And idea my nephew and I had. The great thing about bio-diesel is that it is lower in all kinds of environmental contaminants and is a recycle of used oil. Now there is a lot of oil in use at restaurants.
Why not place some 55 gallon drums at each restaurant, enough for a weeks production. Don't charge them for the collection though maybe a small fee to cover the cost of the drums, and penalties if non-oils are placed in the drums. Then collect it, using a tank truck with a pump system so you don't have to lift the several hundred pounds of oil all at once.
Have a gas station at the front of the refinery and hold tours of the refinery for PR and other exposure. Having decals and bumper stickers to give away for free would help too.
With gas over $2.00 it should be close to making bio-diesel worth doing.