Comparative study on green methanol production: Energy, exergy, economy and environment

Although methanol (MeOH) is increasingly recognized as a promising low-carbon fuel for decarbonizing the shipping industry, comprehensive comparisons of CO2-neutral production pathways remain scarce. Given that shipping currently accounts for about 3 % of global anthropogenic carbon emissions, projected to rise to 5–8 % by 2050 without mitigation, identifying efficient and sustainable MeOH production methods is critical. This study analyzed three CO2-neutral MeOH production processes: natural gas steam reforming, biomass gasification and biogas reforming, using Aspen Plus simulations to calculate mass and energy balances, with energy, exergy, economic and environmental assessments for 500 kg h−1 production. Material flow analysis shows that all three pathways require feedstock inputs of similar magnitude, with natural gas reforming using the least and biomass/biogas slightly more. Steam demand varies more noticeably, as biogas reforming requires substantially less than the other routes. Despite these differences, energy and exergy efficiencies remain comparable at roughly 49–51 %. Natural gas reforming is currently the most economical option, while biomass- and biogas-based routes hold longer-term promise as renewable feedstock costs decrease. Environmentally, biogas reforming achieves the greatest emissions reduction (61.7 %), followed by biomass gasification (51.4 %), underscoring their advantages for low-carbon MeOH production.