Irena and G20 set out strategy for lower carbon steel


Construction uses around half of all global steel production and new report examines opportunities to use less, reuse more and harness waste material. 

The International Renewable Energy Agency and the Indian G20 Presidency have issued a new report detailing the extensive opportunities to reduce the carbon impact of steel-use across the globe, with some significant developments possible in construction.  

While the report examines all uses of steel, it notes that infrastructure and buildings used 52% of all steel produced in 2019 and that construction use has rebounded faster than most sectors since the pandemic. Construction-used steel is also in-situ for longer than for most other uses and so constitutes a significant majority of the world’s steel presently in use. As a result the report examines ways to reduce use, improve re-use, and to use waste material (slag) as a cement alternative. 

Efficient use of construction steel 

The report examines the potential for lighter-steel construction and proposes the use of higher strength rebar and design-optimisation to reduce the use of steel in construction. Higher utilisation of buildings and extending the life of structures through renovation and upgrades would also play a significant part in reducing the demand for new steel. 

The report notes that there are challenges to doing this, however. For example, it highlights that rising metal and construction costs should drive up demand for more efficient design and asset lifetime extension but that prescriptive design conventions and complexity of renovation may be holding these back across the G20. 

Reuse of steel 

Re-use of steel holds particularly strong potential in the infrastructure and construction sectors because such significant quantities of steel are already in situ in many of the assets being replaced or renovated. 

Steel can be recycled infinitely without loss of quality. It can be remade to have any grade and recycling steel scrap from end-of-life products is an established practice that makes economic sense for steel producers as a less-energy-intensive process than producing new steel from iron ore – requiring a quarter of the energy of new steel production. Today, about 30% of the world’s steel is produced from recycled steel scrap. 

Even here, however, there are hindrances to expanding steel recycling even as end-of-life steel products rise in tonnage year-by-year. For construction steel, which tends to be produced to a higher tolerance than steel used in sectors like the motor industry, would benefit from a free trade in reclaimed steel.

A lack of modularisation also means that much of the steel reclaimed has to be put through recycling instead of being put to new use in its present form. And sorting for reuse and recycling can be expensive compared to traditional disposal methods so require some policy interventions to prioritise it, along with regulatory structures to reflect the relatively high environmental risk of doing this in construction (along with ship-breaking and the motor industry). 


For every ten tonnes of steel produced, approximately four tonnes of slag is produced from the refinement process. A further one tonne is produced for every ten tonnes of steel produced through recycling in an electric arc furnace.

Due to its properties, slag can be used as a substitute for different materials in several industrial applications, with a particularly big potential impact in construction as a low-emission substitute for clinker – the most emission-intensive ingredient in cement production. 

Slag can also be used as coarse and fine aggregate for concrete and can be used in the construction of roads and as an aggregate for asphalt concrete.

IRENA director-general Francesco La Camera commented “The global nature of steel necessitates coordinated action to overcome common challenges and seize opportunities. G20 members account for about four-fifths of the world’s production and consumption of steel, and collaboration among members can accelerate the adoption of circularity.”

For the full Towards a Circular Steel Industry, click here