None of the biological activities of anaerobic microorganisms, including their development, breeding and metabolism, requires oxygen. In fact, they are very sensitive to the presence of oxygen. The breakdown of organic materials in the presence of oxygen will produce carbon dioxide; in airless conditions, it produces methane (Buren, 1983; Voermans, 1985). Ferguson and Mah (1987) pointed out that methane-producing bacteria carry out the terminal step in the formation of biogas from the anaerobic decomposition of biomass. Methane is the final product of mineralizing the organic material in digesters and most anaerobic freshwater habitats. Most of the chemical energy in the starting materials (substrates) actually ends up in the methane released by these anaerobic bacteria. Ferguson and Mah (1987) noted further that in direct contrast, aerobic bacterial metabolism releases most of the chemical energy in the starting substrates by oxidizing them to carbon dioxide and water. Buren (1983) noted that if the digester is not sealed to ensure the absence of air. The action of the microorganisms and the production of biogas will be inhibited and some will escape. It is therefore crucial that the biogas digester be airtight and watertight.