Over the past 20 years, use of the steel industry’s co-products has increased significantly.

Innovative technology developments and synergies with other industries have brought the steel industry ever closer to its goal of zero waste to landfill.

In this paper, co-products refer to materials that are produced in parallel to or, as a consequence of, the production of a primary product and which have a potential value.


The main solid co-products produced during iron and crude steel production are slags (90% by mass), dust and sludge.

On average, the production of one tonne of steel results in around 200 kg of co-products for the electric arc furnace (EAF) route and 400 kg for the blast furnace – basic oxygen furnace (BF-BOF) route.

Alongside solid co-products, process gases from coke ovens, BFs or BOFs are also important steelmaking co-products.

Main solid co-products per steelmaking route1 (average outputs in kg/tonne crude steel)
    Ironmaking slag (BF)
    Steelmaking slag (BOF)
    Ironmaking dust and sludge (BF)
    Steelmaking dust and sludge (BOF)
    Steelmaking slag (EAF)
    Steelmaking dust and sludge (EAF)

 1 Steel Industry By-products report, worldsteel 2010

Use of iron and steelmaking slags in Europe*2 in 2016 – total 41 Mt

    Cement, concrete additive, etc.
    Road construction
    Metallurgical use
    Hydraulic engineering
    Interim storage

*At a global level, percentages vary from region to region

2 EUROSLAG – The European Slag Association, 2017

Key points from this report

Legislation should clearly differentiate co-products from waste to facilitate their use and improve their perception

Governments should support research into new applications of co-products, such as the development of Carbon Capture and Use (CCU) technology applied to process gases.

Legislation should not apply stricter regulations on the use of co-products; on the contrary they should be given preferential treatment.

Legislators should take a holistic approach when assessing the sustainability of steel industry co-products.

The growing use of steel industry co-products will make a significant contribution to the circular economy.

The steel industry can be a reliable partner, providing heat and electricity to local communities.

The use of steel industry co-products

Industry application › Recycling of iron bearing materials

A number of co-products with a high iron content are generated throughout the steelmaking process. These include dust and sludge from the wet and dry abatement equipment, mill scale from the hot rolling mill and iron ore and sinter fines.


The valuable iron content from these co-products is recovered and returned to the steelmaking process, replacing virgin material and contributing to a more efficient use of resources.



Value for other industries › From construction to healthcare to agriculture

Tar is a cokemaking co-product that is used as a seal coating material in the construction sector and to produce paints and synthetic dyes. As a medication, tar can be further processed and used in applications such as soap and shampoo to treat dandruff and skin conditions (psoriasis).


Sulphur is used to vulcanise rubber and manufacture sulphuric acid but is also used in insecticides and fertilisers. These are just a few examples that demonstrate the value of co-products for many industries, presenting an environmental advantage by preserving virgin materials.