Anaerobic digestion of cattle slurry in an upflow anaerobic filter

Abstract A 20 litre laboratory-scale upflow anaerobic filter has been successfully used for the mesophilic anaerobic digestion of dairy cattle slurry (4.4% TS). The reactor was operated at 35°C for a total of 111 days at hydraulic retention times from 5–14 days. The gas yield obtained from the filter (0.26 m 3 kg −1 VS added; methane yield 0.18 m 3 kg −1 VS added) compared favourably with that obtained from a conventional partially-stirred digester operating at a hydraulic retention time of 5 days (0.20 m 3 kg −1 VS added; methane yield 0.13 m 3 kg −1 VS added). The performance of the upflow anaerobic filter also compares favourably with that reported previously for other attached biomass reactors treating dairy cattle slurry at a 5-day hydraulic retention time. This is attributed to the greater surface area available for microbial attachment. These advanced reactors may improve the economics of the anaerobic digestion of dairy cattle slurry.