With a share of 8 %, aluminium is the third most abundant element in the earth’s crust. Thus, the availability of raw material supplies for the production of aluminium is almost unlimited.
The common raw material for aluminium production, bauxite is composed primarily of one or more aluminium hydroxide compounds, plus silica, iron and titanium oxides as the main impurities. It is used to produce aluminium oxide through the Bayer chemical process and subsequently aluminium through the Hall-Heroult electrolytic process. On a world-wide average 4 to 5 tonnes of bauxite are needed to produce two tonnes of alumina, from which one tonne of aluminium can be produced. In Europe, usually the average bauxite consumption is 4.1 tonnes per tonne of aluminium.
More than 160 million tonnes of bauxite are mined each year. The major locations of deposites are found in a wide belt around the equator. Bauxite is currently being extracted in Australia (in excess of 40 million tonnes per year), Central and South America (Jamaica, Brazil, Surinam, Venezuela, Guyana), Africa (Guinea), Asia (India, China), Russia (and Kazakhstan) and Europe (Greece). The total area ruined per year is 20 km².
Picture: open cast mining
The material is mainly extracted by open-cast mining, which has a variable and highly site-specific effect on the local environment. The primary ecological concerns connected to this operation are related to the clearing of vegetation, affect on local flora and fauna, and soil erosion.
Bauxite mining in forest areas
The conservation of rain forests is a key concern often voiced with regard to bauxite mining. Only about 12% of the world's bauxite mining is today conducted in tropical rain forests, affecting a total area of around 2,4 km2 per year. The total area of the globe currently covered by rain forest is about 18 million km².
The original flora and fauna of much of the land involved in bauxite mining is restored once mining operations have ceased. For all forest areas used for bauxite mining, 80% is returned to native forests, the rest is replaced by agriculture, commercial forest, or recreational area, thereby making the area more productive for the local community. As far as rain forests in particular are concerned, however, the area used for bauxite mining in rain forests is almost totally reverted back to rain forest. 97% of operations have rehabilitation plans in place.
Reasons for loss of rain forests
Revegetation
Picture: 'Foreground: revegetated open-cast mine'
During the preparation of a site for open-cast mining, the surface soil is removed to get access to the bauxite. In order to avoid soil erosion and to ensure that vegetation is returned to the land, many companies have water drainage practices during mining operations, separate removal of top soil (50 per cent reuse it directly after the mining operation) and over 60 per cent have their own nursery plant facilities. Rehabilitation plans are established prior to the start-up of operations and the investments required to implement these plans are built into mining costs.
The aluminium industry’s reforestation and recultivation techniques are state of the art
Alcoa won for example in 1990 the United Nations Environmental Programmes "Global 500 Roll of Honour for Environmental Achievement" award for exemplary reforestation and recultivation of its bauxite mines in Western Australia. A computer-based system that integrates mining with environmental management was developed : the Geographical Information System (GIS). It helps engineers and scientists to produce accurate mine plans that consider biological diversity, land use value, and water quality.
The aluminium industry land reclamation experience is outstanding
At Mineração Rio de Norte Tromlectas, about 700.000 cuttings for 100 different species are produced evey year in their nursery. By 2002, 17 km² of mined area has been reforested. The process is montored by scientists from local communities.
