The Science Magazine podcast discusses the impacts of land use changes that occur when existing cropland is converted to biofuel production. The research team found that this form of land use change leads to higher, not lower, greenhouse gas emissions than those produced by using oil.
As a result of such concerns from using cropland for biofuels, there has been much political effort to move away from corn-based ethanol (which made up 99% of ethanol feedstock in 2007) toward cellulosic. Cellulosic ethanol is derived from non-food crops, such as corn stover (stalks and leaves left over after harvesting corn) and grasses. Environmental benefits of cellulosic ethanol crops are that they require significantly less energy and water to grow and harvest and, equally importantly, grasses can be grown on marginal lands that could not support food crops.
Meanwhile, corn-based ethanol continues to aggravate environmental and social/political issues. Converting cropland to biofuel production decreases the supply of corn for consumption, which, because corn is used in everything from cattle feed to corn syrup, raises prices of human food. Corn is one of the most energy-intensive crops, so its "ecofootprint" is significantly higher than for most other renewable energies. Corn also requires heavy pesticide and fertilizer use; as we now know, this is one of the leading causes of the Dead Zone in the Gulf of Mexico.
And yet… corn-based ethanol currently receives more than 75% of all federal tax credits and 2/3 of federal subsidies allocated to renewable energy sources. Corn has a stranglehold on renewable energy production. Midwestern farmers don't want to switch to cellulosic because of the high upfront costs required, as well as the fact that infrastructure for cellulosic refineries is not yet fully developed. Petroleum companies don't want the government to encourage/subsidize any liquid fuel other than oil.
But Americans are calling for domestic energy production and energy security, and the government has begun to take action. Iowa currently dominates domestic corn production, as well as corn-based ethanol production (29% of the total), but federal funding was granted in 2007 for the construction of the first commercial-scale cellulosic ethanol plant to be completed in Emmetsburg, IA, by 2011. In 2008, the Farm Bill was revised to cut subsidies for corn-based ethanol from $0.51 to $0.45 per gallon, and created a new subsidy for cellulosic ethanol production of $1.01. The Farm Bill passed despite being twice-vetoed by President George W. Bush. As the U.S. amplifies efforts to cut greenhouse gas emissions, this transition from corn-based to cellulosic ethanol becomes more urgent. Cellulosic ethanol offers environmental, social, and political benefits that corn-based ethanol cannot.
[Sources: “Agriculture-Based Renewable Energy Production.” CRS Report for Congress. 16 Oct. 2007. ; “Ethanol and Biofuels: Agriculture, Infrastructure, and Market Constraints Related to Expanded Production.” CRS Reports for Congress. 16 Mar. 2007. ]