The production of landfill gas from landfill sites is carried out by a complex process involving a succession of microbial population. The initial fermentation is aerobic fermentation which is carried out by bacteria already present in waste. This stage is followed by an anaerobic digestion stage. During the aerobic fermentation stage, the carbon in the biomass is converted into carbon dioxide and water. These reactions are strongly exothermic and increase the temperature of the landfill waste, consequently increasing the activity of the other microorganisms. If this stage continues for long, the amount of methane, which is the product of the
anaerobic digestion stage, decreases. In order to shorten the aerobic fermentation stage, and consequently prevent the reduction in methane yield, the landfill waste is made to pass through compactors, which serves a dual purpose of increasing the density of the landfill waste and simultaneously removing a substantial amount of oxygen from the waste. After an initial phase of aerobic fermentation, the waste gradually becomes anaerobic as oxygen is depleted from it. The subsequent fer­mentation causes the breakdown of complex polymeric components in the biomass into simpler compounds, followed by volatile fatty acids, followed by carbon dioxide, hydrogen, and acetic acid.