Ethanol is often cast as a cleaner fuel than gasoline, but how it is created can make actually make it a more polluting alternative--a conclusion recently confirmed by MIT researchers.
MIT on Monday published a press release detailing research meant to explore the nuances of an ongoing debate over the environmental benefits of ethanol. It was funded in part by BP America.
Overall, it found that current methods of making ethanol from corn consume about the same amount of fossil fuels as required for gasoline. Making ethanol from different sources, including corn stover (the corn plant and husks) and woody substances like switch grass, gives ethanol a "greener" profile, according to the researchers.
"The results show that everybody is basically correct. The energy balance is so close that the outcome depends on exactly how you define the problem." said Tiffany Groode, a graduate student in MIT's Department of Mechanical Engineering who did the research under the supervision of John Heywood, a professor of Mechanical Engineering.
Ethanol can be used in so-called flex fuel vehicles that run on both ethanol and gasoline. U.S. policy favors the production of ethanol because it can be produced domestically.
However, as ethanol production ramps up--spurred in part by incentives to replace gasoline additive MBTE with ethanol--there have been studies examining the overall environmental equation.
Several factors are in play including the amount of energy required for fertilizers, equipment and the amount of fuel required to drive a car (a tank of ethanol has less energy content than gas, MIT confirmed.)
Corn-based ethanol is valuable in that it can serve pave the way for cellulosic ethanol, which consumes less fossil fuel in its production, Groode concluded. Unlike corn-based ethanol, cellulosic ethanol production is relatively immature and not done at commercial scale.
"People can buy flexible-fuel vehicles right now and get used to the idea that ethanol or E85 works in their car. If ethanol is produced from a more environmentally friendly source in the future, we'll be ready for it," she said.