Characteristics and techno-economic potential of bio-compressed natural gas (Bio-CNG) from palm oil mill effluent (POME)

Abstract

This study investigated technical and economic feasibility of converting biogas from palm oil mill effluent (POME) into bio-compressed natural gas (Bio-CNG) for offsite utilization. Purification of raw biogas using biological and physical methods and removal of carbon dioxide (CO2) using membrane separation were evaluated. With about 99% hydrogen sulphide (H2S) and 88% CO2 removal efficiencies, the Bio-CNG was found to contain about 92%, 7% and 0.9% of methane (CH4), CO2 and oxygen (O2), respectively with H2S at trace level of 5 ppm. Biogas purification process also increased the calorific value (CV) of biogas from 20.0 MJ m-3 to 35.0 MJ m-3. The combined biological and physical method was found to be a feasible process for H2S and CO2 removal. The economic analysis conducted for Bio-CNG plant in comparison with existing biogas plant showed an approximate internal rate of 14% with a payback period about 6 years for a mill that processes 60 tonnes of fresh fruits bunches hourly. This study has therefore demonstrated that it is technically and economically viable to produce Bio-CNG as a fuel from POME for offsite utilization.