Emissions of Substitutes for Ozone-Depleting Substances
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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories EMISSIONS OF SUBSTITUTES FOR OZONE-DEPLETING SUBSTANCES ACKNOWLEDGEMENTS This paper was written by Reynaldo Forte, Jr. (USEPA), Archie McCulloch (ICI Chemicals & Polymers, Ltd.), and Pauline Midgley (M&D Consulting). Several reviewers made valuable comments on draft versions of this paper, including Stephen Seidel (USEPA), Thomas Martinsen (IPCC/OECD/IEA Inventories Programme) and Dina Kruger (USEPA). ABSTRACT Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulphur hexafluoride (SF6) are emitted from a number of end use sectors in which they substitute for ozone-depleting substances. These include refrigeration, air conditioning, aerosol applications, fire suppression, foam blowing, sterilants, and solvents. Emissions of these gases may occur within a year of sale or gradually over several years depending on the application. Aerosols, open-cell foam blowing, and solvents are typical sectors where the chemical is rapidly emitted, while these emissions may be delayed for decades in refrigeration, fire suppression and closed-cell foam blowing. Recovery, recycling and destruction can further delay or eliminate the release of these gases into the atmosphere. The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC Guidelines) include two methods: • The Tier 1 or “potential” method estimates emissions as being equal to current chemical consumption, where consumption is defined as chemical production plus imports minus exports and destruction. This method of calculating national emissions is simple to perform and recognises that all material consumed has the potential of being emitted eventually, but it seriously distorts the timing of emission by assuming that it occurs when the chemical is first consumed. However, it is generally easy to obtain an accurate value for the quantity consumed and so this method can be used to report an accurate total emission, and • The Tier 2 or “actual” method uses much more data to estimate when the chemical will be released into the atmosphere by taking into consideration the equipment-dependent delay that occurs between the time a chemical is sold and the time it is emitted from its end use. Since approximately twenty different HFC and PFC chemicals could potentially be used as substitutes to ozone-depleting substances, with numerous and extremely diversified emissions sources, implementing the actual methods would involve dealing with high volumes of data and levels of complexity. Since Tier 2 methods can represent annual emissions more accurately, the Parties have decided that actual emissions of HFCs, PFCs, and SF6 should be estimated and reported, where data are available, and that Parties should make every effort to develop the necessary sources of data (Decision 2/CP.3). There are multiple options for implementing both the Tier 1 and Tier 2 methods. For Tier 1 methods, estimates can be simply based on consumption data (Tier 1a) or they can be adjusted to account for chemicals contained in imported and exported equipment (Tier 1b). For the Tier 2 method, estimates can be developed using a top-down approach that disaggregates chemical consumption data into sectors and then applies time-dependent emission factors. This method requires chemical distribution data that may not exist for some sectors and therefore may need to be derived from information on chemical sales from producers and purchases from users. Alternatively, emissions can be estimated using a bottom-up approach based on an inventory of the number of products and uses where these substances are consumed and emitted. This method does not require consumption data, but it does require extensive data from producers and users of chemicals to facilitate the estimation of emissions from end uses and applications. Reporting has been problematic for this source. Not only have several countries not reported emissions from these chemicals, but the submissions from the Parties that reported lacked transparency [UNFCCC/SBSTA/1998/7]. Currently, HFCs, PFCs and SF6 emissions are reported under the IPCC category 2E (production of halocarbons and sulphur hexafluoride) and 2F (consumption of halocarbons and sulphur hexafluoride). The tables do not have specific entries for the individual species of HFC or PFC. Emissions of different species cannot be summed on a mass basis because there are many different HFCs and PFCs, with Emissions of Substitutes for Ozone-depleting Substances 257 Background Paper different global warming potentials (GWPs) and also it is not clear whether individual country reports have been weighted by GWP. Ensuring the quality of an inventory also requires