Aluminium or steel can be recycled by melting it down and recasting into new products. Currently, 60% of steel and 39% of aluminium is recycled worldwide. However, while recycling is a greener alternative to manufacturing new materials, it has high energy costs which could be avoided if the metals were re-used in their original form. In this extensive analysis, the researchers gathered information on steel and aluminium re-use from academic and industry literature, drawing on 200 sources, and conducted 17 interviews with industry experts. They identified which products use these materials, the key design requirements for components, and the fraction of end-of-life components that could be technically re-used, considering available strategies and the physical barriers to the re-use of the remaining components. From this, they concluded that up to 27% of steel and 33% of aluminium end-of-life components could potentially be re-used. At present, there is little re-use of either material. Information from the interviews revealed that two key factors determine the type of steel or aluminium component that can be re-used and the way in which it is re-used: condition and market demand. If the condition is good and demand is high, components can be simply relocated, i.e. transferred to similar product, with little need for amendment. For example, aluminium car wheels can be transferred to another vehicle. If the condition is poor and demand is low, the component can be cascaded to a different type of product with less demanding use, for example, metals once used to clad buildings can be re-used on agricultural sheds. Alternatively, they can be reformed (or reshaped), as when ship plates are reformed to a reinforcing bar. High demand but poor quality calls for remanufacturing, which involves further disassembly and refurbishment. For steel, the main areas for re-use are the relocation of building components and the reforming of ship plates and line pipes. For aluminium, the main areas of re-use are in buildings and car wheels. These areas of opportunity, if carried out to their full potential, could allow re-use of 180 megatonnes (Mt) of steel (18% of all steel) and 5.5 Mt of aluminium (12% of all aluminium) per year. Policymakers seeking to maximise aluminium and steel re-use should prioritise opportunities to relocate metal, according to the researchers. Their analysis indicates that the greatest barrier to re-use is component incompatibility, i.e. different models of domestic appliances and car parts using different components, followed by degradation, i.e. metal corrosion. Approximately one-fifth of all global steel is used to reinforce concrete (210 Mt in 2008), which also presents a major challenge for re-use, as it is difficult to recover the steel bars without damaging them. Economic and behavioural barriers also limit re-use, such as concerns over increased labour costs, logistical challenges of returning and sorting components and the lack of an established supply chain.

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