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 by the anode baking oven and in the electrolytic potrooms. The prebake plant at the Baie-Comeau Smelter purchases its prebake anodes from other plants. This is why its emissions are lower compared to the other smelters since its emissions are generated strictly during the electrolysis process. The Bécancour and Deschambault smelters manufacture their own anodes. They both have one or more anode baking ovens, in addition to the electrolysis process contributing to emissions.
Sulfur emissions increased in 2011 at the Deschambault and Baie-Comeau smelters due to higher sulfur levels in the coke used.
As part of the environmental performance agreement signed with the Ministère du Développement durable, de l’Environnement et des Parcs, an annual target of 20,500 tonnes of SO2 was set in 2009 for all three smelters. In 2011, we were well below this target, with total emissions of 17,356 t SO2 for the region.