Start-Up Performance of Chicken Manure Anaerobic Digesters Amended with Biochar and Operated at Different Temperatures

Batch anaerobic digestion was conducted using chicken manure (CM) and biochar over the course of 30 days in separate 15, 25, 35, 45, 55, and 65°C reactors. Daily volumetric methane production, hydrogen sulfide concentration, pH, oxidation-reduction potential (ORP), alkalinity (Alk), and soluble chemical oxygen demand (SCOD) were measured. Results showed that the anaerobic reactors started up successfully under all temperature conditions. It needed one week for 35°C and 45°C reactors to peak the methane production rate, 18 days for 25°C and 65°C reactors, and over one month for 55°C reactor, but it was not the peak as the methane production rate for 15°C reactor. The hydrogen sulfide concentrations at various temperature conditions were not more than 538 ppm, and the difference was small, except 65°C reactors with 1148 ppm concentration. Based on the process parameters of the 15°C reactor, the hydrolysis processing was smooth, but the poor activity and slow growth of methanogens were the key problems to make the efficiency poor. Comparison of the added biochar reactor with a control reactor without biochar operated at 35°C showed that the addition of biochar reduced the lag phase by 41%, enhanced the maximum methane production rate by 18%, and reduced the hydrogen sulfide by more than 95%, although no difference was observed in the cumulative methane production.