NOVELTY - The aerobic decomposition tank comprises a decomposition tub equipped with an inlet pipe and a closed storage reactor, a drive motor including a pump and supernatant discharge tube that is equipped in a lower part of the tub and discharges the supernatant to a suction duct connected in a lower end portion of the tub, a feeding line and an aeration pipe positioned in the lower end of the decomposition tub, a pipe adapted to supply oxygen to the decomposition bath and installed in the inlet pipe of the tub, and a diffusing element formed at a terminal upper side of the aeration pipe.    USE - The aerobic decomposition tank for manufacturing liquid fertilizer using food supernatant (claimed).    ADVANTAGE - The aerobic decomposition tub is capable of rapidly producing liquid fertilizer without the generation of environmental contamination and oil and food waste and without using chemicals.    DETAILED DESCRIPTION - The aerobic decomposition tank comprises a decomposition tub equipped with an inlet pipe and a closed storage reactor, a drive motor including a pump and supernatant discharge tube that is equipped in a lower part of the tub and discharges the supernatant to a suction duct connected in a lower end portion of the tub, a feeding line and an aeration pipe positioned in the lower end of the decomposition tub, a pipe adapted to supply oxygen to the decomposition bath and installed in the inlet pipe of the tub, and a diffusing element formed at a terminal upper side of the aeration pipe and the oxygen supply pipe. The diffusing element includes a diffusing plate, a vertical rod placed in top center of the diffusing plate, a guide tube for fixing the vertical rod with a holding fixture while covering the outside of combined vertical rod. A discharge pipe is equipped on the supernatant discharge tube between the aeration pipe and the feeding line and is arranged for transferring the processing water to the storage tank. A branch pipe is connected on the oxygen supply pipe. First to sixth opening/closing valves are positioned on the supernatant suction duct of the decomposition bath, feeding line, aeration pipe, oxygen supply pipe, discharge pipe and branch pipe.