Comprehensive environmental and operating cost assessment of typical methanol synthesis processes under a cradle-to-gate boundary

Under the dual pressure of environmental compliance and cost control, green methanol synthesis is crucial for achieving high methanol production efficiency and reducing pollution. However, carbon emissions or economic performance have been mainly evaluated separately, with only a limited number of studies conducting integrated assessments that consider life cycle burdens, process-specific pollutants, and operating costs. In this study, a comprehensive assessment was conducted for typical methanol synthesis processes, based on life cycle assessment, comprehensive environmental assessment, and operating cost assessment. Three methanol synthesis processes were selected under a cradle-to-gate boundary using a functional unit of 1 t of methanol, these methods were distinguished by their feedstocks (i.e., coal-based methanol (P1), CO2 and electrolytic hydrogen-based methanol (P2), and coke oven gas-based methanol (P3)). Environmental assessment demonstrated that P2 exhibited the lowest overall impact, with a lower global warming potential (0.47 t CO2-eq) than P1 (3.69 t CO2-eq) and P3 (1.87 t CO2-eq). Economic assessment revealed that the total operating costs of P1 and P3 were considerably higher than those of P2 in terms of chemicals and energy. The highest comprehensive evaluation index was achieved by P2, which was attributed to superior environmental performance resulting from (a) the use of green energy and low-pollution feedstocks and (b) reasonable operating costs. This study provides a reproducible multidimensional framework for selecting and optimizing sustainable methanol synthesis processes.