oxidation of chlorocarbons of natural (CH3Cl, CHBr2Cl, CH2BrCl, and CHBrCl2) and anthropogenic (CH2Cl2, CHCl3, C2Cl4, C2HCl3, and CH2ClCH2Cl) origin and (ii) sea-salt aerosol dechlorination. Simulations were performed to quantify tropospheric [Cl], with a focus on the marine boundary layer, and quantify the global significance of Cl atom CH4 oxidation. In agreement with observations, simulated surface levels of hydrogen chloride (HCl), the most abundant Cly reservoir, reach several parts per billion (ppb) over polluted coastal/continental regions, with sub-ppb levels typical in more remote regions. Modeled annual mean surface [Cl] exhibits large spatial variability with the largest levels, typically in the range of 1-5 × 104 atoms cm-3, in the polluted northern hemisphere. Chlorocarbon oxidation provides a tropospheric Cly source of up to 4320 Gg Cl/yr, sustaining a background surface [Cl] of methane sink of 12-13 Tg CH4/yr due the CH4 + Cl reaction ( 2.5% of total CH4 oxidation). Larger regional effects are predicted, with Cl accounting for 10 to >20% of total boundary layer CH4 oxidation in some locations.

  9. Oxidative Condensation of Methane — a New Pathway to the Synthesis of Ethane, Ethylene, and Other Hydrocarbons

    Science.gov (United States)

    Minachev, Khabib M.; Usachev, Nikolay Ya; Udut, V. N.; Khodakov, Yu S.

    1988-03-01

    During the last five years, the chemistry of methane has been enriched by the possibility of obtaining C2 and other hydrocarbons as a result of the oxidative condensation of methane in the presence of a series of catalytic systems. The availability of the starting materials (CH4 and O2) leads to extensive prospects for the replacement of the petroleum raw materials by natural gas in single-stage syntheses of valuable compounds and in the first place ethylene. This review gives a systematic account of the results of the selection of effective catalysts and surveys the information leading to the elucidation of the mechanism for the formation of the products of the extensive oxidation and oxidative condensation of methane. The bibliography includes 118 references.

  10. Kinetics of (reversible) internal reforming of methane in solid oxide fuel cells under stationary and APU conditions

    Science.gov (United States)

    Timmermann, H.; Sawady, W.; Reimert, R.; Ivers-Tiffée, E.

    The internal reforming of methane in a solid oxide fuel cell (SOFC) is investigated and modeled for flow conditions relevant to operation. To this end, measurements are performed on anode-supported cells (ASC), thereby varying gas composition (y CO = 4-15%, yH2 = 5 - 17 % , yCO2 = 6 - 18 % , yH2O = 2 - 30 % , yCH4 = 0.1 - 20 %) and temperature (600-850 °C). In this way, operating conditions for both stationary applications (methane-rich pre-reformate) as well as for auxiliary power unit (APU) applications (diesel-POX reformate) are represented. The reforming reaction is monitored in five different positions alongside the anodic gas channel by means of gas chromatography. It is shown that methane is converted in the flow field for methane-rich gas compositions, whereas under operation with diesel reformate the direction of the reaction is reversed for temperatures below 675 °C, i.e. (exothermic) methanation occurs along the anode. Using a reaction model, a rate equation for reforming could be derived which is also valid in the case of methanation. By introducing this equation into the reaction model the methane conversion along a catalytically active Ni-YSZ cermet SOFC anode can be simulated for the operating conditions specified above.

  11. Partial oxidation of methane to methanol over catalyst ZSM-5 from coal fly ash and rice husk ash

    Directory of Open Access Journals (Sweden)

    Mirda Yanti Fusia

    2017-01-01

    Full Text Available Methane is one of the greenhouse gases that can be converted into liquid fuels such as methanol to retain most of the energy of methane and produce a cleaner environment. The conversion of methane to methanol using ZMS-5 represents a breakthrough in the utilization of methane. However, material sources for zeolite synthesis as catalyst usually are pro-analysis grade materials, which are expensive. Therefore, in this research, coal fly ash and rice husk ash were used as raw materials for mesoporous ZSM-5 zeolite synthesis. First, coal fly ash and rice husk were subjected to pre-treatment to extract silicate (SiO44− and aluminate (AlO45− and impurities separation. The ZSM-5 zeolite was synthesized through hydrothermal treatment using two types of templates. After ZSM-5 was synthesized, it was modified with Cobalt through impregnation method. The catalytic activity of both ZSM-5 and Co/ZSM-5 zeolites as heterogeneous catalysts in partial oxidation of methane were preliminary tested and compared with that commercial one. The result showed that the zeolite catalyst ZSM-5 from fly ash coal and rice husk ash has the potential to be used as catalysts in the partial oxidation of methane to methanol.

  12. Temperature effect on electrochemical promotion of syngas cogeneration in direct-methane solid oxide fuel cells

    Science.gov (United States)

    Huang, Ta-Jen; Huang, Meng-Chin

    Syngas cogeneration in direct-methane solid oxide fuel cells with Ni-yttria-stabilized zirconia (YSZ) anodes was studied with temperature varying from 700 to 900 °C. A phenomenon of electrochemical promotion of bulk lattice-oxygen extraction from the YSZ electrolyte was observed. With increasing temperature, this promotion effect increases while both the rate enhancement ratios of CO and CO 2 formations decrease. The activation energy of CO and CO 2 formation under close circuit is lower than that under open circuit. The activation energy for the lattice-oxygen extraction from the YSZ bulk is higher than that for the oxygen transport through the YSZ bulk. The process of lattice-oxygen extraction from YSZ is rate determining in direct-methane oxidation under the condition of either close circuit or open circuit. The dependence of CO formation rate on the oxygen supply rate is stronger than that of CO 2 formation rate. Electrochemical promotion of bulk lattice-oxygen extraction enhances syngas cogeneration.

  13. Evaluation of respiration in compost landfill biocovers intended for methane oxidation

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Pedicone, Alessio; Pedersen, Gitte Bukh

    2011-01-01

    will compete for O2 with other aerobic microorganisms. If the compost is not mature, a significant portion of the O2 diffusing into the compost layer will be consumed by non-methanotrophs, thereby limiting CH4 oxidation. The results of this study however also suggest that the consumption of O2 in the compost......A low-cost alternative approach to reduce landfill gas (LFG) emissions is to integrate compost into the landfill cover design in order to establish a biocover that is optimized for biological oxidation of methane (CH4). A laboratory and field investigation was performed to quantify respiration...... in an experimental compost biocover in terms of oxygen (O2) consumption and carbon dioxide (CO2) production and emission rates. O2 consumption and CO2 production rates were measured in batch and column experiments containing compost sampled from a landfill biowindow at Fakse landfill in Denmark. Column gas...

  14. Methyl Chloride from Direct Methane Partial Oxidation: A High-Temperature Shilov-Like Catalytic System

    Energy Technology Data Exchange (ETDEWEB)

    Yongchun Tang; John (Qisheng) Ma

    2012-03-23

    The intention of this study is to demonstrate and evaluate the scientific and economic feasibility of using special solvents to improve the thermal stability of Pt-catalyst in the Shilov system, such that a high reaction temperature could be achieved. The higher conversion rate (near 100%) of methyl chloride from partial oxidation of methane under the high temperature ({approx} 200 C) without significant Pt0 precipitation has been achieved. High concentration of the Cl- ion has been identified as the key for the stabilization of the Pt-catalysts. H/D exchange measurements indicated that the over oxidation will occur at the elevated temperature, developments of the effective product separation processes will be necessary in order to rationalize the industry-visible CH4 to CH3Cl conversion.

  15. Kinetic and morphological studies of palladium oxidation in oxygen-methane mixtures

    Science.gov (United States)

    Han, Jinyi

    The oxidation of Pd single crystals: Pd(111), Pd(100) and Pd(110) was studied using Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Low Electron Energy Diffraction (LEED) and Scanning Tunneling Microscopy (STM) as they were subjected to O2 in the pressure range between 1 and 150 Torr at temperatures 600-900 K. The oxygen species formed during oxidation, the oxygen uptake dependence on the sample history, the Pd single crystal surface morphology transformations, and the catalytic methane combustion over Pd single crystals were investigated in detail. The Pd single crystal oxidation proceeded through a three-step mechanism. Namely, (1) oxygen dissociatively adsorbed on Pd surface, forming chemisorbed oxygen and surface oxide; (2) atomic oxygen diffused through a thin surface oxide layer into Pd metal, forming near surface and bulk oxygen; (3) bulk PdO formed when a critical oxygen concentration was reached in the near surface region. The diffusion of oxygen through thin surface oxide layer into Pd metal decreased in the order: Pd(110)>Pd(100)>Pd(111). The oxygen diffusion coefficient was estimated to be around 10-16 cm2 s -1 at 600 K, with an activation energy of 80 kJ mol-1. Once bulk PdO was formed, the diffusion of oxygen through the bulk oxide layer was the rate-determining step for the palladium oxidation. The diffusion coefficient was equal to 10-18 cm2 s-1 at 600 K and the activation energy was approximately 120 kJ mol-1. The oxygen diffusion through thin surface oxide layer and bulk PdO followed the Mott-Cabrera parabolic diffusion law. The oxygen uptake on Pd single crystals depended on the sample history. The uptake amount increased with the population of the bulk oxygen species, which was achieved by high oxygen exposure at elevated temperatures, for example in 1 Torr O2 at above 820 K. Ar+ sputtering or annealing in vacuum at 1300 K depleted the bulk oxygen. The Pd single crystal surface

  16. Field-scale tracking of active methane-oxidizing communities in a landfill-cover soil reveals spatial and seasonal variability

    NARCIS (Netherlands)

    Henneberger, R.; Chiri, E.; Bodelier, P.L.E.; Frenzel, P.; Luke, C.; Schroth, M.H.

    2015-01-01

    Aerobic methane-oxidizing bacteria (MOB) in soils mitigate methane (CH4) emissions. We assessed spatial and seasonal differences in active MOB communities in a landfill cover soil characterized by highly variable environmental conditions. Field-based measurements of CH4 oxidation activity and stable

  17. Surface Reaction Kinetics of Steam- and CO2-Reforming as Well as Oxidation of Methane over Nickel-Based Catalysts

    Directory of Open Access Journals (Sweden)

    Karla Herrera Delgado

    2015-05-01

    Full Text Available An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented. The numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species. Reactions for the conversion of methane with oxygen, steam, and CO2 as well as methanation, water-gas shift reaction and carbon formation via Boudouard reaction are included. The mechanism is implemented in a one-dimensional flow field description of a fixed bed reactor. The model is evaluated by comparison of numerical simulations with data derived from isothermal experiments in a flow reactor over a powdered nickel-based catalyst using varying inlet gas compositions and operating temperatures. Furthermore, the influence of hydrogen and water as co-feed on methane dry reforming with CO2 is also investigated.

  18. Modeling of methane oxidation in landfill cover soil using an artificial neural network.

    Science.gov (United States)

    Abushammala, Mohammed F M; Basri, Noor Ezlin Ahmad; Elfithri, Rahmah; Younes, Mohammad K; Irwan, Dani

    2014-02-01

    Knowing the fraction of methane (CH4) oxidized in landfill cover soils is an important step in estimating the total CH4 emissions from any landfill. Predicting CH4 oxidation in landfill cover soils is a difficult task because it is controlled by a number of biological and environmental factors. This study proposes an artificial neural network (ANN) approach using feedforward backpropagation to predict CH4 oxidation in landfill cover soil in relation to air temperature, soil moisture content, oxygen (O2) concentration at a depth of 10 cm in cover soil, and CH4 concentration at the bottom of cover soil. The optimum ANN model giving the lowest mean square error (MSE) was configured from three layers, with 12 and 9 neurons at the first and the second hidden layers, respectively, log-sigmoid (logsig) transfer function at the hidden and output layers, and the Levenberg-Marquardt training algorithm. This study revealed that the ANN oxidation model can predict CH4 oxidation with a MSE of 0.0082, a coefficient of determination (R2) between the measured and predicted outputs of up to 0.937, and a model efficiency (E) of 0.8978. To conclude, further developments of the proposed ANN model are required to generalize and apply the model to other landfills with different cover soil properties.

  19. Numerical study on soot removal in partial oxidation of methane to syngas reactors

    Institute of Scientific and Technical Information of China (English)

    Weisheng; Wei; Tao; Zhang; Jian; Xu; Wei; Du

    2014-01-01

    The serious carbon deposition existing in catalytic partial oxidation of methane(CPOM) to syngas process is one of the key problems that impede its industrialization. In this study, 3-dimensional unsteady numerical simulations of the soot formation and oxidation in oxidation section in a heat coupling reactor were carried out by computational fluid dynamics(CFD) approach incorporating the Moss-Brookes model for soot formation. The model has been validated and proven to be in good agreement with experiment results. Effects of nozzle type,nozzle convergence angle, channel spacing, number of channels, radius/height ratio, oxygen/carbon ratio, preheat temperature and additional introduction of steam on the soot formation were simulated. Results show that the soot formation in oxidation section of the heat coupling reactor depends on both nozzle structures and operation conditions, and the soot concentration can be greatly reduced by optimization with the maximum mass fraction of soot inside the oxidation reactor from 2.28% to 0.0501%, and so that the soot mass fraction at the exit reduces from0.74% to 0.03%.

  20. Measurements and modeling to quantify emissions of methane and VOCs from shale gas operations: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Presto, Albert A [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2017-06-30

    The objectives of the project were to determine the leakage rates of methane and ozone-forming Volatile Organic Compounds (VOCs) and the emission rates of air toxics from Marcellus shale gas activities. Methane emissions in the Marcellus Shale region were differentiated between “newer” sources associated with shale gas development and “older” sources associated with coal or conventional natural gas exploration. This project conducted measurements of methane and VOC emissions from both shale and non-shale natural gas resources. The initial scope of the project was the Marcellus Shale basin, and measurements were conducted in both the western wet gas regions (southwest PA and WV) and eastern dry gas region (northeast PA) of the basin. During this project, we obtained additional funding from other agencies to expand the scope of measurements to include additional basins. The data from both the Marcellus and other basins were combined to construct a national analysis of methane emissions from oil & gas production activities.

  1. Dynamic changes of carbon isotope apparent fractionation factor to describe transition to syntrophic acetate oxidation during cellulose and acetate methanization.

    Science.gov (United States)

    Vavilin, Vasily A; Rytov, Sergey V

    2017-05-01

    To identify predominant metabolic pathway for cellulose methanization new equations that take into account dynamics of 13C are added to the basic model of cellulose methanization. The correct stoichiometry of hydrolysis, acidogenesis, acetogenesis and methanogenesis steps including biomass is considered. Using experimental data by Laukenmann et al. [Identification of methanogenic pathway in anaerobic digesters using stable carbon isotopes. Eng. Life Sci. 2010;10:1-6], who reported about the importance of ace`tate oxidation during mesophilic cellulose methanization, the model confirmed that, at high biomass concentration of acetate oxidizers, the carbon isotope fractionation factor amounts to about 1.085. The same model, suggested firstly for cellulose degradation, was used to describe, secondly, changes in, and in methane and carbon dioxide during mesophylic acetate methanization measured by Grossin-Debattista [Fractionnements isotopiques (13C/12C) engendres par la methanogenese: apports pour la comprehension des processus de biodegradation lors de la digestion anaerobie [doctoral thesis]. 2011. Bordeaux: Universite Bordeaux-1;2011. Available from: http://ori-oai.u-bordeaux1.fr/pdf/2011/GROSSIN-DEBATTISTA_JULIEN_2011.pdf . French].The model showed that under various ammonium concentrations, at dominating acetoclastic methanogenesis, the value decreases over time to a low level (1.016), while at dominating syntrophic acetate oxidation, coupled with hydrogenotrophic methanogenesis, slightly increases, reaching 1.060 at the end of incubation.

  2. Methane production and oxidation patterns along a hydrological gradient in Luther Bog, Ontario

    Science.gov (United States)

    Praetzel, Leandra; Berger, Sina; Blodau, Christian

    2016-04-01

    Methane emissions from natural peatlands contribute significantly to the global budget of atmospheric CH4. In the northern hemisphere, where climate models predict rising temperatures and precipitation rates, these emissions are likely to rise. So far, little is known about the change of processes of methane production and oxidation, which influence the total amount of methane emissions, in peatland soils under warmer and wetter climate conditions. Our work focuses on anaerobic CH4 production and aerobic CH4 oxidation processes along a hydrological gradient in an ombotrophic bog in Ontario, Canada that was induced by creation of a reservoir in 1952. Along this transect, four sites were established differing in hydrologic conditions and vegetation patterns. We examined depth profiles of CO2 and CH4 concentrations and delta 13C isotope ratios in the peat using silicon samplers, dialysis chambers and multi-level piezometers. Chamber flux measurements were used to determine carbon fluxes. Isotope mass balances were calculated based on 13C isotope ratios and concentration profiles. By this approach the contribution of anaerobic CH4 and CO2 production to the total ER flux and the amount of oxidised CH4 can be determined. In addition meteorological data, soil temperatures, moisture and water table levels were recorded. By raising data at different sites and dates and with the help of the additionally recorded parameters, we will be able to make predictions about changing CH4 production and oxidation processes due to changing climate conditions. Preliminary results show that CH4 concentrations in the soil profile are higher at the sites which are exposed to stronger water table fluctuations, whereas CO2 concentration levels are lower at these sites. At all sites, CO2 concentrations in the peat are increasing but CH4 profiles are fairly stable. Moreover, isotopic signatures of 13CH4 indicate that the importance of the production pathway changes with depth from acetoclastic

  3. Methane oxidation at 55 degrees C and pH 2 by a thermoacidophilic bacterium belonging to the Verrucomicrobia phylum.

    Science.gov (United States)

    Islam, Tajul; Jensen, Sigmund; Reigstad, Laila Johanne; Larsen, Oivind; Birkeland, Nils-Kåre

    2008-01-01

    Methanotrophic bacteria constitute a ubiquitous group of microorganisms playing an important role in the biogeochemical carbon cycle and in control of global warming through natural reduction of methane emission. These bacteria share the unique ability of using methane as a sole carbon and energy source and have been found in a great variety of habitats. Phylogenetically, known methanotrophs constitute a rather limited group and have so far only been affiliated with the Proteobacteria. Here, we report the isolation and initial characterization of a nonproteobacterial obligately methanotrophic bacterium. The isolate, designated Kam1, was recovered from an acidic hot spring in Kamchatka, Russia, and is more thermoacidophilic than any other known methanotroph, with optimal growth at approximately 55 degrees C and pH 3.5. Kam1 is only distantly related to all previously known methanotrophs and belongs to the Verrucomicrobia lineage of evolution. Genes for methane monooxygenases, essential for initiation of methane oxidation, could not be detected by using standard primers in PCR amplification and Southern blot analysis, suggesting the presence of a different methane oxidation enzyme. Kam1 also lacks the well developed intracellular membrane systems typical for other methanotrophs. The isolate represents a previously unrecognized biological methane sink, and, due to its unusual phylogenetic affiliation, it will shed important light on the origin, evolution, and diversity of biological methane oxidation and on the adaptation of this process to extreme habitats. Furthermore, Kam1 will add to our knowledge of the metabolic traits and biogeochemical roles of the widespread but poorly understood Verrucomicrobia phylum.

  4. Dissimilatory perchlorate reduction linked to aerobic methane oxidation via chlorite dismutase

    Science.gov (United States)

    Oremland, R. S.; Baesman, S. M.; Miller, L. G.

    2013-12-01

    The presence of methane (CH4) in the atmosphere of Mars is controversial yet the evidence has aroused scientific interest, as CH4 could be a harbinger of extant or extinct microbial life. There are various oxidized compounds present on the surface of Mars that could serve as electron acceptors for the anaerobic oxidation of CH4, including perchlorate (ClO4-). We examined the role of perchlorate, chlorate (ClO3-) and chlorite (ClO2-) as oxidants linked to CH4 oxidation. Dissimilatory perchlorate reduction begins with reduction of ClO4- to ClO2- and ends with dismutation of chlorite to yield chloride (Cl-) and molecular oxygen (O2). We explored the potential for aerobic CH4 oxidizing bacteria to couple with oxygen derived from chlorite dismutation during dissimilatory perchlorate reduction. Methane (0.2 kPa) was completely removed within several days from the N2-flushed headspace above cell suspensions of methanotrophs (Methylobacter albus strain BG8) and perchlorate reducing bacteria (Dechloromonas agitata strain CKB) in the presence of 5 mM ClO2-. Similar rates of CH4 consumption were observed for these mixed cultures whether they were co-mingled or segregated under a common headspace, indicating that direct contact of cells was not required for methane consumption to occur. We also observed complete removal of 0.2 kPa CH4 in bottles containing dried soil (enriched in methanotrophs by CH4 additions over several weeks) and D. agitata CKB and in the presence of 10 mM ClO2-. This soil (seasonally exposed sediment) collected from the shoreline of a freshwater lake (Searsville Lake, CA) demonstrated endogenous CH4 uptake as well as perchlorate, chlorate and chlorite reduction/dismutation. However, these experiments required physical separation of soil from the aqueous bacterial culture to allow for the partitioning of O2 liberated from chlorite dismutation into the shared headspace. Although dissimilatory reduction of ClO4- and ClO3- could be inferred from the

  5. Methane Oxidation to Methanol Catalyzed by Cu-Oxo Clusters Stabilized in NU-1000 Metal–Organic Framework

    Energy Technology Data Exchange (ETDEWEB)

    Ikuno, Takaaki [Department; Zheng, Jian [Institute; Vjunov, Aleksei [Institute; Sanchez-Sanchez, Maricruz [Department; Ortuño, Manuel A. [Department; Pahls, Dale R. [Department; Fulton, John L. [Institute; Camaioni, Donald M. [Institute; Li, Zhanyong [Department; Ray, Debmalya [Department; Mehdi, B. Layla [Institute; Browning, Nigel D. [Institute; Materials; Farha, Omar K. [Department; Department; Hupp, Joseph T. [Department; Cramer, Christopher J. [Department; Gagliardi, Laura [Department; Lercher, Johannes A. [Department; Institute

    2017-07-17

    The catalyzed conversion of shale gas-derived light hydrocarbons, e.g. methane to methanol, for further application as automotive fuels and/or bulk chemicals is especially attractive in light of improved methods of hydrocarbon extraction. MOF based catalysts have previously been demonstrated to be active for a range of catalytic reactions. In this work we used Cu-NU1000 as a methane-to-methanol oxidation catalyst. In addition to product studies, in-situ X-ray Absorption Spectroscopic (XAS) experiments are performed under catalytic conditions in order to follow the modification of the Cu-species and directly probe the structure/activity properties of the Cu-NU1000 system. The insights reported herein serve as a first look at metal-organic framework materials as catalysts for methane oxidation and be the basis for development of the subsequent generations of materials.

