Abstract: Waste oil on board ship is disposed of usefully by burning in the ship's steam raising boiler. Apparatus for rendering the waste oil burnable comprises a tank with waste oil and fuel oil and fuel oil inlets, a tank heater, a drain pipe and filter for separated water, an agitator, an external pipe and pump and pump for recirculation of waste oil and fuel oil through the turn and a bleed off pipe from the external pipe to the ship's boiler fuel supply line. Other liquid or finely powdered organic waste (e.g. kitchen waste) may also be disposed of in the system.