The decomposition of organic matter in the absence of air could be elicite by the use of physical or chemical processes at high temperature and/or pressure, or the use of microorganisms at near ambient temperature and atmospheric pressure; the preferred method being dependent on the relative polluting impacts on the environment. However, irrespective of the method used, gas is produced; it is referred to as biogas if generated as a result of the action of microorganisms on the organic wastes [6]. This is why biogas – see Table 1 – is now defined as “a by-product of the biological breakdown, under oxygen-free conditions of organic wastes such as plants, crop residues, wood and bark residues, and human and animal manure — and is known by such other names as swamp gas, marsh gas, ‘will o’ the wisp’ or gobar gas” [7], digestion gas [8], natural gas [9], landfill gas (LFG), and sewage gas [10]. The gas is colourless, relatively odourless and flammable: it is also stable and non-toxic. It burns with a blue flame and has a calorific value of 4500–5000 kcal/m3 when its methane content ranges from 60% to 70% [11].