Stanford Researchers: Ethanol Results in Higher Ozone Concentrations than Gasoline
by Louis Bergeron (Stanford University) Ethanol — often promoted as a clean-burning, renewable fuel that could help wean the nation from oil — would likely worsen health problems caused by ozone, compared with gasoline, especially in winter, according to a new study led by Stanford researchers.
E85, a blend of gasoline and ethanol that is 85 percent ethanol, produces different byproducts of combustion than gasoline and generates substantially more aldehydes, which are precursors to ozone.
Ozone production from both gasoline and E85, a blend of gasoline and ethanol that is 85 percent ethanol, is greater in warm sunny weather than during the cold weather and short days of winter, because heat and sunlight contribute to ozone formation. But E85 produces different byproducts of combustion than gasoline and generates substantially more aldehydes, which are precursors to ozone.
“What we found is that at the warmer temperatures, with E85, there is a slight increase in ozone compared to what gasoline would produce,” said Diana Ginnebaugh, a doctoral candidate in civil and environmental engineering, who worked on the study.
…But it was at colder temperatures, below freezing, that it appeared the health impacts of E85 would be felt most strongly. …The problem with cold weather emissions arises because the catalytic converters used on vehicles have to warm up before they reach full efficiency. So until they get warm, a larger proportion of pollutants escapes from the tailpipe into the air.