Little research has been found regarding the anaerobic digestion of pig manure with urine (probably due to current management practices of industrial pig production, through which manure, urine and wastewaters are collected together resulting in the socalled pig slurry). However, in the early work by Hobson and Shaw (1973) it was suggested, in order to build up a balanced digestion process, to either dilute pig manure in water or to seed the digesters with anaerobic inoculum if undiluted pig manure–urine slurry is to be fed. The use of anaerobic inoculum, even from digesters
treating other organic wastes, is in general indicated to start up the process, especially when operating at low temperatures