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RFA: California Takes Big Step Toward E15 Approval with Release of Emissions Study

July 15, 2022

E15, Regulatory, State News


The state of California took an important step toward approving the use of cleaner, lower-cost E15 today by releasing the results of a multi-year study of the fuel’s emissions impacts. The results of the study, which tested 20 vehicles, show that shifting from E10 to E15 reduces emissions of most pollutants that contribute to ozone formation and, ultimately, “smog.” California is one of only two states across the country today that doesn’t currently allow the sale of E15.


“Ozone forming potential showed a decreasing trend for E15 compared to E10, indicating that the introduction of E15 in the California gasoline market will likely not contribute to increases in ozone formation,” according to the study released today. The report also shows E15 significantly reduces emissions of particulate matter, which is another key ingredient in “smog.” The study, which was conducted by researchers at the University of California-Riverside, was supported by the Renewable Fuels Association, California Air Resources Board (CARB), U.S. Council for Automotive Research, National Corn Growers Association, and Growth Energy.


“The results of this study clearly demonstrate that E15 cuts emissions of the nasty tailpipe pollutants that contribute to dirty air and cause respiratory illnesses and other serious health concerns,” said RFA President and CEO Geoff Cooper. “In addition to reducing the potential for smog, E15 also cuts greenhouse gas emissions, displaces petroleum, lowers consumer pump prices, and supports renewable energy jobs in California and across the country. The benefits of E15 to the Golden State are compelling and obvious, and we encourage CARB and the Environmental Policy Council to move swiftly to approve the fuel. Now more than ever, California consumers want and need the option to choose lower-cost, lower-carbon E15 at the pump.”


Among the study’s key conclusions:


  • Particulate matter (i.e., the “soot” or particles that contribute to smog) showed “strong, statistically significant” reductions of 16-54% for E15 compared to E10 across the fleet of 20 vehicles. Solid particle number emissions were 12% lower for E15 than E10, at a statistically significant level.
  • Total hydrocarbon (i.e., unburned hydrocarbons that contribute to ozone) emissions showed statistically significant reductions of 5-6% for E15 compared to E10. For non-methane hydrocarbon emissions, E15 showed a 7-15% reduction compared to E10.
  • Carbon monoxide emissions showed statistically significant reductions of 12-27% for E15 compared to E10.
  • Carbon dioxide tailpipe emissions showed a reduction for E15 compared to E10.
  • Fuel economy showed a reduction of just 1% for E15 compared to E10 across the fleet of 20 vehicles.


CARB noted today that its comprehensive review of the impacts of E15 is “currently in its third year and staff expects the…process would likely take at least another full year to complete.” Once the full review is complete, CARB and other agencies will make a recommendation to the state’s Environmental Policy Council, followed by the adoption of regulatory amendments allowing E15 use in California.


For a primer on E15’s impacts on ozone, click here.