Methane is generated naturally when organic products are allowed to decay and this causes global warming. Where the process is manually carried out under controlled condition of anaerobic digestion it is commonly referred to as ‘Biomethanation’ and the methane generated is commonly referred to as ‘biomethane’. The biomethane generated can be used to produce thermal energy or to generate power using turbines or gas engines. With the concerns being raised on the emissions of Green House Gases (GHGs), especially carbodioxide and methane among others, and their potential for global warming biomethanation could lead to significant reduction of GHGs through commercially viable processes.

Anaerobic digestion is a biological process carried out on organic matter (organic wastes such as livestock manure, food processing waste, etc.) using various types of bacteria under air tight condition. This produces a gas composed mainly of methane (CH4) and carbon dioxide (CO2) otherwise known as biogas. Biogas produced in anaerobic digesters consists of methane (50%-80%), carbon dioxide (20%-50%), and trace levels of other gases such as hydrogen, carbon monoxide, nitrogen, oxygen, and hydrogen sulfide. The relative percentage of these gases in biogas depends on the feed material and management of the process. For gas engine applications the Hydrogen Sulphide, will have to be removed as it is rather corrosive and could interfere with the engine operation. Where the gas is to be piped to gas grids it is preferable to strip the carbon dioxide also.