I have not yet run biofuel, and probably won't. I enjoy the hell out of my 2006 Duramax Chevy Express 2500. It tows what I need it to, and currently, diesel is cheaper than gas (here in Phoenix, anyway).
I love the idea of biodiesel;...however,...the technology in fuel delivery and injectors that has been responsible since 2003 for the great performance gains we now enjoy,...preclude most biodiesel use. Older injection tech was more compatible because it operated at lower psi than current injectors. Biodiesel is thicker and harder to spit at higher psi in the newer injectors. If you don't mind the older engines,...biodiesel is indeed still in the cards for you. The 7.3 Powerstrokes from Ford (1995-2003) were the most recent and yet still powerful motors available in a van that were able to be modified to run on BLENDED biodiesel (usually 20% waste oil). To run a motor on simply pure "greasil" (purified waste oil) only, you would have to go back to the pre-Powerstroke 7.3 IDI motor, which ended production in 1994. The Chevy 6.5 pre-Duramax motors will also run straight waste oil or bio-blend.
The good news is that the older diesel motors that can work well with waste oil are actually much less complicated to work on and cost less both to acquire and to service. The bad news, however, is that they just can't compete with the newer diesel motors and their high-psi in the performance department. Although in my opinion, the 7.3 Powerstroke comes closest and would be the best choice if horsepower numbers are important.