Optimising Process Pathway for Palm Oil Mill Effluent to Compressed Biomethane Off-Site Utilisation

Abstract

The palm oil mill effluent (POME) is a high-strength wastewater as characterised by its high biological oxygen demand and chemical oxygen demand. Through anaerobic digestion, it can be valorised into biogas to serve as sustainable substitution for fossil fuel. In order to fully exploit the potential of POME as sustainable source for renewable energy, the optimisation of the supply-demand chain that covers biogas production, biogas purification to biomethane, biomethane transportation and biomethane off-site utilisation, is crucial for understanding its economical-technical performance. There are many works that had explored the pathway for compressed biomethane (CBM) production, this work further the investigation by including consideration on pressure changes and requirement across the pathway and subsequently identifies suitable incentive rate to improve the economic performance. In this study, a mathematical model to determine the optimal process pathway was developed based on a mixed integer programming model and solved using General Algebraic Modeling System. The model showed that the optimal pathway would result in a payback period of 6 y, with a total capital investment cost of USD 2,934,564. The biomethane off-site utilisations were illustrated through electricity generation and CBM. The sensitivity analysis on Feed-in-Tariff further showed that a rate at USD 0.116 kWh was economically desirable. For CBM, the sales price should be at least USD 8.2-12.9 /MMbtu.