Corn ethanol production is positive 2.3 BTU
 

This link: http://agprofessional.com/show_story.php?id=1124133
details the positive energy efficiency the industry has developed into.

"This report measures all conventional fossil fuel energy used in the production of 1 gallon of corn ethanol. For every British Thermal Unit (BTU) unit of energy required to make ethanol, 2.3 BTUs of energy are produced".

Future gains are expected.