Analyses of lifecycle GHG profiles favor corn ethanol over gasoline. Credit: U.S. Department of Agriculture

Greenhouse gas (GHG) emissions associated with corn-based ethanol in the U.S. are about 43% lower than gasoline-related emissions when measured on an energy-equivalent basis, according to a new lifecycle analysis of corn ethanol released by the U.S. Department of Agriculture (USDA).

This analysis is comparable to reducing GHG emissions in the U.S. transportation sector by as much as 35.5 million metric tons per year.

The report, A Life-Cycle Analysis of the Greenhouse Gas Emissions of Corn-Based Ethanol, cites greater lifecycle GHG benefits from corn ethanol than a number of earlier studies. These derive from improvements in ethanol production from the corn field to the ethanol refinery. Farmers are producing corn more efficiently and using conservation practices that reduce GHG emissions.

U.S. corn yields increased by more than 10% between 2005 and 2015, and ethanol production also increased from 3.9 to 14.8 billion gallons per year. At the same time, advances in ethanol production technologies, such as the use of combined heat and power, using landfill gas for energy, and co-producing biodiesel helped reduce GHG emissions at ethanol refinery plants.

On the basis of current trends, the GHG profile of corn-based ethanol is expected to be almost 50% lower than gasoline by 2022 as a result of improvements in corn yields, process fuel switching, and transportation efficiency.