In the United States, almost all ethanol is made from corn. This means that the sugars in the corn must be fermented, distilled, and dehydrated in order to produce ethanol fuel (ethyl alcohol).

A major downside of producing corn ethanol is the amount of energy required: Ethanol made from corn returns only 25% more energy than is consumed to make it. ...

Basic chemistry dictates that gallon for gallon, burning ethanol produces only 2/3 as much energy as burning gasoline. ...

This means that the efficiency of E15, measured in miles per gallon, can never exceed 95% of the efficiency of regular gasoline. In actuality, it tends to be far lower. ...

Ethanol releases 19% more carbon dioxide than gasoline. For those who believe that human-produced carbon dioxide plays a role in global climate change, this is not a good statistic.

... Given the 21 pounds of corn required to produce one gallon of ethanol, that’s almost 2500 gallons of water used, not including water in the distillation stage. So when filling their gas tanks, most Americans now indirectly consume over 2500 gallons of water. ...

A careful look into the ethanol question in the US leaves one wondering why this trillion dollar industry even exists. Is it attributable to Crony Capitalism?

"Is it attributable to corny capitalism?" Yes. Thanks, Al Gore. Via Blighted harvest: The American corn ethanol disaster | Washington Times Communities.