  6. Methane Emissions from Landfill: Isotopic Evidence for Low Percentage of Oxidation from Gas Wells, Active and Closed Cells

    Science.gov (United States)

    Lowry, David; Fisher, Rebecca; Zazzeri, Giulia; al-Shalaan, Aalia; France, James; Lanoisellé, Mathias; Nisbet, Euan

    2017-04-01

    Large landfill sites remain a significant source of methane emissions in developed and developing countries, with a global estimated flux of 29 Tg / yr in the EDGAR 2008 database. This is significantly lower than 20 years ago due to the introduction of gas extraction systems, but active cells still emit significant amounts of methane before the gas is ready for extraction. Historically the methane was either passively oxidized through topsoil layers or flared. Oxidation is still the primary method of methane removal in many countries, and covered, remediated cells across the world continue to emit small quantities of methane. The isotopic signatures of methane from landfill gas wells, and that emitted from active and closed cells have been characterized for more than 20 UK landfills since 2011, with more recent work in Kuwait and Hong Kong. Since 2013 the emission plumes have been identified by a mobile measurement system (Zazzeri et al., 2015). Emissions in all 3 countries have a characteristic δ13C signature of -58 ± 3 ‰ dominated by emissions from the active cells, despite the hot, dry conditions of Kuwait and the hot, humid conditions of Hong Kong. Gas well samples define a similar range. Surface emissions from closed cells and closed landfills are mostly in the range -56 to -52 ‰Ṫhese are much more depleted values than those observed in the 1990s (up to -35 ) when soil oxidation was the dominant mechanism of methane removal. Calculations using isotopic signatures of the amount of methane oxidised in these closed areas before emission to atmosphere range from 5 to 15%, but average less than 10%, and are too small to calculate from the high-emitting active cells. Compared to other major methane sources, landfills have the most consistent isotopic signature globally, and are distinct from the more 13C-enriched natural gas, combustion and biomass burning sources. Zazzeri, G. et al. (2015) Plume mapping and isotopic characterization of anthropogenic methane

  7. Mitigation of methane and nitrous oxide emissions from animal operations: I. A review of enteric methane mitigation options

    NARCIS (Netherlands)

    Hristov, A.N.; Oh, J.; Firkins, J.; Dijkstra, J.; Kebreab, E.; Waghorn, G.; Makkar, H.P.S.; Adesogan, A.T.; Yang, W.; Lee, C.; Gerber, P.J.; Henderson, B.L.; Tricarico, J.M.

    2013-01-01

    The goal of this review was to analyze published data related to mitigation of enteric methane (CH4) emissions from ruminant animals to document the most effective and sustainable strategies. Increasing forage digestibility and digestible forage intake was one of the major recommended CH4 mitigation

  8. Mitigation of methane and nitrous oxide emissions from animal operations: I. A review of enteric methane mitigation options

    NARCIS (Netherlands)

    Hristov, A.N.; Oh, J.; Firkins, J.; Dijkstra, J.; Kebreab, E.; Waghorn, G.; Makkar, H.P.S.; Adesogan, A.T.; Yang, W.; Lee, C.; Gerber, P.J.; Henderson, B.L.; Tricarico, J.M.

    2013-01-01

    The goal of this review was to analyze published data related to mitigation of enteric methane (CH4) emissions from ruminant animals to document the most effective and sustainable strategies. Increasing forage digestibility and digestible forage intake was one of the major recommended CH4 mitigation

  9. A New IPCC Tier 4 Site-Specific Model for Landfill Methane Emissions Inclusive of Seasonal Methane Oxidation

    Science.gov (United States)

    This project was initiated in the U.S. by the California Energy Commission (CEC) in cooperation with the California Integrated Waste Management Board and the California Air Resources Board to develop improved methods for landfill methane emissions for the California greenhouse gas inventory. This 3-...

  10. Effect of biomass concentration on methane oxidation activity using mature compost and graphite granules as substrata.

    Science.gov (United States)

    Xie, S; O'Dwyer, T; Freguia, S; Pikaar, I; Clarke, W P

    2016-10-01

    Reported methane oxidation activity (MOA) varies widely for common landfill cover materials. Variation is expected due to differences in surface area, the composition of the substratum and culturing conditions. MOA per methanotrophic cell has been calculated in the study of natural systems such as lake sediments to examine the inherent conditions for methanotrophic activity. In this study, biomass normalised MOA (i.e., MOA per methanotophic cell) was measured on stabilised compost, a commonly used cover in landfills, and on graphite granules, an inert substratum widely used in microbial electrosynthesis studies. After initially enriching methanotrophs on both substrata, biomass normalised MOA was quantified under excess oxygen and limiting methane conditions in 160ml serum vials on both substrata and blends of the substrata. Biomass concentration was measured using the bicinchoninic acid assay for microbial protein. The biomass normalised MOA was consistent across all compost-to-graphite granules blends, but varied with time, reflecting the growth phase of the microorganisms. The biomass normalised MOA ranged from 0.069±0.006μmol CH4/mg dry biomass/h during active growth, to 0.024±0.001μmol CH4/mg dry biomass/h for established biofilms regardless of the substrata employed, indicating the substrata were equally effective in terms of inherent composition. The correlation of MOA with biomass is consistent with studies on methanotrophic activity in natural systems, but biomass normalised MOA varies by over 5 orders of magnitude between studies. This is partially due to different methods being used to quantify biomass, such as pmoA gene quantification and the culture dependent Most Probable Number method, but also indicates that long term exposure of materials to a supply of methane in an aerobic environment, as can occur in natural systems, leads to the enrichment and adaptation of types suitable for those conditions. Copyright © 2016 Elsevier Ltd. All rights

  11. Catalytic combustion of methane on La1-xCexFeO3 oxides

    Science.gov (United States)

    Xiang, Xian-Ping; Zhao, Lei-Hong; Teng, Bo-Tao; Lang, Jia-Jian; Hu, Xin; Li, Tie; Fang, Yi-An; Luo, Meng-Fei; Lin, Jian-Jun

    2013-07-01

    A series of La1-xCexFeO3 (x = 0-0.5) perovskite oxides were prepared by a sol-gel method. X-ray diffraction spectrometer (XRD), BET surface area measurements, scanning electron microscopy (SEM) images, and temperature-programmed reduction (TPR) were used to characterize their physical structures and redox properties. Catalytic methane combustion tests for La1-xCexFeO3 (x = 0-0.5) perovskite oxides show that the activity of LaFeO3 was highly improved due to the introduction of Ce in the A-site of the perovskite catalysts. Among all the catalysts, La0.7Ce0.3FeO3 has the maximum oxidative performance with the corresponding T90 as low as 510 °C. Combining with density functional theory calculation, it was suggested that the electrons of Fe ions increase in La0.875Ce0.125FeO3 due to the introduction of Ce4+ ion, which leads to stronger interactions with adsorbed O2. Correspondingly, the adsorption energy of O2 on La0.875Ce0.125FeO3 increases and the Osbnd O bond is activated. Thus, the Ce doped perovskite has higher oxidative activity than pure LaFeO3.

  12. Methane oxidation in a landfill cover soil reactor: Changing of kinetic parameters and microorganism community structure.

    Science.gov (United States)

    Xing, Zhi L; Zhao, Tian T; Gao, Yan H; Yang, Xu; Liu, Shuai; Peng, Xu Y

    2017-02-23

    Changing of CH4 oxidation potential and biological characteristics with CH4 concentration was studied in a landfill cover soil reactor (LCSR). The maximum rate of CH4 oxidation reached 32.40 mol d(-1) m(-2) by providing sufficient O2 in the LCSR. The kinetic parameters of methane oxidation in landfill cover soil were obtained by fitting substrate diffusion and consumption model based on the concentration profile of CH4 and O2. The values of [Formula: see text] (0.93-2.29%) and [Formula: see text] (140-524 nmol kgsoil-DW(-1)·s(-1)) increased with CH4 concentration (9.25-20.30%), while the values of [Formula: see text] (312.9-2.6%) and [Formula: see text] (1.3 × 10(-5) to 9.0 × 10(-3) nmol mL(-1) h(-1)) were just the opposite. MiSeq pyrosequencing data revealed that Methylobacter (the relative abundance was decreased with height of LCSR) and Methylococcales_unclassified (the relative abundance was increased expect in H 80) became the key players after incubation with increasing CH4 concentration. These findings provide information for assessing CH4 oxidation potential and changing of biological characteristics in landfill cover soil.

  13. Water dispersal of methanotrophic bacteria maintains functional methane oxidation in Sphagnum mosses

    Directory of Open Access Journals (Sweden)

    Anuliina ePutkinen

    2012-01-01

    Full Text Available It is known that Sphagnum associated methanotrophy (SAM changes in relation to the peatland water table (WT level. After drought, rising WT is able to reactivate SAM. We aimed to reveal whether this reactivation is due to activation of indigenous methane (CH4 oxidizing bacteria (MOB already present in the mosses or to MOB present in water. This was tested through two approaches: In a transplantation experiment, Sphagna lacking SAM activity were transplanted into flark water next to Sphagna oxidizing CH4. Already after 3 d, most of the transplants showed CH4 oxidation activity. Microarray showed that the MOB community compositions of the transplants and the original active mosses had become more similar within 28 d thus indicating MOB movement through water between mosses. Methylocystis-related type II MOB dominated the community. In a following experiment, SAM inactive mosses were bathed overnight in non-sterile and sterile-filtered SAM active site flark water. Only mosses bathed with non-sterile flark water became SAM active, which was also shown by the pmoA copy number increase of over 60 times. Thus, it was evident that MOB present in the water can colonize Sphagnum mosses. This colonization could act as a resilience mechanism for peatland CH4 dynamics by allowing the re-emergence of CH4 oxidation activity in Sphagnum.

  14. Molecular isotopic evidence for anaerobic oxidation of methane in deep-sea hydrothermal vent environment in Okinawa Trough

    Science.gov (United States)

    Uchida, M.; Takai, K.; Inagaki, F.

    2003-04-01

    Large amount of methane in anoxic marine sediments as well as cold seeps and hydrothermal vents is recycled through for an anoxic oxidation of methane processes. Now that combined results of field and laboratory studies revealed that microbiological activity associated with syntrophic consortium of archaea performing reversed methanogenesis and sulfate-reducing bacteria is significant roles in methane recycling, anaerobic oxidation of methane (AOM). In this study, we examined the diversity of archaeal and bacterial assemblages of AOM using compound-specific stable carbon isotopic and phylogenetic analyses. "Iheya North" in Okinawa Trough is sediment-rich, back arc type hydrothermal system (27^o47'N, 126^o53'E). Sediment samples were collected from three sites where are "bubbling sites", yellow-colored microbial mats are formed with continuous bubbling from the seafloor bottom, vent mussel's colonies site together with slowly venting and simmering, and control site off 100 m distance from thermal vent. This subsea floor structure has important effect in the microbial ecosystem and interaction between their activity and geochemical processes in the subseafloor habitats. Culture-independent, molecular biological analysis clearly indicated the presence of thermophilic methanogens in deeper area having higher temperatures and potential activity of AMOs consortium in the shallower area. AMO is composed with sulfate-reducing bacterial components (Desulfosarcina spp.) and anoxic methane oxidizing archaea (ANME-2). These results were consistent with the results of compound-specific carbon analysis of archaeal biomarkers. They showed extremely depleted 13C contents (-80 ppm ˜ -100 ppm), which also appeared to be capable of directly oxidizing methane.

  15. Spectroscopic and XRD characterisation of zeolite catalysts active for the oxidative methylation of benzene with methane

    Science.gov (United States)

    Adebajo, Moses O.; Long, Mervyn A.; Frost, Ray L.

    2004-03-01

    The benzene methylation with methane over zeolite catalysts was previously shown in our laboratory to require the presence of oxygen. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now reports the results of the characterisation of the zeolite catalysts used for the oxidative benzene methylation reaction in order to provide some information about their composition, structure, properties and their behaviour before and after the reaction. The catalysts were characterised by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), FT-IR and solid state NMR. XRD results indicate that the crystalline structures of all the ZSM-5 and H-beta catalysts remained unchanged after batch reaction of benzene with methane over the catalysts in agreement with the observation that the catalysts recovered from the reactor could be reused without loss of activity. Elemental analyses and FT-IR data show that as the level of metal ion exchange increases, the Brönsted acid concentration decreases but this metal ion exchange does not totally remove Brönsted acidity. FT-IR results further show that only a small amount of acid sites is actually necessary for a catalyst to be active since used catalysts containing highly reduced Brönsted acidity are found to be reusable without any loss of their activity. 29Si and 27Al magic angle spinning (MAS) NMR together with FT-IR spectra also show that all the active zeolites catalysts contain some extra-framework octahedral aluminium in addition to the normal tetrahedral framework aluminium. The presence of this extra-lattice aluminium does not, however, have any adverse effect on the crystallinity of the catalysts both before and after oxidative benzene methylation reaction. There appears also to be no significant dealumination

  16. Low-level 14C methane oxidation rate measurements modified for remote field settings

    Science.gov (United States)

    Pack, M. A.; Pohlman, J.; Ruppel, C. D.; Xu, X.

    2012-12-01

    Aerobic methane oxidation limits atmospheric methane emissions from degraded subsea permafrost and dissociated methane hydrates in high latitude oceans. Methane oxidation rate measurements are a crucial tool for investigating the efficacy of this process, but are logistically challenging when working on small research vessels in remote settings. We modified a low-level 14C-CH4 oxidation rate measurement for use in the Beaufort Sea above hydrate bearing sediments during August 2012. Application of the more common 3H-CH4 rate measurement that uses 106 times more radioactivity was not practical because the R/V Ukpik cannot accommodate a radiation van. The low-level 14C measurement does not require a radiation van, but careful isolation of the 14C-label is essential to avoid contaminating natural abundance 14C measurements. We used 14C-CH4 with a total activity of 1.1 μCi, which is far below the 100 μCi permitting level. In addition, we modified field procedures to simplify and shorten sample processing. The original low-level 14C-CH4 method requires 6 steps in the field: (1) collect water samples in glass serum bottles, (2) inject 14C-CH4 into bottles, (3) incubate for 24 hours, (4) filter to separate the methanotrophic bacterial cells from the aqueous sample, (5) kill the filtrate with sodium hydroxide (NaOH), and (6) purge with nitrogen to remove unused 14C-CH4. Onshore, the 14C-CH4 respired to carbon dioxide or incorporated into cell material by methanotrophic bacteria during incubation is quantified by accelerator mass spectrometry (AMS). We conducted an experiment to test the possibility of storing samples for purging and filtering back onshore (steps 4 and 6). We subjected a series of water samples to steps 1-3 & 5, and preserved with mercuric chloride (HgCl2) instead of NaOH because HgCl2 is less likely to break down cell material during storage. The 14C-content of the carbon dioxide in samples preserved with HgCl2 and stored for up to 2 weeks was stable

  17. Catalytic conversion of methane to methanol on Cu-SSZ-13 using N2O as oxidant.

    Science.gov (United States)

    Ipek, B; Lobo, R F

    2016-11-08

    Direct catalytic methanol production from methane is achieved on Cu-SSZ-13 zeolite catalysts using N2O as the oxidant. The methanol production rate on Cu-SSZ-13 (on a per gram basis) was more than twice the rate on Cu-mordenite and more than four times the rate on Cu-ZSM-5.

  18. Mitigation of ammonia, nitrous oxide and methane emissions from manure management chains: a meta-analysis and integrated assessment

    NARCIS (Netherlands)

    Yong, Y.; Velthof, G.L.; Oenema, O.

    2015-01-01

    Livestock manure contributes considerably to global emissions of ammonia (NH3) and greenhouse gases (GHG), especially methane (CH4) and nitrous oxide (N2O). Various measures have been developed to mitigate these emissions, but most of these focus on one specific gas and/or emission source. Here, we

  19. Mitigation of methane and nitrous oxide emissions from animal operations: II. A review of manure management mitigation options

    NARCIS (Netherlands)

    Montes, F.; Meinen, R.; Dell, C.; Rotz, A.; Hristov, A.N.; Oh, J.; Waghorn, G.; Gerber, P.J.; Henderson, B.L.; Makkar, H.P.S.; Dijkstra, J.

    2013-01-01

    This review analyzes published data on manure management practices used to mitigate methane (CH4) and nitrous oxide (N2O) emissions from animal operations. Reducing excreted nitrogen (N) and degradable organic carbon (C) by diet manipulation to improve the balance of nutrient inputs with production

  20. Mitigation of ammonia, nitrous oxide and methane emissions from manure management chains: a meta-analysis and integrated assessment

    NARCIS (Netherlands)

    Yong, Y.; Velthof, G.L.; Oenema, O.

    2015-01-01

    Livestock manure contributes considerably to global emissions of ammonia (NH3) and greenhouse gases (GHG), especially methane (CH4) and nitrous oxide (N2O). Various measures have been developed to mitigate these emissions, but most of these focus on one specific gas and/or emission source. Here, we

  1. Effect of surface composition of yttrium-stabilized zirconia on partial oxidation of methane to synthesis gas.

    NARCIS (Netherlands)

    Zhu, Jianjun; Ommen, van Jan G.; Knoester, A.; Lefferts, Leon

    2005-01-01

    Catalytic partial oxidation of methane to synthesis gas (CPOM) over yttrium-stabilized zirconia (YSZ) was studied within a wide temperature window (500¿1100 °C). The catalysts were characterized by X-ray fluorescence (XRF) and low-energy ion scattering (LEIS). The influence of calcination temperatur

  2. Nitrous Oxide and Methane Fluxes Following Ammonium Sulfate and Vinasse Application on Sugar Cane Soil.

    Science.gov (United States)

    Paredes, Debora da S; Alves, Bruno J R; dos Santos, Marco A; Bolonhezi, Denizart; Sant'Anna, Selenobaldo A C; Urquiaga, Segundo; Lima, Magda A; Boddey, Robert M

    2015-09-15

    This study aimed to quantify nitrous oxide (N2O) and methane (CH4) emission/sink response from sugar cane soil treated with fertilizer nitrogen (N) and vinasse applied separately or in sequence, the latter being investigated with regard to the time interval between applications for a possible effect on emissions. The study was carried out in a traditional area of unburned sugar cane in São Paulo state, Brazil. Two levels of N fertilization (0 and 100 kg N ha(-1)) with no added vinasse and combined with vinasse additions at different times (100 m(-3) ha(-1) at 3 and 15 days after N fertilization) were evaluated. Methane and N2O fluxes were monitored for 211 days. On average, the soil was a sink for CH4, which was not affected by the treatments. Emissions of N2O were induced by N fertilizer and vinasse applications. For ammonium sulfate, 0.6% of the added N was emitted as N2O, while for vinasse, this ranged from 1.0 to 2.2%. Changes in N2O fluxes were detected the day after application of vinasse on the N fertilized areas, but although the emission factor (EF) was 34% greater, the EF was not significantly different from fertilizer N alone. Nevertheless, we recommend to not apply vinasse after N fertilization to avoid boosting N2O emissions.

  3. Plasma-produced phase-pure cuprous oxide nanowires for methane gas sensing

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Qijin, E-mail: ijin.cheng@xmu.edu.cn; Zhang, Fengyan [School of Energy Research, Xiamen University, Xiamen City, Fujian Province 361005 (China); Yan, Wei [School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, New South Wales 2052 (Australia); Plasma Nanoscience Laboratories, CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Randeniya, Lakshman [Plasma Nanoscience Laboratories, CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Ostrikov, Kostya [Plasma Nanoscience Laboratories, CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Plasma Nanoscience, School of Physics, The University of Sydney, Sydney, New South Wales 2006 (Australia)

    2014-03-28

    Phase-selective synthesis of copper oxide nanowires is warranted by several applications, yet it remains challenging because of the narrow windows of the suitable temperature and precursor gas composition in thermal processes. Here, we report on the room-temperature synthesis of small-diameter, large-area, uniform, and phase-pure Cu{sub 2}O nanowires by exposing copper films to a custom-designed low-pressure, thermally non-equilibrium, high-density (typically, the electron number density is in the range of 10{sup 11}–10{sup 13} cm{sup −3}) inductively coupled plasmas. The mechanism of the plasma-enabled phase selectivity is proposed. The gas sensors based on the synthesized Cu{sub 2}O nanowires feature fast response and recovery for the low-temperature (∼140 °C) detection of methane gas in comparison with polycrystalline Cu{sub 2}O thin film-based gas sensors. Specifically, at a methane concentration of 4%, the response and the recovery times of the Cu{sub 2}O nanowire-based gas sensors are 125 and 147 s, respectively. The Cu{sub 2}O nanowire-based gas sensors have a potential for applications in the environmental monitoring, chemical industry, mining industry, and several other emerging areas.

  4. Modeling and optimization of catalytic partial oxidation methane reforming for fuel cells

    Science.gov (United States)

    Chaniotis, A. K.; Poulikakos, D.

    The objective of this paper is the investigation and optimization of a micro-reformer for a fuel cell unit based on catalytic partial oxidation using a systematic numerical study of chemical composition and inflow conditions. The optimization targets hydrogen production from methane. Additionally, the operating temperature, the amount of carbon formation and the methane conversion efficiency are taking into account. The fundamental investigation is first based on simplified reactor models (surface perfectly stirred reactor (SPRS)). A detailed surface chemistry mechanism is adopted in order to capture all the important features of the reforming process. As a consequence, the residence time of the process is taken into account, which means that the products are not necessary in equilibrium. Subsequently, in order to test the validity of the findings from the simplified reactor model, more detailed simulations (involving the Navier-Stokes equations) were performed for the regions of interest. A region where all the targeted operating conditions are satisfied and the yield of hydrogen is around 80% is identified.

  5. Platinum and palladium doped tin oxide thick film sensors for sensing methane and hydrogen

    Science.gov (United States)

    Choudhary, Meenakshi; Mishra, V. N.; Dwivedi, R.

