Search Here

A first-of-its-kind of analysis has reported that when residents of Sao Paulo, Brazil switched from ethanol to gasoline in their flexible-fuel vehicles, local ozone levels dropped 20 percent. The switch was driven by the fuel prices. 

According to the report, simultaneously nitric oxide and carbon monoxide concentrations tended to go up.  

The study is first real-world trial that looks at the effects of human behavior at the pump on urban air pollution. The four-year study might prove to be an important tool for studying other larger cities like Chicago, New York, London and Beijing. Up until now, researchers came to conclusions mainly through computer simulations of atmospheric chemical reactions based on tailpipe emissions studies. 

"Individuals often don't realize it, but in the aggregate, you can have a real impact on the environment," said Alberto Salvo, formerly with Northwestern's Kellogg School of Management and now an associate professor of economics at the National University of Singapore, in a press release. "In São Paulo, there were more than a million cars switching from ethanol to gasoline in the same season, and we found that ozone levels went down. We didn't expect this, but it is a precise result."

Researchers said it was the two episodes of high sugar prices in 2010 and again in 2011, where the price of ethanol increased, that provided perfect situation for their studies. 

"São Paulo was the place to do this initial study because consumers can and do switch between fuels for reasons unrelated to air quality, roads are gridlocked, and there is so much good data available to researchers," Salvo said.

"This work allows us to start thinking about the urban metabolism of Chicago, which is an emerging megacity surrounded by 'corn country,'" said chemist Franz M. Geiger who helped Salvo with the highly complex chemistry using statistical methods. "Ethanol from corn is a particularly intriguing option for future, possibly more competitive, energy markets. It's an area we need to watch."

The study will be published in the journal Nature Geoscience.