High-rate anaerobic digestion of screened dairy manure

Abstract

Laboratory-scale fixed-film reactors were used for the high rate production of methane from screened dairy manure under mesophilic temperatures. The active biomass, growing on the support structures, enabled the reactors to withstand high organic loadings as well as very short hydraulic retention times down to 1 h. Screened dairy manure (3·25% VS) was added intermittently at loading rates ranging from 2·25 to 778 gram volatile solids per litre per day (g VS 1 −1 d −1) for fixed-film reactors. The maximum methane production rate was 6·20 litre methane per litre reactor per day (6·20 1 CH 4 1 −1 d −1) when operated at a loading rate of 259 g VS 1 −1 d −1 with a 3 h hydraulic retention time. The fixed-film reactor was capable of sustaining a loading rate of 778 g VS 1 −1 d −1 (1 h hydraulic retention time). The data illustrated the advantages of fixed-film reactors. The results obtained with reactors of varying sizes, and different fixed-film support materials are discussed.