Escalating energy costs and energy shortages in recent years have become problems ofnational significance and have prompted the search for new sources of energy. Methane, biogas and biomethane are all names for similar products, which each differ slightly in composition.
Methane is the main component of natural gas and biogas. It is a natural hydrocarbon consisting of one carbon atom and four hydrogen atoms (CH4). The heat content of methane is approximately 1000 Btu/scf (standard cubic feet). Methane is a greenhouse gas with 21 times the global warming potential of carbon dioxide on a weight basis. Biogas is a naturally occurring gas formed as a by-product of the breakdown of organic waste materials in a low oxygen (eg anaerobic) environment (Jeffery et al., 1981).
Biogas is composed primarily of methane (typically 55–70 per cent by volume) and carbon dioxide (typically 30–45 per cent). Biogas may also include smaller amounts of hydrogen sulphide (typically 50–2000 parts per million [ppm])(Table 3.1), water vapour, oxygen, and various trace hydrocarbons (Braun, 2007).