For anyone interested in whether corn ethanol really makes sense from either a scientific or economic standpoint, I highly recommend the scholarly paper "Information Distortion and Competitive Remedies in Government Transfer Programs: The Case of Ethanol" by economists Dr. Ronald Johnson of Montana State University and Dr. Gary Libecap of the University of Arizona. Be warned that this document is 53 pages, but it is worth the effort (it is a pdf file which will require Adobe Acrobat).In a nutshell, they argue that the the primary function of corn ethanol is to deliver subsidies to corn producers in a way that doesn't attract the intense negative publicity that direct deficiency payments do. They refer to this as the 'masking of the transfer'; the transfer they are referring to is the transfer of tax dollars to corn producers. To achieve this, the benefits of ethanol, both as a renewable energy resource and as a clean burning fuel, have been deliberately and grossly exaggerated by politicians and politicized agencies such as the USDA and the EPA to sell it to the public. These claims go mostly unchallenged because there are essentially no stake holders who have enough to gain by opposing these powerful foes.
In 1986, the USDA issued a study to address the question of whether a positive trade-off existed between price support program costs and the ethanol subsidy. It concluded "[i]f the principle argument for subsidizing ethanol is to boost farm income, we conclude from this analysis that it would be more economical to burn straight gasoline in our automobiles and pay corn growers a direct subsidy equal to the amount they would receive as a result of ethanol production". The rewards for such honesty were immediate demands by the ethanol industry that the Secretary of Agriculture fire the person responsible for the report, Earle Gavett, then Director of the USDA's Office of Energy. Legislation was then passed, under the direction of Senator Robert Dole, that in the future would dilute the input of USDA researchers into such reports with ethanol industry representatives' input. The USDA had learned it lesson about the rewards of honesty; once burnt, twice shy. For more details, see Section C. Information Obfuscation in the Absence of Competing Interest Groups: 1978-1986 in Johnson and Libecap's paper.
A popular and less technical paper describing the corporate role in corn ethanol is the 1995 paper "Archer Daniels Midland: A Case Study in Corporate Welfare", by James Bovard from the Cato Institute.