Potential solution to wheat straw-to-methanol for marine fuel under carbon emission restrictions: A comparative energy, exergy, economic, and environmental analysis

Green methanol has emerged as a sustainable alternative marine fuel, yet its industrialization requires a systematic evaluation of technical routes under carbon emission restrictions. This study conducted process modeling and comparative analysis of three wheat straw-to-methanol routes: Route 1 (partial grid electricity), Route 2 (self-generated electricity), and Route 3 (integrated hydrogen production). Route 1, using grid electricity, resulted in a carbon emission of 40.78 g CO2eq/MJ methanol. Route 2, utilizing self-generated electricity, achieved 22.70 g CO2eq/MJ methanol, matching Route 1 when renewable electricity was used. Route 3 achieved the highest methanol yield and energy efficiency, with minimal exergy loss in syngas conditioning, but exhibited the poorest economic performance. Route 3's carbon emissions were highly sensitive to the renewable electricity structure. Overall, Route 1 using grid electricity was unsuitable. Route 2, with its competitive carbon emissions and economic performance, was ideal for early industrialization, especially in regions with limited renewable energy resources. Route 3 was best suited for areas with abundant straw and strong renewable energy resources, suggesting a phased implementation of Routes 1 and 3 using renewable electricity. This study provided potential solutions for the industrialization of biomass-to-methanol under carbon emission restrictions, offering data support and valuable insights for researchers, investors, and industry stakeholders.