Japanese steelmakers will strengthen their efforts to use slag, a by-product in the steelmaking process, to mitigate global warming. JFE Steel will cement steel slag produced in the process to adjust iron’s constituents in the plate shape to use them for the regeneration of coral reefs in Okinawa Prefecture. The company will raise the coral branches planted on the plates in an aquarium and put them back to the sea. It will expand these activities in Indonesia where it is now conducting the preliminary study. Nippon Steel put a total of 500 tons of slag blocks and feed materials made of steel slag and fermented thinned wood in the sea off Hokkaido. Iron of the feed materials steeps in the sea and helps kelps grow. The company plans to produce resins made of kelps to prevent rotten kelps from emitting carbon dioxide. It estimates that 23 million tons of carbon dioxide can be reduced if the same activities spread the coastline throughout Japan. Sumitomo Metal also put slag blocks in the sea off Wakayama Prefecture to proliferate lobsters and algae in alliance with local fisheries cooperatives. Steel slag is mainly used as the road bed in road maintenance and improvement, but demand for steel slag has been decreasing drastically because of the decreasing number of public projects. Currently, only one percent of steel slag is used for marine purposes, and the Japanese steelmaking industry plans to increase the ratio to 25% in the future.