Environmental and economic implications of bioethanol blending for the renewable fuel standard in South Korea

Cellulosic ethanol based on agricultural residues is a potential alternative to fossil fuel. This new alternative is expected to reduce greenhouse gas emissions (GHGs) compared to the current fossil fuel used for transportation. Many countries have legislated a renewable fuel standard (RFS) with biofuel blending regulations for transportation fuel. The aim of this study is to estimate the potential quantity of rice straw and ethanol production with the associated cost and CO₂-equivalent GHGs. It also examines the environmental implications of the RFS considering all stages from cradle to gate, including rice straw collection and ethanol distribution. The available production of rice straw ethanol is about 1.2 billion L considering the current demand, which can achieve the 5% ethanol blended gasoline (E5) standard in South Korea. The optimum cost for ethanol from rice straw is expected to be 0.956 US$ L^-1 with 6,000 Mg d^-1 by constructing two biorefineries in Dangjin and Gwangju. Domestic ethanol from rice straw can reduce CO2-equivalent GHGs to 2,614 g L^-1 (90.6%), and imported ethanol from Brazil can reduce CO₂-equivalent GHGs to 1,907 g L^-1 (66.1%) compared to conventional gasoline (2,885 g of CO₂-equivalent GHGs L_-1). Considering the amount of expected displacement for current domestic gasoline, the potential GHG reduction can be 1.0 million Mg of CO₂-equivalent GHGs per year, and the blended fuel price (1.864 US$ L_-1) would be similar to that of conventional gasoline (1.870 US$ L^-1) with E5.