Aluminium in particular is highly sought after as a scrap metal. Because it is both lightweight and strong, it’s used everywhere from drinks cans to aeroplanes. Extracting aluminium from its ore, bauxite, is relatively expensive, but salvaging it from scrap uses just five per cent of the energy needed to make new aluminium.
Like plastic bottles, a large percentage of recycled aluminium comes from beverage containers. The process is similar to plastics too. Once collected, they’re separated from the other metals by an eddy current separator that splits the non-ferrous aluminium with a powerful magnet. The aluminium is shredded into pieces of uniform size, mechanically cleaned then pressed into blocks to minimise oxidation.
The blocks are loaded into a furnace and heated to around 750 degrees Celsius (1,380 degrees Fahrenheit), at which point it becomes molten. The melted-down aluminium produces a surface scum known in the industry as dross, which is removed, before high-purity aluminium is added to bring the molten aluminium up to the required grade. The furnace is then rolled onto its side and the liquid aluminium poured out. The end product is either atomised aluminium powder or ingots. Because aluminium isn’t transmuted by this process, it’s just as good as the new stuff and can be recycled indefinitely.