He stresses that the environmental challenges related to waste production, emissions and biodiversity should be taken seriously.
Hydro's ambition is to reduce environmental impact to a minimum throughout the entire life cycle of our products. Through the acquisition of Vale's aluminium operations in Brazil in 2011, we have also become a major extractor of bauxite and refiner of alumina. This confronts us with new challenges. At the bauxite mine in Paragominas, extensive programs have been established for the proper rehabilitation of forest and agricultural areas after bauxite is extracted. At the Alunorte alumina refinery in Barcarena, major efforts have been made to ensure the safe storage of the red mud created in the refining process.
Heavy rainfall led to discharge of red mud
Despite this, following one of the worst rainfalls on record, the Alunorte alumina refinery experienced a discharge of water containing red mud in 2009.
The discharge ended up in the Murucupi River where the water was colored red by the mud. An investigation was launched by Alunorte in cooperation with local authorities. The discharge contained traces of caustic soda, which is used in the process of producing alumina from bauxite, but there is no evidence of major damage as a result of the overflow.
No connection to Hungary
However, a tragic red mud accident at the Ajka plant in Hungary in 2010 showed how serious a discharge could be.
Red mud is a waste product from the production of alumina from bauxite. The mud is a residual compound consisting partly of elements that were in the original bauxite ore plus some elements added during the process. It is deposited as a thick slurry or semi-dry paste. Red mud normally contains silicon, aluminium, iron, calcium, titanium and sodium and a host of other minor elements, including potassium, chromium, vanadium, nickel, barium, copper, manganese, lead and zinc.
Methods for handling red mud
Almost all the alumina plants in the world store red mud in artificial pools or landfill sites. The storage facilities can be lined with impermeable clay and/or a synthetic fabric, like at Alunorte, where red mud is filtered and transported by trucks to a special landfill site.
Alunorte has implemented comprehensive environmental programs to ensure the smallest possible environmental impact. The solution is considered to be among the industry's best. The red mud is rinsed and filtered to remove process water and caustic soda and becomes a thick mass that is transported to the landfill site in trucks.
The entire landfill site is lined with membranes to prevent seepage into the ground. All drainage and rainwater is collected and sent to a processing plant where the pH is adjusted and particles are removed to meet the limits set by the authorities. When the site is full, it is covered with soil and planted with local plant species.