I can't quie agree about the biofuel industry dying - to the extent that oil from rapeseed is used for tractors, for example, it is pretty much the same as feeding horses or oxen, except the tractors are able to perform much more work for considerably less input. Unless you wish to be as romantic as some of the original Greens in Germany, and believe that agriculture using farm animals is a viable way to feed people.

Of course, this is not the goal of the biofuel industry as such - and to be honest, pressing something like rapeseed for oil to use in farming doesn't actually require a biofuel industry either.

"[...] except the tractors are able to perform much more work for considerably less input."

Input of what? Input of man-hours? Agreed. Input of fossil fuels? I'm not so sure. In terms of work done for fuel fed, both are probably pretty inefficient. A horse or ox does have the distinct advantage that much of its fuel can be obtained from marginal land. When not working they can get all of their fuel from marginal land.

Certainly, I'm very curious about the Food Energy Return On Food Energy Input (FEROFEI) with bio-diesel tractors compared to draft animal power sources. My guess is that it would depend on what you're doing and how you do it.

I've done some plowing and harrowing behind a team of horses and it is slow going, but not a bad way to spend a morning if the weather is nice as it usually is in spring and fall plowing seasons.

Input of fossil fuels? I'm not so sure. In terms of work done for fuel fed, both are probably pretty inefficient. A horse or ox does have the distinct advantage that much of its fuel can be obtained from marginal land. When not working they can get all of their fuel from marginal land.

In terms of photon->work oil from fossil fuels is least efficient. Photons->pv->...-> work can be better than photon->plant->seedoil->work. Photon->plant->animal->work the conversion of plant to animal energy is poor value.

Marginal land is still taxed. Somehow your animal powered vision has to fit the present economic system.