While the use of ethanol as an automobile fuel additive improves air quality by reducing hydrocarbon and carbon monoxide emissions, it also increases the release of certain other pollutants, according to research by scientists at the U.S. Department of Energy's Argonne National Laboratory
A recent field study in Albuquerque, N.M., published this month in Environmental Science & Technology, showed that use of ethanol fuels leads to increased levels of toxins called aldehydes and peroxyacyl nitrates (PAN).
Aldehydes are much more reactive in the atmosphere than the alcohols they are made from. They react with other chemicals in urban atmospheres to set off chemical reactions leading to PAN.
Argonne scientists have found that once created, PAN can last for many days in the air if the conditions -- especially temperature -- are right. When it's cold, its lifetime is longer.
PAN is highly toxic to plants and is a powerful eye irritant. It has been measured in many areas of the world, indicating that it can be carried by winds throughout the globe.
"Although these pollutants are not currently regulated," said Argonne chemist Jeff Gaffney, "their potential health and environmental effects should be considered in determining the impact of alternative fuels on air quality."
Albuquerque was chosen as a field study site because it is currently required by federal regulations to use ethanol-gasoline fuel blends and to ban wood-burning in order to maintain air quality during the winter months. More than 99 per cent of the vehicles in the area use blended fuels containing 10 percent alcohol in the winter, while blended fuel use declines substantially during the summer. This pattern made Albuquerque an ideal site for studying the urban and downwind effects of alternative fuel use, Gaffney said.
Atmospheric concentrations of ozone, oxides of nitrogen, carbon monoxide, PAN, aldehydes and organic acids were measured in the summer of 1993, before the use of ethanol fuels, and in the winters of 1994 and 1995, when 10 percent ethanol fuel was in use.
"I am not against alternative fuels," Gaffney said. " I am for understanding all the problems and for creating engineering solutions to them."
The study was funded by the Department of Energy's National Renewable Energy Laboratory, Alternative Fuels Utilization Program.
With more than 200 different research programs in basic and applied science, Argonne is one of the nation's largest federally funded scientific laboratories. Argonne is operated by the University of Chicago as part of the Department of Energy's national laboratory system.
Journal
Environmental Science & Technology