Historic emissions of fluorotrichloromethane (CFC-11) based on a market survey

Releases of CFCs occur promptly from applications such as aerosol sprays, or over a period of several years from refrigeration and air conditioning or more slowly still from use as blowing agents for closed cell plastic foams. As a consequence of the Montreal Protocol, the emissions have fallen and their pattern is continuing to change. To help quantify these changes the emissions from closed cell foam blowing have been re-examined in a comprehensive market survey, developing a lifecycle assessment for each foam type, production method and foaming agent. The original model for the time series of emissions from foam applications was shown to remain a robust representation in general terms. There is an "immediate" loss when the foam is manufactured, a slow emission from the foam itself during use and a loss on disposal of the artefact made with the foam. The original model used an initial loss rate of 10% and a subsequent loss of 4.5% yr(-1) over 20yr. The new survey showed a wide range of initial and service loss rates. Immediate release ranges from 95% down to 4%; similarly, the rate of loss during service varies from 0.5% to 5% yr(-1) and the service lifetimes of the artefacts made with the foams varies from 12 to 50 yr. The apparent emission function, in terms of the mean value of the annual fractional release from the bank of CFC-11 residing in foams, was calculated from the survey to be 0.043 +/- 0.008 over 28 yr. There is a small and non-significant fall in this function with time; so that over the last ten years of the data record the more appropriate value is 0.0366 +/- 0.0008. However, up to the early 1990s, it is the original emission function that is consistent with the observed atmospheric concentrations. Thenceforth this function seriously overpredicts the concentrations but, if the new emissions function for foams is used from 1993 onwards in conjunction with the original emission functions for all other uses, the fit becomes better. This suggests that the emission functions for prompt and short term releases remain valid and should be coupled with the new function to calculate emissions of CFC-11 or other fluorocarbon foam blowing agents from the early 1990s onwards. (C) 2001 Elsevier Science Ltd. All rights reserved.