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•  Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some

    diffuses into the atmosphere or accumulates in the ground


carbon methane

Methanogens are archaean microorganisms that produce methane (CH4) as a metabolic by-product in anaerobic conditions

Anaerobic conditions where methanogens may be found include:

  • Wetlands (e.g. swamps and marshes)
  • Marine sediments (e.g. in the mud of lake beds)
  • Digestive tract of ruminant animals (e.g. cows, sheep, goats)

Methanogens produce methane from the by-products of anaerobic digestion, principally 
acetic acid and carbon dioxide:

  • Acetic acid  Methane and Carbon Dioxide  (CH3COO + H+    CH4 + CO2)
  • Carbon Dioxide and Hydrogen  Methane and Water  (CO2 + 4 H2    CH4 + 2 H2O)

Methane may either accumulate under the ground or diffuse into the atmosphere

  • When organic matter is buried in anoxic conditions (e.g. sea beds), deposits of methane (natural gas) may form underground
  • Rising global numbers of domesticated cattle may be increasing the levels of methane being released into the atmosphere

Stages of Methane Production in a Ruminant

methane production

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•  Methane is oxidised to carbon dioxide and water in the atmosphere


When methane is released into the atmosphere as a result of anaerobic reactions, it only persists for ~12 years

Methane will be naturally oxidised to form carbon dioxide and water  (CH4 + 2 O2    CO2 + 2 H2O)

  • This is why methane levels in the atmosphere are not very large, even though significant quantities are being produced  

Oxidation of Atmospheric Methane

methane oxidation