    2013-01-01

    In this work, platinum (Pt) and palladium (Pd) doped SnO2 thick film sensors have been developed using solid state derived tin oxide powder. Thick film sensors were fabricated on a 1˝x1˝ alumina substrate. The crystal structure and particle size are confirmed by X-ray diffraction (XRD) pattern. The fabricated sensors are tested for varying concentration (1-5%) of hydrogen and methane gas at different operating temperatures (200-350 °C). The effect of Pt and Pd doping have been analysed on different operating temperature, sensitivity and response/recovery time. The doping effects are also very important from view point of the gas selectivity. Based on the experimental results, we have observed the formation of tetragonal structure and particle size of the powders is drastically decreases from 26 to 19 nm after replacing the platinum dopant with palladium. Both the doped sensors have been found to be sensitive for hydrogen as compare to methane however, Pd-doped SnO2 sensor are most selective for hydrogen with very fast response and recovery time (20 s, 101 s) due to the small size effect.

  6. Using Carbon Dioxide to Enhance Recovery of Methane from Gas Hydrate Reservoirs: Final Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    McGrail, B. Peter; Schaef, Herbert T.; White, Mark D.; Zhu, Tao; Kulkarni, Abhijeet S.; Hunter, Robert B.; Patil, Shirish L.; Owen, Antionette T.; Martin, P F.

    2007-09-01

    Carbon dioxide sequestration coupled with hydrocarbon resource recovery is often economically attractive. Use of CO2 for enhanced recovery of oil, conventional natural gas, and coal-bed methane are in various stages of common practice. In this report, we discuss a new technique utilizing CO2 for enhanced recovery of an unconventional but potentially very important source of natural gas, gas hydrate. We have focused our attention on the Alaska North Slope where approximately 640 Tcf of natural gas reserves in the form of gas hydrate have been identified. Alaska is also unique in that potential future CO2 sources are nearby, and petroleum infrastructure exists or is being planned that could bring the produced gas to market or for use locally. The EGHR (Enhanced Gas Hydrate Recovery) concept takes advantage of the physical and thermodynamic properties of mixtures in the H2O-CO2 system combined with controlled multiphase flow, heat, and mass transport processes in hydrate-bearing porous media. A chemical-free method is used to deliver a LCO2-Lw microemulsion into the gas hydrate bearing porous medium. The microemulsion is injected at a temperature higher than the stability point of methane hydrate, which upon contacting the methane hydrate decomposes its crystalline lattice and releases the enclathrated gas. Small scale column experiments show injection of the emulsion into a CH4 hydrate rich sand results in the release of CH4 gas and the formation of CO2 hydrate

  7. Greenhouse warming by nitrous oxide and methane in the Proterozoic Eon.

    Science.gov (United States)

    Roberson, A L; Roadt, J; Halevy, I; Kasting, J F

    2011-07-01

    An anoxic, sulfidic ocean that may have existed during the Proterozoic Eon (0.54-2.4 Ga) would have had limited trace metal abundances because of the low solubility of metal sulfides. The lack of copper, in particular, could have had a significant impact on marine denitrification. Copper is needed for the enzyme that controls the final step of denitrification, from N(2) O to N(2) . Today, only about 5-6% of denitrification results in release of N(2) O. If all denitrification stopped at N(2) O during the Proterozoic, the N(2) O flux could have been 15-20 times higher than today, producing N(2) O concentrations of several ppmv, but only if O(2) levels were relatively high (>0.1 PAL). At lower O(2) levels, N(2) O is rapidly photodissociated. Methane concentrations may also have been elevated during this time, as has been previously suggested. A lack of dissolved O(2) and sulfate in the deep ocean could have produced a high methane flux from marine sediments, as much as 10-20 times today's methane flux from land. The photochemical lifetime of CH(4) increases as more CH(4) is added to the atmosphere, so CH(4) concentrations of up to 100 ppmv are possible during this time. The combined greenhouse effect of CH(4) and N(2) O could have provided up to 10° of warming, thereby keeping the surface warm during the Proterozoic without necessitating high CO(2) levels. A second oxygenation event near the end of the Proterozoic would have resulted in a reduction in both atmospheric N(2) O and CH(4) , perhaps triggering the Neoproterozoic "Snowball Earth" glaciations.

  8. Thermodynamic Analysis of Methane-fueled Solid Oxide Fuel Cells Considering CO Electrochemical Oxidation

    Institute of Scientific and Technical Information of China (English)

    Qiong Sun; Keqing Zheng; Meng Ni⁎

    2014-01-01

    abstract Thermodynamic analyses in the literature have shown that solid oxide fuel cells (SOFCs) with proton conducting electrolyte (H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte (O-SOFC). However, these studies only consider H2 electrochemical oxidation and totally neglect the contribution of CO electrochemical oxidation in O-SOFC. In this short communication, a thermodynamic model is developed to compare the theoretically maximum efficiencies of H-SOFC and O-SOFC, considering the electrochemical oxidation of CO in O-SOFC anode. It is found that O-SOFC exhibits a higher maximum efficiency than H-SOFC due to the contribution from CO electrochemical oxidation, which is contrary to the common understanding of electrolyte effect on SOFC performance. The effects of operating temperature and fuel utilization factor on the theoretical efficiency of SOFC are also analyzed and discussed.

  9. Integration of CO2 air capture and solid oxide electrolysis for methane production

    DEFF Research Database (Denmark)

    Ebbehøj, Søren Lyng

    This work studied the production of substitute natural gas (SNG) from CO2 captured from the atmosphere followed by co-electrolysis with H2O in solid oxide electrolyzer cells (SOEC) and downstream catalytic methane production.Over the coming 20 years, Denmark is on a track to remove fossil fuels...... are projected to be used for production of process heat, peak-load power generation and on the longer term to replace hydrocarbons in the most energy intensive parts of the transportation sector; especially aviation. As a prerequisite for the scenario, no biomass can be imported to enhance the supply...... of combustible resources. In such an energy system, technologies for production of CO2 neutral hydrocarbons for easy storage and use in the existing infrastructure; especially in the natural gas grid; may be of great value. The studied technology fulfills those demands.The main goal of the work was to design...

  10. Atmospheric methane and nitrous oxide of the Late Pleistocene from Antarctic ice cores.

    Science.gov (United States)

    Spahni, Renato; Chappellaz, Jérôme; Stocker, Thomas F; Loulergue, Laetitia; Hausammann, Gregor; Kawamura, Kenji; Flückiger, Jacqueline; Schwander, Jakob; Raynaud, Dominique; Masson-Delmotte, Valérie; Jouzel, Jean

    2005-11-25

    The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 +/- 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values. In contrast, the N2O record shows maximum concentrations of 278 +/- 7 ppbv, slightly higher than early Holocene values.

  11. Methane-Sensing Performance Enhancement in Graphene Oxide/Mg:ZnO Heterostructure Devices

    Science.gov (United States)

    Sarkar, Argha; Maity, Santanu; Joseph, Aneesh M.; Chakraborty, S. K.; Thomas, Tiju

    2017-10-01

    Methane-sensing using reduced doped graphene oxide (rGO)/Mg:ZnO heterostructure devices is reported here. All samples are tested with CH4 in dry air ambient by a gas-analyzing set-up. Crystallinity of the sensing film is improved through annealing treatment (at 800°C). The active device area (i.e., the rGO and rGO/Mg:ZnO heterostructures) are characterized using scanning electron microscope imaging, x-ray diffraction, and x-ray spectroscopy measurements. Electrical performance of the fabricated device is optimized. rGO/Mg:ZnO heterostructures are substantially more sensitive and have better transient response than bare rGO-based sensor devices. All fundamental parameters such as sensitivity and response-recovery time are examined and reported in detail.

  12. Modelling the growth of methane-oxidizing bacteria in a fixed biofilm

    DEFF Research Database (Denmark)

    Bilbo, Carl Morten; Arvin, Erik; Holst, Helle

    1992-01-01

    Methane-oxidizing bacteria were grown in a fixed biofilm reactor in order to study their ability to degrade chlorinated aliphatic hydrocarbons. Focus is on the growth behaviour of the mixed culture. The growth is described by a model that includes methanotrophic bacteria in the active biomass...... fraction. The inactive biomass fraction consists of exocellular polymers and biodegradable and inert particulate biomass. The model describes the oxygen respiration in detail. Yield coefficients, decay constants and hydrolysis constants are estimated based on the oxygen respiration. An analysis...... of the observability of the system reveals that several of the coefficients cannot be determined explicitly due to the complexity of the model and the limited amount of variables measured. Estimation procedures based on least squares methods are employed and parameter estimates and confidence intervals are computed...

  13. Partial oxidation of methane to syngas catalyzed by a nickel nanowire catalyst

    Institute of Scientific and Technical Information of China (English)

    Xuebin Hong; Yaquan Wang

    2009-01-01

    A nickel nanowire catalyst was prepared by a hard template method,and characterized by transmission electron microscopy (TEM),N2 physical adsorption,X-ray photoelectron spectrometry (XPS),X-ray diffraction (XRD) and H2 temperature-programmed reduction (H2-TPR).The catalytic properties of the nanowire catalyst in the partial oxidation of methane to syngas were compared with a metallic Ni catalyst which was prepared with nickel sponge.The characterization results showed that the nickel nanowire catalyst had high specific surface area and there was more NiO phase in the nickel nanowire catalyst than in the metallic Ni catalyst.The reaction results showed that the nickel nanowire catalyst had high CH4 conversion and selectivities for H2 and CO under low space velocity.

  14. Oxidative Coupling of Methane over Na-W-Mn/SiO2 Catalysts at Elevated Pressures

    Institute of Scientific and Technical Information of China (English)

    Lingjun Chou; Yingchun Cai; Bing Zhang; Jianzhong Niu; Shengfu Ji; Shuben Li

    2002-01-01

    Na-Mn-W/SiO2 catalysts were studied for the oxidative coupling of methane (OCM) in a micro fixed bed reactor made of stainless steel reactor at elevated pressures. The effect of operating conditions, such as GHSV, pressure, temperature and CH4/O2 ratio on the catalytic performance of OCM was investigated. The C2+ selectivity of 80.3% was obtained at a CH4 conversion of 16.1% at 750℃,1.5× 105h-1 GHSV, and 0.6 MPa. Also, there is a small output of C3 and C4 hydrocarbons in the tail gas. The results show that unfavorable effects due to elevated pressure can be overcome by increasing GHSV, and the OCM reaction is strongly dependent on the operating conditions at elevated pressures,particularly GHSV and the CH4/O2 ratio.

  15. Indirect methane aromatization via oxidative coupling, products separation and aromatization steps

    Energy Technology Data Exchange (ETDEWEB)

    Skutil, Krzysztof; Taniewski, Marian [Silesian Technical University, Chair of Chemical Organic Technology and Petrochemistry, ul. Krzywoustego 4, 44-101 Gliwice (Poland)

    2007-09-15

    Integrated process of indirect methane aromatization, composed of the methane oxidative coupling (OCM), products separation for elimination of some components and aromatization of the remaining compounds to benzene, toluene and naphthalene, has been studied as an alternative to direct non-oxidative methane aromatization (MDA). Two modes of the integrated process were investigated in the continuous flow laboratory unit: IP 1 - composed of OCM, separation of CO{sub 2} and H{sub 2}O and aromatization and IP 2 - composed of OCM, separation of CO{sub 2}, H{sub 2}O and C{sub 2} hydrocarbons and aromatization. The OCM and aromatization steps were carried out in the presence of 1% Li/MgO at 1023 K and 4.3% Mo/HZSM-5 at 998 K, respectively. The aromatization of individuals - CH{sub 4}, C{sub 2}H{sub 4} and C{sub 2}H{sub 6} was also investigated. Under applied aromatization conditions about a half of ethylene was converted to aromatics whereas the other part to undesirable CH{sub 4} and deposit. It was confirmed that the removal from the OCM products such constituents, which exert detrimental effect on the course of aromatization (CO{sub 2} and H{sub 2}O), led to the marked increase in the aromatics yield in IP 1, as compared with MDA. The approximate additivity of the amounts of benzene formed from methane and from C{sub 2} hydrocarbons contained in the OCM products was observed. Thus, it was confirmed that both C{sub 2} hydrocarbons and CH{sub 4} contained in the OCM effluent gases participated in the formation of aromatics. A full conversion of more reactive C{sub 2} hydrocarbons and a partial conversion of less reactive CH{sub 4} were observed in the aromatization step. Hydrogen and benzene were the main products of the integrated IP 1 process. The hydrogen/benzene ratio was lower than in MDA due to participation of less hydrogen-producing C{sub 2}s in the formation of benzene. The overall CH{sub 4} conversion was, under applied conditions, somewhat higher than in MDA

  16. Nitrous Oxide and Methane Emissions as Affected by Water, Soil and Nitrogen

    Institute of Scientific and Technical Information of China (English)

    XIONG Zheng-Qin; XING Guang-Xi; ZHU Zhao-Liang

    2007-01-01

    Specific management of water regimes,soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields.Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments.Two N sources (15N-(NH4)2SO4 and 15N-labeled milk vetch)were applied to two contrasting paddies:one derived from Xiashu loess(Loess)and one from Quaternary red clay(Clay).Both N2O and CH4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period.For both soil,N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons.Soil type affected N2O emission patterns.In soil Clay,the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions.In soil Loess,the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment.Soil type also had a significant effect on CH4 emissions during the flooded season,over which the weighted average flux was 111 mg C m-2 h-1 and 2.2 mg C m-2 h-1 from Clay and Loess,respectively.Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4 emissions during the flooded season.Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.

  17. Methane and nitrous oxide distributions across the North American Arctic Ocean during summer, 2015

    Science.gov (United States)

    Fenwick, Lindsay; Capelle, David; Damm, Ellen; Zimmermann, Sarah; Williams, William J.; Vagle, Svein; Tortell, Philippe D.

    2017-01-01

    We collected Arctic Ocean water column samples for methane (CH4) and nitrous oxide (N2O) analysis on three separate cruises in the summer and fall of 2015, covering a ˜10,000 km transect from the Bering Sea to Baffin Bay. This provided a three-dimensional view of CH4 and N2O distributions across contrasting hydrographic environments, from the oligotrophic waters of the deep Canada Basin and Baffin Bay, to the productive shelves of the Bering and Chukchi Seas. Percent saturation relative to atmospheric equilibrium ranged from 30 to 800% for CH4 and 75 to 145% for N2O, with the highest concentrations of both gases occurring in the northern Chukchi Sea. Nitrogen cycling in the shelf sediments of the Bering and Chukchi Seas likely constituted the major source of N2O to the water column, and the resulting high N2O concentrations were transported across the Arctic Ocean in eastward-flowing water masses. Methane concentrations were more spatially heterogeneous, reflecting a variety of localized inputs, including likely sources from sedimentary methanogenesis and sea ice processes. Unlike N2O, CH4 was rapidly consumed through microbial oxidation in the water column, as shown by the 13C enrichment of CH4 with decreasing concentrations. For both CH4 and N2O, sea-air fluxes were close to neutral, indicating that our sampling region was neither a major source nor sink of these gases. Our results provide insight into the factors controlling the distribution of CH4 and N2O in the North American Arctic Ocean, and an important baseline data set against which future changes can be assessed.

  18. Development of METHANE de-NOX Reburn Process for Wood Waste and Biomass Fired Stoker Boilers - Final Report - METHANE de-NOX Reburn Technology Manual

    Energy Technology Data Exchange (ETDEWEB)

    J. Rabovitser; B. Bryan; S. Wohadlo; S. Nester; J. Vaught; M. Tartan (Gas Technology Institute); R. Glickert (ESA Environmental Solutions)

    2007-12-31

    The overall objective of this project was to demonstrate the effectiveness of the METHANE de-NOX® (MdN) Reburn process in the Forest Products Industry (FPI) to provide more efficient use of wood and sludge waste (biosolids) combustion for both energy generation and emissions reduction (specifically from nitrogen oxides (NOx)) and to promote the transfer of the technology to the wide range of wood waste-fired stoker boilers populating the FPI. This document, MdN Reburn Commercial Technology Manual, was prepared to be a resource to promote technology transfer and commercialization activities of MdN in the industry and to assist potential users understand its application and installation requirements. The Manual includes a compilation of MdN commercial design data from four different stoker boiler designs that were baseline tested as part of the development effort. Design information in the Manual include boiler CFD model studies, process design protocols, engineering data sheets and commercial installation drawings. Each design package is unique and implemented in a manner to meet specific mill requirements.

  19. Anaerobic oxidation of methane at a marine methane seep in a forearc sediment basin off Sumatra, Indian Ocean

    Directory of Open Access Journals (Sweden)

    Michael eSiegert

    2011-12-01

    Full Text Available A cold methane-seep was discovered in a forearc sediment basin off the island Sumatra, exhibiting a methane-seep adapted microbial community. A defined seep centre of activity, like in mud volcanoes, was not discovered. The seep area was rather characterized by a patchy distribution of active spots. The relevance of AOM was reflected by 13C depleted isotopic signatures of dissolved inorganic carbon (DIC. The anaerobic conversion of methane to CO2 was confirmed in a 13C-labelling experiment. Methane fuelled a vital microbial and invertebrate community which was reflected in cell numbers of up to 4 x 109 cells cm 3 sediment and 13C depleted guts of crabs populating the seep area. The microbial community was analysed by total cell counting, catalyzed reporter deposition – fluorescence in situ hybridisation (CARD-FISH, quantitative real-time PCR (qPCR and denaturing gradient gel electrophoresis (DGGE. CARD-FISH cell counts and qPCR measurements showed the presence of Bacteria and Archaea, but only small numbers of Eukarya. The archaeal community comprised largely members of ANME-1 and ANME-2. Furthermore, members of the Crenarchaeota were frequently detected in the DGGE analysis. Three major bacterial phylogenetic groups (δ-Proteobacteria, candidate division OP9 and Anaerolineaceae were abundant across the study area. Several of these sequences were closely related to the genus Desulfococcus of the family Desulfobacteraceae, which is in good agreement with previously described AOM sites. In conclusion, the majority of the microbial community at the seep consisted of AOM related microorganisms, while the relevance of higher hydrocarbons as microbial substrates was negligible.

  20. Syntrophic acetate oxidation in two-phase (acid-methane) anaerobic digesters.

    Science.gov (United States)

    Shimada, T; Morgenroth, E; Tandukar, M; Pavlostathis, S G; Smith, A; Raskin, L; Kilian, R E

    2011-01-01

    The microbial processes involved in two-phase anaerobic digestion were investigated by operating a laboratory-scale acid-phase (AP) reactor and analyzing two full-scale, two-phase anaerobic digesters operated under mesophilic (35 °C) conditions. The digesters received a blend of primary sludge and waste activated sludge (WAS). Methane levels of 20% in the laboratory-scale reactor indicated the presence of methanogenic activity in the AP. A phylogenetic analysis of an archaeal 16S rRNA gene clone library of one of the full-scale AP digesters showed that 82% and 5% of the clones were affiliated with the orders Methanobacteriales and Methanosarcinales, respectively. These results indicate that substantial levels of aceticlastic methanogens (order Methanosarcinales) were not maintained at the low solids retention times and acidic conditions (pH 5.2-5.5) of the AP, and that methanogenesis was carried out by hydrogen-utilizing methanogens of the order Methanobacteriales. Approximately 43, 31, and 9% of the archaeal clones from the methanogenic phase (MP) digester were affiliated with the orders Methanosarcinales, Methanomicrobiales, and Methanobacteriales, respectively. A phylogenetic analysis of a bacterial 16S rRNA gene clone library suggested the presence of acetate-oxidizing bacteria (close relatives of Thermacetogenium phaeum, 'Syntrophaceticus schinkii,' and Clostridium ultunense). The high abundance of hydrogen consuming methanogens and the presence of known acetate-oxidizing bacteria suggest that acetate utilization by acetate oxidizing bacteria in syntrophic interaction with hydrogen-utilizing methanogens was an important pathway in the second-stage of the two-phase digestion, which was operated at high ammonium-N concentrations (1.0 and 1.4 g/L). A modified version of the IWA Anaerobic Digestion Model No. 1 (ADM1) with extensions for syntrophic acetate oxidation and weak-acid inhibition adequately described the dynamic profiles of volatile acid production

  1. Dry reforming of methane on Ni-Mg-Al nano-spheroid oxide catalysts prepared by the sol-gel method from hydrotalcite-like precursors

    Science.gov (United States)

    González, Albert R.; Asencios, Yvan J. O.; Assaf, Elisabete M.; Assaf, José M.

    2013-09-01

    Nanocapsular hydrotalcites (layered double hydroxides - LDHs) were synthesized by the sol-gel method and used as precursors of nano-structured mixed oxides containing various nickel loads (4, 15 and 19 wt%). The best conditions for the preparation of LDHs were analyzed and the structures of the resulting mixed oxides were studied. The optimal nickel load and calcining conditions were optimized. Finally, the resulting catalysts were tested in the dry reforming of methane for 8 h at 800 °C under atmospheric pressure. These materials showed high activity and stability, and the coke deposits were minimal on the catalyst prepared under optimal conditions (19 wt% nickel load and thermal treatment at 650 °C). The best catalyst formed amorphous carbon, which seems not to be prejudicial to the reaction.

  2. Microbiology and potential applications of aerobic methane oxidation coupled to denitrification (AME-D) process: A review.

