Recycling is critical to sustainable development. It allows resources to be saved and waste to be reduced. Aluminium is 100% recyclable without any loss of its natural qualities. Recovery of the metal via recycling has become an important facet of the aluminium industry. The aluminium recycling industry has almost quadrupled its output from 5 million tonnes in 1980 to close to around 18 million tonnes today from old and traded new scrap. Recycled aluminium accounts for almost 30% of the total metal production (primary and recycled) worldwide.
Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore (primary production). However, a significant part (up to 15% of the input material) is lost as dross (ash-like oxide). The dross can undergo a further process to extract aluminium.
Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to the public awareness. In Europe aluminium experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials and 95% of transport vehicles.
Recycled aluminium is also known as secondary aluminium, but maintains the same physical properties as primary aluminium. Secondary aluminium is produced in a wide range of formats and is employed in 80% of the alloy injections. Another important use is for extrusion.
White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium, which can be extracted industrially. The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. Despite the difficulties, however, the waste has found use as a filler in asphalt and concrete.
All aluminium products can be recycled after use. The metal’s recyclability is one of the huge benefits of using aluminium. Scrap must be of appropriate quality before it can be melted down. To obtain this level of quality, all adherent materials must be removed. Depending upon the type of contamination present, some scrap must be processed; for example, beverage cans must have their lacquer removed prior to remelting.
Once sorted, scrap aluminium is then loaded into a furnace, which melts the aluminium completely. This molten metal is then cast or processed - using the same techniques as primary processing. All aluminium that is recycled is described as either new scrap or old scrap.
New scrap is that surplus material that arises during the manufacture and fabrication of aluminium alloys up to the point where they are sold to the final consumer. Examples include the trimmings from the edges of sheet aluminium, turnings and millings from aluminium fabrication and surplus extrusion discards. As such new scrap tends to come from the manufacturing industry, is of a known quality and composition and can be processed with very little preparation.
Old scrap is material that has been used by the consumer and subsequently discarded. This can include a wide range of items such as used beverage cans, car cylinder heads, window frames or electrical cabling.
The light metal is fully recyclable, suffers from no loss of quality when recycled and its recycling process is economical and saves significant energy. As a result used aluminium is considered an important resource, which is highly valuable. For this reason, the aluminium industry has every interest in promoting the recycling of aluminium as part of its industrial strategy.
Text: International Aluminium Institute, Wikipedia, European Aluminium Association
Photos: WtERT, Lucky Group