Here is a news clipping from todays local paper. It highlights one of the problems of making diesel fuel from waste veggie oil.
http://www2.canada.com/comoxvalleyecho/news/story.html?id=0d4930f4-af70-4403-840d-c4a9027e8ea3 This guy spent money and time building the setup to convert WVO to biodiesel. Then he found out that every restaurant in town already has someone taking their old oil.
Moral of the story? Start stock piling and get your source worked out before you build the stuff to use it. I expect the restaurant owners will soon figure out they can charge for their old oil. I expect other energy from waste products ideas will go through the same thing. If you find one, make sure you tell people "how bad it is" (costly/dangerous). If you encourage them you may be cutting off your own supply... or at least raise the cost of it.