The potential of biogas production from municipal solid waste in a tropical climate

The objective of this study was to estimate the potential of organic municipal solid waste generated in an urban setting in a tropical climate to produce biogas. Five different categories of wastes were considered: fruit waste, food waste, yard waste, paper waste, and mixed waste. These fractions were assessed for their efficiency for biogas production in a laboratory-scale batch digester for a total period of 8 weeks at a temperature of 15-30 °C. During this period, fruit waste, food waste, yard waste, paper waste, and mixed waste were observed to produce 0.15, 0.17, 0.10, 0.08, and 0.15 m(3) of biogas per kilogram of volatile solids, respectively. The biogas produced and caloric value of each feedstock was in the range of 1.25 × 10(-3) m(3) (17 kWh)/cap/day (paper waste) to 15 × 10(-3) m(3) (170 kWh)/cap/day (mixed waste). Paper waste produced the least (<1×10(-3)(<17.8 kWh)/cap/day), and mixed waste produced the highest methane yield (10 × 10(-3) m(3) (178 kWh)/cap/day). Thus, mixed waste was found to be more efficient than other feedstocks for biogas and methane production; this was mainly related to the better C/N ratio in mixed waste. Taking the total waste production in Jimma into account, the total mixed organic solid waste could produce 865 × 10(3) m(3) (5.4 m(3)/capita) of biogas or 537 × 10(3) m(3) (3.4 m(3)/capita) of methane per year. The total caloric value of methane production potential from mixed organic municipal solid waste was many times higher than the total energy requirement of the area.