Most every restaurant has a deep fat fryer... Those fryers can only use the fat for a few days, then the restaurants have to get rid of it. (companies charge restaurants to come and pick-up the fat...)
For more than a year James Peret worked 80 hour weeks building a self contained "grease refinery" that would use the fat to power a generator that would help cut the costs for electricity and heating...
Last December the first installation of the "Vegawatt" went into a seafood restarant. 10 to 12 gallons of used fat is poured into the device every day, where the fat goes through a multi-stage filtration system.
The system then uses the filtered grease to run a 15 horsepower diesel generator that provides 5,000 watts of power AND the heat from the exhaust heats water for the restaurant... The savings are a little over $1,000 per month and the restaurant no longer pays to have the fat hauled off (PLUS there are the benefits of "recycling" that help provide a cleaner environment...)