What is aluminium ?
Aluminium is the third most abundant element in the earth's crust after oxygen and silicon, and the most common metallic element: it forms some 8% of the earth's crust, and is extracted from bauxite.

Pure aluminium is a relatively soft, ductile metal, which can be alloyed with small quantities of other metals and elements to extend its properties, while not losing its most important qualities - lightness and strength.

It has low density compared to other metals: about one-third the density of iron and steel, less than one-third that of copper, and one-quarter that of lead and silver.

Aluminium is easily formed: it can be drawn into thin wire and rolled into sheet to make airliners, or coils to make drinks cans, or foil. It can also be cast into engine components, and extruded into complex shapes such as window frames.

It is an excellent conductor of heat and electricity, and has a relatively low melting point (660 ºC). And it is corrosion-resistant, due to a thin, but tough, film of oxide that forms on its surface when exposed to the atmosphere.

Because aluminium is so easily recycled, its products - whether airliners, trains, window frames or drinks cans - are the above-ground mine for the next generation of strong, light-weight objects we use every day.

When a site for open-cast mining is prepared, the topsoil is generally removed as part of the rehabilitation plan, and special nurseries established to grow indigenous plants from collected seed, so that the plants are ready for use once the mining phase is completed. The costs of re-vegetation are built into the site costs, and major companies such as Alcan and Alcoa have won awards for their management of programmes based on biological diversity, re-forestation and water quality.

How is the metal made?
The electrolytic process still used today was discovered in 1886 by Charles Martin Hall in America and Paul Heroult in France, although small-scale processes had enabled aluminium to be produced, for mainly decorative pieces, in time for the Paris Exposition in 1855. The aluminium production process involves two main stages:

2. The electrolytic smelting process involves mixing the alumina with a molten cryolite (sodium-aluminium fluoride) in a pot lined with pitch and coke. The lining acts as a cathode so that when a carbon anode is inserted into the molten bath, and a strong electrical current passed through the pot, the alumina breaks down into molten aluminium and oxygen. The molten aluminium is syphoned off into furnaces where other elements are added to produce particular alloys, before being poured into moulds to form ingots.

It takes four tonnes of bauxite to make two tonnes of alumina, which makes one tonne of aluminium, consuming around 14,000 kwh electricity. Over half the world's primary aluminium (58%) is produced using renewable hydroelectric power, which does not contribute to greenhouse gas emissions. In addition, specifically in the UK, the industry has made a commitment under the climate change levy to improve energy efficiency and so reduce the carbon equivalent emissions by 32% over the period 1990 to 2010. This is a significant contribution to the UK commitment under the Kyoto Protocol of a 12.5% reduction. Since the Kyoto 1990 base year, the aluminium industry has managed to reduce CO2 equivalent emmisions by 26.9% which equates to over 2 million tonnes of carbon dioxide equivalent, despite increasing output by 290 kt (27%).

Choosing lightweight aluminium leads to energy savings during product use, and recycling the metal uses only 5% of the initial energy requirement of primary production. And it is because aluminium can be recycled time and again without loss of properties, and because the energy savings therefore accumulate, that recycling is so important. Around 73% of aluminium used in the UK has been previously recycled.