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Methanogenesis |
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Methanogenesis (bacteria) The microbial formation of methane, which is confined to anaerobic habitats where occurs the production of hydrogen, carbon dioxide, formic acid, methanol, methylamines, or acetate—the major substrates used by methanogenic microbes (methanogens). In fresh-water or marine sediments, in the intestinal tracts of animals, or in habitats engineered by humans such as sewage sludge or biomass digesters, these substrates are the products of anaerobic bacterial metabolism. Methanogens are terminal organisms in the anaerobic microbial food chain—the final product, methane, being poorly soluble, anaerobically inert, and not in equilibrium with the reaction which produces it. Two highly specialized digestive organs, the rumen and the cecum, have been evolved by herbivores to delay the passage of cellulose fibers so that microbial fermentation may be complete. In these organs, large quantities of methane are produced from hydrogen and carbon dioxide or formic acid by methanogens. From the rumen, an average cow may belch 26 gallons (100 liters) of methane per day. Methanogens are the only living organisms that produce methane as a way of life. The biochemistry of their metabolism is unique and definitively delineates the group. Two reductive biochemical strategies are employed: an eight-electron reduction of carbon dioxide to methane or a two-electron reduction of a methyl group to methane. All methogens form methane by reducing a methyl group. The major energy-yielding reactions used by methanogens utilize substrates such as hydrogen, formic acid, methanol, acetic acid, and methylamine. Dimethyl sulfide, carbon monoxide, and alcohols such as ethanol and propanol are substrates that are used less frequently. See Archaebacteria, Bacterial physiology and metabolism How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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Biomethanation of spent wash--heavy metal inhibition of methanogenesis in synthetic medium. In order to reduce the facility's greenhouse gas emissions (methane has 21 times the greenhouse warming potential as carbon dioxide) and to prevent the improper disposal of the animal wastes, the Punjab Energy Development Agency (PEDA) installed and commissioned this demonstration power generation facility based on the biomethanation process of cow manure. |
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