The San Francisco Bay Area and Northern California has thousands of restaurants who end up with massive amounts of used fats, cooking oil, and grease (F.O.G.) from their fryers. In the past Restaurateurs paid to remove this FOG from their establishments, but now-a-days, there are many companies competing to collect this valuable commodity and pay the restaurateurs cold hard cash for the privilege.
Used cooking oil is a valuable resource for the BioFuels industry, where it is most often converted to BioDiesel through a chemical process called trans esterfication. Old cooking oil is filtered, dried to remove water, and then heated and combined with a catalyst, separated into glycerine, and BioDiesel, washed and dried, and then used in Diesel Vehicles for fuel. This is perhaps the best use of fats, oils, and grease, since the old cooking oil is removed from the food chain.
Other uses for used restaurant fryer oil is for animal fattening in feed lots just before slaughter. The animals are fed a potent mixer of rendered animals, and fats and corn for increased caloric intake. This feed is actually toxic to the animals if they are fed it for an extended period. Also, you have to wonder about the effects on animal fed food made from it’s own kind, and being fed something no longer considered fit for human consumption. I think used cooking oil is best used locally as biodiesel feed stock.