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Anaerobic oxidation of methane (AOM) is a methane-consuming microbial process occurring in anoxic marine and freshwater sediments. AOM is known to occur among mesophiles , but also in psychrophiles , thermophiles , halophiles , acidophiles , and alkophiles . [ 1 ]
Some organisms can oxidize methane, functionally reversing the process of methanogenesis, also referred to as the anaerobic oxidation of methane (AOM). Organisms performing AOM have been found in multiple marine and freshwater environments including methane seeps, hydrothermal vents, coastal sediments and sulfate-methane transition zones. [8]
Some specific methanotrophs can reduce nitrate, [19] nitrite, [20] iron, [21] sulfate, [22] or manganese ions and couple that to methane oxidation without syntrophic partner. Investigations in marine environments revealed that methane can be oxidized anaerobically by consortia of methane oxidizing archaea and sulfate-reducing bacteria .
Methane has a limited atmospheric lifetime, about 10 years, due to substantial methane sinks. The primary methane sink is atmospheric oxidation, from hydroxyl radicals (~90% of the total sink) and chlorine radicals (0-5% of the total sink). The rest is consumed by methanotrophs and other methane-oxidizing bacteria and archaea in soils (~5%). [7]
Methane molecules react with hydroxyl radicals (OH)—the "major chemical scavenger in the troposphere" that "controls the atmospheric lifetime of most gases in the troposphere". [60] Through this CH 4 oxidation process, atmospheric methane is destroyed and water vapor and carbon dioxide are produced.
Biological methanation takes place in a separate methanation plant. The gas is completely converted into methane before the infeed into the gas grid. The carbon dioxide, produced in a gas processing system, is converted into methane in a separate methanation plant, by adding hydrogen and can then be fed into the gas grid.
Paul Sabatier (1854-1941) winner of the Nobel Prize in Chemistry in 1912 and discoverer of the reaction in 1897. The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures (perhaps 3 MPa [1]) in the presence of a nickel catalyst.
The oxidative coupling of methane (OCM) is a potential chemical reaction studied in the 1980s for the direct conversion of natural gas, primarily consisting of methane, into value-added chemicals. Although the reaction would have strong economics if practicable, no effective catalysts are known, and thermodynamic arguments suggest none can exist.