Ethanol is already carbon-neutral. You are putting CO2 back into the air THIS YEAR that was taken out of the air by corn THIS YEAR *(or close).

Burning fossil fuels puts CO2 into the air that was taken out millions of years ago.
Thus, it has a cummulative effect now, where fuel ethanol does not, and will not.

If you burn E85 all the time, one TerraPass should cancel out 6 years of driving!

-John