The main waste generated during the aluminium production cycle, is during alumina production and is called «red mud», a thick suspension of water-insoluble silicates, aluminium silicates and metal oxides. The red mixture, which colour is due to a high iron content, is generated during the Bayer process. Producing one tonne of aluminium oxide in turn produces 360–800 kg of mud. However, many experts doesn’t consider this to be waste as, theoretically, it can be used as a raw material for processing. However, using this waste is nowadays not economically efficient and the mud is instead stored at carefully isolated red mud disposal areas. These are arranged so that the penetration of alkalis into ground waters is avoided. As a mud disposal area exhausts its potential, the land can be restored by covering it with sand, ash and turf and planting certain trees and grasses on the area. Full restoration may take many years, but he area will eventually recover its initial appearance.
One source of environmental risks is Soderberg technology, which is very effective and widely applied in Russia. It generates a significant quantity of hazardous gases containing admixtures. However, this problem is being actively addressed now through colloidal anode implementation. A reduction cell using this technology is not less hermetic than using baked anodes.
Though these risks exist, from an ecological point of view, the most important advantage of aluminium is that it can be recycled. Old aluminium products can be used to produce new ones over and over again without any loss of quality. Reprocessing 1 kilogram of aluminium saves 8 kilograms of bauxite. In addition, there are huge power savings: melting and production of secondary aluminium consumes only 5% of the power required for the production of primary aluminium.
For example, one recycled aluminium can saves enough power to watch three hours of television. One tonne of used cans costs about 15,000 rubles. That is why in Russia the number of waste machines allowing the disposal of this precious secondary raw materials is growing.
Aluminium is justly called a light metal. The more aluminium is used to produce vehicles, the lighter they become and the less fuel is required to operate them. This also means a reduction in environmental risks.
