Raw materials extraction of aluminium

Environment

Opencast mining requires lots of space. In recent years, local legislation or contracts between governments or landowners and mining companies has required subsequent complete recultivation of mining sites to protect the environment. Once bauxite mining has finished, the land has to be transformed so that it can be used either for agriculture or recreational purposes.

An example of a successful programme of recultivation is the Gove mine in Australia. Here, the bauxite deposit was 3 to 4 metres thick under a layer of humus only 0.6 metres deep. Over 1100 hectares were recultivated between 1973 and 1989. Germination and field trials had previously been carried out under local conditions to find the method best suited for the recultivation:

  • The vegetation was removed two years before mining started.
  • Before mining began, the humus layer was first enriched with the seeds of indigenous plant species and then stripped away and stored
    (in Gove this was about a million m3 a year).
  • Once the bauxite had been mined, the subsoil was loosened to aerate it and to facilitate subsequent root growth.
  • The humus that had been kept stored was then spread over the aerated ground and grass was sown as the first stage of vegetation in order to protect the humus from erosion in the first few years.
  • Finally, before the rainy season started, seeds from indigenous plants were sown and the humus received an additional, one-off fertiliser treatment with 300 kg per hectare of a phosphorus-based fertiliser.

The Australian government confirmed that within a few years the local fauna and flora had almost returned to its original state. In Europe (e.g. in Hungary and the territory that was formerly Yugoslavia) bauxite is mined at greater depths. These relatively small mines have only a small detrimental effect on the landscape and the environment.

The conservation of rain forests is a key subject that is often raised in connection with bauxite mining. Some 18% of bauxite mining worldwide is currently being carried out in areas within the rain forest, affecting an area of about two square kilometres every year. This compares with a total area of rain forest of some 14 million square kilometres. The 18% being mined that is within the rain forest is not turned over to agriculture once mining operations have ceased; instead, it reverts back completely to rain forest.

You can find out more about the aluminium industry’s efforts to produce the metal in a manner that is both economical and environmentally friendly in the chapter headed Ecological aspects relating to aluminium.