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Testing the Potential of Mid-level Ethanol Blends

July 13, 2009

Are mid-level ethanol fuel blends a feasible solution for meeting U.S. renewable fuel goals? This question is driving a DOE-sponsored study to test the viability of using E15 and E20—gasoline blended with 15% and 20% ethanol—in conventional vehicles to meet the national renewable fuel standard (RFS) goal of 36 billion gallons per year by 2022. In light of projected growth in ethanol production and the new RFS, most experts agree that the existing E10 market will be saturated in the next few years. Given that reality, researchers from NREL and Oak Ridge National Laboratory (ORNL) are collaborating with industry leaders to evaluate the potential of using mid-level blends to meet the growing need for ethanol.

Keith Knoll, Senior Project Leader in the Fuels Performance group of NREL's Center for Transportation Technologies and Systems, recently led the effort in this test program and served as the principal author in the initial report on the research. The report, Effects of Intermediate Ethanol Blends on Legacy Vehicles and Small Non-Road Engines: Report 1-Updated (PDF 2.6 MB) describes the findings from the first stage of a comprehensive investigation into how E15 and E20 will affect emissions, performance, and mechanical durability of conventional automobiles and small engines.

The initial research focused on the impact of mid-level ethanol blends on vehicle and small engine emissions while testing 16 conventional, non-flex-fuel automobiles and 28 small engines typical of those used in lawn and garden equipment. Results showed that boosting ethanol content did not adversely affect regulated tailpipe emissions (hydrocarbons, nitrogen oxides and carbon monoxide), but did increase ethanol and acetaldehyde emissions. Results also showed that mid-level ethanol blends may not be compatible with some small non-road engines because of their less sophisticated control of air-fuel mixing. The study confirmed that adding ethanol to fuel leads to lower fuel economy because of the lower energy density of the fuel blend. In addition, for some vehicles, increased ethanol content increased the catalyst temperature during high-load operating conditions. Implications for catalyst durability are being investigated in a related, ongoing study.

"For ethanol, our long-range focus remains E85," explains Knoll. "But, E85 usage is restricted by distribution (existing stations equal approximately 1,600), and the limited number of flex-fuel vehicles. The data from this research will help provide policymakers with sound technical advice to evaluate the potential of mid-level blends in the marketplace."

Further studies in the test program include evaluating the impact of mid-level ethanol blends on emissions over the full useful life of vehicles, measuring evaporative emissions (which contribute to ozone formation), determining impacts on driveability and fuel specification standards, testing compatibility of fuel system materials, testing marine application engines, and validating small engine results found in the initial study.

This research is led and funded by DOE's Biomass and Vehicle Technologies Programs with technical support from NREL and ORNL. The team is working closely with representatives from the U.S. Environmental Protection Agency, U.S. auto manufacturers, engine companies, oil companies, and other organizations to develop and conduct a robust test program.

From a feature story in the NREL Now newsletter, July 2009.