ORGANIC WASTE CONVERSION VIA CONTINUOUS ANAEROBIC CO-DIGESTION OF OIL PALM EMPTY FRUIT BUNCHES AND COW MANURE: EVALUATION OF FEEDING REGIME ON METHANE PRODUCTION

Anaerobic co-digestion of oil palm empty fruit bunches with cow manure was studied. The research focus was on the evaluation of feeding different solid concentrations of the substrate in the on-going process of anaerobic digestion. The solid concentrations ranged from 0.5 to 12% TS. Results of the study showed that the maximum methane production could be reached with the reactor digesting substrates with 4 to 8% TS, in which the methane produced was from 1300 to 1400 mL per day. A significant drop of pH from 7.02 to 5.97 occurred when the reactor was digesting substrates with 10 and 12% TS. Acidic condition caused by organic matter overloads lowered the efficiency of organic conversion represented in the low removal of COD, which was only 22.4%. This finding is highly significant for the waste management industries in terms of dealing with the digester upset due to the digestion of large amount of organic wastes.