An Analysis of Scenario and Financial Feasibility in Developing Automotive Fuels by Upgrading Biogas Produced from Wastewater of Ethanol Factory

This study aims to evaluate the financial feasibility and scenarios for producing automotive fuel by upgrading biogas from ethanol processing wastewater to bio-methane or compressed biogas (CBG). The analysis scope includes wastewater from sugarcane-based ethanol production, biogas generation, quality enhancement and upgrading, and gas utilization in four replacement scenarios: natural gas (NGV), liquefied petroleum gas (LPG), crude fuel oil, and electricity production. Results demonstrate the viability of upgrading biogas to CBG as an automotive fuel. Key factors affecting the project's success include ethanol plant capacity, input biogas quantity, fuel prices, and energy consumption patterns. Larger plants (0.2–0.5 million liters per day) yield higher net present values (NPV) and shorter payback periods (PP) compared to smaller plants (0.1 million liters), with returns on investment ranging from 2 to 3 times and internal rates of return (IRR) from -4% to 7%, and payback periods of 7 to 13 years. Direct biogas utilization, such as incineration to replace fuel oil, offers higher returns than converting it to bio-methane for automotive use, despite a 36.6–66.3% increase in expenditure. In sensitivity analysis, a 20% rise in energy costs positively impacts the future feasibility of bio-methane production for automotive fuel from biogas. This work contributes to sustainable biofuel production and the utilization of waste resources in the ethanol industry.