Palm Oil Mill Effluent (POME) biogas techno-economic analysis for utilisation as bio compressed natural gas

Abstract

The production of palm oil will continue to rise with increasing demand of fats and oils. The increase of palm oil production will result in high production of palm oil mill effluent (POME). POME is polluting due to its high chemical oxygen demand (COD) and biological oxygen demand (BOD). High COD and BOD of POME has the advantage to produce large amount of biogas through anaerobic digestion (AD). As upgraded biogas has equal composition to natural gas, it can be potentially used as compressed natural gas (CNG) or also known as bio-CNG. Bio-CNG at its current state is too expensive for implementation where subsidies are required to enable the technology, especially for countries where energy price is low such as in Malaysia. This paper studies on the economic potential of the bio-processing technology which consists of an anaerobic digester, purification unit, and compression up to 20 MPa as the biogas will be utilised as CNG. The parameter that is considered in the economic analysis includes the cost of the AD, purification unit, compression of biogas (based on the outlet pressure of the purification unit up to 20 MPa), transportation cost of bio-CNG, and lastly the profit obtained from the sales of bio-CNG. It is revealed that the system that utilises membrane separation technology has the lowest payback period and hence is most economical.