| Anaerobic digestion of biogas has attracted wide attention in releasing the energy shortage and solving the environmental pollution. This research investigated the effect of initial pH on anaerobic digestion characteristics, including biogas production and efficiency, the substrate conversion rate and the process stability by simulating the anaerobic digestion in indoor, obtained the significance of differences among each treatment and the optimum initial pH and substrate concentration of different materials by using SPSS and SAS software. The research is respected to provide a certain reference value for optimizing processes and further mechanism researches about anaerobic digestion of biogas, improve anaerobic digestion characteristics to some extent.The experiment conducted self-designed constant-temperature anaerobic digestion equipment.Most probable agricultural solid wastes(corn straw, cow manure, swine manure) were used as digestion substrate, the digestion sludge of rural household biogas digester was used as inoculums. With a 4% gradient, the substrate concentration was ranged from 4%~16% and initial pH level was set as 6.5, 7.0, 7.5, 8.0 and the control. The relationship between digestion characteristics and initial pH and substrate concentration was explored, and the optimal initial pH and substrate concentration of different digestion materials would be determined. The main results were showed as follows:(1)When the substrate concentration increased from 4%~16%, biogas was produced at different initial pH levels of single-digestion of corn straw and livestock manure, and codigestion of them. Biogas production, substrate conversion rate and process stability were raised firstly, and then were dropped as initial pH and substrate concentration increased, but corn straw was decreased as substrate concentration increased.(2)When corn straw was used as digestion material, the better digestion characteristics and maximum biogas production were achieved at 4% and 7.5, 10.15% and 8.03, respectively.(3)When livestock manure was used as digestion material, the better digestion characteristics were obtained at 16%, 7.5. The maximum biogas production of cow manure and swine manure were achieved at 16.5% and 8.33, 16.9% and 7.31, respectively.(4)When corn straw and livestock manure were used as digestion material for codigestion, the better digestion characteristics were obtained at 8%, 7.5. The maximum biogas production of corn straw and cow manure co-digestion and corn straw and swine manure codigestion were achieved at 7.6% and 7.53, 7.9% and 7.45, respectively.(5)The optimal initial pH value and substrate concentration were different of different digestion materials, which will provide reference value to some extent for the further research of anaerobic digestion influence effectors. |