    Science.gov (United States)

    Zhu, Jing; Wang, Qian; Yuan, Mengdong; Tan, Giin-Yu Amy; Sun, Faqian; Wang, Cheng; Wu, Weixiang; Lee, Po-Heng

    2016-03-01

    Aerobic methane oxidation coupled to denitrification (AME-D) is an important link between the global methane and nitrogen cycles. This mini-review updates discoveries regarding aerobic methanotrophs and denitrifiers, as a prelude to spotlight the microbial mechanism and the potential applications of AME-D. Until recently, AME-D was thought to be accomplished by a microbial consortium where denitrifying bacteria utilize carbon intermediates, which are excreted by aerobic methanotrophs, as energy and carbon sources. Potential carbon intermediates include methanol, citrate and acetate. This mini-review presents microbial thermodynamic estimations and postulates that methanol is the ideal electron donor for denitrification, and may serve as a trophic link between methanotrophic bacteria and denitrifiers. More excitingly, new discoveries have revealed that AME-D is not only confined to the conventional synergism between methanotrophic bacteria and denitrifiers. Specifically, an obligate aerobic methanotrophic bacterium, Methylomonas denitrificans FJG1, has been demonstrated to couple partial denitrification with methane oxidation, under hypoxia conditions, releasing nitrous oxide as a terminal product. This finding not only substantially advances the understanding of AME-D mechanism, but also implies an important but unknown role of aerobic methanotrophs in global climate change through their influence on both the methane and nitrogen cycles in ecosystems. Hence, further investigation on AME-D microbiology and mechanism is essential to better understand global climate issues and to develop niche biotechnological solutions. This mini-review also presents traditional microbial techniques, such as pure cultivation and stable isotope probing, and powerful microbial techniques, such as (meta-) genomics and (meta-) transcriptomics, for deciphering linked methane oxidation and denitrification. Although AME-D has immense potential for nitrogen removal from wastewater, drinking

  3. Oxidative coupling of methane in a fixed bed reactor over perovskite catalyst: A simulation study using experimental kinetic model

    Institute of Scientific and Technical Information of China (English)

    Nakisa Yaghobi; Mir Hamid Reza Ghoreishy

    2008-01-01

    The oxidative coupling of methane (OCM) to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separate energy equations for the gas and solid phases coupled with an experimental kinetic model. A lumped kinetic model containing four main species CH4, O2, COx (CO2, CO), and C2 (C2H4 and C2H6) was used with a plug flow reactor model as well. The results from the model agreed with the experimental data. The model was used to analyze the influence of temperature and feed gas composition on the conversion and selectivity of the reactor performance. The analytical results indicate that the conversion decreases, whereas, C2 selectivity increases by increasing gas hourly space velocity (GHSV) and the methane conversion also decreases by increasing the methane to oxygen ratio.

  4. Kinetics of methane fermentation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y. R.; Hashimoto, A. G.

    1978-01-01

    The kinetics on methane fermentation are described using published data for livestock residue, sewage sludge, and municipal refuse. Methods are presented to determine the kinetic constants and the finally attainable methane production using steady-state methane production data. The effects of temperature, loading rate, and influent substrate concentration on methane fermentation kinetics are discussed. These relationships were used to predict the rate of methane production of a pilot-scale fermentor with excellent results.

  5. Environmental and microbial factors influencing methane and nitrous oxide fluxes in Mediterranean cork oak woodlands: trees make a difference.

    Science.gov (United States)

    Shvaleva, Alla; Siljanen, Henri M P; Correia, Alexandra; Costa E Silva, Filipe; Lamprecht, Richard E; Lobo-do-Vale, Raquel; Bicho, Catarina; Fangueiro, David; Anderson, Margaret; Pereira, João S; Chaves, Maria M; Cruz, Cristina; Martikainen, Pertti J

    2015-01-01

    Cork oak woodlands (montado) are agroforestry systems distributed all over the Mediterranean basin with a very important social, economic and ecological value. A generalized cork oak decline has been occurring in the last decades jeopardizing its future sustainability. It is unknown how loss of tree cover affects microbial processes that are consuming greenhouse gases in the montado ecosystem. The study was conducted under two different conditions in the natural understory of a cork oak woodland in center Portugal: under tree canopy (UC) and open areas without trees (OA). Fluxes of methane and nitrous oxide were measured with a static chamber technique. In order to quantify methanotrophs and bacteria capable of nitrous oxide consumption, we used quantitative real-time PCR targeting the pmoA and nosZ genes encoding the subunit of particulate methane mono-oxygenase and catalytic subunit of the nitrous oxide reductase, respectively. A significant seasonal effect was found on CH4 and N2O fluxes and pmoA and nosZ gene abundance. Tree cover had no effect on methane fluxes; conversely, whereas the UC plots were net emitters of nitrous oxide, the loss of tree cover resulted in a shift in the emission pattern such that the OA plots were a net sink for nitrous oxide. In a seasonal time scale, the UC had higher gene abundance of Type I methanotrophs. Methane flux correlated negatively with abundance of Type I methanotrophs in the UC plots. Nitrous oxide flux correlated negatively with nosZ gene abundance at the OA plots in contrast to that at the UC plots. In the UC soil, soil organic matter had a positive effect on soil extracellular enzyme activities, which correlated positively with the N2O flux. Our results demonstrated that tree cover affects soil properties, key enzyme activities and abundance of microorganisms and, consequently net CH4 and N2O exchange.

  6. Environmental and microbial factors influencing methane and nitrous oxide fluxes in Mediterranean cork oak woodlands: trees make a difference

    Directory of Open Access Journals (Sweden)

    Alla eShvaleva

    2015-10-01

    Full Text Available Cork oak woodlands (montado are agroforestry systems distributed all over the Mediterranean basin with a very important social, economic and ecological value. A generalized cork oak decline has been occurring in the last decades jeopardizing its future sustainability. It is unknown how loss of tree cover affects microbial processes that are consuming greenhouse gas fluxes in the montado ecosystem. The study was conducted under two different conditions in the natural understory of a cork oak woodland in center Portugal: under tree canopy (UC and open areas without trees (OA. Fluxes of methane and nitrous oxide were measured with a static chamber technique. In order to quantify methanotrophs and bacteria capable of nitrous oxide consumption, we used quantitative real-time PCR targeting the pmoA and nosZ gene encoding the subunit of particulate methane mono-oxygenase and catalytic subunit of the nitrous oxide reductase, respectively. A significant seasonal effect was found on CH4 and N2O fluxes and pmoA and nosZ gene abundance. Tree cover had no effect on methane fluxes; conversely, whereas the UC plots were net emitters of nitrous oxide, the loss of tree cover resulted in a shift in the emission pattern such that the OA plots were a net sink for nitrous oxide. In a seasonal time scale, the UC had higher gene abundance of Type I methanotrophs. Methane flux correlated negatively with abundance of Type I methanotrophs in the UC plots. Nitrous oxide flux correlated negatively with nosZ gene abundance at the OA plots in contrast to that at the UC plots. In the UC soil, SOM had a positive effect on soil extracellular enzyme activities (EEA, which correlated positively with the N2O flux. Our results demonstrated that tree cover affects soil properties, key enzyme activities and abundance of microorganisms and, consequently net CH4 and N2O exchange.

  7. Effects of soil temperature and moisture on methane uptake and nitrous oxide emissions across three different ecosystem types

    Directory of Open Access Journals (Sweden)

    G. J. Luo

    2013-05-01

    Full Text Available In this paper, we investigate similarities of effects of soil environmental drivers on year-round daily soil fluxes of nitrous oxide and methane for three distinct semi-natural or natural ecosystems: temperate spruce forest, Germany; tropical rain forest, Queensland, Australia; and ungrazed semi-arid steppe, Inner Mongolia, China. Annual cumulative fluxes of nitrous oxide and methane varied markedly among ecosystems, with nitrous oxide fluxes being highest for the tropical forest site (tropical forest: 0.96 kg N ha−1 yr−1; temperate forest: 0.67 kg N ha−1 yr−1; steppe: 0.22 kg N ha−1 yr−1, while rates of soil methane uptake were approximately equal for the temperate forest (−3.45 kg C ha−1 yr−1 and the steppe (−3.39 kg C ha−1 yr−1, but lower for the tropical forest site (−2.38 kg C ha−1 yr−1. In order to allow for cross-site comparison of effects of changes in soil moisture and soil temperature on fluxes of methane and nitrous oxide, we used a normalization approach. Data analysis with normalized data revealed that, across sites, optimum rates of methane uptake are found at environmental conditions representing approximately average site environmental conditions. This might have rather important implications for understanding effects of climate change on soil methane uptake potential, since any shift in environmental conditions is likely to result in a reduction of soil methane uptake ability. For nitrous oxide, our analysis revealed expected patterns: highest nitrous oxide emissions under moist and warm conditions and large nitrous oxide fluxes if soils are exposed to freeze–thawing effects at sufficiently high soil moisture contents. However, the explanatory power of relationships of soil moisture or soil temperature to nitrous oxide fluxes remained rather poor (R2 ≤ 0.36. When combined effects of changes in soil moisture and soil temperature were considered, the explanatory power of our empirical

  8. Fe-rich carbonate chimney in Okinawa Trough Implication for Fe-driven Microbial Anaerobic Oxidation of Methane (AMO)

    Science.gov (United States)

    Peng, X.; Guo, Z.

    2016-12-01

    Marine sediments associated with cold seeps at continental margins discharge substantial amounts of methane. Microbial anaerobic oxidation of methane (AMO) is a key biogeochemical process in these environments, which can trigger the formation of carbonate chimneys within sediments. The exact biogeochemical mechanism of how AMO control the formation of carbonate chimneys and influence their mineralogy and chemistry remains poorly constrained. Here, we use nano-scale secondary ion mass spectrometry to characterize the petrology and geochemistry of methane-derived Fe-rich carbonate chimneys formed between 5-7 Ma in the Northern Okinawa Trough. We find abundant framboid pyrites formed in the authigenic carbonates in the chimneys, indicating a non-Fe limitation sedimentary system. The δ13C values of carbonate (-18.9‰ to -45.9‰, PDB) show their probable origin from a mixing source of biogenic and thermogenic methane. The δ34S values range from -3.9 ± 0.5‰ to 23.2 ± 0.5‰ (VCDT), indicative of a strong exhaustion of sulfates in a local sulfate pool. We proposed that Fe-rich carbonate chimneys formed at the bottom of the sulfate-methane transition zone, beneath which Fe-driven AOM may happen and provide available ferrous for the extensive precipitation of pyrite in carbonate chimneys. The accumulation of reductive Fe in sediments via this process may widely occur in other analogous settings, with important application for Fe and S biogeochemical cycling within deep sediments at continental margins.

  9. Nitrogen source effects on the denitrifying anaerobic methane oxidation culture and anaerobic ammonium oxidation bacteria enrichment process.

    Science.gov (United States)

    Fu, Liang; Ding, Jing; Lu, Yong-Ze; Ding, Zhao-Wei; Zeng, Raymond J

    2017-05-01

    The co-culture system of denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox) has a potential application in wastewater treatment plant. This study explored the effects of permutation and combination of nitrate, nitrite, and ammonium on the culture enrichment from freshwater sediments. The co-existence of NO3(-), NO2(-), and NH4(+) shortened the enrichment time from 75 to 30 days and achieved a total nitrogen removal rate of 106.5 mg/L/day on day 132. Even though ammonium addition led to Anammox bacteria increase and a higher nitrogen removal rate, DAMO bacteria still dominated in different reactors with the highest proportion of 64.7% and the maximum abundance was 3.07 ± 0.25 × 10(8) copies/L (increased by five orders of magnitude) in the nitrite reactor. DAMO bacteria showed greater diversity in the nitrate reactor, and one was similar to M. oxyfera; DAMO bacteria in the nitrite reactor were relatively unified and similar to M. sinica. Interestingly, no DAMO archaea were found in the nitrate reactor. This study will improve the understanding of the impact of nitrogen source on DAMO and Anammox co-culture enrichment.

  10. Mitigation of methane emissions in a pilot-scale biocover system at the AV Miljø Landfill, Denmark: 2. Methane oxidation

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Cassini, Filippo; De Schoenmaeker, Jan

    2017-01-01

    Greenhouse gas mitigation at landfills by methane (CH4) oxidation in engineered biocover systems is believed to be a cost effective technology but so far a full quantitative evaluation of the efficiency of the technology in full scale has only been carried out in a few cases. A third generation...... semi-passive biocover system was constructed at the AV Miljø Landfill, Denmark. The biocover was fed by landfill gas pumped out of three leachate collection wells. An innovative gas distribution system was used to overcome the often observed uneven gas distribution to the active CH4 oxidation layer...... methods; the carbon mass balance method (based on CH4 and carbon dioxide (CO2) concentrations in the deeper part of the cover and CH4 and CO2 surface flux measurements) and a new-developed tracer gas mass balance method (based on CH4 and tracer inlet fluxes and CH4 and tracer surface flux measurements...

  11. Stability and activity of molybdenum carbide catalysts for the oxidative reforming of methane

    Science.gov (United States)

    Lamont, David Charles

    Molybdenum carbide catalysts have been studied for oxidative reforming, in particular, the effect on reforming activity of the method by which they were synthesized, their stability under conditions of varying mass transfer, and the measurement of their inherent reaction kinetics. These catalysts show promise as possible alternatives to both conventional supported nickel catalysts, as well as to the rare and expensive noble metal catalysts. Samples of Mo 2C were synthesized in house and compared to a commercial sample of Mo2C for the CO2 (dry) reforming of methane. It was found that high surface areas, previously thought to be important for activity, were not a property of the Mo2C, but instead were attributable to large amounts of excess carbon. This carbon had a detrimental effect on catalyst stability under dry reforming conditions, because it enhanced deposition of refractory carbon via methane cracking. The commercial sample of Mo 2C, while of low surface area and containing no excess carbon, behaved more stably over time. In another investigation, Mo2C was studied for its stability under varying mass transfer conditions, because of evidence showing that the Mo2C can undergo redox chemistry at reforming conditions. Under dry reforming conditions, it was found that some feed mixtures are net oxidizing, but that oxidation in the presence of such feed mixtures could be prevented by operating under mass transfer limited conditions, which resulted in sufficiently high partial pressures of CO and H2 in the catalyst boundary layer. Similar stability was achieved by co-feeding CO to the catalyst bed, which allowed for stable operation under conditions that were not mass transfer limited. Using this approach, measurements of the intrinsic reaction kinetics of Mo2C for dry reforming were successfully achieved. These results pointed to a strong dependence of dry reforming rate on both CH4 and CO2 partial pressures, as well as evidence for a reaction mechanism unique from

  12. Anaerobic methane oxidation may be more prevalent in surface soils than was originally thought

    Science.gov (United States)

    Gauthier, Mathieu; Bradley, Robert L.; Šimek, Miloslav

    2013-04-01

    Anaerobic oxidation of methane (CH4) (AOM) is a process that was first reported to occur in deep anoxic marine sediments. In this environment, CH4 is oxidized with sulphate (SO42-) as the terminal electron acceptor. It is mediated by a syntrophic consortium formed by SO42- reducing bacteria and anaerobic CH4 oxidizing Archaea, or by the latter alone. Since this landmark discovery, AOM was found to occur in other environments including freshwater lake sediments and water columns, mud volcanoes, landfill leachate, deep buried Holocene sediments and hydrocarbon contaminated aquifers. All of these situations are very specific and point to AOM as being primarily occurring in highly reducing conditions. Thus, observations of AOM in surface soils with fluctuating REDOX conditions are relatively scarce, although a few independent studies have reported AOM in surface peatlands as well as in a forest soil. Furthermore, AOM may follow different pathways, such as via the coupled oxidation of CH4 and reduction of manganese (Mn(IV)) or iron (Fe(III)), or by a lone denitrifying species that converts nitrite to nitric oxide in order to generate O2 that is then used internally to oxidize CH4. Thus, the goal of our study was to determine whether AOM is more prevalent than was thought in hydromorphic surface soils across different environments, and whether the addition of NO3- or SO4= as alternative electron acceptors may stimulate the process. We collected samples from 3 peatland soils in Scotland, 2 acid-sulphate soils in Finland, and shore sediments of 15 drained fish ponds in the Czech Republic. Subsamples were incubated in the absence of O2 and amended with either NO3-, SO42-, or left unamended (control). The net flux of CH4 and CO2 were assessed by gas chromatography after 2, 20, 40 and 60 days. We also used a 13C-CH4 isotope dilution technique to determine gross production and consumption rates of CH4. We detected AOM in all of our soils, with oxidation rates ranging between 0

  13. Identifying active methane-oxidizers in thawed Arctic permafrost by proteomics

    Science.gov (United States)

    Lau, C. M.; Stackhouse, B. T.; Chourey, K.; Hettich, R. L.; Vishnivetskaya, T. A.; Pfiffner, S. M.; Layton, A. C.; Mykytczuk, N. C.; Whyte, L.; Onstott, T. C.

    2012-12-01

    characterization identified ~350 proteins, confirmed enhanced microbial activities and significant shift in community structure within the microcosms. Although the activity of Shewanella sp. was suppressed by the incubation conditions, other bacteria were activated. This was shown by at least 3-fold increase in the number of identified proteins, which were primarily players in cellular energy metabolism. Among them, Geobacter sp. and methane-oxidizers, Bradyrhizobium sp., Methylosinus sp. and Methylocystis sp. appear dominant. In order to advance the protein database for better biodiversity and functional identification, we are currently using duo extraction protocols and consolidating metagenome data obtained from the same soil samples. A depth profile (from active to permafrost layer) for methanotrophs is being determined by examining pristine cores, thawed cryosols as well as enrichment cultures. The proteome information from these samples will be presented, which will be complemented by molecular studies.

  14. Synthesis and characterization of Cu doped cobalt oxide nanocrystals as methane gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sheikhi Mehrabadi, Z; Ahmadpour, A [Nanotechnology Research Center, Department of Chemical Engineering, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shahtahmasebi, N [Nanotechnology Research Center, Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Bagheri Mohagheghi, M M, E-mail: m_mohagheghee@yahoo.co.uk [School of Physics, Damghan University, Damghan (Iran, Islamic Republic of)

    2011-07-01

    In this paper, nanoparticles of copper-cobalt compound oxide have been prepared by the sol-gel technique with different mole ratios of Cu/Co (ranging from 0.05 to 0.15) for the detection of methane gas, which is chemically a very stable hydrocarbon. The structural properties and morphology of the powders were studied by x-ray diffraction (XRD), Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). By XRD analysis, we confirm that Co{sub 3}O{sub 4} and (CuO{sub 0.3}CoO{sub 0.7}) Co{sub 2}O{sub 4} phases are formed and mean grain size is decreased with increasing Cu doping (from 28 to 24 nm). On the basis of TEM images, it is found that these particles possess a cubic structure with nearly uniform distribution. Also, gas-sensing measurements reveal that the optimal operating temperature is 300 {sup 0}C, that the use of Cu as a dopant improved the sensing properties of cobalt oxide and that the sensitivity increased considerably with Cu concentration. The best sensitivity properties of nanosensors have been found at the mole ratios of Cu/Co of 0.125 and 0.15.

  15. Catalytic Mechanism and Efficiency of Methane Oxidation by Hg(II) in Sulfuric Acid and Comparison to Radical Initiated Conditions

    OpenAIRE

    Fuller, Jack T.; Butler, Steven; Devarajan, Deepa; Jacobs, Austin; Hashiguchi, Brian G.; Konnick, Michael M.; Goddard, William A.; Gonzales, Jason M.; Periana, Roy A.; Ess, Daniel H.

    2016-01-01

    Methane conversion to methyl bisulfate by Hg^(II)(SO_4) in sulfuric acid is an example of fast and selective alkane oxidation catalysis. Dichotomous mechanisms involving C–H activation and electron transfer have been proposed based on experiments. Radical oxidation pathways have also been proposed for some reaction conditions. Hg^(II) is also of significant interest because as a d^(10) transition metal it is similar to d^(10) main-group metals that also oxidize alkanes. Density-functional cal...

  16. Fe/SiO2 catalysts for the selective oxidation of methane to formaldehyde

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Guerrero Fajardo

    2010-04-01

    Full Text Available Selective oxidation of methane to formaldehyde was analysed with iron catalysts supported on silica prepared by the sol-gel method, leading to obtaining a large support surface area facilitating high dispersion of iron on silica’s amorphous surface. Seven catalysts were prepared; one of them corresponded to the silica support and another five having an iron load 0.1-0.5% in weight. Catalyst 7 (0.5% Fe in weight was prepared with neutral pH control and had the most homogeneous characteristics since it did not present isolated iron species, corroborated by SEM and TEM analysis. The highest BET areas were 1,757 and 993 m2.g-1 for 0.5% Fe catalysts, having an average 36% microporosity and 43% mesoporosity. X-ray diffraction confirmed the catalyst’s amorphous structure. Catalytic activity was carried out with catalyser 7 at atmospheric pressure in a quartz reactor using a CH /0 /N =7.5/1/4 reaction mixture at 400-750°C temperature 4 2 2 range. Reaction products were analysed by gas chromatography with TCD. The heterogeneous catalysts displayed greater methane conversion (but with methanol selectivity whereas homogenous catalyst 7 gave better results regarding formaldehyde. The highest conversion percentage (8.60% mol for catalyser 7 was presented at 650°C. Formaldehyde selectivity was 50% mol in the 600-650°C range and maximum yield (0.31g HCH0/Kg catalyst was found in this range; it was thus considered that 650°C for the reaction was thereby the best operating temperature.

  17. Synthesising Fe-Mo catalysts supported on silica for the selective oxidation of methane to formaldehyde

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Guerrero Fajardo

    2010-05-01

    Full Text Available The selective oxidation of methane to formaldehyde was analysed using iron-molybdenum catalysts supported on silica prepared by the sol-gel method which leads to obtaining a greater surface area and high iron and molybdenum metal dispersion on the si-lica’s amorphous surface. Seven catalysts were prepared, one of them as silica support, another as 0.5% wt iron load without molybdenum and the remaining five having 0.1%-1.0% weight molybdenum and 0.5% wt iron loads. The highest BET areas were 830 and 879 m2.g-1 for catalysts 2 (0.5% Fe - 0% Mo and 4 (0.5% Fe - 0.3% Mo respectively, having 28% average micropo-rosity and 47% average mesoporosity. X-ray diffraction confirmed the catalysts’ amorphous structure. The TPR spectrum showed low hydrogen consumption attributed to the absence of isolated Fe and Mo species. ESCA analysis revealed the same Fe/Mo a-tomic ratio on the catalyst surface as in the bulk preparation. Catalytic activity was carried out at atmospheric pressure, CH4/ O2/N2 = 7.5/1/4 reaction mixture, 400-800°C temperature interval. Catalysts 4 (0.5% Fe - 0.3% Mo, 5 (0.5% Fe - 0.5% Mo and 7 (0.5% Fe - 1.0% Mo displayed greater methane conversion, whereas catalysts 5 (0.5% Fe - 0.5% Mo, 4 (0.5% Fe - 0.3% Mo, 2 (0.5% Fe - 0% Mo and 7 (0.5% Fe - 1.0% Mo gave better formaldehyde product results. The highest conversion per- centage (4.07% mol was presented at 700°C for catalyst 4 (0.5% Fe-0.3% Mo. Formaldehyde yield was 202,0 gHCHO.kg-1 cata.h-1 at this temperature.

