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Spent pot lining
Our suppliers: Partners in environmental conservation
Québec smelters achieve recycling rate of nearly 90% for spent pot lining
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Our approach to waste management is to reduce waste generation wherever possible. When waste generation is unavoidable, we attempt to reuse the waste ourselves or make it practical for others to use. A regional committee made up of representatives from each Alcoa Canada Global Primary Products facility identifies and shares solutions to decrease landfilling.
Spent pot lining
The spent lining of electrolytic cells (pots) is the largest source of waste generated by an aluminum smelter. A leader in finding optimal ways to transform this type of waste, Alcoa supplies spent pot lining to a number of plants worldwide (including cement plants), which use them as a fuel source or mineralizer. Throughout the years, we implemented solutions that enabled us to significantly increase our recycling and energy recovery rates for the spent pot lining produced in Québec. Waste products that cannot be recycled or valorized are sent to Alcoa’s Gum Springs plant for treatment and disposal.
Managing the waste produced by an aluminum smelter also involves the treatment of a by-product called casthouse dross. Primarily composed of aluminum, it is recycled internally or by external suppliers, who extract the aluminum content and recycle or landfill the remaining waste products. A technical team developed internal casthouse dross recycling methods which, in 2011, made it possible to recycle internally 8 % of the dross generated. This rate rose to 23 % in 2012, but diminished in 2013 with the curtailment of the Söderberg pots. Fortunately, this did not reflect on the total rate of casthouse dross recycled, which rose to 68 % in 2013.
In addition to spent pot lining and casthouse dross, our plants also generate some waste products that are landfilled because there is currently no other solution. We are actively seeking other avenues for these waste products in an effort to achieve our landfilled waste reduction targets.
In 2013, we were unfortunately forced to landfill 9,295 metric tons of process waste from the Söderberg plant in Baie-Comeau, which had been stored for reuse in the process. This accounts for the higher quantities of landfilled waste, excluding spent pot lining, recorded (17,144 metric tons, compared to 8,401 metric tons in 2012).