that countries implement quality assurance and quality control programmes, which will need to occur at several steps in the process. At the plant or company level, key activities include quality control to ensure the accuracy of data (such as plant level measurements, calculations and data), as well as the provision of sufficient documentation. At the level of the inventory agency, the accuracy of plant or company submissions as well as the compiled inventory must be ensured together with the maintenance of appropriate documentation. One or more different types of external reviews and audits may also be appropriate for these sources. This is particularly important for Tier 2 methodology which relies on subjective data. 258 Industrial Processes Sector Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories 1 INTRODUCTION 1.1 Nature, magnitude, and distribution of source HFCs, PFCs, and SF6 are emitted from a number of sectors in which they substitute for ozone-depleting substances. These include refrigeration, air conditioning, aerosol applications, fire suppression, foam blowing, sterilants, and solvents. Only those portions of HFC-23 and PFC emissions that are used in fire suppression, low-temperature refrigeration, heat transfer fluid and solvents are included in this paper. Table 1 lists most of these chemicals, their atmospheric life-times, global warming potentials (GWP) relative to CO2 at a 100-year integrated-time-horizon and typical sectors or uses. TABLE 1 PROPERTIES AND USES OF HFCS, PFCS, AND SF6 Chemical Life-time GWP Sector/Use (years) (100-yr) HFC-23 264 11,700 Byproduct of HCFC-22, used in very-low temperature refrigeration, blend component in fire suppression, and plasma etching and cleaning in semiconductor production. HFC-32 5.6 650 Blend component of numerous refrigerants. HFC-43-10mee 17.1 1,300 Cleaning solvent. HFC-125 32.6 2,800 Blend component of numerous refrigerants and a fire suppressant. HFC-134a 14.6 1,300 Most widely used refrigerant, blend component of other refrigerants, propellant in metered-dose inhalers and aerosols and foam blowing agent. HFC-152a 1.5 140 Blend component of refrigerant blends and aerosol propellant. HFC-143a 48.3 3,800 Blend component of refrigerant. HFC-227ea 36.5 2,900 Fire suppressant and propellant for metered-dose inhalers. HFC-236fa 209 6,300 Refrigerant and fire suppressant. HFC-245fa 7.71,2 8161,2 Foam blowing agent and refrigerant. HFC-245ca 6.6 560 Not in commercial use today, possible refrigerant in the future. CF4 50,000 6,500 Byproduct of aluminium production. Plasma etching and cleaning in semiconductor production and low temperature refrigerant. C2F6 10,000 9,200 Byproduct of aluminium production. Plasma etching and cleaning in semiconductor production C3F8 2,600 7,000 Low-temperature refrigerant and fire suppressant. C4F10 2,600 7,000 Fire suppressant C6F14 3,200 7,400 Precision cleaning solvent SF6 3,200 23,900 Cover gas in magnesium production and casting, dielectric gas and insulator in electric power equipment, fire suppression discharge agent in military systems, atmospheric and subterranean tracer gas, sound insulation, process flow-rate measurement, medical applications and formerly an aerosol propellant. GWPs and atmospheric lifetimes from IPCC [1995, 1996], except as noted below: 1 Junyi Chen et al. [1997] 2 Personal communication between Don Wuebbles, University of Illinois at Urbana-Campaign and Reynaldo Forte, U.S. Environmental Protection Agency, August 20, 1998 Emissions of these gases may occur within a year of sale or gradually over several years depending on the application. Aerosols, open-cell foam blowing and solvents are typical sectors where the chemical is rapidly emitted, while in Emissions of Substitutes for Ozone-depleting Substances 259 Background Paper refrigeration, fire suppression and closed-cell foam blowing these emissions may be delayed for decades. Recovery, recycling and destruction can further delay or eliminate the release of these gases into the atmosphere. Figure 1 illustrates cumulative emissions for CFC-11 in three end-use sectors (Gamlen et al., 1986). CFC-11 is not a chemical under consideration in this paper and Figure 1 should not be taken to be definitive. However, the patterns illustrate how HFCs and PFCs may be emitted when used in similar applications. Emissions of substitutes in these sectors are likely to follow similar patterns. However, new refrigeration equipment, with better containment is likely to extend the time before full release. Figure 1 Emission functions for CFC-11 Emission Functions for CFC-11 1 0.8 0.6 0.4 0.2 Emission Cum. 0 01234567891011121314151617181920 years since sale Closed-cell foam Aerosol Refrigeration Note: The emission function assumes full release with no destruction on disposal