Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

EMISSIONS OF SUBSTITU TES FOROZONE-DEPLETING SU BSTANCESACKNOWLEDGEMENTS
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 thispaper, including Stephen Seidel (USEPA), Thomas Martinsen (IPCC/OECD/IEA Inventories Programme) andDina Kruger (USEPA).

ABSTRACT
Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulphur hexafluoride (SF6) are emitted from anumber 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 ofthese 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, whilethese 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. Thismethod 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 thequantity 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 theatmosphere by taking into consideration the equipment-dependent delay that occurs between the time achemical is sold and the time it is emitted from its end use. Since approximately twenty different HFC andPFC chemicals could potentially be used as substitutes to ozone-depleting substances, with numerous andextremely diversified emissions sources, implementing the actual methods would involve dealing with highvolumes 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 inimported 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 mayneed 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 anduses 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 fromend uses and applications.
Reporting has been problematic for this source. Not only have several countries not reported emissions fromthese 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 ofdifferent species cannot be summed on a mass basis because there are many different HFCs and PFCs, with

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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 orcompany submissions as well as the compiled inventory must be ensured together with the maintenance ofappropriate documentation. One or more different types of external reviews and audits may also be appropriate forthese sources. This is particularly important for Tier 2 methodology which relies on subjective data.

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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 ofthese 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 1PROPERTIES AND USES OF HFCS, PFCS, AND SF6
ChemicalLife-time(years)

GWP(100-yr)

Sector/Use

HFC-23264

11,700

Byproduct of HCFC-22, used in very-low temperature refrigeration, blend
component in fire suppression, and plasma etching and cleaning insemiconductor production.

HFC-325.6

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-152a1.5

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.

CF450,0006,500

Byproduct of aluminium production. Plasma etching and cleaning insemiconductor production and low temperature refrigerant.

C2F6

10,0009,200

Byproduct of aluminium production. Plasma etching and cleaning insemiconductor 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

23,900Cover gas in magnesium production and casting, dielectric gas andinsulator in electric power equipment, fire suppression discharge agent inmilitary systems, atmospheric and subterranean tracer gas, soundinsulation, process flow-rate measurement, medical applications andformerly 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 inEmissions of Substitutes for Ozone-depleting Substances259

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, thepatterns 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

Cum. Emission

1
0.8
0.6
0.4
0.2
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
years since sale
Closed-cell foam

Aerosol

Refrigeration

Note: The emission function assumes full release with no destruction on disposal at end-of-life.

1.2

The current state of inventory methodologies

The IPCC Guidelines include two methods: potential (Tier 1) and actual (Tier 2) and variations within those methods:•

The 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 thepotential 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 thequantity consumed and so this method can be used to report an accurate total emission.

•

The actual method uses much more data to estimate when the chemical will be released into the atmosphereby taking into consideration the equipment-dependent delay that occurs between the time a chemical is soldand 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 in the IPCC Guidelines would involve
dealing with high volumes of data and levels of complexity.

The IPCC Guidelines acknowledge that the potential method does not take into account accumulation or
possible release of chemicals in various products and equipment, which means that over the short term (e.g.,
10-15 years) estimates will become very inaccurate. The IPCC Guidelines further indicate that sinceaccumulation is thought to be the dominant process at the present time, potential emissions calculations willstrongly overestimate current emissions. On this basis, the Parties decided, at the third Conference of Parties (inKyoto), that the actual emissions of HFCs, PFCs, and SF6 should be estimated, where data are available, andused for the reporting of emissions; and that Parties should make every effort to develop the necessary sources ofdata. (See Annex A: Decision 2/CP.3).
To date, estimation and reporting of emissions from this and other sources of industrial greenhouse gases has
been incomplete and also lack in transparency. As summarised in a recent report of the United Nations

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Framework Convention on Climate Change (UNFCCC) Secretariat, current reporting practices for these gases
varies significantly among reporting Parties (FCCC/SBSTA/1998/7, para.77-81). In fact, several methodologicalissues associated with the reporting of the HFCs, PFCs and SF6 have been identified by reviewing National
Communications. A summary of those issues follows:•

Not all of the reporting Parties reported the three types of gases, and in general, data are incomplete. Only 21 of
the 34 Parties which submitted the second National Communications included estimates for these gases;•

Five Parties only reported aggregated figures for HFCs and PFCs despite the differences between the GWPvalues for these gases;•

The methods used for estimating emissions varied significantly among reporting Parties. Seven out of 21
Parties used the actual approach, three included both approaches, eight Parties used the potential and it is notclear what the others used, and•Estimates for actual and potential emissions can vary to a significant degree, depending on the mix ofdifferent types of HFCs and PFCs.

