Methane is a gas that is produced by the action of microbes. An example of a microbe is bacteria.

The microbes that emit methane are found in places that have food for the microbes, but no oxygen. This process of methane production is called methanogenesis.

There are two places where this occurs: In the rumen of animals (animals which have a rumen include cows and sheep) and in landfills. A rumen is a digestion system that allows an animal to digest grass (our stomach does not have this ability).

Cows burp out methane as a result of the microbial action in their rumen (they don’t fart it out like a lot of people think).