Even though biofuels release carbon dioxide (CO2) when burnt, the same amount of CO2 is reabsorbed as the next plant crop grows. For this reason, biofuels are widely considered an environmentally preferable alternative to fossil fuels. What has not been well understood, however, is whether it is better to convert crops to ethanol that can be burnt in conventional internal combustion engines or to burn the crops to generate electricity that can power electric vehicles.
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. They considered the energy consumed in producing the vehicles and fuels, as well as the energy produced by each technology, and found bioelectricity to be the clear winner. The team reported that cars would travel 81% farther on the energy in biofuels if it were first converted to electricity.
Powering an electric vehicle using crops also means that less CO2 would be released than with bioethanol-powered cars. Electric engines are far more efficient than are internal combustion engines, Campbell noted. “Even the best ethanol-producing technologies with hybrid engines aren’t enough to overcome this,” he told Science.
Still missing from consideration, however, are the cost differences between engine types and possible environmental effects, including air pollution and water use.
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