Biomass — plant matter that’s grown to generate energy — converted into electricity could result in 81% more transportation miles and 108% more emissions offsets than ethanol, according to U.S. researchers. In addition, the electricity option would be twice as effective at reducing greenhouse gas (GHG) emissions.
The study, published in the May 22 issue of the journal Science, was based on two criteria: square miles of cropland and GHG offsets per area (in square miles) of cropland. In both cases, scientists considered a range of feedstock crops (corn and switchgrass) and vehicle types (small car, midsize car, small SUV, and large SUV).
University of California Merced Assistant Professor Elliott Campbell, along with Christopher Field of the Carnegie Institution’s Department of Global Ecology and David Lobell of Stanford University, first looked at how many miles a range of vehicles powered by ethanol could travel versus a range of electric vehicles fueled by electricity. Second, they examined offsets to GHG emissions for ethanol and bioelectricity.
They also considered land use when evaluating each method, saying that globally, the amount of land available to grow biomass crops is limited. "Using existing croplands for biofuels could cause increases in food prices and clearing new land, or deforestation, can have a negative impact on the environment," they said in a statement.
The authors are careful to point out that their study did not examine the performance of electricity and ethanol or other policy-relevant criteria. "We also need to compare these options for other issues such as water consumption, air pollution, and economic costs," Campbell said.
The results suggest that investment in an ethanol infrastructure — even if the ethanol is derived from a more-efficient cellulosic process — may be misguided. In addition, the study notes that it would be possible to capture and store carbon dioxide emissions from biomass power plants — an option not available for ethanol.