Raising the bar

When it comes to decarbonising reinforced concrete (RC) construction, the conversation often focuses on cement replacements, while the carbon footprint of steel reinforcing bars (rebar) is often overlooked.

Rebar is neither traditional structural steel, nor is it impacted by concrete decarbonisation through cement replacement. Looking at import data and domestic production, we can find levers to influence global sustainability as well as project carbon.

Rebar makes up 11% of the mass of a C40 reinforced concrete beam, but over 40% of the carbon footprint, based on ICE carbon values and despite the high scrap content of average UK rebar. Along with cement, rebar is a carbon hotspot for reinforced concrete, but cement replacement dominates the conversation around decarbonising concrete, whereas rebar is relatively overlooked.

We produce rebar domestically and it’s all from scrap

Rebar is produced in significant quantities in the UK, making up about half of current consumption. There are two main producers, 7Steel in Cardiff and Liberty in Rotherham (mill currently dormant), both recycling scrap in electric arc furnaces (EAF) to produce rebar. This makes it relatively low carbon compared to the average structural steel, although there is significant variation in carbon footprints, with Liberty’s product having about 3x the embodied carbon compared to 7Steel. Unfortunately, we still export about 75% of our steel waste to be recycled abroad, where cheaper electricity can be used to run electric arc furnaces more competitively.

Over the last 15 years, the proportion of rebar we import has increased from 30% to 50%, and there have been significant shifts in where it comes from. Rebar is highly standardised and consumed around the world, so geopolitics and current affairs can sway the market. Oversupply in China following the 2008 recession caused large amounts of cheap Chinese rebar to enter the EU market, with the Chinese share in UK rebar increasing from 0% in 2012 to 50% in 2015. In 2015 the EU passed anti-dumping laws to block this Chinese supply, and by 2017 Chinese imports to the UK had dropped back to 0% (the laws were carried over following Brexit). Despite this, UK production dropped from 50% to 35%, and up to 2019 the gap was filled by increasing imports from Portugal, Turkey, Russia, Ukraine, and Belarus.

UK production rebounded to 60% during Covid as imports slowed, and sanctions on Belarus and Russia in 2022 blocked this route. Algeria emerged after Covid as a major supplier, and today the UK produces about 50% domestically, with the remainder coming almost entirely from Portugal, Algeria, and Turkey.

UK produced rebar is about 0.7 kgCO₂e/kg, far lower than the overall UK steel average of 1.74kgCO₂e/kg (BCSA), because all UK rebar is produced via scrap EAF.

Portugal only has two steel mills, both also scrap EAF, with a carbon average of 0.5 kgCO₂e/kg.

Turkey has lots of steel mills, however 88% of Turkish rebar capacity is scrap EAF, but generally higher carbon than those in Portugal, estimated 0.9 kgCO₂e/kg.

Algeria has four steel mills and only one EPD, but 95% of capacity is DRI, estimated 1.5 kgCO₂e/kg. This is higher carbon than the Scrap EAF route, but still far lower than blast furnace steel, which makes up the majority of global steelmaking and typically has a carbon footprint of 2.2 – 2.7kgCO₂e/kg.

• UK rebar is relatively low carbon but is still an overlooked carbon hotspot in reinforced concrete
• Rebar trade is volatile and can swing year on year
• Current UK rebar is 50% domestic produced, 90% Scrap-EAF, and 10% DRI-EAF (almost no BF-BOF)
• Specifying carbon limits on UK rebar would not improve global sustainability as there is no high carbon rebar to remove, although limiting Turkish rebar could reduce project carbon
• Seeking Algerian rebar may increase project carbon but supports the global shift to DRI-EAF, a powerful and exciting lever to decarbonise steelmaking
• Currently usage data is scarce so we are working to track rebar on our projects, and to explore intentional sourcing of DRI-EAF rebar