Switching from Ethanol to Gasoline Causes Ozone Levels to Drop 20 Percent in Four Years

Researchers found that the air quality in São Paulo, Brazil experienced significant improvement with a simple switch in fuels. With high ethanol prices affecting the city, vehicle owners switched to gasoline and helped ozone levels drop 20%.

An economist and chemist at Northwestern University conducted a four-year study that is the first real-world trial examining urban air pollution and the humans that contribute to it. Alberto Salvo and Franz M. Geiger of Northwestern gathered fuel sales data and 14,000 consumer surveys to conduct their study.

Published today in the journal Nature Geoscience, "Reduction in Local Ozone Levels in Urban São Paulo Due to a Shift from Ethanol to Gasoline Use," found that because of the world sugar price, ethanol (made from sugar cane) drastically increased in price in 2010 and 2011, prompting owners of flexible-fuel vehicles to switch to gasoline as their primary source of fuel.

According to the U.S. Environmental Protection Agency, "Ground level or 'bad' ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight," and it can be harmful to breathe. Such ozone levels decreased by 20% over the four-year study, but the researchers also found that nitric oxide and carbon monoxide concentrations increased.

For that reason, the researchers are continuing their study to look into how the concentration of other air pollutants is changing due to the switch in fuels. Between 2009 and 2011 gasoline-fueled vehicles jumped from 14% to 76%. Ethanol is considered the more environmentally friendly fuel option because it is made from renewable plant-based feedstocks, but Salvo and Geiger believe that effects of fuel usage depend on local atmospheric composition.

As they continue on their study, the researchers hope that their use of big data can help policymakers arrive at decisions that will help improve the environment. New energy sources will create new jobs and improve the air quality as long as they're applicable to the specific region.

"This work allows us to start thinking about the urban metabolism of Chicago, which is an emerging megacity surrounded by 'corn country,'" said Geiger in this EurekAlert! news release. "Ethanol from corn is a particularly intriguing option for future, possibly more competitive, energy markets. It's an area we need to watch."