PFC Emissions from Detected Versus Nondetected Anode Effects in the Aluminum Industry

Abstract

Perfluorinated carbon compounds (PFCs) CF 4 and C 2 F 6 are potent greenhouse gases that are generated in aluminum reduction cells during events known as anode effects (AEs). Since the 1990s, the aluminum industry has made considerable progress in reducing PFCs from conventionally defined and detected AEs. However in recent years, the industry has noted the presence of unaccounted PFCs that are generated outside the conventional AE definition. Two additional AE categories have been proposed, namely low-voltage, propagating AEs (LVP-AEs) and nonpropagating AEs (NP-AEs) that relate to continuous, background levels of PFC emissions. These unaccounted PFC phenomena may help explain the recent discrepancy between industry accounting and atmospheric measurements of global PFC emissions. Estimates from AGAGE, a global network of atmospheric observatories, suggest as much as 50% underaccounting of PFCs by the aluminum industry in the 2006–2010 period. The following work reviews this discrepancy and the potential role played by LVP-AEs and NP-AEs.