Methane is an important greenhouse gas, with the potential on a gram per gram basis to cause more atmospheric warming than carbon dioxide. But where does methane come from?

Sources of biological methane are typically divided into two categories: thermogenic and biogenic. A small portion of atmospheric methane is also released through non-biological mechanisms such as volcanic eruptions. Scientists can determine the origin of atmospheric methane using Isotope Ratio Mass Spectrometry(IRMS), due to slight differences in the C¹³/C¹² ratio.

Much of biogenic methane is produced by microorganisms during the anaerobic decomposition of plant material. This process occurs on a large scale in oxygen deficient environments including water-logged areas such as wetlands and rice paddies, the guts of ruminant animals or the depths of landfills.

Humans release additional methane into the atmosphere by burning biomass and distributing natural gas. It is estimated that between 50-70% of atmospheric methane comes from anthropogenic sources. These sources include rice cultivation, landfill emissions and animal husbandry.