George Will has attacked biofuel mandates and subsidies in his Newsweek column. Here's one particularly interesting passage:
James and Stephen Eaves, writing in Regulation quarterly, note that if the entire U.S. corn crop were turned into ethanol— it might have to be to meet the goal of 35 billion gallons of biofuels by 2017—it would displace 3.5 percent of gasoline use, just slightly more than would be displaced if drivers properly inflated their tires. And because the United States produces 40 percent of the world's corn supply and 70 percent of global corn exports, turning corn into fuel will damage the world's poor at a time when rising demand will require a tripling of world food production by 2050.
Will doesn't mention cellulosic ethanol, but I take it that he either doesn't think its development will affect the situation much or that its development won't pan out.