Aluminium recycling

Aluminium recycling is the process by which aluminium can be reused in products after its initial production. The process involves simply melting the metal, which is far less expensive and energy intensive than creating aluminium based products from the ore, which must be done through large-scale electrolysis. Mining and then refining aluminium both require enormous amounts of electricity; recycling it requires only 5% of the energy to produce it. For this reason, recycling has become an important component of the aluminium industry.

A common practice since the early 1900s, aluminium recycling is not new. It was, however, a low-profile activity until the late 1960s when the exploding popularity of aluminium beverage cans finally placed recycling into the public consciousness.

Sources for recycled aluminium include automobile parts, windows and doors, appliances, containers and other products. As recycling does not damage the metal's structure, aluminium can be recycled indefinitely and still used to produce any product for which new aluminium could have been used. ^[1]

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Process

Aluminium is usually recycled in the following basic way^[2]:

1. In the case of products like aluminium drink cans, the cans are shredded and ground into small pieces.
2. The small pieces are then melted in a furnace to produce molten aluminium (by the end of this stage the recycled aluminium is indistinguishable from virgin aluminium and so further processing is identical for both). Some minor adjustments to the actual composition of the final product is required to eliminate impurities and to conform the recycled aluminium to the proper amalgam from which different materials are manufactured, including slightly different compositions for can bodies and lids.
3. The molten aluminium is then poured in to moulds to create large ingots.
4. The ingots are then forced through rollers to create sheets of aluminium of whatever thickness is required for the product the metal will be used in.

The recycled aluminium is generally made into aluminium alloys, mainly silicon aluminium and then cast into ingot form to certain industry standard specifications.

Ingot Production using reverbatory furnaces

The scrap aluminium is separated into a range of categories i.e. irony aluminium (engine blocks etc), alloy wheels, "clean aluminium" Depending on the specification of the required ingot casting will depend on the type of scrap used in the start melt. Generally the scrap is charged to a reverbatory furnace (other methods appear to be either less economical and/ or dangerous)and melted down to form a "bath". the molten metal is tested using spectroscopy on a sample taken from the melt to determine what refinements are needed to produce the final casts. After the refinements have been added the melt may be tested several times to be able to fine tune the batch to the specific standard

Once the correct "recipe" of metal is available the furnace is tapped and poured into ingot moulds, usually via a casting machine. The melt is then left to cool, stacked and sold on as cast silicon aluminium ingot to various industries for re-use.

Cost Savings

The recycling of aluminium generally produces significant cost savings over the production of new aluminium even when the cost of collection, separation and recycling are taken into account. ^[3] Over the long term, even larger national savings are made when the reduction in the capital costs associated with landfills, mines and international shipping of raw aluminium are considered.

The environmental benefits of recycling aluminium are also enormous. Only around 5% of the CO2 is produced during the recycling process compared to producing raw aluminium (and an even smaller percentage when considering the complete cycle of mining and transporting the aluminium)^[3]. Also, open-cut mining is most often used for obtaining aluminium ore, which destroys large sections of world's natural land.

References

1. ^ WasteOnline: Metals aluminium and steel recycling
2. ^ aluminum.org: How Is An Aluminum Can Recycled?
3. ^ ^{a b} International Aluminium Institute: Aluminium Recycling Facts

• Youcanchangetheplanet.org - A non-profit sustainable conservation organization promoting aluminum recyling and the rehabilitation of damaged ecosystems.