This assessment clearly highlights the importance of developing good practices for estimating and reporting
emissions of these gases.

2

METHODOLOGICAL ISSUESThe IPCC has outlined two broad methods for estimating emissions of substitutes for ozone depleting
substances. As discussed previously, the potential method (Tier 1) assumes that all emissions of these chemicals
occur in the year of production/consumption. The advanced method (Tier 2), in contrast, takes into account thetime delay in emissions from various sectors and end uses. Within each method at least two options can be used
to estimate emissions. The following sections briefly describe each method and evaluate them in terms of several
criteria, including resource requirements, the availability and quality of necessary data and accuracy. At the end of thissection, some additional issues are presented which involve the choice and implementation of either of the methods.

2.1

Tier 1 - Potential method

Potential emissions are defined by the IPCC methodology as being equal to the amount of virgin chemical
consumed in the country minus the amount of chemical recovered for destruction or export in the year of
consideration. This is consistent with the method used under the Montreal Protocol to track and reportconsumption of CFCs and other ozone-depleting substances.
The potential method, when compared to the actual method, offers a simple approach to estimating total
emissions of these gases. However, since it assumes that what is produced is emitted within the first year of
consumption, it is not an accurate measure of actual annual emissions. In certain applications, such as aerosol
products and open-cell foam blowing from which emissions are prompt, the potential method provides anadequate estimation of what is actually emitted in individual years. However, in other applications involving
closed systems like refrigeration and fire suppression most of their chemical charges might not be released until
many years or decades later.

2.1.1

Tier 1a - Basic potential method

Under the basic potential method, emissions equal current chemical consumption, where consumption is defined
as chemical production plus imports minus exports and destruction. This is the simplest of all methods in termsof resource and data requirements. The Tier 1 method requires enough data to enable the estimation of totalchemical consumption for each gas, which may be achieved by collecting chemical production, export, import,
transformation and destruction data.
The precision of this type of estimate should be quite high, since it relies on data of commercial importance thatis likely to be carefully tracked. The accuracy of this method as an estimate of actual emissions in a given year,
however, is more problematic. As mentioned above, this method will overestimate emissions, possibly by large
amounts. The review of submissions from countries that have estimated emissions using both actual andpotential emission methods, for example, indicates that potential emission estimates can exceed actual emission
estimates by a ratio of 16 to 1. On the other hand, the estimate of global emissions in AFEAS [2000], which isconsistent with measured atmospheric concentrations, suggests that emissions are one third of production. This
indicates that low national estimates of emissions are incorrect, probably due to flawed emission functions.

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2.1.2

Tier 1b - Adjusted potential method

Tier 1b is similar to Tier 1a except that the estimates are adjusted to take into consideration the chemicals
contained in imported/exported products. By making this adjustment, estimates reflect more accurately thenational distribution of emissions from products, as opposed to assigning emissions to the country where
equipment is manufactured.
Issues associated with Tier 1b are similar to those under Tier 1a in terms of the overestimation of actual
emissions. In addition, resource and data requirements are higher, because Tier 1b requires the same data in Tier
1a plus data on imports and exports of chemicals contained in products. Determining the specific chemicals usedin imported products, including their quantity, could be a difficult task, and access to such data may be limited.
Custom agencies may be a key resource in facilitating the gathering of these data.

