Steel

Steel is one of the primary materials in the construction industry because of its high strength, durability, relatively low weight, fireproofness, and weather resistance. Its remarkable versatility (strength and ductility) enables its use in various structures and components, from frames and columns to roof trusses and beams.

Environmental impact

The steel production process generates air pollutants, such as, for instance, sulfur dioxide, nitrogen oxides, and particulate matter, waste (e.g., steel slag), and is associated with significant water consumption. Moreover, the process is energy-intensive, and its general energy consumption is estimated at 10 GJ/t of steel produced (exact values depend on the type of steel, its finish, application, etc.).

How to reuse and recycle

• Direct reuse of structural steel: structural steel is a durable material that can be reused in several ways, both in its original and modified forms (e.g., by resizing - cutting). It makes steel elements an attractive option for reuse as, for instance, beams, roof cladding, pipes, stairs, or decorative elements. An example is the facade made from used steel sheets at the Kringloop Zuid recycling centre in Maastricht, the Netherlands, or the use of steel elements from an old vehicle hall in constructing the Almere Recycling Center in Almere, the Netherlands.

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The standardisation of steel element dimensions facilitates direct reuse.

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Steel can also be used to construct buildings designed for disassembly and reuse, such as Pre-Engineered Steel Buildings (PEBs).

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In ENTRA's KA13 project, a Norwegian complete full-scale circular project, a test procedure for reused steel with a reduced number of destructive tests was developed, significantly reducing the testing costs. Also, an existing standard (NS EN 1090-2) was used to recertify used steel.

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• Recycling scrap steel: steel can be recycled and reused to create building components.

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Steel scrap processing still takes a toll on the environment, so to further reduce that, direct reuse of steel elements in their original form (e.g., building load-bearing structures, facades) or steel regeneration from composite structures (e.g., steel-concrete composite structures) should be considered.

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• Reusing steel in interior design: steel can be used to create furniture or other furnishings, giving any space an industrial yet modern look.

Sources and further reading

1) International Energy Agency, Driving Energy Efficiency in Heavy Industries - Global energy efficiency benchmarking in cement, iron & steel, 2021.

2) Chen H.M. et al., Reclaiming structural steels from the end of service life composite structures for reuse - An assessment of the viability of different methods, Developments in the Built Environment, 10, 2022.

3) The CIRCON's project website and compendium.

4) Yeung J. et al., Understanding the total life cycle cost implications of reusing structural steel, Environment Systems and Decisions 37, 2016.