Effects of pungency degree on mesophilic anaerobic digestion of kitchen waste

This study investigated the influence of pungency degrees (PDs) on mesophilic anaerobic digestion of kitchen waste (KW). Batch tests were performed to evaluate the methane potential and production rate and the effect of PDs on organics degradation efficiency (in terms of volatile solids, protein and ether extract) at mesophilic temperature. Koch and Drewes model and modified Gompertz model were applied to assess the effects of PDs on the hydrolysis rate constant, biomethane yield rate and lag time. The results revealed that with the increasing contributions of PDs, the methane yield, organics degradation efficiency and hydrolysis rate of KW decreased while the pH values and concentrations of total ammonia nitrogen and free ammonia nitrogen were increased. Additionally, PDs lower than PD3 presented better digestion performance, and according to results of organics degradation and kinetics study, it could be suggested that appropriate range of PD in KW beneficial for AD is PD5-PD4.