Today, upgrading is needed in the detoxification and volume-reduction of the incineration residue of municipal solid waste. Melting the residue at a high temperature destroys toxic organic compounds such as dioxins, turning the residue into stable slag that does not elute heavy metals. This technology is rousing wide interest as the slag can be utilized as a construction aggregate material, while reducing the amount of waste to be landfilled. In 1991 Takuma began developing a DC plasma furnace to be used for melting the residue, and has been conducting basic melting tests since 1993, using a bench scale furnace of 300 kW output and 7.2 ton/day maximum throughput. In 1998, a new demonstration plant with 1710 kW output and 25 ton/day throughput was built, and tests have been continued with this new plant. It successfully concluded a 40-day continuous operation, proving that the by-products from melting are non-toxic and recyclable.