Tailings from bauxite extraction consist of mineral rejects from the extraction process mixed with water. No chemicals are added. The tailings at Paragominas are stored in dedicated tailing ponds, where the particles settle.
Bauxite residue, also known as red mud, is a by-product of the alumina refining process. Alunorte uses the Bayer process, which includes the use of caustic soda. The residue is washed with water to lower the alkalinity and recover caustic soda to be reused in the process. The residue is dry-stacked, which means it is transformed into a clay-like solid with a low moisture content.
Spent potlining (SPL) from the reduction cells used in primary aluminium production is defined as hazardous waste. The production of SPL varies with the relining of smelter cells which is normally done every 4-7 years for established smelters.