  18. Microbial methane oxidation as a means of treating residual emissions during passive landfill venting; Mikrobielle Methanoxidation zur Behandlung von Rest-Emissionen bei der passiven Deponieentgasung

    Energy Technology Data Exchange (ETDEWEB)

    Gebert, J.; Groengroeft, A. [Hamburg Univ. (Germany). Inst. fuer Bodenkunde

    2005-07-01

    Microbial oxidation of methane in biofilters provides a way of treating residual or lean gas emissions from landfills whose methane content and quantities no longer meet the minimum requirements for gas utilisation or flaring. In this process methane is oxidised by methanotropic bacteria in the presence of atmospheric oxygen. This yields carbon dioxide, which is less hazardous on account of its nonflammability and lower global warming potential. This contribution describes the methane degradation performance and performance governing factors of a biofilter which was exposed to a passive gas flow and observed over a period of two years.

  19. On the Role of Vanadia Species for VOx/SiO2 in the Selective Oxidation of Methane

    Institute of Scientific and Technical Information of China (English)

    Shaojun Miao; Ding Ma; Qingjun Zhu; Heng Zheng; Guoqing Jia; Shutian Zhou; Xinhe Bao

    2005-01-01

    Various VOx/SiO2 catalysts were prepared by the methods of physical mixing, conventional wetness impregnation and ultrasonication-assistant impregnation. The catalysts were characterized by XRD, UV-Vis DRS, Raman, TPR, ESR and TPSR techniques and the nature of the vanadium species were correlated to their catalytic performance in the reaction of direct conversion of methane to formaldehyde. It is concluded that highly dispersed monomeric and low oligomeric vanadia species are formed on the sample prepared with both traditional wetness impregnation method and ultrasonication-assistant impregnation, whereas in the latter case, the amount of oligomeric vanadia species is much smaller. The V2O5 microcrystallines are the dominant species on the material prepared by physical mixing method.During the selective oxidation of methane, Vv species are reduced to VⅣ paramagnetic species and both microcrystalline V2O5 species and oligomeric vanadia species are found to further disperse and transform into tetrahedral vanadia species. Based on the results of UV Raman spectroscopy and TPSR, CO2 is suggested to be formed via two different routes, in which one is from the sequence reaction of CH4 → HCHO → CO → CO2 over monomeric vanadia species, and the other is from the direct oxidation of methane to CO2 over oligomeric vanadia species. Oligomeric vanadia species is more active than monomeric vanadia species for methane activation.

  20. Use of gas push-pull tests for the measurement of methane oxidation in different landfill cover soils.

    Science.gov (United States)

    Streese-Kleeberg, Jan; Rachor, Ingke; Gebert, Julia; Stegmann, Rainer

    2011-05-01

    In order to optimise methane oxidation in landfill cover soils, it is important to be able to accurately quantify the amount of methane oxidised. This research considers the gas push-pull test (GPPT) as a possible method to quantify oxidation rates in situ. During a GPPT, a gas mixture consisting of one or more reactive gases (e.g., CH(4), O(2)) and one or more conservative tracers (e.g., argon), is injected into the soil. Following this, the mixture of injected gas and soil air is extracted from the same location and periodically sampled. The kinetic parameters for the biological oxidation taking place in the soil can be derived from the differences in the breakthrough curves. The original method of Urmann et al. (2005) was optimised for application in landfill cover soils and modified to reduce the analytical effort required. Optimised parameters included the flow rate during the injection phase and the duration of the experiment. 50 GPPTs have been conducted at different landfills in Germany during different seasons. Generally, methane oxidation rates ranged between 0 and 150 g m(soil air)(-3)h(-1). At one location, rates up to 440 g m(soil air)(-3)h(-1) were measured under particularly favourable conditions. The method is simple in operation and does not require expensive equipment besides standard laboratory gas chromatographs.

  1. Nitrous oxide and methane emissions and nitrous oxide isotopic composition from waste incineration in Switzerland.

    Science.gov (United States)

    Harris, Eliza; Zeyer, Kerstin; Kegel, Rainer; Müller, Beat; Emmenegger, Lukas; Mohn, Joachim

    2015-01-01

    Solid waste incineration accounts for a growing proportion of waste disposal in both developed and developing countries, therefore it is important to constrain emissions of greenhouse gases from these facilities. At five Swiss waste incineration facilities with grate firing, emission factors for N2O and CH4 were determined based on measurements of representative flue gas samples, which were collected in Tedlar bags over a one year period (September 2010-August 2011) and analysed with FTIR spectroscopy. All five plants burn a mixture of household and industrial waste, and two of the plants employ NOx removal through selective non-catalytic reduction (SNCR) while three plants use selective catalytic reduction (SCR) for NOx removal. N2O emissions from incineration plants with NOx removal through selective catalytic reduction were 4.3 ± 4.0g N2O tonne(-1) waste (wet) (hereafter abbreviated as t(-1)) (0.4 ± 0.4 g N2O GJ(-1)), ten times lower than from plants with selective non-catalytic reduction (51.5 ± 10.6g N2O t(-1); 4.5 ± 0.9g N2O GJ(-1)). These emission factors, which are much lower than the value of 120g N2O t(-1) (10.4g N2O GJ(-1)) used in the 2013 Swiss national greenhouse gas emission inventory, have been implemented in the most recent Swiss emission inventory. In addition, the isotopic composition of N2O emitted from the two plants with SNCR, which had considerable N2O emissions, was measured using quantum cascade laser spectroscopy. The isotopic site preference of N2O - the enrichment of (14)N(15)NO relative to (15)N(14)NO - was found to be 17.6 ± 0.8‰, with no significant difference between the two plants. Comparison to previous studies suggests SP of 17-19‰ may be characteristic for N2O produced from SNCR. Methane emissions were found to be insignificant, with a maximum emission factor of 2.5 ± 5.6g CH4 t(-1) (0.2 ± 0.5g CH4 GJ(-1)), which is expected due to high incinerator temperatures and efficient combustion. Copyright © 2014 Elsevier Ltd

  2. Isolation and Characterization of Microbes Mediating Thermodynamically Favorable Coupling of Anaerobic Oxidation of Methane and Metal Reduction

    Science.gov (United States)

    Glass, J. B.; Reed, B. C.; Sarode, N. D.; Kretz, C. B.; Bray, M. S.; DiChristina, T. J.; Stewart, F. J.; Fowle, D. A.; Crowe, S.

    2014-12-01

    Methane is the third most reduced environmentally relevant electron donor for microbial metabolisms after organic carbon and hydrogen. In anoxic ecosystems, the major sink for methane is anaerobic oxidation of methane (AOM) mediated by syntrophic microbial consortia that couple AOM to reduction of an oxidized electron acceptor to yield free energy. In marine sediments, AOM is generally coupled to reduction of sulfate despite an extremely small amount of free energy yield because sulfate is the most abundant electron acceptor in seawater. While AOM coupled to Fe(III) and Mn(IV) reduction (Fe- and Mn-AOM) is 10-30x more thermodynamically favorable than sulfate-AOM, and geochemical data suggests that it occurs in diverse environments, the microorganisms mediating Fe- and Mn-AOM remain unknown. Lake Matano, Indonesia is an ideal ecosystem to enrich for Fe- and Mn-AOM microbes because its anoxic ferruginous deep waters and sediments contain abundant Fe(III), Mn(IV) and methane, and extremely low sulfate and nitrate. Our research aims to isolate and characterize the microbes mediating Fe- and Mn-AOM from three layers of Lake Matano sediments through serial enrichment cultures in minimal media lacking nitrate and sulfate. 16S rRNA amplicon sequencing of sediment inoculum revealed the presence of the Fe(III)-reducing bacterium Geobacter (5-10% total microbial community in shallow sediment and 35-60% in deeper sediment) as well as 1-2% Euryarchaeota implicated in methane cycling, including ANME-1 and 2d and Methanosarcinales. After 90 days of primary enrichment, all three sediment layers showed high levels of Fe(III) reduction (60-90 μM Fe(II) d-1) in the presence of methane compared to no methane and heat-killed controls. Treatments with added Fe(III) as goethite contained higher abundances of Geobacter than the inoculum (60-80% in all layers), suggesting that Geobacter may be mediating Fe(III) reduction in these enrichments. Quantification of AOM rates is underway, and

  3. Fundamental studies of the mechanism of catalytic reactions with catalysts effective in the gasification of carbon solids and the oxidative coupling of methane. Quarterly report, October 1, 1994--December 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, E.; Perry, D.L.; Heinemann, H.

    1994-12-01

    This report describes research on the oxidative coupling of methane and catalysts involved in coal gasification. Topics include methane pyrolysis and catalysts, and magnetic properties of the coal gasification catalyst Ca-Ni-K-O system.

  4. The Effect of Nb Loading on Catalytic Properties of Ni/Ce0.75Zr0.25O2 Catalyst for Methane Partial Oxidation

    Institute of Scientific and Technical Information of China (English)

    Sitthiphong Pengpanich; Vissanu Meeyoo; Thirasak Rirksomboon; Johannes Schwank

    2007-01-01

    In this study,the effect of Nb loading on the catalytic activity of Ce0.75Zr0.25O2-supported Ni catalysts was studied for methane partial oxidation.The catalysts were characterized by BET,H2 chemisorption,XRD,TPR,TEM and tested for methane partial oxidation to syngas in the temperature range of 400-800 ℃ at atmospheric pressure.The results showed that the activity of methane partial oxidation on the catalysts was apparently dependent on Nb loading.It seemed that the addition of Nb lowered the catalytic activity for methane partial oxidation and increased the extent of carbon deposition.This might be due to the strong interaction between NiO and Nb-modified support and reduction of surfaceoxygen reducibility.

  5. Effect of palladium on the reducibility of Mn based materials: correlation with methane oxidation activity.

    Science.gov (United States)

    Baylet, A; Royer, S; Labrugère, C; Valencia, H; Marécot, P; Tatibouët, J M; Duprez, D

    2008-10-21

    Mn-based oxide supports were synthesized using different procedures: (i) carbonate co-precipitation method, leading to the formation of a hexaaluminate crystallized solid (La(0.2)Sr(0.3)Ba(0.5)MnAl(11)O(19)) and (ii) solid-solid diffusion method, leading to the formation of a doped theta-Al(2)O(3) crystallized solid (nominal composition: 60 wt% La(0.2)Sr(0.3)Ba(0.5)MnAl(11)O(19) + 40 wt% Al(2)O(3)). Impregnation of 1.0 wt%Pd was carried out on both oxides. The solids were tested for the catalytic methane combustion up to 700 degrees C. It was observed that adding palladium resulted in an important increase in the catalytic activity. The combined use of H(2)-TPR and XPS techniques reveals that only Mn(3+)/Mn(2+) redox "couple" is present in the solids, whatever the synthesis procedure used. The fraction Mn(3+)/Mn is proportional to the total Mn content in the solid support, whatever the sample structure (hexaaluminate or doped theta-Al(2)O(3)) and its morphology (large crystals or aggregates of small particles, respectively). Pd impregnation and further calcination at 650 degrees C has no significant effect on the Mn(3+)/Mn fraction. However, some changes in Mn(3+) reduction profile are observed, depending on the solid structure. Indeed, palladium addition strongly affects the manganese reducibility with an important shift of the reduction process to lower temperatures (approximately 100 degrees C). On the basis of redox properties observed for the different catalysts, a Mars-van-Krevelen redox mechanism, with oxygen transfer from support oxides to palladium particles, is proposed to explain the difference in terms of catalytic conversion and stability with respect to a 1.0 wt%Pd/Al(2)O(3) reference sample.

  6. Market research on biogas valorizations and methanization. Final report; Etude de marche de la methanisation et des valorisations du biogaz. Rapport final

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-09-15

    This market research aims at giving an overview of the existing methanization installations and of their dynamics in France, at assessing biogas production and use, at analyzing the methanization market, and at defining development perspectives for this sector by 2020. Based on a survey of methanization installations, on interviews with many actors of this sector, and on a seminar organized on this topic, this report presents and comments market data for biogas valorization and methanization in different sectors: household, agricultural, and industrial and waste water processing plants. It comments evolution trends by 2020 for these sectors, and the role that the emerging sector of centralized methanization could have in the years to come

  7. Methane and nitrous oxide emissions from livestock agriculture in 16 local administrative districts of Korea.

    Science.gov (United States)

    Ji, Eun Sook; Park, Kyu-Hyun

    2012-12-01

    This study was conducted to evaluate methane (CH4) and nitrous oxide (N2O) emissions from livestock agriculture in 16 local administrative districts of Korea from 1990 to 2030. National Inventory Report used 3 yr averaged livestock population but this study used 1 yr livestock population to find yearly emission fluctuations. Extrapolation of the livestock population from 1990 to 2009 was used to forecast future livestock population from 2010 to 2030. Past (yr 1990 to 2009) and forecasted (yr 2010 to 2030) averaged enteric CH4 emissions and CH4 and N2O emissions from manure treatment were estimated. In the section of enteric fermentation, forecasted average CH4 emissions from 16 local administrative districts were estimated to increase by 4%-114% compared to that of the past except for Daejeon (-63%), Seoul (-36%) and Gyeonggi (-7%). As for manure treatment, forecasted average CH4 emissions from the 16 local administrative districts were estimated to increase by 3%-124% compared to past average except for Daejeon (-77%), Busan (-60%), Gwangju (-48%) and Seoul (-8%). For manure treatment, forecasted average N2O emissions from the 16 local administrative districts were estimated to increase by 10%-153% compared to past average CH4 emissions except for Daejeon (-60%), Seoul (-4.0%), and Gwangju (-0.2%). With the carbon dioxide equivalent emissions (CO2-Eq), forecasted average CO2-Eq from the 16 local administrative districts were estimated to increase by 31%-120% compared to past average CH4 emissions except Daejeon (-65%), Seoul (-24%), Busan (-18%), Gwangju (-8%) and Gyeonggi (-1%). The decreased CO2-Eq from 5 local administrative districts was only 34 kt, which was insignificantly small compared to increase of 2,809 kt from other 11 local administrative districts. Annual growth rates of enteric CH4 emissions, CH4 and N2O emissions from manure management in Korea from 1990 to 2009 were 1.7%, 2.6%, and 3.2%, respectively. The annual growth rate of total CO2-Eq was 2

  8. Catalysis by Nanostructures: Methane, Ethylene Oxide, and Propylene Oxide Synthesis on Ag, Cu or Au Nanoclusters

    Science.gov (United States)

    2008-02-07

    well-dispersed on the interior walls of nanotubular TiO2. The TiO2 nanotubes were shown by x-ray diffraction to be entirely anatase . Transmission...oxidation on a doped rutile TiO 2(1 10): Effect of ionic Au in catalysis. Catalysis Lett. 107, 143-147 (2006) 5. S. Chrdtien and H. Metiu, Density...functional study of the charge on Aun clusters (n=l-7) supported on a partially reduced rutile TiO 2(1 10): Are all clusters negatively charged? J. Chem

  9. The Leeuwenhoek Lecture 2000 The natural and unnatural history of methane-oxidizing bacteria

    OpenAIRE

    Dalton, Howard

    2005-01-01

    Methane gas is produced from many natural and anthropogenic sources. As such, methane gas plays a significant role in the Earth's climate, being 25 times more effective as a greenhouse gas than carbon dioxide. As with nearly all other naturally produced organic molecules on Earth, there are also micro-organisms capable of using methane as their sole source of carbon and energy. The microbes responsible (methanotrophs) are ubiquitous and, for the most part, aerobic. Although anaerobic methanot...

  10. Nitrous oxide and methane emissions and nitrous oxide isotopic composition from waste incineration in Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Eliza, E-mail: eliza.harris@empa.ch [Empa, Laboratory for Air Pollution and Environmental Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Zeyer, Kerstin [Empa, Laboratory for Air Pollution and Environmental Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Kegel, Rainer; Müller, Beat [FOEN, Federal Office for the Environment, Air Pollution Control and Chemicals, CH-3003 Berne (Switzerland); Emmenegger, Lukas; Mohn, Joachim [Empa, Laboratory for Air Pollution and Environmental Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland)

    2015-01-15

    plants with SNCR, which had considerable N{sub 2}O emissions, was measured using quantum cascade laser spectroscopy. The isotopic site preference of N{sub 2}O – the enrichment of {sup 14}N{sup 15}NO relative to {sup 15}N{sup 14}NO – was found to be 17.6 ± 0.8‰, with no significant difference between the two plants. Comparison to previous studies suggests SP of 17–19‰ may be characteristic for N{sub 2}O produced from SNCR. Methane emissions were found to be insignificant, with a maximum emission factor of 2.5 ± 5.6 g CH{sub 4} t{sup −1} (0.2 ± 0.5 g CH{sub 4} GJ{sup −1}), which is expected due to high incinerator temperatures and efficient combustion.

  11. Non-oxidative dehydroaromatization of methane:an effective reaction regeneration cyclic operation for catalyst life extension

    OpenAIRE

    Portilla Ovejero, Mª Teresa; LLOPIS ALONSO, FRANCISCO; LLOPIS ALONSO, FRANCISCO JAVIER; Martínez, Cristina

    2015-01-01

    Non-oxidative methane aromatization is an attractive direct route for producing higher hydrocarbons. It is highly selective to benzene despite the low conversion due to thermodynamic limitations, and Mo/H-ZSM-5, the first catalyst proposed for this reaction, is still considered as one of the most adequate. The major problem of this process is the severe catalyst deactivation due to the rapid build-up of carbonaceous deposits on the catalysts. Here we present an effective regeneration procedur...

  12. Miniaturized extinction culturing is the preferred strategy for rapid isolation of fast-growing methane-oxidizing bacteria

    OpenAIRE

    Hoefman, Sven; van der Ha, David; De Vos, Paul; Boon, Nico; Heylen, Kim

    2012-01-01

    Summary Methane‐oxidizing bacteria (MOB) have a large potential as a microbial sink for the greenhouse gas methane as well as for biotechnological purposes. However, their application in biotechnology has so far been hampered, in part due to the relative slow growth rate of the available strains. To enable the availability of novel strains, this study compares the isolation of MOB by conventional dilution plating with miniaturized extinction culturing, both performed after an initial enrichme...

  13. Mechanistic insights into heterogeneous methane activation.

    Science.gov (United States)

    Latimer, Allegra A; Aljama, Hassan; Kakekhani, Arvin; Yoo, Jong Suk; Kulkarni, Ambarish; Tsai, Charlie; Garcia-Melchor, Max; Abild-Pedersen, Frank; Nørskov, Jens K

    2017-02-01

    While natural gas is an abundant chemical fuel, its low volumetric energy density has prompted a search for catalysts able to transform methane into more useful chemicals. This search has often been aided through the use of transition state (TS) scaling relationships, which estimate methane activation TS energies as a linear function of a more easily calculated descriptor, such as final state energy, thus avoiding tedious TS energy calculations. It has been shown that methane can be activated via a radical or surface-stabilized pathway, both of which possess a unique TS scaling relationship. Herein, we present a simple model to aid in the prediction of methane activation barriers on heterogeneous catalysts. Analogous to the universal radical TS scaling relationship introduced in a previous publication, we show that a universal TS scaling relationship that transcends catalysts classes also seems to exist for surface-stabilized methane activation if the relevant final state energy is used. We demonstrate that this scaling relationship holds for several reducible and irreducible oxides, promoted metals, and sulfides. By combining the universal scaling relationships for both radical and surface-stabilized methane activation pathways, we show that catalyst reactivity must be considered in addition to catalyst geometry to obtain an accurate estimation for the TS energy. This model can yield fast and accurate predictions of methane activation barriers on a wide range of catalysts, thus accelerating the discovery of more active catalysts for methane conversion.

  14. Field-scale tracking of active methane-oxidizing communities in a landfill cover soil reveals spatial and seasonal variability.

    Science.gov (United States)

    Henneberger, Ruth; Chiri, Eleonora; Bodelier, Paul E L; Frenzel, Peter; Lüke, Claudia; Schroth, Martin H

    2015-05-01

    Aerobic methane-oxidizing bacteria (MOB) in soils mitigate methane (CH4 ) emissions. We assessed spatial and seasonal differences in active MOB communities in a landfill cover soil characterized by highly variable environmental conditions. Field-based measurements of CH4 oxidation activity and stable-isotope probing of polar lipid-derived fatty acids (PLFA-SIP) were complemented by microarray analysis of pmoA genes and transcripts, linking diversity and function at the field scale. In situ CH4 oxidation rates varied between sites and were generally one order of magnitude lower in winter compared with summer. Results from PLFA-SIP and pmoA transcripts were largely congruent, revealing distinct spatial and seasonal clustering. Overall, active MOB communities were highly diverse. Type Ia MOB, specifically Methylomonas and Methylobacter, were key drivers for CH4 oxidation, particularly at a high-activity site. Type II MOB were mainly active at a site showing substantial fluctuations in CH4 loading and soil moisture content. Notably, Upland Soil Cluster-gamma-related pmoA transcripts were also detected, indicating concurrent oxidation of atmospheric CH4 . Spatial separation was less distinct in winter, with Methylobacter and uncultured MOB mediating CH4 oxidation. We propose that high diversity of active MOB communities in this soil is promoted by high variability in environmental conditions, facilitating substantial removal of CH4 generated in the waste body.

  15. Hierarchical multiscale mechanism development for methane partial oxidation and reforming and for thermal decomposition of oxygenates on Rh.

    Science.gov (United States)

    Mhadeshwar, A B; Vlachos, D G

    2005-09-08

    A thermodynamically consistent C1 microkinetic model is developed for methane partial oxidation and reforming and for oxygenate (methanol and formaldehyde) decomposition on Rh via a hierarchical multiscale methodology. Sensitivity analysis is employed to identify the important parameters of the semiempirical unity bond index quadratic exponential potential (UBI-QEP) method and these parameters are refined using quantum mechanical density functional theory. With adjustment of only two pre-exponentials in the CH4 oxidation subset, the C1 mechanism captures a multitude of catalytic partial oxidation (CPOX) and reforming experimental data as well as thermal decomposition of methanol and formaldehyde. We validate the microkinetic model against high-pressure, spatially resolved CPOX experimental data. Distinct oxidation and reforming zones are predicted to exist, in agreement with experiments, suggesting that hydrogen is produced from reforming of methane by H2O formed in the oxidation zone. CO is produced catalytically by partial oxidation up to moderately high pressures, with water-gas shift taking place in the gas-phase at sufficiently high pressures resulting in reduction of CO selectivity.

  16. Methyl-coenzyme M reductase from methanogenic archaea: isotope effects on the formation and anaerobic oxidation of methane.

