Beginning in summer 2012, the prices of ethanol and corn reached levels where production costs at relatively simple ethanol plants exceeded revenue. These simple plants, which are not able to recover corn oil, make up a diminishing portion of the ethanol industry. Reacting to the market conditions, several ethanol plants temporarily shut down. By January 2013, the number of idled ethanol plants had grown to at least 20.
Source: U.S. Energy Information Administration, and U.S. Department of Agriculture