2.2

Tier 2 - Advanced method (actual)

The IPCC recommended method combines the use of chemical consumption and detailed emissions from areasof application to estimate what is actually emitted in a given year. It requires calculation or estimation of theconsumption of each individual HFC and PFC chemical at its application level (i.e., refrigerators, foam blowing,
fire suppression equipment) to establish the volume basis for emissions calculations. Estimates of emissions arethen developed on the basis of the consumption distribution among the different sectors. In other words, under
this method, emissions are estimated by combining data on sector consumption with emissions information fromproducts and applications from within that sector.
The actual method explicitly accounts for the fact that chemicals are released in different forms and at different
times, ranging from when they are manufactured and charged into equipment to the time of disposal of theequipment. Thus, this method can reflect the emissions that may occur as fugitive losses during chemical
manufacturing, distribution, or product assembly, or be related to operation and maintenance or disposal of theequipment using the chemicals. The method can also allow for recovery of chemicals from equipment at
disposal.
The actual method incorporates emissions functions designed to simulate these chemical releases on a sectoral or
end-use basis. For example, the emissions from household refrigerators may be estimated by adding up
emissions during chemical manufacturing, equipment assembly, operation, and disposal. This requires thecalculation or estimation of average values for chemical charge, equipment lifetime, operation leak rates, percent
of chemical in the system at disposal, percent of recovery, etc. The IPCC Guidelines currently include default
values for various sectors and categories where the HFCs and PFCs are used, and suggest that these values may
be adjusted based on country circumstances. A series of equations is also included in the IPCC Guidelines tofacilitate emissions calculations.
The actual method may be implemented using two very distinctive approaches: the "top-down" (consumption
derived) or a "bottom-up" (application based). Both approaches are described below.

2.2.1

Tier 2 Top - down method

The top-down approach relies on the establishment of a history of consumption of each chemical in each sector
and estimation of emissions from those sectors based on emissions functions. As discussed above, the emissions
functions take into consideration when and how these chemicals are emitted within each sector. For sectors orapplications where the chemical is fully released during product manufacturing or use, such as open-cell foams
and metered-dose inhalers, the emissions may be estimated as being equal to the consumption in that sector orapplication. However, emissions from other products may continue over several years, and so the functions are
established as time series, which produce estimates of emissions over the service life of the product.
The top down approach requires the same data used in Tier 1b plus data on the sectoral distribution of chemicals.
Countries that are Parties to the Montreal Protocol may already be familiar with determining and reporting
annual consumption (based on similar reporting for CFCs). This approach goes beyond that required under theMontreal Protocol by requiring disaggregation of consumption data into the sectors where such consumption
takes place. Chemical distribution data may not exist for some sectors and therefore may need to be derived frominformation on chemical sales from producers and purchases from users.
The top-down approach estimates emissions from equipment stocks (the "bank") by including the temporal
distribution of emissions from equipment into the emissions functions i.e., the equations produce estimates forthe year of chemical sale or product introduction up to the present and into the future, until equipment disposal.

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Therefore, in a given year, the method will estimate emissions for equipment introduced in that same year aswell as its future emissions through its estimated service life.
Starting in any particular year, these emissions functions can take into consideration emissions from equipment
sold in prior years and still in service. However, the method requires an initial study to estimate the size of theexisting bank and how it has accumulated so that emissions can be calculated for current and future inventories.
Depending on its scope and depth, this study could also be used to adjust or validate default values for averagecharges, service life, leak rates, etc.
To develop a top-down actual emission estimate, countries should undertake the following steps:•

Estimate chemical consumption: firstly, countries must determine how much chemical is consumed. Thiscan be achieved by using the data described in Tier 1b above;•

Allocate consumption data to sectors: the unique element of this method is the allocation of chemical
consumption data to sectors. In some cases, these data may be readily available. Countries may haveproducers, importers, and exporters of HFCs and PFCs (and also the manufacturers of equipment) reporting
confidentially to a government department, annual consumption by chemical and sector e.g., x metric tonsof HFC-134a sold into (alternatively, purchased by) the mobile air-conditioning sector. For other sectors,
however, it may be difficult to determine the exact amounts of a chemical going into a particular sector,
especially when the chemical is sold through many distributors before reaching its application. A one-time
study may assist in determining typical chemical distribution. Sector experts may want to discuss means to
overcome this data limitation and defaults for the fractions so distributed may be required for particulargeographical regions;•

