Co-digestion of cow manure (CM) with the organic fraction of municipal solid waste (OFMSW) were investigated by using a semi-continuous flow, completely mixed reactor. The experiments were conducted under mesophilic (35°C) condition and HRT of 30days to 15days by using three different substrates, CM, OFMSW and a mixture of CM with OFMSW. The influent concentration of total solids was constant at 3%. At a long HRT of 30 days, the methane fermentations was stable for each substrate, and the biogas productions for CM, OFMSM and co-digestion of 90% CM with 100FMSW was 0.27, 0.73 and 0.45m
3/kg-VS, respectively. When the HRT was shorten to 15 days, volatile fatty acid (VFA) in the OFMSW reactor gradually accumulated because trace metal was not present, resulting in methane fermentation failure. The increase of CM ratio in the co-digestion solved the VFA accumulation problem because the CM had more Ni and Fe. It was also found that co-digestion with OFMSW could increase the biogas production and degradation efficiency of CM.
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