Conceptual design and economic analysis of biomethanol production process from palm oil mill effluent for sustainable biodiesel production

Biodiesel is one of the most potential sustainable alternatives to fossil fuels in transportation sector. However, methanol used in biodiesel production is usually synthesized from natural gas. In this work, a feasibility study of biomethanol (bio-MeOH) production from palm oil mill effluent is conducted. Biogas produced from palm oil mill effluent (POME) via anaerobic digestor is used to synthesize bio-MeOH to support sustainable biodiesel production. The treated biogas is converted into syngas via methane steam reforming (MSR) and water gas shift (WGS) processes. Raw syngas from WGS reactor is dehumidified and mixed with an additional amount of carbon dioxide (CO₂) to achieve desired 2:1 H₂/CO₂ molar ratio before being fed into a CO₂ hydrogenation reactor to produce bio-MeOH. The raw bio-MeOH is then purified to 99.9 mol% via distillation columns. To reduce utility consumption and CO₂ emissions, the bio-MeOH production process is further enhanced via heat integration. The optimized results show that the levelized production cost and carbon emission of the intensified design are 1,101.56 USD and 3.42 tonne-CO₂ per tonne-MeOH. For the internal rate of return (IRR) to attain the profitable threshold of 5 %, the selling price of bio-MeOH must be higher than $1,600 USD per tonne-MeOH.