Exploring novel biogas-to-bio methanol conversion: Exergy-driven hybrid pathways for enhanced methanol yield
Mahdi Enayati, Francesco Di Maria
Abstract
Amid the growing global urgency to mitigate climate change and reduce dependence on fossil fuels, sustainable energy solutions have become increasingly critical. Biogas, a renewable mixture primarily composed of methane (CH 4 ) and carbon dioxide (CO 2 ), is widely utilized in the EU and beyond, offering substantial potential as a feedstock for green energy and chemical production. This study proposes novel process configurations for converting biogas into bio-methanol, offering a more efficient and environmentally favorable alternative to conventional biomethane production for grid injection. Two process scenarios were analyzed using rigorous simulation combined with exergy assessment. Scenario 1 involves direct steam methane reforming (SMR) of raw biogas followed by methanol synthesis, whereas Scenario 2 first removes CO 2 to produce biomethane, which is subsequently reformed and converted to methanol. Both scenarios considered a biogas feed of 368 kg/h. Scenario 1 achieved a higher methanol yield (321.4 kg/h vs. 210.1 kg/h) but required greater steam input (551.8 kg/h vs. 195.4 kg/h) and produced more gas sent to the flare system (22.2 kg/h). Scenario 2 consumed less steam, generated lower flaring gas (1.2 kg/h), and achieved higher CO 2 capture (132.4 kg/h vs. 237.7 kg/h), demonstrating its environmental advantage. The exergy efficiencies were calculated as 64.4 % for Scenario 1 and 60.9 % for Scenario 2. Overall, Scenario 1 is optimal for maximizing methanol production, while Scenario 2 better aligns with emission reduction goals. This comparative analysis elucidates the trade-offs between energy efficiency, production yield, and environmental impact in bio-based energy systems.