Substitutes for Potent Greenhouse Gases 1 BackgroundIn 1997, Danish industry utilised app. 890 tonnes of
HFCs, app. 13 tonnes of SF6 and app. 8 tonnes of PFCs.
(44%, 52%, 4%) GWP (Global Warming Potential) for HFC-143a is 3800 and GWP for HFC-125 is 2800. In comparison the definition of GWP = 1 for CO2 Figures showing the amount of consumption appear from a survey performed by the Danish EPA on ozone layer depleting substances and potent greenhouse gases (the Danish EPA, 1998). This report has been prepared by Jan Holmegaard Hansen and Tomas Sander Poulsen, COWI. It appears that if the entire amount of these substances is released to the atmosphere, it will cause an increased emission of greenhouse gases, corresponding to app. 1.69 million tonnes, which is nearly 3% of the Danish CO2 emission (57.3 million tonnes in 1997, corrected for electricity export). It should be emphasised that the figure represents the consumption of raw materials and for that reason the potential emission of these substances. The actual emission will depend on the extent of recollection and successful destruction of the substances. A substantial increase in the consumption of HFC substances has been registered. In some cases these substances are used as substitutes for CFCs and HCFCs. However, consumption in 1997 is at the same level as in 1996. In 1997, 1225 tonnes of HCFC were used in Danish industry and it can be expected that part of the consumption will be converted into HFC substances when the use of HCFC becomes prohibited in the year 2000/2002. From an environmental point of view the use of HFC substances instead of CFCs and HCFCs is an improvement, because the impact on the ozone layer is eliminated. CFCs and HCFCs are also very strong greenhouse gases, but a certain amount of disagreement currently prevails about how the substances exactly contribute to the greenhouse effect. The substances contribute with two contradicting effects: On the one hand they are very strong greenhouse gases with GWP values of 4000 (CFC-11), 8500 (CFC-12) and 1700 (HCFC-22). On the other hand, the substances contribute to the decomposition of stratospheric ozone, which also is a green house gas. In addition, it should be mentioned that the contribution to the greenhouse effect for different HFC substances covers a wide field. For instance GWP values range from 140 (HFC-152a) to 11700 (HFC-23). A substantial increase in the consumption of PFC substances is also expected because of an intensive sales campaign for a drop-in substitute for CFC-12 in refrigeration systems. This drop-in refrigerant contains a PFC substance with a high GWP factor and a very long atmospheric life (see chapter 5). Achievements so far By means of the now completed CFC programme (initiated by the Danish EPA) and the Cleaner Technology programme, various activities have been supported to encourage development of products and production processes that do not use HFC or other potent greenhouse gases. In co-operation with industry various developments have been carried out, e.g. refrigerators and pre-insulated district heating pipes using hydrocarbons as blowing agent for insulating foam, apparatus for charging hydrocarbons in refrigerators, application of water and inert gases in fire extinguishers etc. Natural refrigerants comprise the consumption of substances which already form part of nature's own cycle, i.e. ammonia, hydrocarbons, CO2, water and air. Some of these refrigerants might be chemically produced, e.g. ammonia. The Cleaner Technology activity that at present is in progress is called "Programme for Natural Refrigerants" and is carried out by DTI Energy in co-operation with a number of industrial companies. Several initiatives have already been put into action: development of methods to produce small ammonia refrigeration systems, a machine for production of ice slurry (a mixture of water, alcohol and ice, applicable as secondary refrigerant) and a preliminary project on cooling containers (reefers). In addition, a major international conference on natural refrigerants was held in Aarhus, Denmark in September 1996, and it received financial support from the Danish EPA. In addition, the Danish Energy Agency supports the development of new energy saving refrigeration systems using natural refrigerants. The following projects can be mentioned: Development of a refrigerant plant, using water as refrigerant (the "LEGO-plant"), development of commercial refrigerators using hydrocarbons as refrigerants, application of ammonia as refrigerants in supermarkets and an ammonia cooling system as demonstration plant in a big city hotel. It should be mentioned that the total consumption of CFC substances in the late 1980's amounted to app. 6000 tonnes. Most of the previous applications of CFC have now been replaced by natural substances, i.e. hydrocarbons in aerosol cans, in insulating foam and in certain refrigeration systems, water for cleaning electronic components, ammonia in certain refrigeration systems, etc.
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