A. McCulloch

Emission Functions

HCFC-22 (CHClF₂, chlorodifluoromethane) is used primarily within refrigeration and air conditioning systems as the working fluid. Some material is released into the atmosphere when these systems are first filled but the bulk of the losses occur subsequently during maintenance, or as the result of accidental damage or when the equipment is finally removed from service and scrapped. There are other minor uses in foam blowing and hermetically sealed systems.

As a consequence of the delay between first use and release, it is necessary to calculate emissions from time series of data on production and sales into three end-use categories having short, medium and long-term "banking times". The calculation method is described in Midgley and Fisher (1993).

Of the sales into "Short Banking Times" (mainly open cell foam), 83% are released in the year of manufacture and the remainder in the year following. Releases from "Medium Banking Times" (predominantly refrigeration) are distributed approximately normally about a 4.5 year mean following a 30% initial loss, so that all of the charge is expected to be lost within 10 years. Material in "Long Banking Times" applications is released at the rate of 2%/year. Emissions do not depend on the season of the year.

Basic Data on Sales

There is no single data set for global sales of any of the fluorocarbons. That compiled by industry (AFEAS, 2001) is compound specific and audited to ensure quality control, but has incomplete geographical coverage; production in China, India, Korea and Russia is not included. The data on production and consumption (the latter equating to sales) compiled by the United Nations Environment Programme to verify the application of the Montreal Protocol are neither compound specific nor audited although they do cover all parties to the Protocol (UNEP, 2002). UNEP data are reported as the aggregate total of all HCFCs in ODPtonnes (Ozone Depletion Potential multiplied by metric tonnes). Submissions by individual countries are incorporated into the UNEP database with no further checks and reported values have been revised, without explanation, several years after they were first submitted.

These data sets have been amalgamated to provide global consumption values with defined quality and uncertainty and the distributed emissions described here were based on Midgley and McCulloch (1997) and Aucott et al. (1999).

Geographical Distribution of Emissions

The calculated global emissions of HCFC-22 were distributed among countries using the distribution of CFC-12, calculated in McCulloch et al. (1994), as a surrogate. Within each country, emissions were distributed to individual gridsquares using the population distribution in Li (1996).

Results are presented here as the percentage distribution among gridsquares, with no cut-off at low values. Absolute emission from each gridsquare in 1990 should be calculated by multiplying global emission for 1990 in Table 1 by the gridsquare percentages in Table 2. For other years, the distribution in Table 2 should be applied to the global emission for the appropriate year. While global emissions change relatively rapidly, distribution is affected only by relative economic activity and population dynamics, which have slower rates of change with time. It is expected that the distribution can be applied to the years 1985 to 1995 without significantly increasing uncertainty but this has not been tested. It can be applied to years beyond this range only with caution and new distributions for more recent years are under development.

Time Series of Global Emissions

Taken from McCulloch et al., 2002 (itself compiled from AFEAS, 2001 and UNEP, 2002), the time series (1943 to 2000) of HCFC-22 emissions and their uncertainties is shown in Table 1 .

Future emissions will be governed by the controls required by the Montreal Protocol and by the quantity of material currently in the "bank" (that is: material which is in use but has not yet been emitted). A scenario for future releases of HCFC-22 was described in Madronich and Velders (1999). This scenario has been updated and will be published in Fraser and Montzka (2003).