The study, "A Life-Cycle Analysis of the Greenhouse Gas Emissions of Corn-based Ethanol," which was released Jan 12, said GHG emissions from corn ethanol will be almost 50 percent lower than gasoline in 2022 if current trends in the industry continue.  

At present, the study said corn ethanol's GHG emissions are 43 percent lower than gasoline. 

The study said the current low emissions from ethanol are a result of farmers producing corn more efficiently and using conservation practices to reduce GHG emissions such as reduced tillage, cover crops and improved nitrogen management. 

It added that previous concerns of converting grasslands and forests for corn production have been unfounded as "primary land use change response of the world's farmers to rising commodity prices has been to use available land resources more efficiently rather than to expand the amount of land used for farming."

Corn ethanol's GHG emissions could decrease to 50 percent of gasoline in 2022, the study said, if ethanol producers switch their process fuel to natural gas, current trends in corn yields per acre continue and fuel efficiency in trucking improves.

In fact, the study said, GHG emissions from corn ethanol could be 76 percent lower than gasoline if ethanol producers switched their process fuel to biomass, contracted farmers to reduce tillage and manage nitrogen applications and locate confined livestock operations close to refineries. 

You can read the study here