The idea behind is less pollution, however

 CH3CH2OH is less C% thank octane C8H18. The energy density is less. Like Brazil, which grows enormous sugar cane and produce lot of ethanol. It makes sense by using ethanol engine. While in US, ethanol are main from corn, the processing burns lot of energy too. Promoting ethanol(Obama did) is simply giving subsidize to middle west states and "green energy " propaganda