    Science.gov (United States)

    Scheller, Silvan; Goenrich, Meike; Thauer, Rudolf K; Jaun, Bernhard

    2013-10-09

    The nickel enzyme methyl-coenzyme M reductase (MCR) catalyzes two important transformations in the global carbon cycle: methane formation and its reverse, the anaerobic oxidation of methane. MCR uses the methyl thioether methyl-coenzyme M (CH3-S-CH2CH2-SO3(-), Me-S-CoM) and the thiol coenzyme B (CoB-SH) as substrates and converts them reversibly to methane and the corresponding heterodisulfide (CoB-S-S-CoM). The catalytic mechanism is still unknown. Here, we present isotope effects for this reaction in both directions, catalyzed by the enzyme isolated from Methanothermobacter marburgensis . For methane formation, a carbon isotope effect ((12)CH3-S-CoM/(13)CH3-S-CoM) of 1.04 ± 0.01 was measured, showing that breaking of the C-S bond in the substrate Me-S-CoM is the rate-limiting step. A secondary isotope effect of 1.19 ± 0.01 per D in the methyl group of CD3-S-CoM indicates a geometric change of the methyl group from tetrahedral to trigonal planar upon going to the transition state of the rate-limiting step. This finding is consistent with an almost free methyl radical in the highest transition state. Methane activation proceeds with a primary isotope effect of 2.44 ± 0.22 for the C-H vs C-D bond breakage and a secondary isotope effect corresponding to 1.17 ± 0.05 per D. These values are consistent with isotope effects reported for oxidative cleavage/reductive coupling occurring at transition metal centers during C-H activation but are also in the range expected for the radical substitution mechanism proposed by Siegbahn et al. The isotope effects presented here constitute boundary conditions for any suggested or calculated mechanism.

  17. The variability of methane, nitrous oxide and sulfur hexafluoride in Northeast India

    Directory of Open Access Journals (Sweden)

    A. L. Ganesan

    2013-11-01

    Full Text Available High-frequency atmospheric measurements of methane (CH4, nitrous oxide (N2O and sulfur hexafluoride (SF6 from Darjeeling, India are presented from December 2011 (CH4/March 2012 (N2O and SF6 through February 2013. These measurements were made on a gas chromatograph equipped with a flame ionization detector and electron capture detector, and were calibrated on the Tohoku University, the Scripps Institution of Oceanography (SIO-98 and SIO-2005 scales for CH4, N2O and SF6, respectively. The observations show large variability and frequent pollution events in CH4 and N2O mole fractions, suggesting significant sources in the regions sampled by Darjeeling throughout the year. By contrast, SF6 mole fractions show little variability and only occasional pollution episodes, likely due to weak sources in the region. Simulations using the Numerical Atmospheric dispersion Modelling Environment (NAME particle dispersion model suggest that many of the enhancements in the three gases result from the transport of pollutants from the densely populated Indo-Gangetic Plains of India to Darjeeling. The meteorology of the region varies considerably throughout the year from Himalayan flows in the winter to the strong south Asian summer monsoon. The model is consistent in simulating a diurnal cycle in CH4 and N2O mole fractions that is present during the winter but absent in the summer and suggests that the signals measured at Darjeeling are dominated by large-scale (~100 km flows rather than local (<10 km flows.

  18. On the relevance of the methane oxidation cycle to ozone hole chemistry

    Science.gov (United States)

    Mueller, Rolf; Crutzen, Paul J.

    1994-01-01

    High concentrations of active chlorine are clearly responsible for the observed ozone depletion during the Antarctic polar spring. However, the mechanism behind the activation of chlorine from the reservoirs species HCl and ClONO2 and the maintenance of extremely high levels of active chlorine after polar sunrise is less well understood. Here, we focus on the influence of the methane oxidation cycle on 'ozone hole' chemistry through its effect on HOx and ClOx radicals. We demonstrate the great potential importance of the heterogeneous reaction HCl + HOCl yields Cl2 + H2O and the gasphase reaction ClO + CH3O2 yields ClOO + CH3O under sunlight conditions in polar spring. Under these conditions, the heterogeneous reaction is the main sink for HOx radicals. Through this channel, the HCl reservoir may be almost completely depleted. The gas phase reaction may control the levels of the CH3O2 radical, provided that high levels of ClO exist. Otherwise this radical initiates a sequence of reactions leading to a considerable loss of active chlorine. Moreover, the production of HOx radicals is reduced, and thereby the efficiency of the heterogeneous reaction limited. The two reactions together may accomplish the complete conversion of HCl into active chlorine, thereby leading to a rapid destruction of ozone.

  19. Selective oxidation of methane to formaldehyde by oxygen over silica-supported iron catalysts

    Institute of Scientific and Technical Information of China (English)

    Jieli He; Yang Li; Dongli An; Qinghong Zhang; Ye Wang

    2009-01-01

    FeO_x-SiO_2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeO_x-SiO_2 with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeO_x-SiO_2 catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeO_x/SiO_2 prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H_2-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeO_x-SiO_2 by phosphorus enhanced the formaldehyde selectivity,and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeO_x-SiO_2 catalyst (P/Fe = 0.5) at 898 K. Raman spectroscopic measurements indicated the formation of FePO_4 nanoclusters in this catalyst,which were more selective toward formaldehyde formation.

  20. Prophylactic Modulation of Methane and Nitrous Oxide Emitted from Ruminants Livestock for Sustainable Animal Agriculture

    Directory of Open Access Journals (Sweden)

    J. Takahashi

    2014-12-01

    Full Text Available Major greenhouse gases (GHG attributed to animal agriculture sector are methane (CH4 and nitrous oxide (N2O, either generated from enteric fermentation or manure. The abatement mechanism of rumen CH4 emission may be divided to direct and indirect suppression to methanogens in the rumen.The most significant strategy to mitigate ruminal CH4 emission in indirect manner is to promote alternative metabolic pathway to dispose of the reducing power, competing with methanogenesis for H2 uptake. This includes prebiotics and probiotics (mostly propionate enhancers which consume metabolic hydrogen (H2 compete with methanogens and abate rumen methanogenesis in indirect manner. With regard to mitigate GHG emissions from manure, such waste has been proposed as a renewable energy and nitrogen sources through biogas plant. Furthermore, in advanced new biogas system, the ammonia stripping from digested slurry of livestock manure in biogas plant has been examined to apply to nitrogen recycling-options mitigating N2O emission. These options are: (1 ammonolysis on fiber-rich feedstuffs, (2 saccharification of the NH3 treated cellulose biomass to produce bio-ethanol, and (3 reformed hydrogen into NH3 fuel cell to generate electricity with proton exchange membrane fuel cell (PEM.

  1. Ecosystem respiration, methane and nitrous oxide fluxes from ecotopes in a rewetted extracted peatland in Sweden

    Directory of Open Access Journals (Sweden)

    S. Jordan

    2016-09-01

    Full Text Available Ecosystem respiration (carbon dioxide; CO2, methane (CH4 and nitrous oxide (N2O fluxes to the atmosphere were determined using an opaque closed chamber method within various ecotopes (vegetation covered, bare peat and open water in a rewetted extracted peatland and within an adjacent open poor fen in Sweden. Ecotopes had a significant impact on CO2 and CH4 fluxes to the atmosphere. Ecosystem respiration and CH4 emissions from the bare peat site, the constructed shallow lake and the open poor fen were low but were much higher from ecotopes with Eriophorum vaginatum tussocks and Eriophorum angustifolium. A combination of vascular plant cover and high soil temperatures enhanced ecosystem respiration, while a combination of vascular plant cover, high water table levels and high soil temperatures enhanced CH4 emissions. N2O emissions contributed little to total greenhouse gas (GHG fluxes from the soil-plant-water systems to the atmosphere. However, the overall climate impact of CH4 emissions from the study area did not exceed the impact of soil and plant respiration. With regard to management of extracted peatlands, the construction of a nutrient-poor shallow lake showed great potential for lowering GHG fluxes to the atmosphere.

  2. Investigation of the ignition behaviour of the noble metal catalyzed catalytic partial oxidation of methane

    Energy Technology Data Exchange (ETDEWEB)

    Stoetzel, J; Luetzenkirchen-Hecht, D; Frahm, R [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany); Kimmerle, B; Baiker, A [Department of Chemistry and Applied Biosciences, ETH Zuerich, CH-8093 Zuerich (Switzerland); Nachtegaal, M [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Beier, M J; Grunwaldt, J-D, E-mail: j.stoetzel@uni-wuppertal.d [Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800 Kgs. Lyngby (Denmark)

    2009-11-15

    Catalytic partial oxidation (CPO) of methane to hydrogen and carbon monoxide over Pt-Rh/Al{sub 2}O{sub 3} and Pt/Al{sub 2}O{sub 3} was studied in-situ with a new QEXAFS setup. The structural changes of the catalysts were investigated on the subsecond timescale during two reaction steps by recording both XANES and full EXAFS spectra: (1) heating and ignition in 6%CH{sub 4}/3%O{sub 2}/He, (2) periodic changes between the reaction gas mixture and H{sub 2} atmosphere. The results showed that the ignition occurred at lower temperatures for Pt-Rh/Al{sub 2}O{sub 3} while it was completed in a significant shorter time interval for Pt/Al{sub 2}O{sub 3}. Some structural changes during the heating phase were detectable before the reaction ignited, especially for Pt/Al{sub 2}O{sub 3}, as reflected by the performed principle component analysis. However, a closer analysis of the FT-QEXAFS data did not evidence a defined intermediate. In addition, the composition of the gas atmosphere was altered between hydrogen and the reaction mixture, enabling modulation excitation spectroscopy. This technique was for the first time applied to QEXAFS data and resulted in significantly enhanced data quality.

  3. Aircraft emissions of methane and nitrous oxide during the alternative aviation fuel experiment.

    Science.gov (United States)

    Santoni, Gregory W; Lee, Ben H; Wood, Ezra C; Herndon, Scott C; Miake-Lye, Richard C; Wofsy, Steven C; McManus, J Barry; Nelson, David D; Zahniser, Mark S

    2011-08-15

    Given the predicted growth of aviation and the recent developments of alternative aviation fuels, quantifying methane (CH(4)) and nitrous oxide (N(2)O) emission ratios for various aircraft engines and fuels can help constrain projected impacts of aviation on the Earth's radiative balance. Fuel-based emission indices for CH(4) and N(2)O were quantified from CFM56-2C1 engines aboard the NASA DC-8 aircraft during the first Alternative Aviation Fuel Experiment (AAFEX-I) in 2009. The measurements of JP-8 fuel combustion products indicate that at low thrust engine states (idle and taxi, or 4% and 7% maximum rated thrusts, respectively) the engines emit both CH(4) and N(2)O at a mean ± 1σ rate of 170 ± 160 mg CH(4) (kg Fuel)(-1) and 110 ± 50 mg N(2)O (kg Fuel)(-1), respectively. At higher thrust levels corresponding to greater fuel flow and higher engine temperatures, CH(4) concentrations in engine exhaust were lower than ambient concentrations. Average emission indices for JP-8 fuel combusted at engine thrusts between 30% and 100% of maximum rating were -54 ± 33 mg CH(4) (kg Fuel)(-1) and 32 ± 18 mg N(2)O (kg Fuel)(-1), where the negative sign indicates consumption of atmospheric CH(4) in the engine. Emission factors for the synthetic Fischer-Tropsch fuels were statistically indistinguishable from those for JP-8.

  4. Emissions of ammonia, nitrous oxide and methane from cattle manure heaps: effect of compaction and covering

    Science.gov (United States)

    Chadwick, D. R.

    The effect of compaction and covering during storage of beef cattle ( Bos taurus) farmyard manure (FYM) on ammonia (NH 3), nitrous oxide (N 2O) and methane (CH 4) emissions was determined. Gaseous emission measurements were made over three separate storage periods of between 90 and 109 days. The effect of the different storage treatments on manure chemical composition was also determined. Compaction was carried out as the manure was put into store and the compacted manures covered with plastic sheeting. Compaction and covering significantly reduced NH 3 emissions from manure by over 90% during the first summer storage period (Ppersistent rainfall during heap establishment and the following week appeared to reduce NH 3 emissions markedly. The low ammonium-N content of the FYM in the third storage period may have reduced the risk of NH 3 emission and reduced the relative effect of the compaction/covering treatment. Compaction and covering also significantly reduced N 2O emissions from cattle FYM (Pbenefits are that N and K are retained in the manure heap for agronomic benefit.

  5. Nanoporous and highly active silicon carbide supported CeO₂-catalysts for the methane oxidation reaction.

    Science.gov (United States)

    Hoffmann, Claudia; Biemelt, Tim; Lohe, Martin R; Rümmeli, Mark H; Kaskel, Stefan

    2014-01-29

    CeOx @SiO2 nanoparticles are used for the first time for the generation of porous SiC materials with tailored pore diameter in the mesopore range containing encapsulated and catalytically active CeO2 nanoparticles. The nanocasting approach with a preceramic polymer and subsequent pyrolysis is performed at 1300 °C, selective leaching of the siliceous part results in CeOx /SiC catalysts with remarkable characteristics like monodisperse, spherical pores and specific surface areas of up to 438 m(2) ·g(-1) . Porous SiC materials are promising supports for high temperature applications. The catalysts show excellent activities in the oxidation of methane with onset temperatures of the reaction 270 K below the onset of the homogeneous reaction. The synthesis scheme using core-shell particles is suited to functionalize silicon carbide with a high degree of stabilization of the active nanoparticles against sintering in the core of the template even at pyrolysis temperatures of 1300 °C rendering the novel synthesis principle as an attractive approach for a wide range of catalytic reactions.

  6. Characteristics of methane and nitrous oxide emissions from the wastewater treatment plant.

    Science.gov (United States)

    Hwang, Kum-Lok; Bang, Cheon-Hee; Zoh, Kyung-Duk

    2016-08-01

    The nitrous oxide (N2O) and methane (CH4) emissions were measured from a municipal wastewater treatment plant (WWTP) using a flux chamber to determine the emission factors. The WWTP treats sewage using both the activated-sludge treatment and anaerobic/anoxic/aerobic (A(2)O) methods. Measurements were performed in the first settling, aeration, and secondary settling basins, as well as in the sludge thickener, sludge digestion tank, and A(2)O basins. The total emission factors of N2O and CH4 from the activated-sludge treatment were 1.256gN2O/kg total nitrogen (TN) and 3.734gCH4/kg biochemical oxygen demand (BOD5), respectively. Those of the advanced treatment (A(2)O) were 1.605gN2O/kg TN and 4.022gCH4/kgBOD5, respectively. These values are applicable as basic data to estimate greenhouse gas emissions.

  7. Oxidative Coupling of Methane over Lithium Doped (Mn+W)/SiO2 Catalysts

    Institute of Scientific and Technical Information of China (English)

    A. Malekzadeh; A. Khodadadi; A.K. Dalai; M. Abedini

    2007-01-01

    Modification and performance of Li induced silica phase transition of (Mn+W)/SiO2 catalyst,under reaction conditions of oxidative coupling of methane (OCM), have been investigated employing textural characterizations and redox studies. Stability and precrystalline form of fresh Li induced silica phase transition catalyst depend on the Li loading. A catalyst, with high lithium loading, destabilizes on OCM stream. This destabilization is not due to Li evaporation at OCM reaction conditions. α-cristobalite is proposed to be an intermediate in the crystallization of amorphous silica into quartz in the Li-induced silica phase transition process. However, the type of crystalline structure was found to be unimportant with regard to the formation of a selective catalyst. Metal-metal interactions of Li-Mn, Li-W and Mn-W,which are affected during silica phase crystallization, are found to be critical parameters of the trimetallic catalyst and were studied by TPR. Role of lithium in Li doped (Mn+W)/SiO2 catalyst is described as a moderator of the Mn-W interaction by involving W in silica phase transition. These interactions help in the improvement of transition metal redox properties, especially that of Mn, in favor of OCM selectivity.

  8. Estimates for biogenic non-methane hydrocarbons and nitric oxide emissions in the Valley of Mexico

    Science.gov (United States)

    Velasco, Erik

    Biogenic non-methane hydrocarbons (NMHC), 2-methyl-3-buten-2-ol (methylbutenol or MBO) and nitrogen oxide (NO) emissions were estimated for the Valley of Mexico developing a spatially and temporally resolved emission inventory for air quality models. The modeling domain includes all the Metropolitan Mexico City Area, the surrounding forests and agriculture fields. The estimates were based on several sources of land use and land cover data and a biogenic emission model; the biomass density and tree characteristics were obtained from reforestation program data. The biogenic emissions depend also on climatic conditions, mainly temperature and solar radiation. The temperature was obtained from a statistical revision of the last 10 yr data reported by the Mexico City Automatic Atmospheric Monitoring Network, while the solar radiation data were obtained from measurements performed in a typical oak forest in the Valley and from sources of total solar radiation data for Mexico City. The results indicated that 7% of total hydrocarbon emissions in Mexico Valley are due to vegetation and NO emissions from soil contribute with 1% to the total NO x emissions.

  9. Methane oxidation at redox stable fuel cell electrode La0.75Sr0.25Cr0.5Mn0.5O(3-delta).

    Science.gov (United States)

    Tao, Shanwen; Irvine, John T S; Plint, Steven M

    2006-11-02

    Because of its widespread availability, natural gas is the most important fuel for early application of stationary fuel cells, and furthermore, methane containing biogases are one of the most promising renewable energy alternatives; thus, it is very important to be able to efficiently utilize methane in fuel cells. Typically, external steam reforming is applied to allow methane utilization in high temperature fuel cells; however, direct oxidation will provide a much better solution. Recently, we reported good electrochemical performance for an oxide anode La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) in low moisture (3% H2O) H2 and CH4 fuels without significant coking in CH4. Here, we investigate the catalytic activity of this oxide with respect to its ability to utilize methane. This oxide is found to exhibit fairly low reforming activity for both H2O and CO2 reforming but is active for methane oxidation. LSCM is found to be a full oxidation catalyst rather than a partial oxidation catalyst as CO2 production dominates CO production even in CH4-rich CH4/O2 mixtures. X-ray adsorption spectroscopy was utilized to confirm that Mn was the redox active species, clearly demonstrating that this material has the oxidation catalytic behavior that might be expected from a Mn perovskite and that the Cr ion is only present to ensure stability under fuel atmospheres.

  10. Methane alleviates copper-induced seed germination inhibition and oxidative stress in Medicago sativa.

    Science.gov (United States)

    Samma, Muhammad Kaleem; Zhou, Heng; Cui, Weiti; Zhu, Kaikai; Zhang, Jing; Shen, Wenbiao

    2017-02-01

    Recent results discovered the protective roles of methane (CH4) against oxidative stress in animals. However, the possible physiological roles of CH4 in plants are still unknown. By using physiological, histochemical and molecular approaches, the beneficial role of CH4 in germinating alfalfa seeds upon copper (Cu) stress was evaluated. Endogenous production of CH4 was significantly increased in Cu-stressed alfalfa seeds, which was mimicked by 0.39 mM CH4. The pretreatment with CH4 significantly alleviated the inhibition of seed germination and seedling growth induced by Cu stress. Cu accumulation was obviously blocked as well. Meanwhile, α/β amylase activities and sugar contents were increased, all of which were consistent with the alleviation of seed germination inhibition triggered by CH4. The Cu-triggered oxidative stress was also mitigated, which was confirmed by the decrease of lipid peroxidation and reduction of Cu-induced loss of plasma membrane integrity in CH4-pretreated alfalfa seedlings. The results of antioxidant enzymes, including ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (POD) total or isozymatic activities, and corresponding transcripts (APX1/2, Cu/Zn SOD and Mn-SOD), indicated that CH4 reestablished cellular redox homeostasis. Further, Cu-induced proline accumulation was partly impaired by CH4, which was supported by the alternation of proline metabolism. Together, these results indicated that CH4 performs an advantageous effect on the alleviation of seed germination inhibition caused by Cu stress, and reestablishment of redox homeostasis mainly via increasing antioxidant defence.

  11. Effects of organic nitrification inhibitors on methane and nitrous oxide emission from tropical rice paddy

    Science.gov (United States)

    Datta, A.; Adhya, T. K.

    2014-08-01

    We have studied the effects of application of different nitrification inhibitors on methane (CH4) and nitrous oxide (N2O) emissions from rice paddy and associated soil chemical and biological dynamics during wet and dry seasons of rice crop in a tropical climate of eastern India. The experiment consisted of four treatments viz. (i) Prilled urea amended control (ii) urea + Dicyandiamide (DCD), (iii) urea + Nimin and (iv) urea + Karanjin. CH4 emission was significantly higher from the DCD (372.36 kg ha-1) and Karanjin (153.07 kg ha-1) applied plots during the wet and dry season, respectively. N2O emission was significantly inhibited in the Nimin applied plots during both seasons (69% and 85% over control during wet season and dry season respectively). CH4 and N2O emissions per Mg of rice grain yield were lowest from the Nimin applied plots during both seasons. Global warming potential (GWP) of the plot treated with DCD (13.93) was significantly higher during the experimental period. CH4 production potential was significantly higher from the nitrification inhibitor applied plots compared to control. While, CH4 oxidation potential followed the order; urea + Nimin > urea + Karanjin > urea + DCD > control. Application of Nimin significantly increased the methanotrophic bacterial population in the soil during the maximum tillering to flowering stage and may be attributed to low CH4 emission from the plots. Denitrification enzyme activity (DEA) of the soil was significantly low from the Nimin and Karanjin applied plots. Results suggest that apart from being potent nitrification inhibitors, Nimin and Karanjin also have the potential to reduce the denitrification activity in the soil. This in turn, would reduce N2O emission from flooded paddy where both nitrification and denitrification processes causes N2O emission.

  12. Geochemical, metagenomic and metaproteomic insights into trace metal utilization by methane-oxidizing microbial consortia in sulphidic marine sediments.

