Environmental Burdens of China's Propylene manufacturing: Comparative life-cycle assessment and scenario analysis

China's propylene feedstock shifts from oil to imported cheap propane and local coal. However, the associated environmental loads of this feedstock change have seldom been investigated for China's propylene industry. Herein, environmental impacts of the four typical propylene production routes, coal to olefin (CTO), propane dehydrogenation (PDH), steam cracking (SC), and catalytic cracking (CC) process, were compared by life-cycle-assessment (LCA) methodology. Two metrics, midpoint environmental impacts (including nine indicators) and the comprehensive index of energy conservation and emission reduction (ECER), were adopted for this evaluation. The midpoint-impact indices show the trade-offs across the nine environmental dimensions. Thus, it is not easy to rank the environmental advantage of the four production routes. The ECER indices indicate the highest environmental loads in the CTO process, followed by PDH and the comparable SC and CC routes. Raw materials consumption dominates the environmental burden generations of the PDH, SC, and CC routes. Scenario analysis shows that feedstock shift and capacity growth jointly increase the environmental burdens of China's propylene industry by 27-66% in 2025 and 60-111% in 2030, relative to the 2018 baseline. Notably, global-warming potential inevitably increases due to replacing the conventional oil-fed SC/CC capacity either by coal-fed CTO or by propane-fed PDH route. The findings suggest that the feedstock shift of the propylene industry deserves close attention to promote the environmental sustainability of the Chinese chemical manufacturing industry.