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 tons of SO2 was set for all three smelters in the environmental performance agreement with the ministère du Développement durable, de l’Environnement et de la Lutte aux changements climatiques (MDDELCC). This target was met in 2013. In fact, emissions declined to 17.24 kt in 2013, from 19.18 kt in 2012, due to the closure of the Söderberg plant in Baie-Comeau.