I remember before the Iowa caucus for the 2008 election. As I recall, Obama came out big for corn ethanol. At the time, from other readings, it seemed the environment cost in fuel, fertilizer, processing etc were more than just using gasoline. Plus it takes land out of conservation lands and food production.
I don't know how the equation has changes since then. It seemed at the time like a calculate play for Iowa votes, and that was maintained until now. Maybe I'm just suspicious.