TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The biodegradable plastic, which is a contaminant in organic-refuse state waste material is pulverized in a wet grinding mill, and classified . Recirculation of the plastic is carried out into the circulation flow path until required particle size of plastic is attained. The average particle size of the pulverized plastic is approximately 1 mm. The pulverized plastic is cooled with a cooler in the circulation flow path. The plastic is decomposed with alkali, preferably ammonia, neutralized and mixed with organic metallic slurry. The energy required for pulverization is provided by transduction of biogas generated during methane fermentation.Preferred Apparatus: The grinding apparatus has bath injected with biodegradable plastic, wet grinding mill with transportation function connected to bath, and circulation flow path connecting the exit of the grinder and bath through switching valve apparatus. The processing system has coarse crusher (2) for rough grinding and for supplying biodegradable plastic into grinding apparatus, at the wet grinding mill, and decomposition tank (4) for decomposing plastic grain with alkali, provided between the grinding apparatus and mixing unit, neutralization tank (5) provided between decomposition tank and mixing unit, sorting apparatus (1) for classifying and inducing the plastic and organic material to the grinding apparatus and slurry tank. The sorting apparatus has horizontal cylinder with intake and inlet port drilled along longitudinal-direction one end vicinity, discharge port drilled by the other end, and pore group drilled between one end of the cylinder bottom valve and discharge port. The cylinder has a rotary blade fixed to the rotary shaft in the longitudinal-direction access line of cylinder and a radial direction tip opposing cylinder bottom valve through a micro gap. An air intake blade is attached to the rotary shaft or air-intake opening end of the rotary blade, and an air flow path is formed between the rotation region of rotary blade and cylinder top valve. An organic material conveying unit is connected to the pore group and slurry tank. The plastic conveying unit is connected to the discharge port and coarse crusher or grinding apparatus. The processing system further has energy recovery equipment (14) for collecting and converting biogas generated in the bioreactor into energy, and supplying the energy to the coarse crusher and/or grinding apparatus.