Estimate Emissions from each Sector: the IPCC Guidelines include a series of emissions equations anddefault values to go with those equations for estimating the emissions profile of particular sectors. Theseequations may be expressed in a time series to estimate current and future year emissions for each selected
sector. The validity of these factors should be considered, and for some sources, countries may want todevelop customized factors or further disaggregate factors to account for national conditions;•

Estimate emissions from the existing bank: a one-time study may be necessary to estimate current and future
emissions from HFC and PFC equipment units sold prior to the year of method implementation. This study
should include an estimate of the inventory of units in use, their remaining service life, average charge, leakrates, disposal quantities, and recovery practices. Data on quantities of chemical sold for the servicing ofthese units could also help in estimating emission profiles;•

Estimate fugitive emissions: fugitive emissions may be estimated by using a production emissions factor as
illustrated in the IPCC Guidelines. The one-time study in third bullet may also be used to assess fugitive
emissions from equipment assembly and chemical distribution (from chemical manufacturers to suppliers
and users), and•Compile the estimate: a country’s emissions then become the sum of the estimates developed under fourth,fifth and sixth bullets.

A useful, simple, variation of the top-down method employs the assumption that material sold into a particularsector is used in one of two ways: (a) In filling original equipment, in which case it becomes part of the bank andis not emitted promptly, and (b) In the servicing of existing systems, in which case it is actually being used toreplace material that has been emitted. Thus, to a first approximation for each year, if the total sales and thequantity used in original equipment are known, then the emissions can be calculated simply and robustly.
Countries would need to gather the following data as part of implementing this method:•

Total annual sales of each chemical: annual sales should include manufacturer and importer sales of new
chemical both in bulk and in equipment sold to equipment manufacturers;•

The portion of new chemical sales used to charge new equipment: for certain end uses, manufacturers andimporters of chemicals are likely to track how much chemical is sold for use in new equipment versus
servicing of existing units. However, this type of information may not be readily available for all end uses,
in which case, industry statistics or trade information may be available to generate a reasonable estimate of
the sales allocation;•

The amount of chemical originally used to charge equipment that is being phased out: a portion of the total
new chemical sales is used to charge units that replace phased out equipment, and such equipment may havelost its charge by the time it is phased out. Had these units been charged, the amount would have been
considered as part of the chemical used for servicing, and therefore added to the total emissions. These

Emissions of Substitutes for Ozone-depleting Substances263

Background Paperamounts may be estimated based on current and historical data on production growth of the equipment underconsideration or estimates of equipment in service;•

Destruction amounts: in the event that chemicals are used to replace material that has been destroyed, rather
than emitted, the emissions estimates would need to be adjusted to account for the associated emissions
reductions, and•Emissions the resulting emissions can then be estimated by subtracting the amount of chemical used tocharge phased out equipment and chemical destroyed to the total sales of chemical and adding the amount ofchemical used to charge phased out equipment.

Note that above approach makes it unnecessary to separately calculate emissions from disposal, recycling,
maintenance, or equipment assembly since such emissions are reflected on the total amount of chemical sales.

2.2.2

Tier 2 Bottom-up (application based) method

The "bottom-up" approach is based on an inventory of the number of products and uses where these substances
are consumed and emitted. It estimates the number of equipment units that use these substances, averagechemical charges, average service life, emissions rates, recycling, disposal and other pertinent parameters.
Annual emissions are then estimated as a function of these parameters through the life of these units. Since
equipment units vary significantly in the amount of chemical used, service life and emissions rates,
characterisation of this equipment becomes a resource intensive task. The “bottom-up” approach can provide agood estimate of emissions if detailed equipment and end-use data are available but relies critically on accurate
and realistic emissions functions for the whole range of equipment.
The “bottom-up” method does not require consumption data although, if available, it could be used as a quality
assurance check. This method does require extensive data from producers and users of chemicals to facilitate theestimation of emissions from end uses and applications.
The method includes estimation of new units sold in a given year as well as those in the existing stock. Once thenumber of equipment units is estimated, and associated emissions characterised, an estimate of total emissions
can be derived by simply summing up all the individual emissions. Since the number of units varies continually
due to new additions every year and the phasing out of old or dysfunctional units from service, the equipment
inventories will need annual updating.
The need to update equipment inventories on an annual basis can be a major implementation issue for countries
with limited resources. One possible alternative may involve the inclusion of algorithms that account forequipment phased out and additions based on their estimated average lifetimes and production growth.
Another issue with this method is that because it takes a micro approach, the need for data and assumptions
becomes greater. In contrast with the “top-down” approach, where the consumption may be estimated with highcertainty, the bottom-up approach does not include an equivalent set of data to formally limit the magnitude oferrors. This may create the need for extensive data gathering or more reliance on expert judgement.
The detailed steps for implementing the “bottom-up” approach include:•

