How is Aluminium Made?

Sustainability

If you’re thinking about choosing new aluminium windows and doors, it’s reassuring to know that aluminium is one of the most sustainable materials on the planet. It can be infinitely recycled without losing any of its properties, and it’s actually estimated that around 75% of all the aluminium produced over the last 140+ years (1bn tonnes) is still in circulation today.

The material used to manufacture your new window and door profile might well have been through several previous lives then, but have you ever wondered where it comes from in the first place?

Where it comes from?

At 8%, aluminium is the third most abundant element in the earth’s crust – after oxygen and silicon. It’s generally found in tropical and subtropical regions around the world - Guinea, Brazil, Jamaica, Australia and India account for a massive 73% of the world’s supply, with 28% in Guinea alone.

The process of extracting aluminium

The ‘Bayer’ process of extracting aluminium from bauxite might have been discovered more than a century ago, but it’s still the standard method used today. It relies on dissolving the aluminium oxide in bauxite at a very high temperature in concentrated caustic soda (NaOH), and then separating it from the other minerals as it cools and recrystalises separately.

To make the aluminium oxide into aluminium though, it has to go through electrolytic reduction at a smelting plant in a bath of molten cryolite using huge amounts of electric current. There is then a further process of remelting at 800°C to remove impurities that can affect the final properties.

The result 

The finished result is supplied either as small aluminium pigs for casting into different shapes, as large ingots which can be rolled into the sheets used for aluminium drinks cans, or as the 7m long billets which are used to extrude AluK aluminium window and door systems. Each of these has other metals added beforehand to suit the final application, and for windows and doors, this is usually silicon and magnesium for optimum strength and corrosion resistance.

Unsurprisingly, most smelting plants worldwide are powered by either hydroelectric or geothermal energy to reduce costs and emissions, and they are all equipped with closed loop gas recycling systems which filter out the fluoride compounds which come from the cryolite.

What makes aluminium both affordable and sustainable as a construction material though is that, while it takes a lot of energy to extract the material in the first place, it takes only 5% of that to recycle it into a product that can be used again – and again, and again, and again.