The farming practice is a different issue. It's gotten better since no-till became more common but the over-fertilizing is still there. E85 has less of a factor on corn prices and food prices. The biggest cost is still manufacturing and distribution of products. Farming is pretty unsteady in itself too, with recent weather being very unstable it's record drought one year then record rainfall the next. Growing corn for ethanol is still a much more efficient solution than building more gasoline refineries.
The amount of power in a gallon of E85 can be found
here, it's something like 65.5% of a gallon of gasoline and comes from the USDA's report. Figuring the fact that the worst flexfuel vehicles get 70% of their original mileage, E85 is about 5 points more efficient.
Fuel injection systems can adjust 20% from the factory. I found a good conversion guide
here.
Bascially converting to E85 is easier if you don't want the flexfuel. The adjustable injectors are an issue. I read through the entire turbobricks article and besides requiring a block heater or simply dumping fuel for cold startups the flexfuel injectors are a little harder to find. Getting 42% bigger injectors is easy with all the aftermarket performance parts out there. No change in the ECU required. But they'll run really rich/lean if you try to run a fuel mixture outside of the injector's range. Running injectors sized for E50 and carrying a little extra E85 to mix for fuel ups might work for those who want a little more room for filling up on gasoline.