Methane

The simplest hydrocarbon, methane is a gas with a chemical formula of C H₄.

  C
  |
C-H-C  
  |
  C

A principal component of natural gas, methane is a significant fuel. Burning one molecule of methane in the presence of oxygen releases one molecule of CO₂ (carbon dioxide) and two molecules of H₂O (water):

CH₄ + 2O₂ → CO₂ + 2H₂O

The strength of the carbon-hydrogen covalent bond in methane is among the strongest in all hydrocarbons, and thus its use as a chemical feedstock is limited. The search for catalysts which can facilitate C-H bond activation in methane and other low alkanes is an area of research with considerable industrial significance.

Methane is a greenhouse gas with a global warming potential of 22 (meaning that it has 22 times the warming ability of carbon dioxide).

Methane results from the decomposition of certain organic matters in the absence of oxygen. It is therefore also classified as a biogas.

Principal sources are

decomposition of organic wastes
natural sources (marshes) : 23 %
fossil fuel extraction : 20 % See Coal bed methane extraction
the processes of digestion of animals (cattle) : 17 %
bacteria found in rice plantations : 12 %
biomass anaerobic heating or combustion

80% of the world emissions are of human source. They come primarily from agricultural and other human activities. During the past 200 years, the concentration of this gas in the atmosphere doubled, passing from 0.8 to 1.7 ppm.

See also methyl group, which is a functional group similar to methane.