    Science.gov (United States)

    Glass, Jennifer B; Yu, Hang; Steele, Joshua A; Dawson, Katherine S; Sun, Shulei; Chourey, Karuna; Pan, Chongle; Hettich, Robert L; Orphan, Victoria J

    2014-06-01

    Microbes have obligate requirements for trace metals in metalloenzymes that catalyse important biogeochemical reactions. In anoxic methane- and sulphide-rich environments, microbes may have unique adaptations for metal acquisition and utilization because of decreased bioavailability as a result of metal sulphide precipitation. However, micronutrient cycling is largely unexplored in cold (≤ 10°C) and sulphidic (> 1 mM ΣH(2)S) deep-sea methane seep ecosystems. We investigated trace metal geochemistry and microbial metal utilization in methane seeps offshore Oregon and California, USA, and report dissolved concentrations of nickel (0.5-270 nM), cobalt (0.5-6 nM), molybdenum (10-5600 nM) and tungsten (0.3-8 nM) in Hydrate Ridge sediment porewaters. Despite low levels of cobalt and tungsten, metagenomic and metaproteomic data suggest that microbial consortia catalysing anaerobic oxidation of methane (AOM) utilize both scarce micronutrients in addition to nickel and molybdenum. Genetic machinery for cobalt-containing vitamin B12 biosynthesis was present in both anaerobic methanotrophic archaea (ANME) and sulphate-reducing bacteria. Proteins affiliated with the tungsten-containing form of formylmethanofuran dehydrogenase were expressed in ANME from two seep ecosystems, the first evidence for expression of a tungstoenzyme in psychrophilic microorganisms. Overall, our data suggest that AOM consortia use specialized biochemical strategies to overcome the challenges of metal availability in sulphidic environments. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  13. A laboratory-scale comparison of compost and sand--compost--perlite as methane-oxidizing biofilter media.

    Science.gov (United States)

    Philopoulos, Andrew; Ruck, Juliane; McCartney, Daryl; Felske, Christian

    2009-03-01

    Municipal solid waste landfills produce methane, a potent greenhouse gas. A treatment approach is to passively vent landfill gas through a methane-oxidizing biofilter medium, a porous substrate that facilitates the growth of methanotrophic bacteria. Two substrates, compost and a sand-compost-perlite (SCP) mixture, were evaluated in a laboratory-scale experiment for their suitability as biofilter media. The SCP mixture was investigated to minimize settlement and was based on a particle size distribution specification used for turf grass. The long-term (218 days) methane removal rates showed that both compost and SCP were capable of removing 100% of the methane influent flux (134 g CH(4) m( -2) day(-1)). The post-experiment analysis showed that compost had compacted more than SCP. This did not affect the results; however, in a field installation, traffic on the biofilter surface (e.g. maintenance) could cause further compaction and negatively affect performance. Exopolymeric substance produced by the methanotrophic bacteria, attributed by others for declining removal rates due to bio-clogging, was not observed to affect the results. The maximum exopolymeric substance values measured were 23.9 and 7.8 mg D-glucose g(-1) (dry basis) for compost and SCP, respectively.

  14. Geochemical, metagenomic and metaproteomic insights into trace metal utilization by methane-oxidizing microbial consortia in sulphidic marine sediments

    Energy Technology Data Exchange (ETDEWEB)

    Glass, DR. Jennifer [California Institute of Technology, Pasadena; Yu, DR. Hang [California Institute of Technology, Pasadena; Steele, Joshua [California Institute of Technology, Pasadena; Dawson, Katherine [California Institute of Technology, Pasadena; Sun, S [University of California, San Diego; Chourey, Karuna [ORNL; Pan, Chongle [ORNL; Hettich, Robert {Bob} L [ORNL; Orphan, V [California Institute of Technology, Pasadena

    2013-01-01

    Microbes have obligate requirements for trace metals in metalloenzymes that catalyse important biogeochemical reactions. In anoxic methane- and sulphiderich environments, microbes may have unique adaptations for metal acquisition and utilization because of decreased bioavailability as a result of metal sulphide precipitation. However, micronutrient cycling is largely unexplored in cold ( 10 C) and sulphidic (> 1 mM H2S) deep-sea methane seep ecosystems. We investigated trace metal geochemistry and microbial metal utilization in methane seeps offshore Oregon and California, USA, and report dissolved concentrations of nickel (0.5 270 nM), cobalt (0.5 6 nM), molybdenum (10 5600 nM) and tungsten (0.3 8 nM) in Hydrate Ridge sediment porewaters. Despite low levels of cobalt and tungsten, metagenomic and metaproteomic data suggest that microbial consortia catalysing anaerobic oxidation of methane (AOM) utilize both scarce micronutrients in addition to nickel and molybdenum. Genetic machinery for cobalt-containing vitamin B12 biosynthesis was present in both anaerobic methanotrophic archaea (ANME) and sulphate-reducing bacteria. Proteins affiliated with the tungsten-containing form of formylmethanofuran dehydrogenase were expressed in ANME from two seep ecosystems, the first evidence for expression of a tungstoenzyme in psychrophilic microorganisms. Overall, our data suggest that AOM consortia use specialized biochemical strategies to overcome the challenges of metal availability in sulphidic environments.

  15. Stimulation by ammonium-based fertilizers of methane oxidation in soil around rice roots

    NARCIS (Netherlands)

    Bodelier, P.L.E.; Roslev, P.; Henckel, T.; Frenzel, P.

    2000-01-01

    Methane is involved in a number of chemical and physical processes in the Earths atmosphere, including global warming(1), Atmospheric methane originates mainly from biogenic sources, such as rice paddies and natural wetlands; the former account for at least 30% of the global annual emission of metha

  16. Methane oxidation by an extremely acidophilic bacterium of the phylum Verrucomicrobia

    NARCIS (Netherlands)

    Dunfield, P.F.; Yurgey, A.Q.; Senin, P.; Smirnova, A.V.; Stott, M.B.; Hou, S.; Ly, B.; Saw, J.H.; Zhou, Z.; Ren, Y.; Wang, J.; Mountain, B.W.; Crowe, M.A.; Weatherby, T.M.; Bodelier, P.L.E.; Liesack, W.; Feng, L.; Wang, L.; Alam, M.

    2007-01-01

    Aerobic methanotrophic bacteria consume methane as it diffuses away from methanogenic zones of soil and sediment1. They act as a biofilter to reduce methane emissions to the atmosphere, and they are therefore targets in strategies to combat global climate change. No cultured methanotroph grows optim

  17. Estimation of methane and nitrous oxide emission from livestock and poultry in China during 1949-2003

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J.B.; Jiang, M.M.; Chen, G.Q. [National Laboratory for Complex Systems and Turbulence, Department of Mechanics, Peking University, Beijing 100871 (China)

    2007-07-15

    To investigate the greenhouse gases emission from enteric fermentation and manure management of livestock and poultry industry in China, the present study presents a systematic estimation of methane and nitrous oxide emission during 1949-2003, based on the local measurement and IPCC guidelines. As far as greenhouse gases emission is concerned among livestock swine is found to hold major position followed by goat and sheep, while among poultry chicken has the major place and is followed by duck and geese. Methane emission from enteric fermentation is estimated to have increased from 3.04 Tg in 1949 to 10.13 Tg in 2003, an averaged annual growth rate of 2.2%, and methane emission from manure management has increased from 0.16 Tg in 1949 to 1.06 Tg in 2003, an annual growth rate of 3.5%, while nitrous oxide emission from manure management has increased from 47.76 to 241.2 Gg in 2003, with an annual growth rate of 3.0%. The total greenhouse gas emission has increased from 82.01 Tg CO{sub 2} Eq. in 1949 to 309.76 Tg CO{sub 2} Eq. in 2003, an annual growth rate of 2.4%. The estimation of livestock methane and nitrous oxide emissions in China from 1949 to 2003 is shown to be consistent with a linear growth model, and the reduction of greenhouse gas emission is thus considered an urgent and arduous task for the Chinese livestock industry. (author)

  18. Kinetic Studies of Oxidative Coupling of Methane Reaction on Model Catalysts

    KAUST Repository

    Khan, Abdulaziz M.

    2016-04-26

    With the increasing production of natural gas as a result of the advancement in the technology, methane conversion to more valuable products has become a must. One of the most attractive processes which allow the utilization of the world’s most abundant hydrocarbon is the oxidative coupling. The main advantage of this process is the ability of converting methane into higher paraffins and olefins (primarily C2) in a direct way using a single reactor. Nevertheless, low C2+ yields have prevented the process to be commercialized despite the fact that great number of attempts to prepare catalysts were conducted so that it can be economically viable. Due to these limitations, understanding the mechanism and kinetics of the reaction can be utilized in improving the catalysts’ performance. The reaction involves the formation of methyl radicals that undergo gas-phase radical reactions. CH4 activation is believed to be done the surface oxygen species. However, recent studies showed that, in addition to the surface oxygen mediated pathway, an OH radical mediated pathway have a large contribution on the CH4 activation. The experiments of Li/MgO, Sr/La2O3 and NaWO4/SiO2 catalysts revealed variation of behavior in activity and selectivity. In addition, water effect analysis showed that Li/MgO deactivate at the presence of water due to sintering phenomena and the loss of active sites. On the other hand, negative effect on the C2 yield and CH4 conversion rate was observed with Sr/La2O3 with increasing the water partial pressure. Na2WO4/SiO2 showed a positive behavior with water in terms of CH4 conversion and C2 yield. In addition, the increment in CH4 conversion rate was found to be proportional with PO2 ¼ PH2O ½ which is consistent with the formation of OH radicals and the OH-mediated pathway. Experiments of using ring-dye laser, which is used to detect OH in combustion experiments, were tried in order to detect OH radicals in the gas-phase of the catalyst. Nevertheless

  19. Nitrous oxide and methane emissions following application of animal manures to grassland

    Energy Technology Data Exchange (ETDEWEB)

    Chadwick, D.R.; Pain, B.F.; Brookman, S.K.E.

    2000-02-01

    Nitrous oxide (N{sub 2}O) and methane (CH{sub 4}) emissions were measured from grassland following manure applications at three times of the year. Pig (Sus scrofa) slurry and dairy cow (Bos taurus) slurry were applied in April, at equal rates of ammoniacal-N (NH{sub 4}{sup +}-N), and in July, at equal volumetric rates (50 m{sup 3}ha{sup {minus}1}). In October, five manure types were applied to grassland plots at typical application rates: pig slurry, dilute diary cow effluent, pig farm yard manure (FYM), beef FYM and layer manure. Emissions were measured for 20, 22, and 24 d, respectively. In April, greater cumulative emissions of N{sub 2}O-N were measured following application of dairy cow slurry (1.51 kg ha{sup {minus}1}) than pig slurry (90.77 kg ha{sup {minus}1}). Cumulative CH{sub 4} emissions following application in April were significantly greater from the dairy cow slurry treatment (0.58 kg ha{sup {minus}1}) than the pig slurry treatment (0.13 kg ha{sup {minus}1}) (P < 0.05). In July, significantly greater N{sub 2}O-N emissions resulted from pig slurry-treated plots (0.57 kg ha{sup {minus}1}) than dairy cow slurry-treated plots (0.34 kg ha{sup {minus}1}). Cumulative net CH{sub 4} emissions were very low following July applications (<10 g ha{sup {minus}1}). In October, the lowest N{sub 2}O-N emission resulted from application of dilute dairy effluent, 0.15 kg ha{sup {minus}1}, with the greatest net emission from the application of pig slurry, 0.74 kg ha{sup {minus}1}. Methane emissions were greatest from the plots that received pig FYM, resulting in a mean cumulative net emission of 2.39 kg ha{sup {minus}1}.

  20. Modelling TCE degradation by a mixed culture of methane-oxidizing bacteria

    DEFF Research Database (Denmark)

    Broholm, Kim; Christensen, Thomas Højlund; Jensen, Bjørn K.

    1992-01-01

    A model describing the growth of bacteria and the degradation of methane and trichloroethylene (TCE) based on the concept of competitive inhibition is proposed. The model has been applied to laboratory batch experiments representing different initial TCE concentrations (50–4300 μg/l) and initial...... methane concentrations (0.53–3.2 mg/l). The proposed model simulated successfully the data obtained for initial methane concentration (less than 1.8 mg/l), causing constant experimental growth conditions during the experiments. This indicates that the interactions between methane and TCE degradation can...... be explained as competitive inhibition. The model simulations of the results from the experiments with the highest initial methane concentration of 3.2 mg/l failed, supposedly because the growth conditions changed during the experiments. The proposed model is a useful engineering tool for design of treatment...

  1. Studies of the Effects of Alkali Metal Oxides Promoter on the Oxidative Methylation of Toluene with Methane over KY Zeolite Catalysts

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The toluene conversion, the selectivity to styrene and ethylbenzene( C8 selectivity) in the oxidative methylation of toluene with methane have been studied comparatively for the KY zeolite catalyst promoted with Li2O, Na2O, K2O, and Cs2O respectively. It was found that the effect of promoter decreased in the order: Cs2O>Na2O>Li2O>K2O.

  2. Thermochemical methane reforming using WO{sub 3} as an oxidant below 1173 K by a solar furnace simulator

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, T.; Shimizu, K. [Niigata Univ., Graduate School of Science and Technology, Niigata (Japan); Kitayama, Y.; Kodama, T. [Niigata Univ., Dept. of Chemistry and Chemical Engineering, Niigata (Japan)

    2001-07-01

    Thermochemical methane reforming by a reactive redox system of WO{sub 3} was demonstrated under direct irradiation of the metal oxide by a concentrated, solar-simulated Xe-lamp beam below 1173 K, for the purpose of converting solar high-temperature heat to chemical fuels. In the proposed cycling redox process, the metal oxide is expected to react with methane as an oxidant to produce syngas with a H{sub 2}/CO ratio of two, which is suitable for the production of methanol, and the reduced metal oxide which is oxidised back with steam in a separate step to generate hydrogen uncontaminated with carbon oxide. The ZrO{sub 2}-supported WO{sub 3} gave about 45% of CO yield and 55% of H{sub 2} yield with a H{sub 2}/CO ratio of about 2.4 in a temperature range of 1080-1160 K at a W/F ratio of 0.167 g min Ncm {sup -3} (W is the weight of WO{sub 3} phase and F is the flow rate of CH{sub 4}). The activity data under the solar simulation were compared to those for the WO{sub 3}/ZrO{sub 2} heated by irradiation of an infrared light. This comparison indicated that the CO selectivity was much improved to 76-85% in the solar-simulated methane reforming, probably by photochemical effect due to WO{sub 3} phase. The main solid product of WO{sub 2} in the reduced WO{sub 3}/ZrO{sub 2} was reoxidised to WO{sub 3} with steam to generate hydrogen below 1173 K. (Author)

  3. Catalytic studies of nitric oxide: A. Reduction of nitric oxide with methane over alumina supported rhidium. B. Characterization of alumina supported cobalt molybdate for olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Hardee, J.R.

    1978-01-01

    Kinetic studies at 300/sup 0/-400/sup 0/C in a gradientless recirculating reactor showed that nitric oxide reduction was first order in methane and -0.63 order in nitric oxide, with an activation energy of 18.4 kcal/mole, and a deuterium kinetic isotope effect of 1.9, suggesting that dissociative methane adsorption is the rate-determining step. Nitrogen-15 tracer studies showed that the reaction involves N/sub 2/O as a surface intermediate, and a mechanism is proposed involving two-step dissociation of adsorbed NO to adsorbed N/sub 2/O and N/sub 2/ and surface oxygen atoms, which rapidly poison the catalyst unless removed by methane. Propylene metathesis to ethylene and 2-butene over cobalt molybdate was studied by nitric oxide poisoning and shown to follow Langmuir-Hinshelwood kinetics. Two different dual-site mechanisms, one involving propylene adsorption on adjacent molybdenum atoms and the other involving adsorption of two propylene molecules on one molybdenum atom, fit the data equally well. An upper limit to the active site density was determined as 2.5 x 10/sup 13//sq cm at 27/sup 0/C, i.e., only 9Vertical Bar3< of the surface molybdenum atom density.

  4. Selective Methane Oxidation Catalyzed by Platinum Salts in Oleum at Turnover Frequencies of Large-Scale Industrial Processes.

    Science.gov (United States)

    Zimmermann, Tobias; Soorholtz, Mario; Bilke, Marius; Schüth, Ferdi

    2016-09-28

    Direct catalytic methane functionalization, a "dream reaction", is typically characterized by relatively low catalyst activities. This also holds for the η(2)-(2,2'-bipyrimidyl)dichloroplatinum(II) [(bpym)PtCl2, 1] catalyst which oxidizes methane to methyl bisulfate in sulfuric acid. Nevertheless, it is arguably still one of the best systems for the partial oxidation of methane reported so far. Detailed studies of the dependence of activity on the SO3 concentration and the interplay with the solubility of different platinum compounds revealed potassium tetrachloroplatinate (K2PtCl4) as an extremely active, selective, and stable catalyst, reaching turnover frequencies (TOFs) of more than 25,000 h(-1) in 20% oleum with selectivities above 98%. The TOFs are more than 3 orders of magnitude higher compared to the original report on (bpym)PtCl2 and easily reach or exceed those realized in commercial industrial processes, such as the Cativa process for the carbonylation of methanol. Also space-time-yields are on the order of large-scale commercialized processes.

  5. Simultaneous enrichment of denitrifying anaerobic methane-oxidizing microorganisms and anammox bacteria in a hollow-fiber membrane biofilm reactor.

    Science.gov (United States)

    Ding, Zhao-Wei; Lu, Yong-Ze; Fu, Liang; Ding, Jing; Zeng, Raymond J

    2017-01-01

    In this study, the coculture system of denitrifying anaerobic methane oxidation (DAMO) microbes and anaerobic ammonium oxidation (anammox) bacteria was successfully enriched in a hollow-fiber membrane biofilm reactor (HfMBR) using freshwater sediment as the inoculum. The maximal removal rates of nitrate and ammonium were 78 mg N/L/day (131 mg N/m(2)/day) and 26 mg N/L/day (43 mg N/m(2)/day), respectively. Due to the high rate of methane mass transfer in HfMBR, the activity of DAMO archaea continued to increase during the enrichment period, indicating that HfMBR could be a powerful tool to enrich DAMO microorganisms. Effects of partial methane pressure, temperature, and pH on the cocultures were obvious. However, the microbial activity in HfMBR could be recovered quickly after the shock change of environmental factors. Furthermore, the result also found that DAMO bacteria likely had a stronger competitive advantage than anammox bacteria under the operating conditions in this study. High-throughput sequencing 16S rRNA genes illustrated that the dominant microbes were NC10, Euryarchaeota, Proteobacteria, Planctomycetes, and Chlorobi with relative abundance of 38.8, 26.2, 13.78, 6.2, and 3.6 %, respectively.

  6. Anaerobic oxidation of methane (AOM) in marine sediments from the Skagerrak (Denmark): II. Reaction-transport modeling

    Science.gov (United States)

    Dale, A. W.; Regnier, P.; Knab, N. J.; Jørgensen, B. B.; Van Cappellen, P.

    2008-06-01

    A steady-state reaction-transport model is applied to sediments retrieved by gravity core from two stations (S10 and S13) in the Skagerrak to determine the main kinetic and thermodynamic controls on anaerobic oxidation of methane (AOM). The model considers an extended biomass-implicit reaction network for organic carbon degradation, which includes extracellular hydrolysis of macromolecular organic matter, fermentation, sulfate reduction, methanogenesis, AOM, acetogenesis and acetotrophy. Catabolic reaction rates are determined using a modified Monod rate expression that explicitly accounts for limitation by the in situ catabolic energy yields. The fraction of total sulfate reduction due to AOM in the sulfate-methane transition zone (SMTZ) at each site is calculated. The model provides an explanation for the methane tailing phenomenon which is observed here and in other marine sediments, whereby methane diffuses up from the SMTZ to the top of the core without being consumed. The tailing is due to bioenergetic limitation of AOM in the sulfate reduction zone, because the methane concentration is too low to engender favorable thermodynamic drive. AOM is also bioenergetically inhibited below the SMTZ at both sites because of high hydrogen concentrations (∼3-6 nM). The model results imply there is no straightforward relationship between pore water concentrations and the minimum catabolic energy needed to support life because of the highly coupled nature of the reaction network. Best model fits are obtained with a minimum energy for AOM of ∼11 kJ mol-1, which is within the range reported in the literature for anaerobic processes.

  7. Partial Oxidation of Methane to Syngas Using Lattice Oxygen of La1-xSrxFeO3 Perovskite Oxide Catalysts Instead of Molecular Oxygen

    Institute of Scientific and Technical Information of China (English)

    Ranjia Li; Changchun Yu; Shikong Shen

    2002-01-01

    Catalytic partial oxidation of methane to syngas using the lattice oxygen of La1-xSrxFeO3 perovskite oxide catalysts in place of molecular oxygen was studied. La1-xSrxFeO3 (x=0, 0.1, 0.2,0.5) perovskite oxides were prepared by the "auto-combustion method". XRD analysis showed that all La1-xSrxFeO3 samples have a single-phase perovskite-type oxide. The redox properties of the catalysts were investigated by temperature programmed reduction with hydrogen (H2-TPR). Reducibility of the catalysts increase with the increasing of the Sr2+ content. The oxygen species of the catalysts and their reaction with CH4 were studied by the temperature programmed surface reaction (CH4-TPSR). In the absence of gas phase oxygen, there exist two kinds of oxygen species on the catalysts. One kind of the oxygen species with strong oxidative ability is produced first, which can oxidize CH4 completely to CO2 and H2O.Then, the second oxygen species with weak oxidative ability is formed, which can oxidize CH4 partially to CO and H2 with high selectivity. The number of the oxygen species with strong oxidative ability in the CH4-TPSR tends to become zero at low x values (x≤0.1). Under suitable reaction conditions, switching alternatively the reactions of 11% O2-Ar and 11% CH4-He over a La0.sSr0.2FeO3 catalyst at 900 ℃ allows methane to be selectively converted to synthesis gas (CH4 conversion ~90%, CO selectivity >93%) using the lattice oxygen of the perovskite oxide catalyst in a redox mode.

  8. Studies on the Performance and Structure of Supported Catalysts for the Partial Oxidation of Methane to Syngas

    Institute of Scientific and Technical Information of China (English)

    Tinghua Wu; Mingqiao Zhu; Zhenjiang Niu; Yijun Zhong; Yan Guan; Ya Liu; Qiangu Yan; Zelin Li; Huilin Wan

    2002-01-01

    The catalytic properties of several supported metal catalysts on different carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst performances were significantly influenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also affected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.

  9. Intrinsic kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts

    Institute of Scientific and Technical Information of China (English)

    Benzhen Yao; Jin Chen; Dianhua Liu; Dingye Fang

    2008-01-01

    The intrinsic reaction kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts was studied in the quartz pipe-reactor under ordinary pressure with the temperature ranging from 913.15 to 973.15 K and the space velocity from 700 to 2100 ml/(g-h). The Langmuir-Hinshelwood model was chosen to describe the intrinsic kinetics while Levenberg-Marquardt method was selected to determine the parameters in the kinetic model. Statistical test and residual error distribution diagrams showed that experimental data were in good agreement with calculated data, and Langmuir-Hinshelwood model was suitable for the description of the intrinsic kinetics of methane aromatization under the reaction conditions discussed in this article.

