Biofuels work better if you don't put them directly into your car. That's the conclusion of a new study that shows that ethanol derived from corn and switchgrass allows cars to drive farther and emit less greenhouse gases if these crops are converted to electricity for powering electric vehicles rather than pouring the ethanol into the gas tank.
Biofuels are widely considered a better environmental alternative than fossil fuels. Even though they release carbon dioxide (CO2) when burned, the same amount of CO2 is reabsorbed as the next crop of plants grows. What hasn't been well-understood is whether it's better to convert crops to ethanol that can be burned in conventional internal combustion engines or to burn the crops to generate electricity that can power electric vehicles.
To find out, Elliott Campbell, an environmental engineer at the University of California, Merced, and his colleagues carried out a life-cycle analysis of bioethanol and bioelectric technologies. The analysis took into account not only the energy produced by each technology but also the energy consumed in producing the vehicles and fuels.
Bioelectricity was the clear winner. Cars would travel 81% farther on the energy in biofuels if it were first converted to electricity, the team reported today in Science. Powering an electric vehicle using crops would also prevent the release of up to 10 tons of CO2 per acre compared with a similar sized gasoline-powered car. That "offset" of unreleased CO2 is roughly double that of bioethanol-powered cars. According to Campbell, the primary reason bioelectricity came out looking so much better is that electric engines are far more efficient than are internal combustion engines. "Even the best ethanol-producing technologies with hybrid engines aren't enough to overcome this," he says.
"It really is an important paper," says Jason Hill, a bioenergy economist at the University of Minnesota, Twin Cities. But Hill cautions that the new analysis doesn't take all of the issues into account. Still missing from consideration are the cost differences between electric vehicles and those with internal combustion engines, as well as other possible environmental effects of biofuel technology such as increased air pollution and water use.