Lifecycle energy consumption and greenhouse gas emissions from corncob ethanol in China

Converting corncobs into fuel ethanol is different from converting stover because cobs have higher hemicellulose and lower lignin than stover. Current research provides life-cycle assessments of greenhouse gas (GHG) emissions for stover ethanol but lacks such assessments for corncob ethanol. This study attempts to fill this gap by estimating the lifecycle energy consumption and carbon emissions for corncob ethanol using the GREET (Greenhouses gases, Regulated Emissions, and Energy use in Transportation) model. Our well-to-pump (WTP) estimate of fossil fuel consumption is 0.51-0.84 MJ MJ(-1) of ethanol produced. The estimated GHG emissions are 39.44-49.97 gCO(2eq)/MJ of ethanol; about 90% is attributed to the conversion process. If glucose and xylose are co-fermented, it requires 10% less energy and emits about 20% fewer GHGs from well to pump. The estimates are sensitive to the variations in corn yield and hydropower supply. Pump-to-wheel emissions are also assessed for representative vehicles with spark-ignition engines in China. We find that hybrid and plug-in hybrid electric vehicles have 18-20% lower emissions than internal combustion engine vehicles (ICEVs), and flexible-fuel vehicles using E85 have similar WTP emissions to ICEVs. (c) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd