A study by a team from UC Riverside has assessed the potential of increasing ethanol content in California reformulated gasoline (CaRFG) by investigating the exhaust emissions from a fleet of 20 Tier 3 light-duty vehicles. A baseline CaRFG E10 (10% ethanol by volume) fuel was splash-blended with denatured ethanol to create an E15 fuel. Each vehicle/fuel combination was then exercised over triplicate Federal Test Procedure (FTP) cycles on a chassis dynamometer.

The team noted that this is the largest study to date in the US focusing on the effects of ethanol fuels on tailpipe emissions from current technology vehicles.

In a paper published in the journal Fuel, the team reported:

• No statistically significant fuel effect on nitrogen oxide (NO_x) emissions for E15.

• Total hydrocarbons (THC), non-methane hydrocarbons (NMHC), and carbon monoxide (CO) showed either marginally or statistically significant reductions for E15.

• Acetaldehyde and ethanol emissions responded strongly with ethanol across the fleet of 20 vehicles.

• Formaldehyde emissions did not show a statistically significant effect.

• Particulate matter (PM) and solid particle number emissions were positively impacted by ethanol, exhibiting statistically significant reductions.

• Monoaromatic species and 1,3-butadiene showed mixed results, with ethylbenzene and the xylene isomers showing strong fuel differences.

• Although no strong differences were found for carbon dioxide (CO₂) emissions, E15 showed lifecycle greenhouse gas (GHG) emissions savings when compared to E10.

In California, gasoline is currently blended with up to 10% ethanol by volume, which is the maximum ethanol content allowed by California gasoline regulations.

The Renewable Fuels Association—which was one of the supporters of the study —hailed the report as proof of the value of E15 for California.

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. 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.

—RFA President and CEO Geoff Cooper

California is one of only two states that has not yet approved E15; Montana is the other.

This work was supported by the California Air Resources Board, Renewable Fuels Association, Growth Energy, National Corn Growers Association, and the United States Council for Automotive Research (USCAR).

Resources

• Tianbo Tang, Cavan McCaffery, Tianyi Ma, Peng Hao, Thomas D. Durbin, Kent C. Johnson, Georgios Karavalakis (2023) “Expanding the ethanol blend wall in California: Emissions comparison between E10 and E15,” Fuel, Volume 350 doi: 10.1016/j.fuel.2023.128836.