Corn Ethanol Production Emits 51% Less Greenhouse Gas Than Gasoline

Corn ethanol directly emits an average of 51 percent less greenhouse gas than gasoline per gallon produced. This is result of a recent study conducted by researchers at University of Nebraska-Lincoln. According to the research, recent improvements in efficiency throughout the ethanol production process account for the difference.

The research was conducted by an interdisciplinary team of UNL researchers, which evaluated dry-mill ethanol plants that use natural gas. Such plants account for close to 90 percent of current ethanol production capacity in the U.S.

This research quantifies the impact of recent improvements throughout the corn-ethanol production process, including crop production, biorefinery operations and co-product use according to Ken Cassman, a UNL agronomist who was part of the research team.

"Critics claim that corn ethanol has only a small net energy yield and little potential for direct reductions in GHG emissions compared to use of gasoline," Cassman said. "This is the first peer-reviewed study to document that these claims are not correct."

Recently built, more efficient plants now represent close to 60 percent of total ethanol production and will account for 75 percent by the end of 2009, Cassman said. These newer biorefineries have increased energy efficiency and reduced emissions through the use of improved technologies.

Many of these plants are also located near cattle feeding or dairy operations, which allows efficient use of the co-product distillers grains as cattle feed. For example, the distillers grains don't have to be dried to facilitate long-distance travel. Drying uses up to 30 percent of total energy use in the ethanol plant.

The ethanol industry currently is producing a fuel that is 48 to 59 percent lower in direct-effect lifecycle greenhouse gas emissions than gasoline, the researchers claim. That's two to three times the reduction reported in earlier studies that did not take into account recent advances in corn-ethanol production.

The net energy ratio, which averaged 1-1.2 in earlier studies, is 1.5-1.8 to 1 in the recent research, Cassman said. That means that for every unit of energy it takes to make ethanol, 1.5 to 1.8 units of energy are produced as ethanol.

The study did not take into account indirect land use change, because there is not yet a scientific consensus about how to estimate the magnitude of these effects as a component of the greenhouse gas intensity of biofuels, the researchers said.

For more information on the study, click here.