Low Temperature Anaerobic Digestion of Swine Manure

Abstract

Anaerobic digestion of swine manure at low process temperatures was studied in two pilot-scale experiments where the effect of process temperature was evaluated in terms of biogas production, COD removal, and volatile solids destruction. The first experiment compared 25°C digestion with 35°C to 40°C digestion while the second experiment evaluated various solids retention times for digestion. Gas production rates were comparable to those reported in the literature for domestic sewage sludge digestion at low temperatures. In addition, the relative stability of low temperature digestion as measured by unionized volatile acid concentrations was good when compared to digestion at higher temperatures.