Develop an inventory of existing HFC/PFC-containing units: some countries may have data published in
trade magazines or technical reports. However, it is more likely that a study may be necessary to come up
with good estimates of the inventory of existing units and/or chemical. Expert panels can also facilitate thegeneration of this information;•

Estimate annual inventories of new HFC/PFC-containing units: countries may decide to conduct annual
studies to update their inventories of sector units. An alternative to this may be to calculate or estimate
production growth for each one of the sectors under consideration. The method needs to reflect that newunits are introduced every year while a number of old or dysfunctional ones are phased out. Phasing out ofunits should be calculated based on the average service lives of those units;•

Estimate emissions from each sector: similar to the third bullet under the top-down approach - countries
implementing this approach should conduct a study to estimate remaining service lives of units in stock,average charges, leak rates, disposal quantities, and recovery practices. The IPCC Guidelines include default
values for some of the parameters that are not necessarily country-specific. These values can be used toestimate the annual emissions from all of the equipment in service in each year in the country;•

Estimate fugitive emissions: the discussion for fugitive emissions under the top-down approach is also
applicable to the bottom-up approach;

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Estimate emissions from applications where the HPF/PFC is released within a year of being manufactured:these emissions are easier to estimate on the basis of consumption i.e., by using the top-down approach, and•Compile the estimate: country's emissions will be the sum of the estimates developed under fourth, fifth andsixth bullets.

2.3

Uncertainty assessment

Parallel to the IPCC sector-specific workshops on good practice guidance, the IPCC is completing a programmeof work on emissions inventory uncertainty. This work will result in recommendations to the UNFCCC on
approaches to assessing and managing uncertainty. During the IPCC Inventory Experts Group Meeting in Paris(October 1998), technical experts in the uncertainty subgroup developed a series of questions to be answered in
the sector workshops. Specifically, the sector workshops should provide answers to these questions in theindividual source context, to inform work of the uncertainty programme on establishing a general
methodological approach.

2.4

CompletenessFor this source, ensuring completeness requires that all uses of these chemicals as substitutes for ozone depleting
substances are estimated and reported. Given the many chemicals and end uses, it may be difficult for countries
to develop complete emission estimates for numerous end-uses and also difficult for those that review
inventories to identify gaps or missing sources. To address these issues, good practice guidance should consider
the following issues for this source:•

Clear definitions of what is included in a particular source category;•

Clear definitions of thresholds for reporting and the use of terms such as Not Applicable (NA) and Not
Estimated (NE), and•Identification of the documentation needed to demonstrate completeness, including confirmation of nonoccurring sources.

2.4.1

Defining what is included

As mentioned above, completeness for this source requires that emissions of all chemicals used as substitutes forozone depleting substances be estimated and reported. Depending on the method employed, meeting thisrequirement will be more or less difficult. For “top-down” methods, completeness will be a function of theavailability of consumption data. Countries with access to annual chemical production, export, import, anddestruction should be able to account for all emissions of these gases. “Bottom-up” methods, on the other hand,must ensure that all of the sectors or end uses taken into consideration account for all the HFCs, PFCs, and SF6that are consumed.
Potential method
Completeness may be readily attainable under a potential or Tier 1 method, since this method is based on theestablishment of consumption. By estimating or calculating total consumption for these gases a country is
considering all emissions.
Actual method
The Actual method can be implemented in two ways – “top down” or “bottom up” – which have different
implications for completeness.
Option 1: “Top-down” Similar to the potential method, the “top-down” approach may be implemented in acomprehensive manner by establishing total HFC and PFC consumption and allocating such consumption todifferent sectors. Sectors or applications that are relatively small and difficult to track may be grouped as "other"and still be included in inventories (see Section 2.2).
Option 2: “Bottom-up” It becomes more difficult to account for all uses and products because this approachrelies on inventories of HFC and PFC using-units. When this method is used, ensuring completeness will requirea review of all end-uses and sectors where ODS have been used to determine which chemicals are being used as
substitutes and estimation of emissions of each chemical for every sector. Given the pace of change in this area,

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it will also be necessary to review and revise the assessment of which chemicals are being used in various sectors
and end-uses at yearly intervals. It is also necessary to cross-check the results against the potential emissions(which define the maximum).

