EVALUATING THE EFFECT OF LOW AND HIGH TEMPERATURE MODE OF SUBCRITICAL WATER PRE-TREATED EMPTY FRUIT BUNCHES ON CO-DIGESTION PERFORMANCE AND KINETIC STUDY FOR METHANE PRODUCTION

Abstract

Anaerobic digestion of oil palm empty fruit bunches (EFB) is considered an effective method for nonrenewable energy substitution through biogas production. However, lignocellulosic recalcitrance structure of EFB is one of the main difficulties in achieving high biogas production for anaerobic co-digestion with palm oil mill effluents (POME). In this study, EFB was pre-treated with subcritical water (SCW) at low (120°C) and high (180°C) temperatures for 10-30 min to enhance biogas production. The characteristics of EFB after SCW pre-treatment were evaluated to identify changes in physicochemical characteristics. The combination pre-treatment of 180°C for 10 min with 546.18 mL g–1 volatile solid (VS) biogas yield and 421.41 mL CH4 g–1 VS methane yield revealed the highest biogas production. Meanwhile, co-digestion of SCW pre-treated EFB with POME led to a removal of more than 66% VS. The sugars released were analysed in liquid fraction of SCW pre-treated EFB where glucose, xylose, cellobiose, mannose and galactose were detected. Notably, kinetic study of biogas production of pre-treated EFB using modified Gompertz model revealed that pre-treatment improved the lag phase, and the highest biogas production rate was observed at 19.80 mL g–1 VS. day. In conclusion, co-digestion of EFB with POME for methane production can be improved with the use of SCW pre-treatment.