PURPOSE: To decompose shutter slats completely at the time of disposal in soil by manufacturing the shutter slats out of kneaded matter formed of polyvinyl chloride, surface-treated starch, and an additive in specific mixture ratios.

CONSTITUTION: 75 kg of polyvinyl chloride, 4 kg of a stabilizer, 1 kg of a lubricant, 45 kg of calcium carbonate, 10 kg of surface-treated starch, and a coloring agent as necessary are kneaded, then heated, and crushed to form a pellet. The pellet is heated, melted, molded to form a sheet by an extruding molding machine. Furthermore, the sheet is cut into predetermined shapes and sizes to form shutter slat. At the time of disposal, the shutter slats are embedded in soil and completely decomposed by microorganism after a lapse of approximately one and a half years to two years. By this constitution, it is possible to dispose the shutter slats similarly to domestic waste, to improve rigidity, heat insulation, and resistance to impacts, and to perform printing on them easily as they have capillary holes on the surfaces.