How is Aluminium Made?
Aluminium is one of our most widely-used metals, found in everything from beer cans to aeroplane parts.
However, the lightweight metal doesn’t occur naturally, and producing it is a complex process.
The above infographics use data from the USGS, Aluminium Leader, and other sources to break down the three stages of aluminium production.
The Three Stages of Aluminum Production
Each year, the world produces around 390 million tonnes of bauxite rock, and 85% of it is used to make aluminium.
Bauxites are rocks composed of aluminium oxides along with other minerals and are the world’s primary source of aluminium. After mining, bauxite is refined into alumina, which is then converted into aluminium.
Therefore, aluminium typically goes from ore to metal in three stages.
Stage 1: Mining Bauxite
Bauxite is typically extracted from the ground in open-pit mines, with just three countries—Australia, China, and Guinea—accounting for 72% of global mine production.
Australia is by far the largest bauxite producer, and it’s also home to the Weipa Mine, the biggest bauxite mining operation globally.
Guinea, the third-largest producer, is endowed with more than seven billion tonnes of bauxite reserves, more than any other country. Additionally, Guinea is the top exporter of bauxite globally, with 76% of its bauxite exports going to China.
After bauxite is out of the ground, it is sent to refineries across the globe to make alumina, marking the second stage of the production process.
Stage 2: Alumina Production
In the 1890s, Austrian chemist Carl Josef Bayer invented a revolutionary process for extracting alumina from bauxite. Today—over 100 years later—some 90% of alumina refineries still use the Bayer process to refine bauxite.
Here are the four key steps in the Bayer process:
Digestion: Bauxite is mixed with sodium hydroxide and heated under pressure. At this stage, the sodium hydroxide selectively dissolves aluminium oxide from the bauxite, leaving behind other minerals as impurities.
Filtration: Impurities are separated and filtered from the solution, forming a residue known as red mud. After discarding the mud, aluminium oxide is converted into sodium aluminate.
Precipitation: The sodium aluminate solution is cooled and precipitated into a solid, crystallized form of aluminium hydroxide.
Calcination: The aluminium hydroxide crystals are washed and heated in calciners to form pure aluminium oxide—a sandy white material known as alumina.
The impurities or red mud left behind in the alumina production process is a major environmental concern. In fact, for every tonne of alumina, refineries produce 1.2 tonnes of red mud, and there are over three billion tonnes of it stored in the world today.
China, the second-largest producer and largest importer of bauxite supplies more than half of the world’s alumina.
Several major producers of bauxite, including Australia, Brazil, and India, are among the largest alumina producers, although none come close to China.
Alumina has applications in multiple industries, including plastics, cosmetics, and chemical production. But of course, the majority of it is shipped to smelters to make aluminium.
Stage 3: Aluminum Production
Alumina is converted into aluminium through electrolytic reduction. Besides alumina itself, another mineral called cryolite is key to the process, along with loads of electricity. Here’s a simplified overview of how aluminium smelting works:
In aluminium smelter facilities, hundreds of electrolytic reduction cells are filled up with molten cryolite.
Alumina (composed of two aluminium atoms and three oxygen atoms) is then dumped into these cells, and a strong electric current breaks the chemical bond between aluminium and oxygen atoms.
The electrolysis results in pure liquid aluminium settling at the bottom of the cell, which is then purified and cast into its various shapes and sizes.
China dominates global aluminIum production and is also the largest consumer. Its neighbor India is the second-largest producer, making only a tenth of China’s output.
As is the case for alumina production, some countries that produce bauxite and alumina also produce aluminium, such as India, Australia, and Russia.
Roughly a quarter of annually produced aluminium is used by the construction industry. Another 23% goes into vehicle frames, wires, wheels, and other parts of the transportation industry. Aluminium foil, cans, and packaging also make up another major end-use with a 17% consumption share.
Aluminium’s widespread applications have made it one of the most valuable metal markets. In 2021, the global aluminium market was valued at around $245.7 billion, and as consumption grows, it’s projected to nearly double in size to $498.5 billion by 2030.
Govind Bhutada, Graphics/Design: Sabrina Fortin