In 2009, the US expects 33% of the corn it produces will go to biofuels. The FT:
In Chicago, spot corn hit a record high of $6.43 a bushel and corn for delivery next year – by which time the US forecasts that about 33 per cent of its corn crop will be consumed by the biofuels industry – hit a high of $6.97 a bushel.
Given how much corn the US Midwest grows, that strikes me as a lot.
Update: Economics of contempt -- in a comment -- argues that the US biofuels industry is set to consume at least 13% of global corn production.