Ethanol is a fuel alternative to standard gasoline.  Primarily a corn derivative (though sugar cane is used in some countries), the ethanol product used to fuel vehicles is actually 85% ethanol and 15% gasoline.  Proponents point out that use of ethanol as compared to gasoline significantly reduces emissions of nitrogen oxides, carbon monoxide, total hydrocarbons and greenhouse gases.  While that sounds great, critics argue that there are other factors to consider including the energy and waste products from the actual corn production and processing required to make the ethanol.  The debate continue.