Pros

Greenhouse Gas Reduction - Corn-based ethanol reduces GHG emissions by 18% to 29% per vehicle mile traveled compared to petroleum-based fuels.

Positive Net Energy Balance - Corn-based ethanol has a positive net energy balance of 1.06btu per gallon for 1.00btu of energy used without ethanol by-product credits. With these credits, for things such as DDGS, corn-based ethanol has a positive net energy balance of 1.67btu per gallon for 1.00btu of energy used.

Biodegradable - As ethanol is made with organic materials it is highly biodegradable making spills far less worrysome than petroleum spills. When spilled, 74% of ethanol is broken down within 5 days.

Usable By-Products - The two chief by-products of corn-based ethanol are CO2 and DDGS, both of which are usable in other industries. The CO2 can be captured for use in the food and beverage industry. DDGS can be used for cattle feed or further crushed to extract corn oil, for food or biodiesel production uses.

Most Infrastructure In-place - There are few changes that would need to be made to widely adopt ethanol. Most automobiles available in the U.S. are Flex Fuel capable and there are roughly 2,000 stations already serving E85. While most of these stations are lumped in the Midwest, they are increasing nationwide.

Cons

Food vs. Fuel - 2.4 to 2.8 gallons of ethanol can be produced per bushel of corn. As a result, there has been massive media coverage over the use of food as fuel. While there are mountains of findings showing how the use of corn has increased food costs and equal amounts showing it does not, in the end food crops are being used as fuel, making corn-based ethanol inferior to cellulosic ethanol in this regard.

Reduced MPG - Based on 2009 flex fuel vehicles, E85 miles per gallon is expected to be roughly 28.5% lower in the city and 26.5% lower on the highway. This means it takes 1.35 to 1.40 gallons of E85 to equal the mileage of 1.00 gallons of gasoline.

Fuel Transportation - Ethanol absorbs water and is corrosive, which make it difficult to ship through existing pipelines from the Midwest of the U.S., where most production occurs. Remedies include shipping or building dedicated ethanol pipelines, however the most likely scenario seems to involve rail or road transport. The best scenario would be local ethanol plants, with the easiest way to accomplish this through continued development of cellulosic ethanol, where feedstocks are abundant everywhere as opposed to corn or sugar.

Water Absorbtion - Ethanol absorbs water, which can contaminate it as a fuel and makes it more difficult to ship through pipelines. As a result, ethanol has a shorter shelf and tank life than gasoline.

Fueling Locations - There are roughly 2,000 E85 fueling stations in the U.S., with the majority in Illinois, Indiana, Iowa, Minnesota and Wisconsin. A U.S. E85 fueling station map and locator can be found here.