Life-cycle environmental burdens of ethylene production in the context of China's chemical feedstock transition from naphtha to coal and shale gas by-product of ethane

Abstract

China is experiencing an ethylene-feedstock transition from naphtha to cheap coal and ethane by-product of shale gas. This transition leads to the variation in the environmental burdens of ethylene production. Here, we compared the life-cycle environmental loads of ethylene, produced by four typical routes—naphtha to ethylene (OTE), ethane to ethylene (ETE), coal-based methanol to ethylene (CMTE), and bioethanol to ethylene (BETE). Global midpoint environmental impacts (with 12 indicators) and China-contextualized Energy Conservation and Emission Reduction (ECER) index were used. We found that the trade-off across the 12 environmental dimensions impedes directly comparing the environmental sustainability of the four ethylene routes. The emerging ethane-fed ETE route, as an example, generates low climate change loads (GWP) but high abiotic resource depletion potentials (ADP). China's indigenous ECER index, addressing this trading-off issue, shows the highest environmental burdens of the coal-fed CMTE route, followed by the BETE, ETE, and OTE routes. Raw material consumption dominates 58–85% environmental burdens of the four ethylene routes. Referring to the 2018 baseline, replacing the coal-fed CMTE route with the ethane-fed ETE would reduce the environmental load per tonne of ethylene product by 2–25% in 2030 and 6–42% in 2050. However, the total environmental loads of China's ethylene sector would still increase by 1–44% and 6–68% due to the continued industrial expansion. Given ethylene as the primary chemical material, our findings provide policymakers with reference to promote the environmental sustainability of chemical manufacturing sector.