Methane is one of the six greenhouse gases to be mitigated under the Kyoto Protocol and is the major component of natural gas and associated with all hydrocarbon fuels, animal husbandry and agriculture. Coal-bed methane is the gas found in coal seams. (IPCC)
Methane (US /ˈmɛθeɪn/ or UK /ˈmiːθeɪn/) is a chemical compound with the chemical formula CH4 (one atom of carbon and four atoms of hydrogen). It is a group 14 hydride and the simplest alkane, and is the main component of natural gas. The relative abundance of methane on Earth makes it an attractive fuel, though capturing and storing it poses challenges due to its gaseous state under normal conditions for temperature and pressure. In its natural state, methane is found both below ground and under the sea floor. When it finds its way to the surface and the atmosphere, it is known as atmospheric methane. The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases (these gases don't include water vapor which is by far the largest component of the greenhouse effect). Methane breaks down in the atmosphere and creates CH3· with water vapor.
Source: Wikipedia - Methane