As far as I can tell the only way to make bulk ethanol without using up food crops is to use yard waste cellulosic ethanol. The only practical way to make ethanol from cellulose is to first break it down into glucose molecules so your yeast can eat it. The only way to do that that is energy effocient is to grind the cellulose into fine mush and mix it with clean water an cellulase enzymes.
http://www.worthington-biochem.com/cel/pl.html
The biggest hold up is the cellulase enzyme is flipping expensive! Sure it is an enzyme catalyst so with proper procedure you get 85% of it back from each cycle and can use it for the next cycle again. However even if your yard waste of grass clippings and leaves is free the energy to grind it and the cost of clean water and kilograms of cellulase per cycle are going to add up in a hurry. I have yet to see a rigorous breakdown of the costs where all the inputs are accounted for, almost all of them make assumptions that some chosen feedstock will be grown like switchgrass. This is done so that federal subsidies can be set up for the chosen winner, not as the most EROEI efficient choice.
Our system n America is now dependent on government approval and subsidy to function.