Atmospheric methane

About: Atmospheric methane is a research topic. Over the lifetime, 2034 publications have been published within this topic receiving 119616 citations.

[Biogeochemical processes of methane cycle in the soils, swamps and lakes of Western Siberia].

Abstract: The biogeochemical processes of methane production and oxidation were studied in the upper horizons of tundra and taiga soils and of raised bogs and lake bottom sediments nearby the Tarkosalinsk gas field in western Siberia. Both in dry and water-logged soils, the total methane concentration (in soil particles and gaseous phase) was an order of magnitude higher than in the soil gaseous phase alone (22 and 1.1 nl/cm3, respectively). In bogs and lake bottom sediments, methane concentration was as high as 11 microliters/cm3. Acetate was the major precursor of the newly formed methane. The rate of aceticlastic methanogenesis reached 55 ng C/(cm3 day), whereas that of autotrophic methanogenesis was an order of magnitude lower. The most active methane production and oxidation were observed in bogs and lake sediments where the delta 13C values of CO2 were inversely related to the intensity of bacterial methane oxidation. Methane diffusing from bogs and lake bottom sediments showed delta 13C values ranging from -78 to -47@1000, whereas the delta 13C value of carbon dioxide ranged from -18 to -6@1000. In these ecosystems, methane emission comprised from 3 to 206 mg CH4/(m2 day). Conversely, the dry and water-logged soils of tundra and taiga took up atmospheric methane at a rate varying from 0.3 to 5.3 mg CH4/(m2 day). Methane consumption in soils was of biological rather than of adsorptive nature. This was confirmed by the radioisotopic method and chamber experiments, in which weighting of methane carbon was observed (the delta 13C value changed from -51 to -41@1000).

Subsurface CO2 Disposal with Enhanced Gas Recovery and Biogeochemical Carbon Recycling

Abstract: An enormous amount of methane has accumulated in the shallow subsurface in many part of the world. However, most of this natural gas resource is not economically recoverable at the present time as the methane is adsorbed in coal seams, trapped in methane hydrate (clathrate), or dissolved in saline groundwater. Shallow accumulations of methane pose the threat of potentially increasing the rate of global warming. Enhanced gas recovery by subsurface CO2 injection (CO2-EGR) is potentially an option for greenhouse gas control, combined with use of potential energy resources. CO2 injection coupled with extraction of coal mine methane and coal-bed methane may make emission-free closed circuit power plants possible. Coal seams in Japan and under the seabed around Japan could potentially adsorb about 10 Gtonnes of CO2 and in so doing displace 2.5 trillion cubic meters of coal-bed methane. About 12 Gtonnes of CO2 could potentially be sequestered in hydrate layers, displacing 6 trillion cubic meters of methane hydrate under the deep seabed around Japan. Similarly, about 26 Gtonnes of CO2 could potentially be sequestered in saline groundwater, displacing 6 trillion cubic meters of methane in sedimentary basins in Japan. CO2-EGR could potentially sequester a total of 48 Gtonnes of CO2 in and around the Japanese Islands, with the prospect of also having enhanced production of nearly 10 trillion cubic meters of methane. The extremely light isotopic compositions of carbon in methane suggest that methanogens formed many of the subsurface accumulations of methane-rich natural gas in the world. Chemolithotrophic methanogens form methane from CO2, thereby obtaining energy without sunlight under anoxic circumstances. Methanogens are often blamed for greenhouse gas emissions as they produce methane in organisms and in rice paddies, for example. However, application of CO2-EGR for production of subsurface biogenic methane displaced by sequestration of CO2 might result in enhanced carbon recycling. Present-day subsurface ecosystems are probably somewhat similar to ancient ecosystems adapted to exist in an anoxic CO2-rich atmosphere under high pressure and temperature. Biogenic methanogenesis is thought to occur even in deep basaltic aquifers offering the opportunity for deep subsurface biogeochemical carbon recycling utilizing CO2-EGR to produce enhanced sequestration of greenhouse gases accompanied by the development of potential new energy resources.