Reducing embodied carbon with greener steel

Using environmentally friendly construction materials

As the construction industry strives to meet net zero targets, contractors seek to reduce embodied carbon. One way of doing this is to opt for greener construction materials. 

‘Embodied carbon’ refers to the emissions created by the construction process. This includes the sourcing, transport, and erection of materials that were used to construct the building. It also includes the deconstruction and recycling or reuse of materials at the building’s end-of-life. 

EAF Steel is a lower carbon choice

Steel is one of the most environmentally friendly construction materials because it is resilient, long-lasting, and infinitely recyclable. However, there are two main ways to manufacture structural steel, and they have different sustainability credentials. 

  • Basic oxygen steel making route (Bf- BOF) uses raw materials in a gas furnace. 
  • Electric arc furnace (EAF) route melts scrap steel in an electric arc furnace.

Using recycled steel reduces CO2 emissions by 58%

EAF steel is made from up to 100% scrap steel that’s melted in an electric arc furnace, which reduces greenhouse gasses. It is also a more flexible and efficient process compared to BOS, resulting in a reduced amount of embodied carbon. 

In fact, using scrap steel instead of virgin ore reduces CO2 emissions by 58%. Recycling one tonne of steel saves 1.4 tonnes of iron ore, 0.8 tonnes of coal and 0.3 tonnes of limestone and additives and 1.67 tonnes of CO2. 

Getting closer to net zero with a greener steel

ArcelorMittal has developed a ‘greener’ type of steel by using renewably produced electricity. XCarb® is their label for recycled and renewably produced steel. 

The manufacturing process uses wind and solar energy from a grid that is local to the factory. Although, there are some carbon emissions associated with things such as transport, it’s a huge step in the right direction. 

Here you can see the difference in carbon per tonne of finished structural steel: 

BOS = 2.5t. 

EAF= 0.5t. 

XCarb = 0.333t. 

Working with sub-contractors to reduce embodied carbon

More than half of the world’s carbon emissions come from fossil fuel use. This is another reason why EAF steel is a critical technological pathway for decarbonizing construction projects. 

A steelwork contractor will be able to advise how you can reduce embodied carbon, including which parts of your structure can be fabricated with EAF steel.

It’s estimated that 60 to 70% of a typical project’s steelwork can be made using the EAF manufacturing process. It’s not possible to manufacture certain parts in EAF steel and the steel fabricator will be able to advise on this.

They may also be able to minimise the environmental impact of the construction process. Early contractor involvement is key for discussing and improving environmental impacts during the planning and costing stage of projects.

Whole life carbon assessments 

This includes the emissions generated from construction, use and demolition and disposal. For more information on designing to reduce embodied carbon, see our article: Reducing embodied carbon in structural steel. This explains why module D in embodied carbon calculations is essential if benchmarking steel’s carbon footprint against its construction counterparts.

Completing WLCAs on all projects is now essential, to build evidence and understanding of the construction and built environment sectors’ carbon emissions. And since it’s estimated that 80% of the built environment we’ll be using in 2050 is already built, new solutions will need to extend to retrofitting existing building stock.

For contractors delivering at construction stage, this requires circular economy principles, to:

  • Build less – prioritising refurbishment of existing stock or reuse of materials
  • Build light – considering the impact of a building’s structure
  • Build wise – understanding a building’s longevity and local context.
  • Build low carbon – reviewing building material’s specifications and whole-life carbon
  • Build for the future – understanding a building’s adaptability or recyclability at end-of-life
  • Build collaboratively – involving all contractors; as with the ‘golden thread

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