CARB releases E15 emissions study

By Erin Voegele | July 15, 2022

The California Air Resources Board on July 15 released the results of a multi-year study on the emissions impact of E15. The study highlights the air quantity benefits that could be achieved by adopting the use of E15 within the state.

California does not currently allow the use of E15, as state regulations currently limit the ethanol content of gasoline to 10 percent. The Multimedia Evaluation (MME) of E15 initiated by CARB aims to understand any potential environmental or public health impacts from the use of E15 in California. California law generally requires that an MME be completed prior to adopting new motor vehicle fuel specifications.

As part of the MME for E15, CARB contracted with the University of California at Riverside Bourns College of Engineering – Center for Environmental Research and Technology to evaluate exhaust emissions from the use of California reformulated gasoline (CaFRG) that contains 15 percent ethanol.

The study, which was supported by the Renewable Fuels Association, Growth Energy, the National Corn Growers Association, and U.S. Council for Automotive Research,  looked at the impact of increased ethanol content on exhaust emissions in 20 vehicles. All vehicles used in the study were model year 2016 or newer and equipped with three-way catalysts (TWc). Measured emissions include oxides of nitrogen (NOx), total hydrocarbons (THC), non-methane hydrocarbon (NMHC), carbon monoxide (CO), carbon dioxide (CO2), PM mass, particulate number, 1,3-butadiene, benzene, toluene, ethylbenzene, xylene isomers, ethanol, and carbonyl compounds.

The study found that E15, when compared to E10, achieved statistically significant particular matter (PM) reductions of 16-54 percent across the fleet of 20 vehicles. Solid partial number emissions were 12 percent lower for E15. Total hydrocarbon missions were also reduced 5-6 percent for E15. For non-methane hydrocarbon emissions, E15 achieved a 7-15 percent reduction when compared to E10. E15 also resulted in 12-27 percent reduction in carbon monoxide emissions. Weighted carbon dioxide emissions were 17 percent lower across the fleet of 20 vehicles. The study also indicates that E15 caused only a 1 percent reduction in fuel economy.

Release of the new study represents a significant step forward in California’s process to enable the adoption of E15. The process, however, will take at least another year—perhaps more—to complete.

According to CARB, the MME is currently in its third year. The agency estimates development process is expected to take at least another full year to complete. After that time, CARB would be able to formally release a proposed regulation change, after which the multimedia working group (MMWG) would make a recommendation to the Environmental Policy Council on whether the potential regulatory amendments to allow E15 use in California would have significant impacts on public health or the environment. If the EPC determines that the adoption of E15 would not significantly impact public health or the environment, CARB would then be able to consider the adoption of regulatory amendments to allow the use of E15.

The RFA said the study represents a big step toward California’s approval of E15. “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,” Geoff Cooper, president and CEO of the RFA. “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.”

Growth Energy is also welcoming release of the study. “CARB’s report adds to the vast trove of public, private, and academic research illustrating the vital role that higher ethanol blends play in protecting our air, our climate, and our health,” said Emily Skor, CEO of Growth Energy. “No other solution offers the same immediate benefits in the fight against particulate matter, carbon monoxide, and smog-forming pollutants linked to cancer, as well as neurological, cardiovascular, and reproductive damage. Drivers across the country are looking for better options at the pump, and E15 delivers the savings they need and the cleaner air they deserve. California has long been a leader on clean energy, but it has lagged behind most other states in expanding access to E15 fuel blends. Today’s report should serve as all the motivation CARB needs to accelerate biofuel adoption and fast-track progress on the state’s clean energy goals.”

Additional information is available on the CARB website.