The U. S. government‘s Renewable Fuel Standard mandates that by 2022, the U. S. use 15 billion gallons of corn-based ethanol, 1 billion gallons of biodiesel, and 16 billion gallons of cellulosic fuels. A recent peer-reviewed report from the National Academy of Science prepared for Congress concludes that the goals for corn-based ethanol and biodiesel can be met, but those for cellulosic fuels are probably unreachable.
“The U. S. has more than 200 plants that convert corn into more than 14 billion gallons of ethanol and it took more than 30 years to get to this point,” says Wally Tyner, a professor of agricultural economics at Purdue and cochair of the committee that wrote the report. “We have only 11 years to reach even higher numbers for cellulosic biofuels. Therefore, to reach the goal, we would need to build refineries at three times the rate we built refineries for corn ethanol. And with corn, we had the technology, we had the feedstock, and prices for corn were relatively low. We don’t have any of that with cellulosic.”
For example, there are currently no refineries that can turn cellulosic feedstock into ethanol. And the amount farmers would have to be paid to earn a profit raising cellulosic materials is more than ethanol producers are willing to pay. There are also questions about the environmental effect of growing the needed materials because additional land would need to be put under cultivation, a process that releases greenhouse gases. According to Tyner, what it would take to meet the mandate is a major technological breakthrough, a substantial increase in the price of oil, or an increase in subsidies for cellulosic-ethanol producers.