Greenhouse gas emissions embedded in US-China fuel ethanol trade: A comparative well-to-wheel estimate

The US-China biofuel trade has experienced exponential growth in the past few years. This study conducts life cycle analysis on the US-China fuel ethanol trade and compares the greenhouse gas (GHG) emissions from ethanol produced in China with ethanol imported from the U.S. We conduct lifecycle analysis for five China ethanol production pathways - corn, cassava, sweet sorghum, corn stover, and corncob, using the GREET (Greenhouse gases, Regulated Emissions and Energy use in Transportation) model. The well-to-pump (WTP) GHG emissions are estimated to be 54-234 gCO2e/MJ. The WTP emissions of ethanol imported from the U.S. are lower than starch- and sugar-based ethanol in China. By building vehicle pathways for passenger cars in China, we estimate the well-to-wheel emissions to be 184-253 gCO2e/km for spark-ignition (SI) engine vehicles. Overall, importing ethanol from the U.S. is estimated to reduce emissions by 34.21 gCO2e/MJ on average, suggesting great potential of imported ethanol on curbing China's GHG emissions.