Mass‐Balance Analysis of Anaerobically Decomposed Refuse

Methane production from the decomposition of municipal refuse is well documented. However, there is little information on the extent to which the chemical constituents of refuse degrade. Decomposition of shredded municipal refuse was studied under laboratory conditions with leachate recycle and neutralization. Containers were destructively sampled weekly for solids analysis. Cellulose and hemicellulose accounted for 91% of the methane potential of municipal refuse. Mineralization of 71% of the cellulose and 77% of the hemicellulose was measured in a container sampled after 111 days. The average carbon recovery obtained from mass balances on the decomposed refuse was 88.4% with a range of 64–111%. The measured methane yield was between 77 L and $107L{\mathrm{CH}}_4\mathrm{per}\mathrm{dry}\mathrm{kg}$ of refuse. Mass balances suggested that the yield may be as high as $152L{\mathrm{CH}}_4\mathrm{per}\mathrm{dry}\mathrm{kg}$ of refuse. Mass balances also showed an imbalance between the soluble sugar concentration of fresh refuse and the mass of terminal electron acceptors (oxygen and nitrate) available for sugar oxidation to carbon dioxide. This imbalance explained an observed decrease in refuse pH and the accumulation of carboxylic acids shortly after the initial incubation.