Methanogens
Methanogens are archea which, as a result of breathing process, produce methane – a flammable greenhouse gas that is produced by the anaerobic degradation of plant debris. The methanogenic environment must be oxygen free, neutral or slightly alkaline, and must contain at least 50% water.
Most of the methanogens are found in marshes and peatbogs. They are also present in the permafrost and the glaciers.