Slag

Slag is a by-product of smelting (pyrometallurgical) ores and recycled metals.^[1] Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-products of recovering non-ferrous materials like copper, nickel, zinc and phosphorus).^[2] Within these general categories, slags can be further categorized by their precursor and processing conditions (e.g., blast furnace slags, air-cooled blast furnace slag, basic oxygen furnace slag, and electric arc furnace slag). "Slag generated from the EAF process can contain toxic metals, which can be hazardous to human and environmental health".^[3]

Global production of iron and steel, 1942–2018, according to USGS.^[4]

Due to the large demand for these materials, slag production has also significantly increased throughout the years despite recycling (most notably in the iron and steelmaking industries) and upcycling efforts. The World Steel Association (WSA) estimates that 600 kg of by-products (about 90 wt% is slags) are generated per tonne of steel produced.^[5]

^ Piatak, Nadine M.; Parsons, Michael B.; Seal, Robert R. (2015). "Characteristics and environmental aspects of slag: A review". Applied Geochemistry. 57: 236–266. Bibcode:2015ApGC...57..236P. doi:10.1016/j.apgeochem.2014.04.009. ISSN 0883-2927.
^ Stroup-Gardiner, Mary; Wattenberg-Komas, Tanya (2013-06-24). Recycled Materials and Byproducts in Highway Applications—Summary Report, Volume 1. doi:10.17226/22552. ISBN 978-0-309-22368-3.
^ Health Risk Considerations for the Use of Unencapsulated Steel Slag. Washington, D.C.: National Academies Press. 17 Nov 2023. doi:10.17226/26881. ISBN 978-0-309-70011-5.
^ "Iron and Steel Statistics and Information". www.usgs.gov. Retrieved 2021-11-27.
^ "worldsteel | Steel industry co-products position paper". www.worldsteel.org. Retrieved 2021-11-27.

[:0-1] Piatak, Nadine M.; Parsons, Michael B.; Seal, Robert R. (2015). "Characteristics and environmental aspects of slag: A review". Applied Geochemistry. 57: 236–266. Bibcode:2015ApGC...57..236P. doi:10.1016/j.apgeochem.2014.04.009. ISSN 0883-2927.

[2] Stroup-Gardiner, Mary; Wattenberg-Komas, Tanya (2013-06-24). Recycled Materials and Byproducts in Highway Applications—Summary Report, Volume 1. doi:10.17226/22552. ISBN 978-0-309-22368-3.

[National_Academies_Press_2023_p.-3] Health Risk Considerations for the Use of Unencapsulated Steel Slag. Washington, D.C.: National Academies Press. 17 Nov 2023. doi:10.17226/26881. ISBN 978-0-309-70011-5.

[4] "Iron and Steel Statistics and Information". www.usgs.gov. Retrieved 2021-11-27.

[5] "worldsteel | Steel industry co-products position paper". www.worldsteel.org. Retrieved 2021-11-27.

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