Effects of thermal pretreatment on degradation kinetics of organics during kitchen waste anaerobic digestion

The influence of thermal pretreatment on degradation properties of organics in kitchen waste (KW) was investigated. The kinetics results showed that thermal pretreatment could enhance the degradation efficiency of crude protein (CP), fat, oil and grease (FOG), volatile solid (VS) and volatile fatty acids (VFA). Thermal pretreatment showed no significant difference in the final concentration of protein but could decrease the FOG degradation potential (7-36%), while increased the lag phase for degradation of protein and FOG respectively by 35-65% and 11-82% compared with untreated KW. Cumulative biogas yield increased linearly and exponentially with the removal efficiency of VS and other organics (CP and FOG) respectively. Additionally, the reduction of CP increased exponentially with FOG removal efficiency. The calculating methods of biogas yield, organics reduction and corresponding appropriate digestion retention based on FOG and CP reduction amount and pretreatment parameters were suggested.