Around 1,500 people visit an industrial waste treatment facility in central Japan each year to see up close how the operator can recycle more than 99 percent of the solid garbage it receives from a variety of manufacturers and municipalities. Nakadai Co., which covers the Kanto region, accepts 60 tons of waste each day, which it recycles and resells to about 50 customers. The waste includes wooden materials, plastics, cardboard boxes, personal computers, auto parts and fluorescent lamps. Most industrial waste treatment companies specialize in handling a single type of waste for disposal. But Nakadai, founded as a scrap iron processor in Tokyo in 1937, has tried to diversify its sources of income by obtaining most of the nearly 20 types of licenses required for waste disposal since the late 1990s. Sumiyuki Nakadai, the 44-year-old executive managing director and a son of the president, joined the company in 1999 after working at a securities brokerage. One of the skills he shows potential customers is how to distinguish polystyrene and polyethylene by the smells they produce when burned.