Effects of temperature on biogas production efficiency and fermentation time of four manures

In order to investigate the relationships between the temperature and biogas production efficiency and digestion time of anaerobic digestion, experiments were conducted in a self-manufactured anaerobic fermentation device, and the pig dung, cattle manure, chicken manure, and human feces were used as the digestion material and the substrate of constant temperature fermentation pool as the inoculation substances, and with temperatures increasing by increments of 5oC from 25～40oC. A batch of experiments were conducted to study the biogas yield, digestion time and the optimal temperature for anaerobic digestion of four kinds of manure. The results show that the optimal temperature of four kinds of manure and the corresponding digestion time and cumulative biogas yield of dry matter were 35.9oC, 81 d, and 0.495 L/g for pig manure; 33.8oC, 74 d, and 0.398 L/g for cattle manure; 32.2oC, 73 d, and 0.324 L/g for chicken manure; and 25.1oC, 84 d, and 0.294 L/g for human feces, respectively. Different kinds of manure in the optimal digestion temperature range, biogas production rate was the largest, biogas yield increased with the increase of temperature, when the temperature range was beyond the optimal, but biogas production rate decreased and biogas yield dropped. The digestion time does not shorten with the increase of temperature. It is not realistic to judge the length of digestion time solely by the temperature.