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AhstructThe roles of temperature and organic input in determining the rate of methane flux from anoxic sediments were examined under various laboratory and field conditions in two small Michigan lakes. As in other studies, rapid temperature increases in incubating sediment caused immediate increases in methane production rates (avg Q10 = 2.4). Under in situ conditions, where the hypolimnetic temperature is relatively cold and unchanging for long periods, methane flux was linearly related (P < 0.01) to organic input in these two and three other lakes for which data were available. In addition, the proportion of organic input released as methane (47 + 94 ) o was close to the theoretical maximum (40 -+ 8%) and was not related to temperature.When temperature is constant for long periods, as during summer stratification, CH, production adjusts maximally to organic input, When temperature changes rapidly, its effect will be predictably superimposed upon that of organic input.

The biochemical methane potential of several MSW fractions was determined in order to compare extents and rates of their conversion to methane. Based on MSW samples analyzed, the methane yield of MSW was estimated to be as high as 0.20 m3 kg−1 VS added, which indicates that more than 50% of the VS in MSW can be destroyed in anaerobic processing. Yard waste fractions of MSW can be expected to exhibit a high variability in yields due to the variety of plant materials which can be included. While some yard waste components, such as grass, exhibited yields as high as 0.21 m3 kg−1 VS, yields for mixed yard waste were much lower, in the range of 0.14 m kg−1. The make-up of the paper fraction can strongly affect the methane yields of MSW due to variations in methane yields of different paper classes. Bleached kraft papers, regardless of coating, exhibited maximum methane yields of 0.37 m3 kg−1 VS, indicating complete conversion. Unbleached kraft paper found in corrugated box-board exhibited a yield of 0.28 m3 kg−1 VS, while newsprint exhibited yields as low as 0.08 m3 kg−1 VS. Inks used in newsprint did not lower methane yields over unprinted newsprint. The paper used in food packaging was highly biodegradable and its degradation was not affected by polymer coatings when samples were finely ground. These results provide a data base on extent and rates of the major biodegradable organic components of MSW and should be considered when contemplating anaerobic bioconversion of MSW.

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