SO2 emissions depend on the percentage of sulfur in the tar pitch and coke used to manufacture anodes. It is increasingly difficult to find coke that is low in sulfur content.
Sulfur emissions are generated at the anode baking oven and in the electrolytic potrooms. Since the Baie-Comeau Smelter does not have anode manufacturing or baking facilities, it sources its anodes from the other smelters. Its emissions are generated strictly during the electrolysis process and, therefore, are slightly lower compared to the other plants.
An annual target of 20,500 tonnes of SO2 was set in the environmental performance agreement with the Ministère du Développement durable, de l’Environnement et des Parcs. This target was met in 2012, despite an increase in emissions at all three smelters that manufacture anodes due to changes in the sulfur content of the coke used.