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University of California Research Shows Emissions-Reducing Benefits of E15 Blend

June 7, 2023

E15, Environment, LCFS, Regulatory, State News


A newly released, peer-reviewed study from the University of California, Riverside, shows that the E15 ethanol blend provides notable emissions reductions compared to California’s regular reformulated gasoline. The Renewable Fuels Association hailed the report as proof of the value of E15 for The Golden State, which has yet to allow the E15 blend to be used.


“This new study shows what we’ve been arguing all along—that E15 offers emissions benefits that would help meet environmental goals in California, where the state’s 27 million drivers log more than 340 billion miles a year on the road,” RFA President and CEO Geoff Cooper said. “We continue to call on California’s regulators to move quickly to permit E15 to be sold in the state, a blend that also offers cost savings in a place where gasoline prices are higher than anywhere else in the country.” California is one of only two states that has not yet approved E15; Montana is the other.


According to the study, emissions of total hydrocarbons, non-methane hydrocarbons, and carbon monoxide all showed either marginally or statistically significant reductions for E15 compared to regular California gasoline. In addition, particulate matter (PM) and solid particle number emissions dropped substantially with E15, and E15 showed lifecycle greenhouse gas emissions savings when compared to E10. Nitrogen oxide (NOx) emissions when using E15 showed marginal reductions in many cases, but the changes in NOx were not statistically significant.


The research will appear in the October 2023 journal Fuel, and was supported by RFA, the California Air Resources Board and other organizations. Researchers noted that this is the largest U.S. study to date that focuses on the effects of ethanol fuels on tailpipe emissions from current technology vehicles.


Related LCFS Workshop Comments Submitted


Approval of E15 by the state also could help facilitate greater near-term carbon emissions reductions under California’s Low Carbon Fuel Standard, according to comments and analysis filed Tuesday by RFA in response to a workshop held late last month by California’s Air Resources Board.


In the comments, RFA Chief Economist Scott Richman suggested CARB “stepdown” its compliance curve with more stringent greenhouse gas reduction targets. RFA is working with a broad coalition of low-carbon fuel providers on a report to demonstrate the clean fuels industry’s capabilities to deliver more significant carbon intensity reductions.


“If E15 had been used in California in 2022 rather than E10, that alone would have allowed the LCFS compliance target to be nearly 2 percent lower. Migration of the market to E15 over the course of this decade would enable a 2.5 percent reduction of the current 2030 target against the 2010 baseline.”


Analysis accompanying the comment letter showed that using E15 instead of E10 in 2022 would have further reduced GHG emissions by 2.5 million metric tons and cut petroleum consumption by 500 million gallons. Because CARB has not yet approved E15, those additional GHG reductions are being left on the table.