The above graph shows the combined results of fluoride emissions for the stacks at the fume treatment centers and the roof vents at the potrooms. The limit for annual fluoride emissions changed in 2011 and is now 0.95 kg F/t Al for the three plants using the prebake technology (the Deschambault Smelter has been subject to this standard since 2007).
In Baie-Comeau, we recorded a slight improvement at the scrubbers but a decline at the roof vents, similar to our 2010 performance. This decline is attributable to a number of operational factors. For the Bécancour Smelter, we recorded improvement at the scrubbers but emissions at the roof vents remained just as high as in 2010. At the Deschambault Smelter, total fluoride emissions remained stable in 2011.
Fluoride emissions – Söderberg Plant
While fluoride emissions at the Söderberg potrooms were higher in 2011 than in 2010, they still met the target established in the environmental performance agreement signed with the Ministère du Développement durable, de l’Environnement et des Parcs. Emissions remain well below the newly established limit of 2.25 kg F/t Al.