Having lived in So Paulo, Salvo realized the city offered the best possible "natural laboratory" -- a real-life situation as opposed to hypothetical -- to study consumer behavior and its impact on air quality using big data. The air-monitoring network in the megacity is superb, and the weather is moderate, with temperatures fluctuating little throughout the year.
During two episodes of high sugar prices in 2010 and again in 2011, the price of ethanol increased, causing consumers to switch their fuel usage to gasoline. (Brazil is a big producer of sugar, and the country's ethanol is made from sugar cane.) These two episodes provided the perfect situation for Salvo and Geiger's study.
"So 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.
So Paulo has the world's largest flexible-fuel vehicle fleet, with cars that can run on all gasoline, all ethanol or some mix of the two. Gasoline prices in Brazil are controlled by the government, and the domestic sugar price -- and therefore the domestic price of ethanol -- is determined by the world sugar price.
Scientific studies using big data can help take policymakers a long way in figuring out how to mitigate air pollution given local conditions, the researchers said. Effects of fuel usage will depend on local atmospheric composition, such as fine particle pollutants.
"Ozone and nitric oxide are both contributors to urban smog, so depending on how well a city is able to mitigate air pollution, ethanol may not be the 'green fuel' that it is often called," said Geiger, professor of chemistry in the Weinberg College of Arts and Sciences. He and Salvo are now analyzing how the concentration of other air pollutants in So Paulo, specifically fine particles, change in response to the choices of motorists in
|Contact: Megan Fellman|