Process performance and methane production optimizing of anaerobic co-digestion of swine manure and corn straw.

During anaerobic digestion (AD) process, process parameters e.g., VFA, pH, COD removal … and kinetic parameters e.g., hydrolysis rate, lag phase and methane production potential… are the important indicator for illustrating AD process performance, however, the AD process performance based on these parameters remains poorly understood. To estimate process performance focusing on initial pH and substrate composition, the effects of initial pH and swine manure to corn straw ratio on biogas production and these parameters and linkages of these parameters were analyzed. Also, the methane production was optimized. The results revealed that the maximum methane yield and methane production rate were obtained with initial pH 7.5 and SM/CS ratio of 70:30. Kinetic parameters are coupled with process parameters, especially for COD removal rate, VS degradation rate, VFA and pH. Hydrolysis constant positively correlated with pH, COD removal rate and VS degradation rate, then impacted methane production and lag phase. Meanwhile, lag phase and the maximum methane production rate were directly determined by VFA and COD removal rate. The optimum initial pH and SM/CS ratio were 7.15 and 0.62, respectively, with a predicted maximum methane content of 55.12%. Thinking these findings together, they provide a scientific theory for estimating AD performance.