A cogeneration process and system which provides for the reclamation of a grease fuel from a concentrated grease trap pumping waste stream and the use of said grease fuel in a compression ignition reciprocating engine for the production of electric power. The concentrated grease trap pumpings are heated and mixed in the first stage of the process to ensure all grease is liquefied. This warm mixed stream is then separated by centrifuge into a heavy stream consisting of water and sediments and an oil-rich stream consisting of oil, grease/water emulsion and residual water. This oil-rich mixture is heated sufficiently to evaporate the residual water as well as the water of emulsion yielding a water free grease fuel suitable for use in the compression ignition engine. Heat energy for grease liquefaction and emulsion breaking is supplied by an engine jacket water cooling circuit and an exhaust heat recovery, respectively.