Digestion tests of livestock wastes

In this 8/sup 1///sub 2/ week duration laboratory study eight 3.4 l digesters were operated at temperatures of 23/sup 0/ and 35/sup 0/C with detention times of approximately 25 days. Four of the digesters were fed chicken manure at loading rates of 2.76 to 4.89 g VS/l/day and the remaining four were fed dairy cow feces and urine at 2.11 to 3.44 g VS/l/day. The tops of the digesters were removed twice weekly for feeding and the digesters were stirred twice daily. The destruction of volatile matter in the dairy units was low (10-16%) but the amount of gas produced was 700 to 1000 ml/g VS destroyed. The digesters which operated on chicken manure suffered from incipient souring, the cause of which remained unexplained. Tables and graphs present figures for COD and BOD, pH, alkalinity and volatile acids concentrations, nitrogen, and gas production.