A proposal by the U.S. Environmental Protection Agency to change ethanol blending rules would significantly increase carbon emissions to the equivalent of adding nearly one million more passenger vehicles on the road, according to an analysis conducted by the Energy Resources Center at the University of Illinois at Chicago (ERC).

The findings come in the wake of proposed rules by the U.S. EPA that call for a reduction of the volume of ethanol blended in gasoline as mandated by the Renewable Fuel Standard (RFS), a program of the Energy Policy Act of 2005 signed into law 10 years ago this month. If the rules are adopted as proposed, a total of 17.5 billion gallons of ethanol would be blended with gasoline by 2016, 3.75 billion fewer gallons than originally mandated by Congress.

“The RFS has been one of the most successful federal policies enacted in the United States because it achieved exactly what it was intended to do: spur research and investment, lower greenhouse gas emissions and reduce dependence on foreign oil. Our work has demonstrated that, over the last 10 years, steady reductions in greenhouse gas emissions have materialized as biofuels became a more efficient, high quality product,” said Steffen Mueller, Ph.D., principal economist at the Energy Resources Center.

The peer-reviewed analysis was conducted using the GREET Model (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) developed by Argonne National Laboratory which examines the full life cycle emissions impacts of energy sources. As part of the analysis, carbon emissions related to the planting, growing, harvesting, transportation and production of corn into ethanol were compared to that of oil recovery and production.

Under the EPA’s proposed rules, conventional starch ethanol would likely be reduced to 13.4 billion gallons from 15 billion gallons in 2015. In this scenario, the analysis found that 4,520,000 tonnes of additional CO2 emissions would be incurred in 2015.

The single year of carbon emissions is the equivalent to the annual greenhouse gas emissions of 951,600 passenger vehicles, according to the EPA’s equivalency calculator. Overall findings of the analysis are based on peer reviewed, published research that shows that greenhouse gas emissions from ethanol are close to one-third lower than those from gasoline.

“We are disappointed that the same federal agency charged to protect human health and the environment is proposing a rule change that would directly lead to greater greenhouse gas emissions,” said Ken Hartman, president of the Illinois Corn Growers Association. “After 18 months of delay in proposing new rules, the EPA has chosen not only to shirk its legal obligation as set forth by Congress, but to lose sight of its own mission.”

The EPA rulemaking proposal concerning the RFS was released on May 29. The EPA is expected to conclude the rulemaking process and issue a final rule in November. Testimony submitted to the EPA regarding the ERC’s analysis can be found here.