The debate is about to change in a big way. Corn ethanol is going to build out to about 12-15 billion gallons/yr. That much is in the pipeline now. There may be some growth beyond that as yields increase and/or more acreage shifts into corn, but the emerging story is cellulosic ethanol.
The first commercial scale cellulosic ethanol plants are being built now. If they can hit their projected price points, the buildout will begin in the next couple of years. What the feedstocks will be a decade from now is anyone's guess; there are hundreds of potential feedstocks being investigated, and all involved recognize that we have barely scratched the surface in terms of investigating the biosphere for candidates.
The conventional estimate is that we have the biomass potential right now to supply 30% of our transportation fuel needs from currently identified cellulosic feedstocks: mainly current farm and forest wastes and some recycling. That is without the development of dedicated energy crops. This is an open door. There is some neat stuff out there. In hand -- no, of course not. Yet.
But biofuels are clearly a live option as are, further down the road, electric cars and hydrogen fuel cells, singly or in combination. Lots of options.
Corn ethanol has a net of +25% gain in energy. Biofuels net 540% gain over production. Seems like a no-brainer. If I lose some money on GFET so what. Everthing else is going down anyway.
WMM
My money would be on white mustard. American agrarian soils can produce two crops per year of mustard versus one of corn and mustard’s volume planted:yield ratio is anywhere from 1:280 under worse conditions to 1:800 in better, normal yields - some have even been as high as 1:1200. In other words, for one bushel of mustard seed sown, it would yield 280 to 800 bushels of seed, some as much as 1200. Corn is 1:120 at best, 1:60 and below at worse.
Mustard (42% oil) also produces oil at ten times the amount expressed from corn (3.5-4.5% oil) and the extract is initially volatile, meaning less energy/effort would be required to produce an end product as fuel.
To sum it up, mustard has the potential to out produce corn for an energy source by 135 times. More produce on less land resources means more land left for foodstuff production.