Life-Cycle Analysis of Ethanol, Dextrose, and Feed Products from Corn Wet Mills in the United States

This work concerns the United States corn wet milling industry, offering insights into the life-cycle greenhouse gas (GHG) emissions of ethanol, dextrose, and feed products, including corn germ, gluten meal, and fibers from the wet mills. Process-level energy and material balances for various products were collected and processed through an extensive industry survey of the U.S. corn wet mills. Life-cycle analyses (LCAs) were completed for specific products following a process-level allocation method that meticulously allocates energy and emission burdens to each product across major unit operations at major wet mills. The study found that on average the life-cycle GHG emissions are about 59.6 g CO2e/MJ for ethanol, about 1.1 kg CO2e/kg for dextrose, and range from 1.2 to 1.3 kg CO2e/kg for germ and other animal feeds. The emission reduction potentials of mitigation options were assessed. The capture and storage of fermentation CO2 could reduce ethanol’s GHG emissions by 52%. Transitioning from coal to natural gas or renewable natural gas, coupled with capture and storage of onsite flue gas, emerged as promising avenues for emission reduction with the potential for achieving negative emissions. This work offers insights into the GHG emission intensities and mitigation strategies for the U.S. corn wet mill industry.