2.4.2

Defining thresholds for reporting

Given the possible difficulties in ensuring complete coverage of all chemicals and/or sectors, it may be necessary
to consider thresholds for reporting. The IPCC has developed guidelines for the use of various terms that could
be applied to estimates of these gases (i.e., “0” when the source is estimated to be zero; “NE” when notestimated; “IE” for sources estimated but included elsewhere; and “NO” for not occurring.) If thresholds are to
be used, they must be clearly defined as to their meaning and when they are to be used.
Reporting thresholds may or may not be necessarily based on which method is selected. For any of the methods
that are consumption-based, completeness is likely to be less of a challenge. It may be discussed, however,whether countries should disregard small-volume chemicals with low GWPs in cases where the obtaining of thecorresponding consumption data becomes too resource intensive. Another area where a compromise may beconsidered is in accounting for imported chemicals contained in products.
For methods based on application, such as “the bottom-up”, thresholds may be needed to avoid intensive datacollection efforts associated with small and extraneous uses.

2.4.3

Meaning of “other” categories

Since the phasing-out of ozone-depleting substances is still in progress and expected to continue for the next 20
or 30 years, it is possible for new substitutes, which are greenhouse gases but not listed by the IPCC, to be
introduced in different applications. Since the listing of the HFCs, PFCs, and SF6 in the IPCC Second
Assessment Report, a few new gases have already been identified as possible source of emissions e.g.,
HFC-245fa, HFC-365mfc, and a couple of hydrofluoroethers. Estimation and reporting of these new gases may
be desirable in order to ensure complete coverage of chemicals used in this sector.
It is also likely that new sectors or uses not presently anticipated may be identified.
Emissions from these other sources may be estimated as part of the estimation methods that rely in consumption
as the basis for estimating emissions. One option may be to group these uses as "other" categories, allocate gas
consumption and establish corresponding emissions functions. If the “bottom-up” approach is implemented,
however, it becomes more difficult to gather data on these uses or to process them as "other" categories.

2.5
2.5.1

Other important issues
Consistency among national methods

Experts may want to consider whether there are problems posed by the possibility that some countries will use
actual methods and others will use potential methods in terms of developing an accurate accounting ofemissions. This issue may be of particular concern if there is no agreement on how to treat imported/exported
equipment (as discussed below). For example, a country that imports equipment but neither produces nor
consumes the chemical directly, could estimate its emissions as “0” using the Tier 1a potential approach. At thesame time, a country that exports equipment could use an actual approach that does not include emissions fromchemicals used in equipment for export. Under this case, emissions from the chemical produced in the second
country but contained in equipment sold to the first country would be unaccounted for.

2.5.2

Treatment of imported and exported equipment

The only method that explicitly accounts for chemicals contained in equipment that is imported or exported isTier 1b. In other cases, not including these chemicals, results in inaccuracies. In considering how to treat
chemicals contained in imported/exported equipment, experts should consider the following:•

Data requirements - data may be difficult obtain, although custom agencies may be a key resource infacilitating the gathering of these data;•Significance - are the amounts significant enough to warrant their estimation, and266

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Added complexity - a process for accounting for imports/exports of chemicals contained in products may
also be difficult to implement. Accounting for emissions from import or export of chemicals contained in
products may be complex.

2.5.3

Establishing baselines

Experts should consider whether it will be difficult to develop estimates that use consistent methods and data
sets between the base year (either 1990 or 1995) and later years.

2.5.4

Accounting for fugitive emissions

In addition to emissions from equipment, some emissions will also occur during chemical manufacturing andproduct assembly. These fugitive emissions should be included in emission estimates. Experts should consider
the extent to which various methodological approaches can address fugitive emissions.

