Methane has many sources, both natural and human-related, but just two major sinks: its destruction in the atmosphere, and its use by certain soil bacteria. Methane is a potent greenhouse gas, each kg. Emitted to the atmosphere having a global warming potential (GWP) 23 times greater than that of a kg. of carbon dioxide over a 100-year time horizon.
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 GWP is from the IPCC’s Fourth Assessment Report (AR4).