An evaluation on the environmental consequences of residual CFCs from obsolete household refrigerators in China
Introduction
Chlorofluorocarbons (CFCs), a compound composed of carbon, fluorine, and chlorine elements and first synthesized in the 1930s, has been widely used in refrigeration units, foam and other industrial products because of its excellent characteristics (James, 2008). Since 1974, however, it has been recognized that CFCs are ozone-depleting substances (ODSs) (Molina and Rowland, 1974, Archie, 2003), with high ozone-depleting potential (ODP) values, and can exist in the atmosphere for as long as 100 years (Ravishankara et al., 1993, Volk et al., 1997). CFCs are released into the environment from various means (Gamlen et al., 1986, McCullocha et al., 2001, Kjeldsen, 2008), and can decompose into chlorine atoms when exposed to ultraviolet radiation after diffusing into the stratosphere – a situation that can lead to ozone depletion. Furthermore, ozone depletion can lead to increased ultraviolet radiation reaching the surface of the earth, which endangers human health and ecosystems. The important reaction mechanisms are as follows:
CFCs are also greenhouse gases (GHGs) (Wigley, 1988, James, 2002), with high global warming potential (GWP) when compared to CO2. The GWP of CFCs ranges around 4680–10,720 (IPCC, 2005).
In order to protect the ozone layer, a total of 24 countries signed the Montreal Protocol on substances that deplete the ozone layer, an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. The treaty was created on September 16, 1987 and entered into force on January 1, 1989 followed by a first meeting in Helsinki, in May 1989. So far, 191 countries have signed the Montreal Protocol. According to the protocol, CFCs are restricted in both production and consumption, and need to be phased out by specified dates (Richard, 2002). China ratified the Montreal Protocol in 1991, and established the Chinese National Program to phase out ozone-depleting substances in 1992 (SEPA, 2007).
In China, CFCs contained in household refrigerators consist mainly of CFC-11 and CFC-12, which are used as refrigerants and foaming agents, respectively (SEPA, 2007). CFCs were to be phased out in the household refrigeration industry, starting in 1994, and to be completely banned by 2005. Considering the average lifetime of household refrigerators, the quantity of obsolete household refrigerators that contain CFCs is anticipated to peak in the upcoming years. Consequently, the release of residual CFCs will soon reach their maximums.
This study aimed to investigate the potential release of residual CFCs and their substitutes from obsolete household refrigerators, in order to clearly address and evaluate their associated environmental impacts, including their contributions to ozone depletion and greenhouse effect, compared to other recognized ozone-depleting substances (ODS) and greenhouse gases (GHGs).
Section snippets
CFCs and substitute substances
Various substitutes have been used in the household refrigeration industry since CFCs were initially targeted to be phased out in China in 1994. The major substitutes for CFC-11 are cyclopentane and HCFC-141b; for CFC-12, HFC-134a, isobutane and HFC-152a. The characteristics of CFCs and their substitutes are listed in Table 1.
Quantity of obsolete household refrigerators
The annual quantity of obsolete household refrigerators containing CFCs can be estimated based on the annual production for use in China, the lifetime of the units, and
Contribution to ozone depletion
The main ODSs of high production and consumption in China included CFC-11, CFC-12, CFC-113, halons, carbon tetrachloride (CTC), 1,1,1-trichloroethane (TCA, cleaning solvent), HCFC-22 and HCFC-141b (Wan et al., 2009). CFC-11 was used mainly as a foaming carrier agent in the foam-blowing sector, an expanding agent in the tobacco sector, and an early refrigerant in the industrial and commercial refrigeration sector (SEPA, 2007). CFC-12 was used mainly as a refrigerant, and partly as a foaming
Conclusion
In the present paper, the release of residual CFCs and their substitutes from obsolete household refrigerators in China was examined. Contributions of CFCs to ozone depletion and greenhouse effect were compared to other recognized ODSs and GHGs. The following conclusions can be drawn:
- (1)
The quantity of obsolete household refrigerators which contain CFCs will reach its maximum at 11.5 million in 2011, and then decrease theoretically to zero until 2020. Accordingly, the annual release amounts of
Acknowledgements
This study was funded by a special subject of the 2007 National Environmental Protection Nonprofit Industry Scientific Research (No. 200709040).
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