  10. Catalytic methanation reaction over alumina supported cobalt oxide doped noble metal oxides for the purification of simulated natural gas

    Institute of Scientific and Technical Information of China (English)

    Wan Azelee Wan Abu Bakar; Rusmidah Ali; Abdul Aziz Abdul Kadir; Salmiah Jamal Mat Rosid; Nurul Shafeeqa Mohammad

    2012-01-01

    A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co( 10∶90 )/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co( 10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co( 10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis (EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co( 10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co( 10∶90)/Al2O3 catalyst.

  11. Oscillations during partial oxidation of methane to synthesis gas over Ru/Al_2O_3 catalyst

    Institute of Scientific and Technical Information of China (English)

    Meiliu Wang; Weizheng Weng; Haozhuan Zheng; Xiaodong Yi; Chuanjing Huang; Huilin Wan

    2009-01-01

    Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al_2O_3 in the temperature range of 600 to 850 ℃. XRD,H_2-TPR and in situ Raman techniques was used to characterize the catalyst. Two types of ruthenium species,i.e. the rutbenium species weakly interacted with Al_2O_3 and that strongly interacted with the support,were identified by H2-TPR experiment. These species are responsible for two types of oscillation profiles observed during the reaction. The oscillations were the result of these ruthenium species switching cyclically between the oxidized state and the reduced state under the reaction condition. These cyclic transformations,in turn,were the result of temperature variations caused by the varying levels of the strongly exothermic CH_4 combustion and the highly endothermic CH4 reforming (with H_2O and CO_2) reactions (or the less exothermic direct partial oxidation of methane to CO and H_2),which were favored by the oxidized and the metallic sites,respectively. The major pathway of synthesis gas formation over the catalyst was via the combustion-reforming mechanism.

  12. An N-bridged high-valent diiron-oxo species on a porphyrin platform that can oxidize methane

    Science.gov (United States)

    Kudrik, Evgeny V.; Afanasiev, Pavel; Alvarez, Leonardo X.; Dubourdeaux, Patrick; Clémancey, Martin; Latour, Jean-Marc; Blondin, Geneviève; Bouchu, Denis; Albrieux, Florian; Nefedov, Sergey E.; Sorokin, Alexander B.

    2012-12-01

    High-valent oxo-metal complexes are involved in key biochemical processes of selective oxidation and removal of xenobiotics. The catalytic properties of cytochrome P-450 and soluble methane monooxygenase enzymes are associated with oxo species on mononuclear iron haem and diiron non-haem platforms, respectively. Bio-inspired chemical systems that can reproduce the fascinating ability of these enzymes to oxidize the strongest C-H bonds are the focus of intense scrutiny. In this context, the development of highly oxidizing diiron macrocyclic catalysts requires a structural determination of the elusive active species and elucidation of the reaction mechanism. Here we report the preparation of an Fe(IV)(µ-nitrido)Fe(IV) = O tetraphenylporphyrin cation radical species at -90 °C, characterized by ultraviolet-visible, electron paramagnetic resonance and Mössbauer spectroscopies and by electrospray ionization mass spectrometry. This species exhibits a very high activity for oxygen-atom transfer towards alkanes, including methane. These findings provide a foundation on which to develop efficient and clean oxidation processes, in particular transformations of the strongest C-H bonds.

  13. Archaeal and anaerobic methane oxidizer communities in the Sonora Margin cold seeps, Guaymas Basin (Gulf of California).

    Science.gov (United States)

    Vigneron, Adrien; Cruaud, Perrine; Pignet, Patricia; Caprais, Jean-Claude; Cambon-Bonavita, Marie-Anne; Godfroy, Anne; Toffin, Laurent

    2013-08-01

    Cold seeps, located along the Sonora Margin transform fault in the Guaymas Basin, were extensively explored during the 'BIG' cruise in June 2010. They present a seafloor mosaic pattern consisting of different faunal assemblages and microbial mats. To investigate this mostly unknown cold and hydrocarbon-rich environment, geochemical and microbiological surveys of the sediments underlying two microbial mats and a surrounding macrofaunal habitat were analyzed in detail. The geochemical measurements suggest biogenic methane production and local advective sulfate-rich fluxes in the sediments. The distributions of archaeal communities, particularly those involved in the methane cycle, were investigated at different depths (surface to 18 cm below the sea floor (cmbsf)) using complementary molecular approaches, such as Automated method of Ribosomal Intergenic Spacer Analysis (ARISA), 16S rRNA libraries, fluorescence in situ hybridization and quantitative polymerase chain reaction with new specific primer sets targeting methanogenic and anaerobic methanotrophic lineages. Molecular results indicate that metabolically active archaeal communities were dominated by known clades of anaerobic methane oxidizers (archaeal anaerobic methanotroph (ANME)-1, -2 and -3), including a novel 'ANME-2c Sonora' lineage. ANME-2c were found to be dominant, metabolically active and physically associated with syntrophic Bacteria in sulfate-rich shallow sediment layers. In contrast, ANME-1 were more prevalent in the deepest sediment samples and presented a versatile behavior in terms of syntrophic association, depending on the sulfate concentration. ANME-3 were concentrated in small aggregates without bacterial partners in a restricted sediment horizon below the first centimetres. These niche specificities and syntrophic behaviors, depending on biological surface assemblages and environmental availability of electron donors, acceptors and carbon substrates, suggest that ANME could support

  14. Estimating UK methane and nitrous oxide emissions from 1990 to 2007 using an inversion modeling approach

    Science.gov (United States)

    Manning, A. J.; O'Doherty, S.; Jones, A. R.; Simmonds, P. G.; Derwent, R. G.

    2011-01-01

    Methane (CH4) and nitrous oxide (N2O) have strong radiative properties in the Earth's atmosphere and both are regulated through the United Nations Framework Convention on Climate Change. Through this convention the United Kingdom is obliged to report an inventory of annual emission estimates from 1990. This paper describes a methodology that estimates emissions of CH4 and N2O completely independent of the inventory values. Emissions have been estimated for each year 1990-2007 for the United Kingdom and for NW Europe. The methodology combines high-frequency observations from Mace Head, a monitoring site on the west coast of Ireland, with an atmospheric dispersion model and an inversion system. The sensitivities of the inversion method to the modeling assumptions are reported. The 20 year Northern Hemisphere midlatitude baseline mixing ratios, growth rates, and seasonal cycles of both gases are also presented. The results indicate reasonable agreement between the inventory and inversion results for the United Kingdom for N2O over the entire period. For CH4 the agreement is poor in the 1990s but good in the 2000s. The UK CH4 inventory reported reduction from 1990-1992 to 2005-2007 (over 50%) is dominated by changes to landfill and coal mine emissions and is more than double the corresponding drop in the inversion estimated emissions (24%). The inversion results suggest that the United Kingdom has met its Kyoto commitment (-12.5%) but by a smaller margin (-14.3%) than reported (-17.3%). The results for NW Europe with the United Kingdom removed show reasonable agreement in trend, on average the inversion results for N2O are 25% lower and for CH4 21% higher.

  15. Effects of Plant Species on Methane and Nitrous Oxide Emissions from Constructed Wetlands Treating Municipal Wastewater

    Directory of Open Access Journals (Sweden)

    Sukanda Chuersuwan

    2014-05-01

    Full Text Available This study was conducted to quantify emissions of greenhouse gases (GHGs, methane (CH4 and Nitrous Oxide (N2, from free water surface constructed wetlands used for domestic wastewater treatment. All constructed wetlands were monoculture and each plot was planted with Phragmites sp., Cyperus sp., or Canna sp. The average CH4 and N2 O emissions were in the range of 5.9-11.2 and 0.9-1.8 g/m2/h, respectively. Seasonal fluctuations of CH4 and N2 O emissions were observed. The highest fluxes of both GHGs occurred during hot rainy season (July-October followed by summer and the lowest found in cool season. The mean of CH4 and N2O emissions from different plants species were significantly different (p<0.05. Average CH4 emissions from constructed wetlands planted with Phragmites sp., Cyperus sp. and Cannasp. were 11.2, 6.0 and 5.9 mg/m2/h, respectively, while mean N2O emissions were 0.9, 1.0 and 1.8 mg/m2/h, respectively. Calculated of Global Warming Potential (GWP found that GWP of CH4 and N2O flux from constructed wetlands planted with Cyperus sp., was the highest (669 mg CO2 equivalent/m2/h, followed by Phragmite sp., (524 mg CO2 equivalent/m2/h and Cannasp., (434 mg CO2 equivalent/mm2/h, respectively. These results suggested that municipal wastewater treatment by constructed wetlands planted with Canna sp. and Phragmite sp., had potential of lower GHGs emissions into the atmosphere and Phragmite sp., provided the highest removal rate of Biochemical Oxygen Demand (BOD and Chemical Oxygen Demand (COD.

  16. Stable isotopic indicators of nitrous oxide and methane sources in Los Angeles, California

    Science.gov (United States)

    Townsend-Small, A.; Pataki, D.; Tyler, S.; Trumbore, S.

    2008-12-01

    As urbanization increasingly encroaches upon agricultural landscapes, there are greater potential sources of greenhouse gases and other atmospheric contaminants. Measurements of the isotopic composition of trace gases have the potential to distinguish between pollutant sources and quantify the proportional contribution of agricultural activities to the total atmospheric pool. In this study, we are measuring the isotopic composition of greenhouse gases N2O and CH4 emitted from cropland, animal feeding operations, and urban activities in the South Coast Air Basin in southern California. The ultimate goal of our project is to utilize atmospheric measurements of the isotopic composition of N2O and CH4 combined with studies of source signatures to determine the proportional contributions of cropland, animal operations, and urban sources of greenhouse gases to the atmosphere. Measurements of the δ13C of methane show excellent separation between urban sources, such as vehicle emissions, power plants, oil refineries, landfills, and sewage treatment plants and agricultural sources like cows, biogas, and cattle feedlots. For nitrous oxide, soil N2O sources showed good separation from wastewater treatment facilities using δ15N and δ18O. Within soil N2O sources, the isotopic composition of N2O from cropland soils was similar to N2O emissions from urban turfgrass. These data indicate that nitrification may be as important a source of N2O as denitrification in urban soils. We are also measuring N2O fluxes from soils and from sewage treatment processes, and preliminary data indicate that urban N2O fluxes are higher than initially assumed by managers and regulatory agencies.

  17. Influence of nutrients on oxidation of low level methane by mixed methanotrophic consortia.

    Science.gov (United States)

    Karthikeyan, Obulisamy Parthiba; Chidambarampadmavathy, Karthigeyan; Nadarajan, Saravanan; Heimann, Kirsten

    2016-03-01

    Low-level methane emissions from coal mine ventilation air (CMV-CH4; i.e., 1 % CH4) can significantly contribute to global climate change, and therefore, treatment is important to reduce impacts. To investigate CMV-CH4 abatement potential, five different mixed methanotrohic consortia (MMCs) were established from soil/sediment sources, i.e., landfill top cover soil, bio-solid compost, vegetated humus soil, estuarine and marine sediments. Enrichment conditions for MMCs were as follows: nitrate mineral salt (NMS) medium, pH ~ 6.8; 25 °C; 20-25 % CH4; agitation 200 rpm; and culture period 20 days, in mini-bench-top bioreactors. The enriched cultures were supplemented with extra carbon (methanol 0.5-1.5 %, formate 5-15 mM, and acetate 5-15 mM), nitrogen (nitrate 0.5-1.5 g L(-1), ammonium 0.1-0.5 g L(-1), or urea: 0.1-0.5 g L(-1)), and trace elements (copper 1-5 μM, iron 1-5 μM, and zinc 1-5 μM) in different batch experiments to improve low-level CH4 abatement. Average CH4 oxidation capacities (MOCs) of MMCs varied between 1.712 ± 0.032 and 1.963 ± 0.057 mg g(-1)DWbiomass h(-1). Addition of formate improved the MOCs of MMCs, but the dose-response varied for different MMCs. Acetate, nitrate and copper had no significant effect on MOCs, while addition of methanol, ammonium, urea, iron and zinc impacted negatively. Overall, MMCs enriched from marine sediments and landfill top cover soil showed high MOCs which were largely resilient to nutrient supplementation, suggesting a strong potential for biofilter development for industrial low-level CH4 abatement, such as those present in CMV.

  18. Methane and nitrous oxide concentration and emission flux of Yangtze Delta plain river net

    Institute of Scientific and Technical Information of China (English)

    WANG DongQi; CHEN ZhenLou; SUN WeiWei; HU BeiBei; XU ShiYuan

    2009-01-01

    Methane (CH4) and nitrous oxide (N2O) saturation concentration and gas-water interface emission flux in surface water of the Yangtze Delta plain river net were investigated in summer at representative sites including the upper reaches of the Huangpu River and the rivers in the Chongming Island. The results show that the CH4 concentration in river water ranged from 0.30±0.03 to 6.66±0.14 μmoI.L-1, and N2O concentration ranged from 13.8±2.33 to 435±116 nmol.L-1. River surface water had a very high satura-tion level of CH4 (from 468±49.0% to 11560±235%) and that of N2O (from 175±29.5% to 4914±1304%).Dissolved oxygen (DO) was the primary factor controlling the CH4 concentration in water. N2O concen-tration had significant negative correlation with salinity and a significant positive correlation with ni-trate (NO3-), nitrite (NO2-), chemical oxygen demand (CODcr) concentration and pH of river water. CH4 and N2O of river water were brought about mainly by methanogenesis and denitrification in river bot-tom sediment that diffused through sediment-water interface into the water body and then into at-mosphere through the gas-water interface. The emission flux of CH4 and N2O at river gas-water inter-face reached 778±59.8 and 236±03.6 μmol.m-2.h-1, respectively in summer. The river net was a potential source of atmospheric CH4 and N2O because of eutrophication of the water body.

  19. Methane and nitrous oxide concentration and emission flux of Yangtze Delta plain river net

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Methane (CH4) and nitrous oxide (N2O) saturation concentration and gas-water interface emission flux in surface water of the Yangtze Delta plain river net were investigated in summer at representative sites including the upper reaches of the Huangpu River and the rivers in the Chongming Island. The results show that the CH4 concentration in river water ranged from 0.30±0.03 to 6.66±0.14 μmol.L-1, and N2O concentration ranged from 13.8±2.33 to 435±116 nmol.L-1. River surface water had a very high satura- tion level of CH4 (from 468±49.0% to 11560±235%) and that of N2O (from 175±29.5% to 4914±1304%). Dissolved oxygen (DO) was the primary factor controlling the CH4 concentration in water. N2O concentration had significant negative correlation with salinity and a significant positive correlation with nitrate (NO3-), nitrite (NO2-), chemical oxygen demand (CODcr) concentration and pH of river water. CH4 and N2O of river water were brought about mainly by methanogenesis and denitrification in river bottom sediment that diffused through sediment-water interface into the water body and then into atmosphere through the gas-water interface. The emission flux of CH4 and N2O at river gas-water interface reached 778±59.8 and 236±63.6 μmol.m-2.h-1, respectively in summer. The river net was a potential source of atmospheric CH4 and N2O because of eutrophication of the water body.

  20. Magnesium carbide synthesis from methane and magnesium oxide - a potential methodology for natural gas conversion to premium fuels and chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, A.F.; Modestino, A.J.; Howard, J.B. [Massachusetts Institute of Technology, Cambridge, MA (United States)] [and others

    1995-12-31

    Diversification of the raw materials base for manufacturing premium fuels and chemicals offers U.S. and international consumers economic and strategic benefits. Extensive reserves of natural gas in the world provide a valuable source of clean gaseous fuel and chemical feedstock. Assuming the availability of suitable conversion processes, natural gas offers the prospect of improving flexibility in liquid fuels and chemicals manufacture, and thus, the opportunity to complement, supplement, or displace petroleum-based production as economic and strategic considerations require. The composition of natural gas varies from reservoir to reservoir but the principal hydrocarbon constituent is always methane (CH{sub 4}). With its high hydrogen-to-carbon ratio, methane has the potential to produce hydrogen or hydrogen-rich products. However, methane is a very chemically stable molecule and, thus, is not readily transformed to other molecules or easily reformed to its elements (H{sub 2} and carbon). In many cases, further research is needed to augment selectivity to desired product(s), increase single-pass conversions, or improve economics (e.g. there have been estimates of $50/bbl or more for liquid products) before the full potential of these methodologies can be realized on a commercial scale. With the trade-off between gas conversion and product selectivity, a major challenge common to many of these technologies is to simultaneously achieve high methane single-pass conversions and high selectivity to desired products. Based on the results of the scoping runs, there appears to be strong indications that a breakthrough has finally been achieved in that synthesis of magnesium carbides from MgO and methane in the arc discharge reactor has been demonstrated.

  1. Microbial reefs in the Black Sea fueled by anaerobic oxidation of methane

    DEFF Research Database (Denmark)

    Michaelis, W.; Seifert, R.; Nauhaus, K.

    2002-01-01

    Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong (13)C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of d...... precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.......Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong (13)C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist...

  2. Evidence for Anaerobic Methane Oxidation Under Iron-Reducing Conditions in a Crude-Oil Contaminated Aquifer

    Science.gov (United States)

    Bekins, B. A.; Amos, R. T.; Cozzarelli, I. M.; Voytek, M. A.; Kirshtein, J.; Jones, E. J.; Delin, G. N.

    2008-12-01

    Although anaerobic methane oxidation (AMO) under iron reducing conditions is energetically feasible, its existence is still an open question. At a crude oil spill site near the town of Bemidji, MN, methanogenic degradation of entrapped oil floating at the water table has been occurring for more than 20 years. In the anaerobic portion of the hydrocarbon plume there is evidence for AMO under iron-reducing conditions between 75 m and 120 m downgradient of the oil body. In this zone, dissolved methane concentrations decrease steadily from over 0.6 mmol/L to less than 0.06 mmol/L. Decreases in dissolved methane are accompanied by an increase in δ13C-CH4 indicating that methane attenuation occurs through microbially mediated oxidation. The dissolved methane decrease of ~0.5 mmol/L occurs where dissolved sulfate is below 0.06 mmol/L, dissolved oxygen is below 3 μmol/L, and nitrate is below 0.02 mmol/L. Together these electron acceptors can account for degradation of only 0.07 mmol/L of methane. Moreover, hydrocarbon contaminants contribute an additional ~1 mmol/L total organic carbon in this area. Active iron- reduction is indicated by dissolved iron concentrations exceeding 0.15 mmol/L. To investigate the sediment bioavailable iron and microbial populations, 2-m-long cores were collected at four locations spaced 15 m horizontally and sampled at 50-cm-depth intervals. Values of bioavailable Fe(III) averaged 8 mmol/kg (n=16), which is over eight times the amount required to degrade 0.5 mmol/L methane. Geobacter detected by qPCR averaged over 2,600/g, while sulfate reducing bacteria were detected in only four samples with 100/g being the highest abundance measured. Laboratory incubations were performed with eight sediment samples from these cores. For each location, 1 g of sediment was added to 10 mL anaerobic medium and amended with amorphous FeOOH, Fe(III)NTA, sulfate, or nitrate. Loss of methane occurred in 33% of the iron-amended treatments, 25% of the nitrate

  3. AISI waste oxide recycling program. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Aukrust, E.; Downing, K.B.; Sarma, B.

    1995-08-01

    In March 1995 AISI completed a five-year, $60 million collaborative development program on Direct Steelmaking cost-shared by DOE under the Metals Initiative. This program defined an energy-efficient and environmentally-friendly technology to produce hot metal for steelmaking directly from coal and iron ore pellets without incurring the high capital costs and environmental problems associated with traditional coke oven and blast furnace technology. As it becomes necessary to replace present capacity, this new technology will be favored because of reduced capital costs, higher energy efficiency, and lower operating costs. In April 1994, having failed to move forward with a demonstration plant for direct ironmaking, despite substantial efforts by both Stelco and Geneva Steel, an alternative opportunity was sought to commercialize this new technology without waiting until existing ironmaking capacity needed to be replaced. Recycling and resource recovery of steel plant waste oxides was considered an attractive possibility. This led to approval of a ten-month, $8.3 million joint program with DOE on recycling steel plant waste oxides utilizing this new smelting technology. This highly successful trial program was completed in December 1994. The results of the pilot plant work and a feasibility study for a recycling demonstration plant are presented in this final technical report.

  4. Large fractionations of C and H isotopes related to methane oxidation in Arctic lakes

    Science.gov (United States)

    Cadieux, Sarah B.; White, Jeffrey R.; Sauer, Peter E.; Peng, Yongbo; Goldman, Amy E.; Pratt, Lisa M.

    2016-08-01

    Microbial oxidation of methane (CH4) plays a central role in carbon cycling in Arctic lakes, reducing potential CH4 emissions associated with warming. Isotopic signatures of CH4 (δ13C and δ2H) are indicators of microbial oxidation, wherein the process strongly enriches 13C and 2H in residual CH4. We present δ13C and δ2H measurements obtained from sampling the water column and sediment for dissolved CH4 from three, small Arctic lakes in western Greenland under both open-water and ice-covered conditions from 2013 to 2014. Despite substantial variations in aquatic chemistry among the lakes, δ13C and δ2H of CH4 suggested that CH4 was produced predominantly by acetoclastic methanogenesis in the littoral sediments and hydrogenotrophic methanogenesis in the profundal sediments in all of the lakes. Surprisingly large variations for both δ13C and δ2H of CH4 were observed, with δ13C extending from -72‰ to +7.4‰ and δ2H from -390‰ to +250‰. The CH4 isotopic values reported here were significantly more enriched (p < 0.0001) in both 13C and 2H than values reported from other Arctic freshwater environments. As is characteristic of methanotrophy, the enrichment in 13C and 2H was associated with low CH4 concentrations. We suggest that the CH4 most enriched in 13C and 2H may reflect unusually efficient methanotrophic communities in Arctic ice-margin lakes. This study provides the first measurement of δ2H for CH4 in an Arctic freshwater environment at concentrations <10 μM. The extreme enrichment of 13C and 2H of CH4 from Arctic methanotrophy has significant implications for interpreting sources and sinks of CH4. Without knowledge of local geology, stable isotope values of CH4 higher than -30‰ for δ13C and -150‰ for δ2H could be misinterpreted as thermogenic, geothermal, or abiogenic origins. Given crystalline bedrock and the strong positive correlation between δ13C and δ2H throughout the water columns in three Arctic lakes confirms that CH4 heavily