No role seen for ethanol, MTBE in cutting smog
Ethanol, an oxygenate added to gasoline, does little to lower emissions of vehicle pollutants, according to a National Research Council report
May 13, 1999
Web posted at: 11:30 AM EDT
The National Research Council reported Tuesday that oxygen additives used in reformulated gasoline have had little to do with a decrease in the emission of smog-forming chemicals.
"Although additives do reduce some pollutants from motor vehicles emissions, the oxygenates appear to have little impact on lowering ozone levels," said committee chair William Chameides, regents professor of Earth and Atmospheric Sciences at the Georgia Institute of Technology, Atlanta.
"Moreover, it is not possible to attribute a significant portion of past reductions in smog to the use of these gasoline additives." Instead, credit for the reduction goes to better emissions control equipment and other, nonoxygen-additives to gasoline.
The National Research Council was asked to examine the differences between the additives ethanol and methyl tertiary-butyl ether, better-known as MTBE. The use of reformulated gasoline is required in certain states under amendments to the Clean Air Act of 1990 to lower emissions of vehicle pollutants.
However, the oxygen additives have raised environmental concerns. The state of California has decided to phase out the use of MTBE in its gasoline because it has contaminated the state's drinking water.
According to the study, Ozone-Forming Potential of Reformulated Gasoline, the influence of both MTBE and ethanol in lowering smog levels will continue to decrease as other measures to reduce vehicle emissions take effect.
Other effective measures include tougher air quality regulations and improvements to vehicles over the last few decades. New technologies could further decrease motor vehicle emissions in the coming years, according to the report.
Terry Wigglesworth, the executive director of the Oxygenated Fuels Association, said that the findings of the report are "completely at odds with a host of real-world findings compiled by state and federal environmental agencies."
According to Wigglesworth, the study admits that the use of reformulated gasoline can cause a decrease in both the exhaust and evaporative emissions from motor vehicles, including carbon monoxide. However, these findings are disregarded in the report's overall findings.
Eric Vaughn, president of the Renewable Fuels Association, said that the report falls short of answering critical questions regarding the benefits of oxygenates, such as a noted beneficial impact on emissions from higher emitting vehicles -- such as older cars.
"It is simply impossible to draw conclusions about the efficacy of oxygenates in reformulated gasoline without considering the dilution effect of oxygenates and the impact on air quality of the gasoline components that might be used to replace the large volume of octane lost if oxgenates were not used in reformulated gasoline," he said.
"As the NRC report did neither, its conclusions regarding the air quality impacts of oxygenates are unjustified," said Vaughn.
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