From a working paper at the National Bureau of Economic Research

"The current US ethanol mandate requires that about 5 percent of world caloric production from corn, wheat, rice, and soybeans be used for ethanol generation. As a result, world food prices are predicted to increase by about 30 percent and global consumer surplus from food consumption is predicted to decrease by 155 billion dollars annually."

Harvard's Jeffrey Miron opines: "In other words, the mandate needs to generate at least $155 billion worth of annual benefits from reduced global warming to pass a cost-benefit test. Since ethanol use appears to increase GHG emissions, the mandate fails big time! Before the U.S. adopts costly new policies to reduce global warming, it should eliminate existing policies that contribute to global warming and make no sense from any other perspective."

My only problem with the post is this:

Since ethanol use appears to increase GHG emissions

For Corn and Soybean ethanol, this is quite possibly true. However, not so much with algae, kelp or waste sources of ethanol.

The issue is the Corn lobby got it's talons into energy legislation.