First of all, ethanol is less efficient than gasoline. You get less mileage on it than a regular gas-burning car. It pollutes the environment indirectly. To produce ethanol requires more energy than producing oil. That translates into more emissions.
Most important, is world hunger. Ethanol is produced from food sources such as corn and sugarcane. This leaves less for the world to eat. And less for the farmers to feed to their livestock. That means that food prices would rise and stop us form helping those in need. The only economy would be if we would be able to make fuels from grass or wood chips, which is years away.
Most ethanol supporters say that ethanol can reduce our dependence on oil from the Middle East. Well there has been a study which has discovered that even if we transform ALL of America's corn into ethanol, they would still have to buy from the Middle East.
The planet can produce enough food to feed all of its people a European diet several times over, but the global food crisis persists due in a large part to such misplaced government priorities as the push for biofuels, a Netherlands-based doctor of economics said in Saskatoon Wednesday.http://www.montrealgazette.com/technology/environment/Biofuel+push+leads+world+hunger+economist+says/2238202/story.html
Obviously, ethanol solves none of our problems. It will only show promise once we discover how to transform grass of wood into this fuel. We should not subsidize nor support it.