Impacts of Temperatures on Biogas Production in Dairy Manure Anaerobic Digestion

Abstract

Batch anaerobic digestion of dairy manure was performed at low (25 o C), mesophilic (37 o C), and thermophilic (52.5 o C) temperatures to determine the influences of temperatures on biogas production. The experiment was run for 76, 40 and 29 days at 25, 37, and 52.5 o C, respectively. The biogas production was measured daily at each temperature. To estimate the solid reductions, we measured total solids (TS) and volatile solids (VS) over time. The biogas production at 52.5 o C and 37 o C were 49 and 17 times higher than that at 25 o C. Over incubation periods, the TS reduction at 25, 37, and 52.5 o C were 5.6, 57, 34%, respectively. The VS reductions were 127, 58.4, 42.5%, respectively. At 25 and 37 o C, pH was reduced, while at 52.5 o C pH was increased. The Oxidation Reduction Potential (ORP) values at 37 and 52.5 o C were negative over the incubation period. But at 25 o C, however, the ORP values were positive after Day 19. Findings from this study are useful for enhancing anaerobic digesters’ performance.