At Nippon Steel’s Hirohata Steel Works, efforts to recycle scrap tires began in 1998. The underlying concept was to fully utilize scrap tires as raw materials and fuel in the steelmaking process, rather than simply disposing of them through incineration or landfilling. The Hirohata Steel Works utilized the SMP (Cold Iron Source Melting) process, which began operations in 1993, to use the carbon contained in waste tires as a reducing agent and fuel, while recovering the steel cord as a source of iron. Documents from 1999 describe a system in which waste tires were fed into the steelmaking process, with carbon black used as a reducing agent, iron content as raw material for molten iron, and synthetic rubber converted into gas. Subsequently, gasification recycling facilities were also introduced, establishing a system capable of recycling oil, gas, carbon residue, and even iron. According to a report by Nippon Steel, the company built a system capable of processing approximately 120,000 metric tons of scrap tires annually, reaching a scale that accounted for more than 10 percent of the scrap tires generated in Japan. This system—which returns tires to steel mills not as waste but as a resource containing iron, carbon, and energy—has become a symbolic example of circular recycling that bridges different industries.
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