A Technical and Economic Analysis of Heat and Power Generation from Biomethanation of Palm Oil Mill Effluent

Palm oil mill effluent (POME) has been identified as one of the major sources of aquatic pollution in Malaysia. due to its high strength and economic importance. With more than 330 palm oil mills in operation, Malaysia produces some 10.6 million tonnes of crude palm oil annually, accounting for 52% of the total world production, and concomitantly generates some 27 x 10 m POME. To meet with the regulatory requirement, more than 85% of the mills use solely lagoon systems in wastewater treatment, typically anaerobic first stage followed by facultative treatment. Research data associated with this study revealed that methane yield ranging from 0.47 to 0.92 mkg-BODadded was attainable in the biomethanation of POME for reaction temperature of between 35 to 55oC. Considering the associated socio-environmental impact, an analysis of the research data indicates that about 375 x 10 m, or 225 Gg of CH4 is evolved from open ponding systems used in POME treatment, accounting for 10% of the CH4 inventory in Malaysia. In terms of greenhouse gas effect, this source amounts to 5,170 Gg in CO2 equivalent, or 3.6% of the estimated total emissions in Malaysia. As methane can be harnessed for the generation of either thermal or electric energy, an economic assessment based on a life-cycle cost-benefit model as elucidated in this study shows that an annual return on investment of 31 to 58%, or payback period of 2.5 to 1.5 years, is possible in resource recovery systems utilising methane for heat generation and land application of digester effluent. The corresponding figures for electricity generation systems are 1.8 to 6.4% and 9.6 to 6.7 years. In the latter case, the palm oil industry as a whole would be in a position to potentially contribute 2,250 x 10 kWh annually, equivalent to about 4% of the national electricity demand. This compares favourably with the Malaysian Government policy to achieve 5% of the total electricity generation by 2005 from renewable bioenergy sources. In terms of thermal energy generation, the potential would be equivalent to 715 x 10 litres, worth some USD 120 million according to the prevailing price. Bioenergy recovery from the treatment of POME therefore not only contributes towards the sustainable growth of the palm oil industry, but also assists Malaysia in achieving its sustainable development objectives in connection with the United Nations Framework Convention on Climate Change. Electricity Supply Industry in Transition: Issues and Prospect for Asia 14-16 January 2004