Aspen Plus Simulation of Palm Oil Mill Effluent-to-Power Conversion: Anaerobic Digestion, Biogas Upgrading, and Turbine Performance

Abstract

Palm oil mill effluent (POME) is a high-strength wastewater whose organic load can be converted to methane-rich biogas for renewable power generation. This study reformulates and evaluates a steady-state Aspen Plus V11 simulation integrating stoichiometric anaerobic digestion, a three-stage packed scrubber, gas conditioning, compression, and turbine power recovery. Direct simulator screenshots were used as the primary numerical evidence where the source narrative contained conflicting values. The digester gas contained 59.90 mol% CH4, 35.05 mol% CO2, 2.60 mol% H2S, 0.49 mol% NH3, and 1.95 mol% H2O. After scrubbing, CH4 increased to 72.50 mol%, while CO2 and H2S decreased to 23.19 and 0.35 mol%, respectively. The water-trap stage further reduced H2O from 3.96 to 1.22 mol% and produced a conditioned gas containing 73.71 mol% CH4. The Aspen turbine block reported 510.64 kW at an isentropic efficiency of 72%. Relative to the digester gas, the scrubber increased CH4 concentration by 21.0%, reduced CO2 by 33.8%, and reduced H2S by 86.5%. The results support the technical potential of integrated POME-to-power conversion but also reveal important reproducibility and consistency issues, including conflicting POME feed units, incomplete digester reaction specifications, and a mismatch between the stated gas-engine concept and the turbine model used for power prediction. These limitations define priorities for model validation and scale-up.