ENVIRONMENTAL-FACTORS INFLUENCING METHANOGENESIS FROM REFUSE IN LANDFILL SAMPLES

Samples were excavated from the Fresh Kills Landfill and used to identify some of the environmental factors influencing refuse methanogenesis. The endogenous rate of methane production in these samples was significantly correlated with the moisture content, but not as highly correlated with other variables. Increasing moisture accelerated methanogenesis in 67% of the samples, but the rates decreased or remained unchanged in other samples. Aqueous refuse extracts were also assayed for the presence of alternate electron acceptors. Nitrate was not detected, but all samples had soluble sulfate levels ranging from 1.2 to 79.7 mmol/dry kg of garbage. Manipulation of the electron donor, acceptor, and metabolic inhibitor status in selected samples suggested that sulfate could inhibit refuse methanogenesis. An assay of individual refuse components revealed that paper and textile samples were associated with the highest concentrations of sulfate, but this anion was not detected when fresh refuse materials were similarly analyzed. Our findings suggest that moisture, pH extremes, and high sulfate levels influence the landfill methanogenesis and that absorbent refuse components may represent reservoirs of sulfate in a landfill.