The steel industry is an essential part of the circular economy by reusing scrap metals and producing residual products that can be valuable inputs for various industries. Höganäs, the world’s largest provider of powdered metals, has gradually increased the reuse of its residual materials over the past 20 years towards its vision to inspire industry to make more with less.
Creating value from waste
Höganäs’ iron and steel processes at its facilities in Höganäs and Halmstad, Sweden, produce residual materials or by-products that can be used or reused in its own processes and as valuable raw materials in other industries. Around 80 percent of the residual materials are different kinds of slag and most of the rest is metal dust.
“In 2019, we ensured that around 80 percent of our residual materials were reused either internally or externally,” explains Björn Haase, Manager Non-metal products at Höganäs AB, who manages and promotes the use of the company’s residual materials. “Our long-term vision is to create zero waste by finding innovative uses for all our residual materials – and even higher value uses for them.”
Around 75 percent of Höganäs’ sponge iron slag goes straight back into its production processes and a large proportion of dust with high iron content is remelted. Most of the slag that is sold to external partners is used in the manufacture of stone wool insulation or used as gravel or macadam in load-bearing groundwork layers or in asphalt manufacturing.
Circularity makes financial and environmental sense
By using large quantities of scrap metal as raw material, reusing residual materials in its processes and making residuals available for other industries, Höganäs can contribute to reducing the amount of virgin materials society uses, such as metals that are mined or stone that is quarried.
“An important aspect of my work is helping our employees and external partners to understand that our residuals can be valuable resources – with both economic and environmental value,” says Haase.
Finding innovative uses for a unique slag
Höganäs is the only European producer of sponge iron slag, which has a high lime and coke content and some exciting applications are currently being trialled with external partners.
“We are looking into the potential to use sponge iron slag for energy generation at district heating plants where it can be combusted with agricultural waste to produce less fly ash, which is difficult to manage,” says Haase. “We are also working with our lime supplier to test the slag as a safe way of improving clay soils for agriculture, with initial results showing similar or better results than ordinary lime but with the added benefit of increasing the carbon level in the soil to benefit plant growth.”
Another interesting application being tested is using slag for purifying household and industrial wastewater. “Our tests have shown that slag filtration beds can significantly reduce costs compared with traditional solutions,” says Haase.“We are now using slag to purify the wastewater from our own steel plant in Halmstad for example.”
By altering its processes, Höganäs can determine the properties of the slag it produces for particular uses.
“So long as we don’t affect our production of high-quality metal powder, which is of course our primary purpose, we can customise our processes to chemically as well as physically design the kind of slag we produce,” says Haase. “This means we can optimise our slag for a particular purpose in close cooperation with our customers and industry partners.”
Collaboration for societal benefit
Höganäs directly collaborates with other steel plants, universities and research institutes and through Jernkontoret’s (the Swedish steel producers' association) networking group to identify and develop innovative opportunities to use residual materials.
“Together, we are developing solutions that benefit the entire steel industry and other industries that can use our residual materials as valuable raw materials,” says Haase. “Our work with using residual materials not only makes our company and the industry more sustainable – it also contributes to the circularity and sustainability of our society.”