Biomethane is a naturally occurring gas which is produced by the so-called anaerobic digestion of organic matter such as dead animal and plant material, manure, sewage, organic waste, etc. Chemically, it is identical to natural gas which is stored deep in the ground and is also produced from dead animal and plant material. However, there are several important differences between biomethane and fossil fuel derived methane despite the fact that both are produced from organic matter.