This study aims to evaluate how inoculum’s origin affects the methane yield of palm oil mill effluent (POME) by measuring the specific methanogenic activities (SMA) and bio-methane potential (BMP) of POME at different dilutions (100, 80, 60, 40, and 20 % of initial POME) and by using active anaerobic sludge (as inocula) from 3 palm oil mills (S1, S2, S3). The anaerobic digesters were operated in batch mode at a temperature of 40 °C until methane generation ceased. The corresponding SMA were 0.0159, 0.0098 and 0.0333 gCOD /(gVSS d) for S1, S2 and S3, respectively. The results showed that POME without dilution gave the highest cumulative biogas, 4162, 2857 and 2678 mL for S2, S3 and S1, respectively. However, 20 % dilution from original POME gave the highest methane yield (as BMP) 126, 88 and 84 mL CH4/gCOD removed for S2, S3 and S1, respectively. In this study, 2 mathematical models were selected including the corrected Gompertz equation and Gompertz two substrate models. They were applied to characterize the kinetics of the anaerobic digestion processes and to compare the BMP data from the experiments. Both models could represent all BMP data satisfactory although only Gompertz 2 substrate model showed almost perfect fitting and could characterize the influence of slowly degradable portion of POME. Accordingly, the slowly degradable portion of POME was estimated to be 10 % of total COD.
Effect of Operating Parameters on Process Stability of Continuous Biohydrogen Production from Palm Oil Mill Effluent under Thermophilic Condition