steel has a low embodied energy content it is produced in the largest quantity (about one billion tonnes per year). The annual production of aluminium is much lower than that of steel (about 38 million tonnes per year) but it is far more energy intensive and aluminium production is responsible for around 3% of .
Recycling aluminium uses only about 5% of the energy used to extract it from bauxite. Avoiding the environmental problems in the extraction of aluminium from the bauxite. Not having to find space to dump the unwanted aluminium if it wasn't recycled.