methane (CH4)

A gaseous hydrocarbon present in the atmosphere. It is the second trace gas that contributes most to the Earth's greenhouse effect, behind water vapor. Its origin is both natural and anthropogenic. It is produced by the decomposition of organic matter of plant origin, being generated in large quantities in marshes and swampy terrain. Ruminant animals also represent a significant source of emission. This colorless, flammable gas is the main component of natural gas, and is also part of the rest of fossil fuels.