Awakening of the Aluminum Industry to PFC Emissions and Global Warming

摘要

Perfluorocarbons (PFCs) do not affect stratospheric ozone depletion; however, they have extremely long atmospheric lifetimes. They are very stable because of the strength of the carbon-fluorine bond, one of the strongest in organic chemistry, and it is because of their inertness that PFCs are powerful greenhouse gases (GHGs). CF_4 has a global warming potential (GWP) over 100 years 6,630 times more potent than CO_2, whereas C_2F_6 and the lesser known C_3F_8 have GWPs of 11,100 and 8,900, respectively. The high GWP of atmospheric PFCs led to an increase of public concern about the effects of their accumulation in the earth's atmosphere in the 1990s. At that time significant PFCs were only considered to occur during 'anode effects' (AEs) in the aluminum industry. There was a renewed worldwide concern about greenhouse gases which focused attention on PFC emissions from aluminum smelting. In response, aluminum producers initiated aggressive programs to decrease both the frequency and duration of AEs at most smelters globally. International voluntary programs to reduce AE frequency and duration proved to be exceptionally successful as PFC emissions were reduced in ten countries by 31%-78% relative to 1990 levels; the overall average reduction in PFCs for countries was 46%. This paper provides a historic overview of the discovery of PFCs, and highlights some of the first investigators in every phase of the journey to understand, measure, account for, and reduce the emission of these potent GHGs.