Biohydrogen Production from Palm Oil Mill Effluent Pretreated by Chemical Methods Using Thermoanaerobacterium-Rich Sludge

The effect of alkaline and acid pretreatment on solubilization of solid organic matter in palm oil mill effluent (POME) and hydrogen production by Thermoanaerobacterium-rich sludge was studied. Organic matter solubilization of alkaline and acid pretreatments were increased up to 28 and 15.7% of initial soluble COD in POME, respectively. That corresponds to carbohydrate solubilization of 41 and 32% of initial soluble carbohydrate in POME, respectively. A maximum hydrogen production yield of 4.6 l H2/l-POME was achieved from POME pretreated with 1.5% w/v NaOH, which was 3-fold greater than raw POME and 1-fold greater than POME pretreated with 1.5% w/v HCl. Optimum conditions for biohydrogen production from alkaline pretreated POME using Thermoanaerobacterium-rich sludge was found at initial pH 5.5 and temperature of 60°C, which gives a maximum hydrogen production yield of 5.2 l H2/l-POME and increased 51% as compared to raw POME. The biogas was mainly composed of hydrogen and carbon dioxide with the percentage of hydrogen ranging from 55-60% of biogas and free of methane. During the conversion of alkaline pretreated POME into hydrogen, the acetic and butyric acids were main by-products in the metabolism. The results showed that alkaline pretreatment is an effective pretreatment methods for enhancing the hydrogen production yield from POME. The use of Thermoanaerobacterium-rich sludge is promising for future engineering practice of biohydrogen production from alkaline pretreated POME.