joerocker said:
I'm calling BS on this.
There is no way that ANY of these bio crops are going to give back 90% MORE energy than they consume TOTALLY to grow and convert to biodiesel...NO WAY!
You're absolutely right, based on conservation of mass and energy, but most of that energy is free (sunlight), so it probably doesn't figure into the calculations.
It's all a cost/benefit analysis anyway. Think of it this way: I take one soybean seed, plant it in my yard, don't water it, don't fertilize it, don't do anything besides put it in the ground and the only energy I've expended is bending over to plant it and I get a return in oil (seeds). (Not counting any energy used to get me the seed, but we have to start somewhere).
Now my total yield is pretty pathetic and I can choose to use machinery, fertilizer, irrigation, etc, BUT as soon as the yield benefits don't outstrip the costs, it's not in my best interests, but I might have to do that for scale anyway.
Keep in mind too that soy for biodiesel only has to be grown for one characteristic (oil content) vs. soy grown for animal or human consumption which needs to balance oil with other factors (protein levels, minerals, phytate, etc.)
