Today a fellow called who has a business using heavy equipment mentioned today that he gets around 4,000 gallons a month of used vegetable oil which he is able to add methanol and create fuel that runs in diesel engines at a couple bucks a gallon. It shows that even energy can be recycled! Though there is a layer of sludge filtered out from crispy pieces left (of food) they can be used as compost or possibly animal/sled dog feed.  BTU’s have many uses whether for heat, electricity or calories.