From the Summary: "Ethanol plays a key role in policy discussions about energy, agriculture, taxes, and the environment. In the United States it is mostly made from corn; in other countries it is often made from cane sugar. Fuel ethanol is generally blended in gasoline to reduce emissions, increase octane, and extend gasoline stocks. Recent high oil and gasoline prices have led to increased interest in alternatives to petroleum fuels for transportation. Further, concerns over climate change have raised interest in developing fuels with lower fuel-cycle greenhouse-gas emissions. Supporters of ethanol argue that its use can lead to lower emissions of toxic and ozone-forming pollutants, and greenhouse gases, especially if higher-level blends are used. They further argue that ethanol use displaces petroleum imports, thus promoting energy security. Ethanol's detractors argue that various federal and state policies supporting ethanol distort the market and amount to corporate welfare for corn growers and ethanol producers. Further, they argue that the energy and chemical inputs needed to turn corn into ethanol actually increase emissions and energy consumption, although most recent studies have found modest energy and emissions benefits from ethanol use relative to gasoline. The market for fuel ethanol is heavily dependent on federal incentives and regulations. Ethanol production is encouraged by a federal tax credit of 51 cents per gallon. This incentive allows ethanol-which has historically been more expensive than conventional gasoline-to compete with gasoline and other blending components."
CRS Report for Congress, RL33290
National Agricultural Law Center http://www.nationalaglawcenter.org/crs/