鉄鋼スラグの有効活用

start date (planned), etc.
description of technology and business model

In the iron and steel-making process, over 600 kg of by-products, such as steel slag, dust, sludge, and used refractory bricks are generated for each ton of crude steel produced. Steel slag which accounts for the majority of this by-product, is almost entirely utilized. Approximately 70% of blast furnace slag is used for cement, while steelmaking slag is used for materials for road bases, civil engineering work, fertilizer, soil improvement, iron supply materials to the sea area etc.

Among them, the creation of shallow areas by effectively utilizing soft dredged soil using steel slag and the improvement of the marine environment by artificially producing and supplying humic acid iron by mixing waste wood and slag* is expected to contribute to the biodiversity conservation and measure against climate change (blue carbon).

*We stated our agreement with the Challenge Zero declaration, announced by Keidanren in June 2020. Through this, we disclosed this activity with other 10 specific challenges.

achievements and targets

“Blast furnace cement,” a mixture of pulverized blast furnace slag and ordinary Portland cement, contributes to a 40% reduction of CO2 emissions during manufacturing, since the cement-making process can be omitted. It also exhibits superior long-term strength and is registered as an Eco Mark product. Due to the effects of reduction in mining of natural crushed stone and less energy consumption in the cement making process, steel slug products are designated as a “designated procurement item” under the Green Purchasing Law, and included in the Common Specifications for Civil Engineering Work compiled by the Ministry of Land, Infrastructure, Transport and Tourism.

Nippon Steel’s pavement materials, KATAMATM SP, taking advantage of characteristics of steel slag, are used for forest roads and farm roads, as well as for weed preventive pavement to be installed near mega-solar panel installations and other locations.

Geo-TizerTM made of steel slag can be mixed with soft soil (mud, such as surplus excavated soil from construction sites or farmland soil) to reform the soil to make it usable. Unlike conventional soil-improvement materials (i.e., cement and lime), this soil produces less dust, significantly controls CO2 emissions, and is less expensive, enabling reduction of construction cost. The remediated soil is outstanding in compacting and can also be easy to be dug again, without being excessively solidified.

Calcia modified soil — a mixture of steelmaking slag and dredged soil — has been used to improve the marine improvement, such as by backfilling deep-dug seabed areas and creating shallow bottoms and tideland. In addition, Nippon Steel’s VivaryTM iron supply units, which are composed of steel slag and humus made from waste wood, provides iron needed for seaweeds to flourish, promoting regeneration of an area of the sea bed that had lost much of its living organisms.Moreover, as steel slag contains nutrition that helps plants grow, it is also widely used as fertilizer, contributing to improving farming productivity.

URLs that introduce our activities

https://www.nipponsteel.com/en/csr/env/circulation/zeroemission.html

https://www.nipponsteel.com/en/csr/env/circulation/sea.html

https://www.challenge-zero.jp/en/casestudy/529