Across the world in 2020, around 1900 million tonnes of crude steel were produced, with just over 50% of that used for buildings and infrastructure. Steel used in buildings accounts for around 8% of the world’s carbon emissions, and on average every tonne of steel produced leads to the emission of 1.85 tonnes of CO2 into the atmosphere.
However, the greenhouse gas emissions (referred to in this document as ‘carbon’) and the carbon factor (the quantity of greenhouse gas emitted per kg of material) for every steel member can vary depending on:
• Raw material extraction
• Manufacturing location and techniques
• Transportation mode and distance.
As designers we can exert influence via our designs and specifications by working collaboratively with contractors and clients. To do this, we need to understand the carbon emissions associated with the different parts of the steel manufacturing process and ensure that the impact of our decisions is felt throughout the supply chain.
This document provides information relevant to carbon steel products typically used in construction including:
• Structural steel sections (both open and closed) – used for beams, columns, bracing etc.
• Structural plate – used for connections, bespoke girders etc.
• Profiled metal decking – used for composite floors, roof and façade panels
• Structural bolts, shear studs, welds
• Structural reinforcement, cables, tendons, ties
• Light gauge structural channels, and metal framing systems
• Façade brackets
• Mechanical ducting, steel pipes and tanks.
This document aims to set out the factors that contribute towards the emission of carbon through the whole life cycle of steel products, stage by stage used for buildings and infrastructure. It also highlights the potential route to decarbonising the production of steel.
Using less material as an industry is fundamental to reducing emissions. We cannot rely on production processes to eradicate emissions. At an industry scale, there is limited scope to expand electric arc furnace production due to the quantity of recyclable steel that is available. Similarly, reuse of steel elements is only carbon-efficient if the sections are utilised to a sufficiently high level. This paper aims to provide the reader with information on the status of the industry and best practice, so that they can understand the impact of their design choices and avoid greenwashing.