Since the creation of the domestic market for corn ethanol after the energy crisis of the 1970s, the federal government has nurtured and maintained the ethanol industry with a steady stream of subsidies. Originally sold as a way to achieve energy independence and reduce greenhouse gas emissions, ethanol has been a favorite of many lawmakers: ethanol producers have received favorable treatment under the tax code, tariff protection from foreign competition, and even a government mandate for its use. As a result, taxpayers have spent tens of billions of dollars over the last 30 years subsidizing the production of corn ethanol, while at the same time creating unintended costs for consumers and the environment.
https://www.taxpayer.net/energy-natural-resources/federal-subsidies-corn-ethanol-corn-based-biofuels/