Here is a recent summary article on a recent life cycle analysis (LCA) study comparing CO2 emissions associated with biofuels (e.g. corn ethanol) to CO2 emissions from gasoline:
http://phys.org/news/2016-08-biofuels-decrease-heat-trapping-carbon-dioxide.html
The full study was just published in the journal Climatic Change and is titled “Carbon balance effects of U.S. biofuel production and use”:
