Adjusting the steelmaking infrastructure requires long-term planning, so stakeholders should start acting now to prevent this problem in the future. We have identified technical interventions to reduce copper along the steel supply chain, and policies that would encourage their implementation.

Katie Daehn

The quality of recycled steel is being compromised by copper contamination. In the future this problem will constrain steel recycling, limiting the environmental benefits of steel recycling over new steel production.

Steel is the most recycled material on Earth, and recycling steel produces one third of the greenhouse gas emissions of producing new steel from iron ore. Fortunately, the global amount of steel scrap available is expected to treble until 2050, as products made of steel we have been accumulating are discarded, and therefore a greater proportion of steel demand could be supplied by recycled steel with substantial environmental gains. However, steel scrap often contains copper, which damages the material properties and prevents the use of recycled steel for high-quality products.

Currently, discarded vehicles, equipment and appliances are shredded and small pieces of copper attach from the embedded wiring and motors. Copper causes problems such as cracking in steel, but currently there is no commercial process to remove copper. Recycled steel can be used for lower-quality steel products, such as reinforcing bar, or alternatively scrap can be diluted with virgin steel made from iron ore.

In the future, demand for higher-quality steel, stricter climate policies, and greater availability of scrap would make it impossible to continue current practices of diluting steel scrap or using recycled steel only for lower quality products. The paper "How Will Copper Contamination Constrain Future Global Steel Recycling?" uses available data to estimate the amount of copper in the global steel system, and how much could be tolerated by future demanded products. The research team found that the current practice cannot be sustained for much longer: it is likely that by 2050 the amount of copper in scrap would exceed the copper tolerated by demanded products, thus preventing the use of all available scrap for recycling (see figure below).

Katie Daehn concludes "Adjusting the steelmaking infrastructure requires long-term planning, so stakeholders should start acting now to prevent this problem in the future. We have identified technical interventions to reduce copper along the steel supply chain, and policies that would encourage their implementation."