Evidence against corn ethanol has been accumulating in recent years. It takes a lot of energy to grow corn and to ferment the kernels to produce ethanol, and considerable amounts of greenhouse gases are produced in the process. Hill’s analysis suggests that corn ethanol could also create more health problems than gasoline.
However, Satish Joshi, an environmental economist at Michigan State University, who wasn’t involved in Hill’s study, says that he “wouldn’t rule out corn ethanol” yet: “It’s proven, well-established technology.” Although Joshi says that he’s pleased to see more evidence of the advantages of cellulosic ethanol, it’s a newer development, and there isn’t yet a way to produce it economically. Conversely, “corn has the longer history and the established manufacturing base … Cellulosic ethanol is still technologically unproven,” Joshi says.
Hill’s study compared three ways of making ethanol from corn–using natural gas, coal, or corn stover to generate heat at biorefineries–and four processes that produce cellulosic ethanol–from corn stover, switchgrass, prairie grasses, or Miscanthus, a tall perennial grass–and he says that the results show how much difference production methods can make in the overall impacts associated with fuels.
The impacts associated with fuels vary according to where the fuel is produced, Hill found. The health costs associated with airborne particles vary considerably, he says, depending on atmospheric conditions and population density.
“Maybe there’s a way to spatially locate production of biofuel to get maximal health benefits” out of a switch from gasoline, Hill says–something that he plans to investigate.
His analysis assumes, for the sake of simplicity, that the additional corn or other plant material needed to produce biofuel is grown on grasslands that are currently part of the U.S. Conservation Reserve Program. Hill says that in reality, increased biofuel production will likely encroach on land that’s now used to produce other crops, triggering a cascade of land-use changes. If rain forests in other countries are cleared to make way for crops, for example, the impacts in terms of climate change could negate the benefits of switching to biofuel to reduce greenhouse-gas emissions.
By taking into account the health consequences of fine particles, Hill looked at “one additional thing off a huge list” of possible effects that also include erosion, pesticide contamination, and petroleum spills”, says Soren Anderson, an assistant professor at Michigan State University, who focuses on biofuels as part of his research on energy and environmental economics. “That additional thing made clear that corn ethanol is actually worse than gasoline, and cellulosic ethanol looks to be better.”