How is aluminium made?

How Aluminium is made

Aluminium is one of the most widely used metals, found in many of the products people use, from beer cans to car and aircraft parts.

Although aluminium is the most commonly used metal by humans after steel, it does not occur naturally in the environment and its production is an energy-intensive and complex process.

The three stages of aluminium production

Approximately 390 million tonnes of bauxite rock are produced worldwide each year, of which 85% is used in the production of aluminium.

Bauxite is not a specific mineral, but a sedimentary clayey rock, consisting mainly of hydrated aluminium oxides (hydrargilite, bemite or diaspore), which are formed in tropical and subtropical climates. The minerals associated with bauxite deposits are usually clay minerals, silica, iron oxides and hydroxides. They are formed in the greatest quantities at weathering sites of aluminosilicate rocks in hot climates, which is why bauxite mining is best developed in Australia, Brazil, China, Central America, Africa, France and Greece. In Poland, bauxite is found near Nowa Ruda in Lower Silesia, among other places.

After mining, bauxite is refined into alumina, which is then converted into aluminium.

Aluminium is converted from bauxite ore to metal in three stages.

Stage 1: Bauxite extraction

Bauxite is typically extracted from the ground in open-pit mines, with only three countries - Australia, China and Guinea - accounting for the for 72% global bauxite production.

2022 Bauxite production at the mine
Country 2022 Bauxite production at the mine (tonnes) % in general
Australia 110,000,000 28.2%
China 86,000,000 22.1%
Guinea 85,000,000 21.8%
Brazil 32,000,000 8.2%
India 22,000,000 5.6%
Indonesia 18,000,000 4.6%
Russia 6,200,000 1.6%
Jamaica 5,800,000 1.5%
Kazakhstan 5,200,000 1.3%
Saudi Arabia 4,300,000 1.1%
Rest of the world 15,500,000 4.0%
Total 390,000,000 100.0%

Australia is the largest producer of bauxite and is also home to the world's largest bauxite mine called Weipa.

Guinea, the third largest producer of bauxite, has more than seven billion tonnes of bauxite reserves, more than any other country in the world. In addition, Guinea is the largest exporter of bauxite in the world. As much as 76% Guinea's exports go to China.

Once the bauxite has been extracted from the ground, it is sent to a smelter to produce alumina, the second step in the production process.

Stage 2: Production of alumina

In 1890, Austrian chemist Carl Josef Bayer invented a revolutionary process for extracting alumina from bauxite. Today, more than 100 years later, approximately 90% smelters still use the Bayer process to refine bauxite.

The four key stages of the Bayer process:

  • Mineralisation:
    The bauxite is mixed with sodium hydroxide and heated under pressure. At this stage, the sodium hydroxide selectively dissolves the alumina from the bauxite, leaving the other minerals as impurities.
  • Filtration:
    The impurities are separated and filtered from the solution, forming a residue known as red sludge. Once the sludge is precipitated, the alum is converted to sodium aluminate.
  • Precipitation:
    The sodium aluminate solution is cooled and precipitated to a solid, crystallised form of aluminium hydroxide.
  • Calcination:
    Aluminium hydroxide crystals are washed and heated in calciners to form pure aluminium oxide - a sandy white material.

The sludge generated in the alumina production process is a serious environmental problem. For every tonne of alumina, smelters produce 1.2 tonnes of red sludge, which is stored and with which it is not entirely clear what to do next. Currently, there are more than three billion tonnes of this material.

China, is the second largest producer of alumina and the largest importer of bauxite, supplying more than half of the world's alumina.

 

Aluminium oxide production in 2022.
Country Aluminium oxide production in 2022 (tonnes) % in general
China 74,000,000 53%
Australia 21,000,000 15%
Brazil 11,000,000 8%
India 6,800,000 5%
Russia 3,100,000 2%
Germany 1,900,000 1%
Ireland 1,900,000 1%
Saudi Arabia 1,800,000 1%
Ukraine 1,700,000 1%
Spain 1,600,000 1%
Rest of the world 15,100,000 11%
Total 139,900,000 100%

Aluminium oxide has applications in many industries, including plastics, cosmetics and chemicals. Nevertheless 85% aluminium is converted into aluminium.

Stage 3: Aluminium production

Aluminium oxide is converted into aluminium by electrolytic reduction. In addition to alumina itself, the production of aluminium requires cryolite and plenty of electricity.

Cryolite is mainly used as a temperature-reducing flux in electrolytic production. aluminium. Due to its high demand and rarity, a synthetic compound is now used. 

Below is a simplified process for producing aluminium:

  • In aluminium smelters, hundreds of electrolytic baths along with reduction cells are filled with molten cryolite.
  • Aluminium oxide (consisting of two aluminium atoms and three oxygen atoms) is then dropped into these baths, where a strong electric current breaks the chemical bond between the aluminium and oxygen atoms.
  • Electrolysis deposits pure liquid aluminium at the bottom of the cell, which is then purified and cast in various shapes and sizes.

The largest producer of aluminium is China, which is also its largest consumer. Neighbouring China, India is the second largest producer, producing just a tenth of China's output.

2021 Aluminium smelter production
Country 2021 Aluminium smelter production (tonnes) % in general
China 39,000,000 59%
India 3,900,000 6%
Russia 3,700,000 6%
Canada 3,100,000 5%
United Arab Emirates 2,600,000 4%
Australia 1,600,000 2%
Bahrain 1,500,000 2%
Iceland 880 1%
United States 880 1%
Rest of the world 9,400,000 14%
Total 66,560,000 100%

As with alumina production, some countries that produce bauxite and alumina also produce aluminium. These include India, Australia and Russia.

In 2022, the global aluminium market was valued at approx. USD 245.7 billion, the aluminium market is expected to almost double in size by 2030 to USD 498.5 billion.