The study, titled "The Greenhouse Gas Benefits Of Corn Ethanol - Accessing Recent Evidence," also states that the GHG emissions from ethanol produced at plants powered by natural gas is 43 percent lower than gasoline. All the ethanol plants in Minnesota are powered by natural gas. 

The study attributed much of the GHG savings to revised estimates to the impact of land use change.

"Where previous estimates anticipated farmers bringing additional land into production as a result of increased corn prices, recent analysis finds only modest increases in crop acreage. Additional improvements at ethanol refineries, combined with on-farm conservation practices that reduce greenhouse gas emissions, such as reduced tillage and cover crops, have further decreased emissions associated with corn ethanol," the USDA said in a statement. 

The USDA said the study projects that with added improvements in refineries and on farms, a reduction of over 70 percent in lifecycle emissions is possible by 2022.

“These new findings provide further evidence that biofuels from America's heartland reduce greenhouse gases even more than we thought, and that our farmers and ethanol plants continue to become more efficient and effective,” said Agriculture Secretary Sonny Perdue in the same statement.

He added that expanding the sale of E15 year-round would provide consumers with more choices when they fill up at the pump, including environmentally-friendly fuels with decreased emissions.

More information on the USDA's greenhouse gas profile of biofuels is available at www.usda.gov/oce/oeep.