Seen at the Infopop forum:

"I also find it highly likely that in the big picture with all things taken into account, ( energy input, pollution etc, )commercial Biodiesel produced here, if not most everywhere, is probably less beneficial than burning straight Diesel and being done with it.

If you've seen both a petroleum refinery and a biodiesel plant, then you're laughing at this question. And while the land use argument (food versus fuel) is a really good one against certain types of biofuels, it doesn't change the facts regarding renewability, energy balance, and emissions, all of which dramatically favor biodiesel.