The "french frymobiles" as they are lovingly called are a good option. The hurdle has to do with some of the regulations dealing with "disposing" of the waste. Basically, if a union-controlled company can't "properly" dispose of it then it will be blocked for average Joe to get his hands on it in bulk. In general I have no problem with the restaurants making a few bucks off of selling their old oil. It is a legitimate commodity and there would be a legitimate market for it.

Remember, when Deisel invented his engine it was designed to run on vegetable oil. Ditto for Ford and his engine.