About 7 percent of the earth’s crust is aluminium, making it the third-most abundant element after oxygen and silicon. Aluminium production starts with the raw material bauxite.
Bauxite is a mineral found mostly in a belt around the equator. Bauxite, containing 15-25 percent aluminium, is the only ore that is used for commercial extraction of aluminium today.
The bauxite occurs mostly in the tropics, in horizontal layers normally beneath a few meters of overburden. The layers are usually mixed with various clay minerals, iron oxides and titanium dioxide. It is the iron that gives bauxite a deep red color.
How much bauxite is there?
Known reserves of bauxite are around 29 billion metric tons. At the current rate of extraction, these reserves will last more than 100 years.
When we include undiscovered bauxite resources, this number is estimated at 55-75 billion metric tons.
This extends the time perspective to 250-340 years.
Bauxite mining in million metric tons per year
Other aluminium ores
The aluminium industry is also preparing to use ores other than bauxite in the future. Research to develop extraction processes from other minerals is ongoing, and in the future we envision using more recycled metal, from buildings, for example.
World production (right) and reserves (left) of bauxite
How do we get bauxite from the mines?
Bauxite is usually covered by an overburden of several meters of rock and clay, which must be removed before the bauxite can be recovered.
Then, the bauxite is transported to crushing or washing plants, before it is transported for processing.
The clay is then usually deposited in tailing ponds. After its use, these tailing ponds are replanted using local species to re-establish natural vegetation.
How much does bauxite mining affect the environment?
Because the bauxite is located close to the surface, mining disrupts the surface.
Every year, the worldwide use of new land related to bauxite mining is 40-50 square kilometers. However, after the mining operations have been completed in one area, it is normally re-vegetated with local species.
Environmental issues caused by bauxite mining
- Change of landscape and impact on biodiversity: Removal and re-establishment of vegetation
- Control of erosion and run off from the mine – the landscape being affected when rock and soil are removed
- Disturbance of hydrology – the movement, quality and distribution of water.
- Waste disposal
- Dust and noise caused by mining operations and transport
- When new areas are opened, this can provide access to illegal logging, hunting, etc.
On average, one square meter of land is mined (including roads and infrastructure) in order to produce one metric ton of aluminium metal.
What do we do about it?
Most bauxite mining companies have subscribed to voluntary improvement programs, involving land rehabilitation, for example.
A survey covering the period 2002-2006, showed that the land rehabilitation equaled the land being mined during the period. The mines in the survey included 66 percent of the world’s bauxite production.
Mining in tropic forest areas
The health of the ecosystems, preserving variation of life forms, is one of the world’s top environmental issues.
The tropical forest areas are among the most threatened areas.
The aluminium industry is a minor player in the greater picture:
- The global rate of destruction of tropical forests = 80,000 km2per year.
- 20% of the 40-50 km2 annual land taken by bauxite mining is in tropical forest areas.
- These 8 km2 = 0.01% of the annual loss of tropical forest due to other causes.
Considering the rehabilitation programs, where we aim at no net loss of forests, the influence is even less. Most of the tropical forest areas were already impacted by for example logging before bauxite mining started.
Replanting in Paragominas
Hydro is the majority owner in the Paragominas bauxite mine in Brazil. Paragominas is located in the deforestation belt around the Amazon River, and this is one of the places where reforestation is put into practice.
2006: Bauxite extraction started in Paragominas
2009: Reforestation program started
2017: Our goal is to level out land impacted by mining and land rehabilitated by 2017.
The landscape is systematically shaped back to how it looked before mining. The topsoil is then added and seedlings are planted in a grid in the areas prepared. The seedlings grow into a forest similar to the natural forest in the areas.