Running vehicles on biofuels such as ethanol reduces CO2 emissions and offers a way to lessen the world's reliance on oil. While this sounds great from an environmental perspective, the energy required to produce the biofuel and the land clearing for crops that can result means biofuels aren't necessarily the environmentally friendly solution they initially appear to be. Recognizing this, researchers have analyzed the best way to maximize the "miles per acre" from biomass and discovered that the far more efficient option is to convert the biomass to electricity, rather than ethanol. Another tick for the electric car.
Writing in a recent online edition of Science, the researchers calculate that, compared to ethanol used for internal combustion engines, bioelectricity used for battery-powered vehicles would deliver an average of 80% more miles of transportation per acre of crops, while also providing double the greenhouse gas offsets to mitigate climate change.
The researchers performed a life-cycle analysis of both bioelectricity and ethanol technologies, taking 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 in the transportation-miles-per-acre comparison, regardless of whether the energy was produced from corn or from switchgrass, a cellulose-based energy crop. For example, a small SUV powered by bioelectricity could travel nearly 14,000 highway miles on the net energy produced from an acre of switchgrass, while a comparable internal combustion vehicle could only travel about 9,000 miles on the highway.
Bioelectricity also offers more possibilities for reducing greenhouse gas emissions through measures such as carbon capture and sequestration, which could be implemented at biomass power stations, but not individual internal combustion vehicles.
Lead author of the study, Elliott Campbell of the University of California, Merced, says, "there is a big strategic decision our country and others are making: whether to encourage development of vehicles that run on ethanol or electricity. Studies like ours could be used to ensure that the alternative energy pathways we chose will provide the most transportation energy and the least climate change impacts."