Ethanol and Air Quality: Influence of Fuel Ethanol Content on Emissions and Fuel Economy of Flexible Fuel Vehicles

by Carolyn P. Hubbard , James E. Anderson , and Timothy J. Wallington (Environmental Science and Technology) Engine-out and tailpipe emissions of NOx, CO, nonmethane hydrocarbons (NMHC), nonmethane organic gases (NMOG), total hydrocarbons (THC), methane, ethene, acetaldehyde, formaldehyde, ethanol, N2O, and NH3 from a 2006 model year Mercury Grand Marquis flexible fuel vehicle (FFV) operating on E0, E10, E20, E30, E40, E55, and E80 on a chassis dynamometer are reported. With increasing ethanol content in the fuel, the tailpipe emissions of ethanol, acetaldehyde, formaldehyde, methane, and ammonia increased; NOxand NMHC decreased; while CO, ethene, and N2O emissions were not discernibly affected. NMOG and THC emissions displayed a pronounced minimum with midlevel (E20–E40) ethanol blends; 25–35% lower than for E0 or E80. Emissions of NOx decreased by approximately 50% as the ethanol content increased from E0 to E30–E40, with no further decrease seen with E55 or E80. We demonstrate that emission trends from FFVs are explained by fuel chemistry and engine calibration effects. Fuel chemistry effects are fundamental in nature; the same trend of increased ethanol, acetaldehyde, formaldehyde, and CH4 emissions and decreased NMHC and benzene emissions are expected for all FFVs. Engine calibration effects are manufacturer and model specific; emission trends for NOx, THC, and NMOG will not be the same for all FFVs. Implications for air quality are discussed. READ MORE and MORE (Green Car Congress)

Excerpt from Green Car Congress: A team at Ford Motor Company’s Research and Innovation Center in Dearborn conducted a detailed study of the effect of ethanol blend level in emissions, using a 2006 model Mercury Grand Marquis flexible fuel vehicle (FFV) operating on E0, E10, E20, E30, E40, E55, and E80 on a chassis dynamometer. The study thus included the current predominant market fuel (E10); a range of possible future midlevel ethanol blends (E20−E40); and the new range for high-level ethanol blends (E55, E80).
The number of blends they studied is about twice that of previous studies, and delivers a more detailed picture of the effect of ethanol blend level on emissions. Further, they reported data for engine-out emissions and tailpipe emissions; operating temperatures (engine-out and catalyst); and ethanol concentrations used in the engine control strategy. Comparing these data allows for differentiation between fuel chemistry and engine calibration effects—the two general mechanisms by which increased ethanol content in fuel affects the emissions.
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Broadly, with increasing ethanol content in the fuel, they found that the tailpipe emissions of ethanol, acetaldehyde, formaldehyde, methane, and ammonia increased; NO_xand NMHC decreased; while CO, ethene, and N₂O emissions were not discernibly affected.
NMOG and THC emissions displayed a pronounced minimum with midlevel (E20–E40) ethanol blends; 25–35% lower than for E0 or E80. Emissions of NO_x decreased by approximately 50% as the ethanol content increased from E0 to E30–E40, with no further decrease seen with E55 or E80.
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