Results on exhaust emissions from E15 released by CARB

The California Air Resources Board (CARB) has released the results of a multiyear study evaluating exhaust emissions from the use of California Reformulated Gasoline (CaRFG) that contains 15 volume percent ethanol (E15).

The study was performed by a team from the University of California at Riverside (UCR) Bourns College of Engineering – Center for Environmental Research and Technology (CE-CERT).

California currently limits the ethanol content of gasoline to 10 percent. The Multimedia Evaluation (MME) of E15 looked at the effects of increased ethanol content on exhaust emissions in 20 vehicles—all model year 2016 or newer.

The study used two fuels – an E10 and E15. The summer-grade E10 fuel was sourced from four different refineries that were selected by CARB. The E10 fuels were blended together in four equal parts to create the final E10 fuel. The E15 fuel was created by splash-blending denatured ASTM D4806 fuel grade ethanol with the final E10 fuel.

The twenty light-duty gasoline vehicles included a mixture of technologies, such as gasoline direct injection (GDI), port fuel injection (PFI) as well as PFI+GDI fuel systems that are representative of the current California gasoline fleet. One hybrid electric vehicle (HEV) equipped with a PFI engine was also used. The vehicle test matrix had provisions for five vehicles on each emissions standards category (i.e., SULEV30, ULEV50, ULEV70, and ULEV125).

Measured emissions included: 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 test fleet showed statistically significant effects for some pollutants, but not for others. NOx emissions, a target pollutant of concern for this program, did not show any statistically significant difference between the fuels for the FTP nor for each individual FTP phase.