Hi Dano.
I'm a bit pissed to give sensible advice at the mo, but here's my (slowly typed) best effort.
Bio-diesel produced to the relevent Euro standard (forgot the number) should work in any diesel engine. The only problem is that most manufacturers void the warranty at >5% blend with fossil diesel (wankers), so best use an old van with no warranty left.
I know a couple of manufacturers that supply it but a google search should find your nearest source. The debate on energy-crop vs recycled bio is long & best left to the sober - but I WILL say that recycled is what you should go for.
Home-made bio diesel can sometimes have an excess of methanol which can rot natural-rubber engine components. It IS possible to use a home-made less-refined bio-diesel too, but that requires a hefty fuel-pump. I hear that BMW's are good for this, but best leave it to the owner to decide.
I think that I'm gonna set a world record for the greatest number of hyphens in a post here
It could be a pretty neat publicity thing to collect all the used frying oil from the caterers & refine that on site. It can be done with an old paladin-bin, a heating element, a stirer & some other bits & bobs. Not sure if the caterers would produce enough oil to make this worthwhile though. ANd operating kit that uses methanol, NaOH, hot stuff, flammable stuff & electricity is probably left to those who aren't fully availing themselves of the delights on offer at a good festy
I will spout some more bollox when sober if you really want me to
