As the construction industry rises to meet the climate challenge, embodied carbon – the emissions associated with building materials and construction processes – has become a critical focus. We recognise that decarbonising the built environment means addressing not only how we operate, but what we build with.
One of the most significant contributors to embodied carbon on many of our projects is structural steel. Embodied carbon assessments consistently show that steel-framed buildings lock in a large proportion of total carbon within the primary structure.
Steel is predominantly manufactured via two routes:
- Basic Oxygen Furnace (BOF): Most steel comes via this manufacturing method, which uses high proportions of virgin iron ore along with some scrap steel which is then melted at high temperatures. The result is a very carbon intense material, that can emit up to 2,500 kg embodied carbon per tonne of steel.
- Electric Arc Furnace (EAF): Uses much higher proportions of scrap (up to 100%) and is produced in furnaces operating at much lower temperatures. This reduction in virgin material and energy helps EAF steel deliver carbon savings of up to 80% per tonne over BOF steel.
The emissions associated with BOF steel are incompatible with the delivery of our carbon targets. In recognition of the carbon benefits of building with EAF steel, we’ve made a bold shift to prioritise the specification and procurement of this where feasible on our projects. While not all structural sections are yet available in EAF steel, approximately 70–75% of the structural frame components on a typical project should be able to be sourced using EAF technology. This move supports our ambition to deliver lower carbon buildings, and is also in line with the growing number of customers and frameworks requiring measurable reductions in whole-life carbon.
Sarah Frith, Design Director for London & East said:
“Increasingly our customers, particularly those affected by planning requirements such as the London Plan, are taking greater interest in the whole life carbon of their planned developments. We partner with them to offer support and advice on how best to deliver lower carbon buildings by minimising embodied carbon emissions.
“Traditionally steel frame structures are very high carbon and drive a significant proportion of the total embodied carbon for that building. But if we can specify more electric arc furnace steel in our primary frame, we know we can make big inroads to reducing carbon for our customers. We have already seen the positive impact of this on our Leighton Linslade project, and other projects currently in design are also looking at opportunities to use electric arc furnace steel in primary frame.”
In 2024 alone, we used EAF steel on eight projects, including:
- Leighton Linslade Leisure Centre in Central Bedfordshire, where use of EAF steel produced an average of 0.947 tonnes of CO₂ per tonne of steel, compared to 2.53 tonnes for BOF steel. Using EAF steel delivered embodied carbon savings of 185 tonnes.
- Hastings High School in Hinckley, Leicestershire, where a total saving of 190 tonnes of embodied carbon was achieved.
- Chichester College STEM Building, where the EAF steel frame (below) achieved a 64% reduction in embodied carbon, equating to 462 tonnes of CO₂ saved.
Across these projects, comparative reporting between BOF and EAF steel sections has enabled us to realise total embodied carbon savings of over 1,300 tonnes through the use of of EAF steel, equivalent to powering around 250 average UK homes for an entire year.
Working with our supply chain in 2024, we found that eight of our ten key partners are currently sourcing and supplying EAF steel. Although the UK currently has four operational EAF plants, they primarily serve the defence and aerospace sectors and produce a limited product range. As a result, most EAF steel on our projects is currently sourced from mainland Europe, including Spain, Germany, and Luxembourg.
Despite needing to be transported into the UK, the carbon emissions associated with EAF steel are still significantly lower than those associated with BOF steel production. The tables below shows the figures for our Leighton Linslade project, a 5,225m² community health and wellbeing hub.
As this shows, total tonnes of carbon for transport of EAF steel far outweigh those of UK-sourced BOF steel. However, the significantly lower emissions associated with production of EAF steel means that it is still better environmentally to import EAF than it is to use UK-sourced BOF steel.
*At Leighton Linslade, the use of EAF steel generated 73% less carbon per tonne.
The planned Tata Steel EAF facility in South Wales, expected by 2027, will represent a critical step toward increasing the availability of low-carbon steel for UK construction through the use of electronic arc furnaces, similar to the one shown below.
