Methane (CH₄) is a hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 21. Methane is produced through Anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion.

The atmospheric concentration of methane as been shown to be increasing at a rate of about 0.6 percent per year and the concentration of about 1.7 per million by volume (ppmv) is more than twice its pre-industrial value. However, the rate of increase of methane in the atmosphere may be stabilizing.

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"Methane" is in the UNSPSC Code "15111502"
Methane

Other /More definition:
Methane is one of many greenhouse gases that trap heat in the atmosphere, resulting in a "greenhouse effect.” It is the second-most prevalent greenhouse gas emitted by U.S. sources. Methane's overall contribution to global warming is significant because it is estimated to be 21 times more effective at trapping heat in the atmosphere than carbon dioxide. Currently, Methane represents approximately 10 percent of the greenhouse gas emissions from U.S. activities that contribute to global warming. Over the last two centuries, Methane's concentration in the atmosphere has more than doubled due to increasing Methane emissions from several human activities, including placing municipal solid waste (MSW) in landfills, producing natural gas and petroleum, mining coal, and burning fossil fuels. Methane emissions from the production and processing of fossil fuels contribute to almost one-third of the total Methane emitted in the U.S. For more information on EPA's voluntary Methane programs, visit EPA's Methane Web site.