On March 18, Dr. Steffen Mueller, Principal Research Economist of the Energy Resources Center and Director of the Agriculture and Bioenergy Research Center at the University of Illinois, released an analysis of the impact on greenhouse gas emissions of moving from the standard E10 blend (10 percent ethanol, 90 percent gasoline) to an E15 blend (15 percent ethanol, 85 percent gasoline). According to Dr. Mueller, if just seven states (IA, IL, KS, NC, OH, MI, WI) transitioned to exclusive use of E15 instead of E10, an additional 3.4 million metric tons of carbon dioxide (CO2) emissions would be avoided annually (this would be equivalent to taking 700,000 cars off the road).

Using the “Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model” (GREET) developed by Argonne National Laboratory, Dr. Mueller finds that a gallon of E15 saves an additional 1.25 grams of carbon dioxide per megajoule (gCO2e/MJ) compared to a gallon of E10. GREET analyses estimate that corn ethanol greenhouse gas emissions are on average 34 percent lower than those of regular gasoline.

GREET measures the carbon intensity of fuels, which refers to the amount of greenhouse gases (including CO2, nitrous oxide, and methane) that are released per unit of fuel. “Wells to wheels” assessments are calculated by adding the emissions at each production step. For biofuels, this includes carbon sequestration as well as impacts to land use associated with growing biofuel feedstocks.

According to Dr. Mueller, the carbon intensity of biofuels has steadily dropped over the last 10 years.  This is due to a better understanding of the various factors that influence fuel carbon intensity, and technological advances in biofuels refining and agricultural practices.  The evolving science of carbon intensity is reflected in the latest GREET model, released in late 2014.

Despite the evidence of the benefits of ethanol-blended fuels, and the moderate cost of switching to E15, increasing the amount of ethanol in the fuel supply has proven difficult.  According to the Renewable Fuels Association, E15 was available for purchase in only 12 states in 2014. A recent analysis by the National Renewable Energy Lab notes that barriers toward shifting the fuel supply from E10 to E15 are largely economic and not technical.  

E15 is the most tested fuel in the marketplace today. The Department of Energy and the Environmental Protection Agency have certified its use in model years 2001 and newer, which represents more than 80 percent of all vehicles on the road today. Additionally, more than 70 percent of auto manufacturers have certified the use of E15 in new 2015 vehicles. These fuels have been found safe for use with existing infrastructure, including gas station pumping equipment.   



For more information see: 

Assessment: Role of E15 in Reducing GHG Emissions, Dr. Steffen Mueller

New study says ethanol could cut carbon emissions more than many think, Crain's Cleveland Buisness

More Gas Stations Commit to Selling E15, Oil Industry Fights Against Higher Ethanol Blends, EESI