3

REPORTING AND DOCUMENTATION

3.1

Reporting substitute HFC/PFC emissions to
the UNFCCCThe UNFCCC Secretariat report mentioned in section 1.2 noted some reporting problems. Not only have several
countries not reported emissions from this source, but reports from the countries that reported lacked
transparency. This section provides information on the current IPCC Guidelines and outlines some options for
improving reporting transparency.

3.2

Current IPCC reporting guidelines

The IPCC Guidelines are used to guide countries in the preparation and submissions of annual greenhouse gas
emissions inventories to the UNFCCC Secretariat. The IPCC Guidelines establish:•

Standard tables, definitions, units, and time intervals for reporting all types of emissions;•

The necessary documentation to enable comparison of national inventories, including worksheets, major
assumptions, methodological descriptions and enough data to allow a third party to reconstruct the inventory
from national activity data and assumptions, and•An uncertainty assessment.

HFC/PFC/SF6 emissions are reported in Table 2: Sectoral Report for Industrial Processes, which calls for entries foreach source of emissions totals of carbon dioxide, methane, nitrous oxide, precursor gases (NOX, CO, NMVOCs,
SO2), HFCs, PFCs and SF6. Table 2 further disaggregates the reporting of these gases into Production andConsumption of Halocarbons and Sulphur Hexafluoride and within Consumption, the following sectors are listed:•

Refrigeration and Air Conditioning Equipment;•

Foam Blowing;•Fire Extinguishers;•

Aerosols;•

Solvents, and•Other.

Currently, the table incorporates aggregated entries for the HFC, PFC, and SF6 gases. The following are theseveral problems encountered when presenting the data in this aggregated format:•

Because there are many different HFCs and PFCs, with different global warming potentials (GWPs) anddifferent masses, aggregating emissions within a class of gas (i.e., for all HFCs) on a mass of chemical basis
does not enable derivation of the carbon equivalent emissions, and•At the same time, providing emission estimates in terms of carbon equivalent emissions does not allow forreconstruction of the inventory since a third party will not know the relative share of each gas to the total sum.

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In addition to the lack of transparency in the emissions estimates, there is also a lack of clear information on how
the estimate was prepared. Among the issues to be considered are:•

Reporting on what method was used for estimation;•

Reporting on what chemicals, and if necessary sources/end-uses, are included in the estimate;•

Reporting on how data were obtained, and•Reporting on how QA/QC was conducted.

3.3

Confidential business information

The issue of confidential business information may complicate the desire for clear and transparent reporting. Just
as for production and consumption of ozone-depleting substances, the HFCs, PFCs, and SF6 consumption data
will require confidential handling. Countries may need to establish a confidential data tracking and reporting
system similar to that used for the ozone-depleting substances to ensure the accuracy of consumption data.
Emissions estimates that could be back-tracked into consumption amounts should not be released. To avoid this,emissions of certain gases may need to be reported in aggregated amounts. Nevertheless, the reporting country
should be able to produce the data to substantiate their aggregated reports if requested by the UNFCCC
Secretariat. These data MUST be held in commercial confidence. Countries may also want to explore additionalsources of data to derive consumption estimates.

4

INVENTORY QUALITY

For this source, inventory QA/QC process will need to be applied at several points in the inventory process.
Figure 2 outlines a possible model for the flow of information and the inventory quality process at each step.
As illustrated in Figure 2, internal audits on HFC and PFC consumption should be done at plant or company-levelby plant/company personnel, and at the national aggregation level by government agencies. Independent objective
review by a third party aimed at assessing the effectiveness of the internal QC programme and the quality of theinventory and reducing or eliminating any inherent bias in the inventory processes will also be necessary.

4.1
4.1.1

Internal inventory QA/QC process
Plant and company-level activities

Given that the number of plants producing substitute chemicals, the number of chemicals under consideration(i.e., over 20) and the complexity of the methods used, experts may want to consider the feasibility of
establishing a rigorous QA/QC programme at plant level for each of these gases. On the other side, periodic
internal audits of plant production, transformation and destruction data should be conducted. Similar audits may
be required for company-level compilation of these data as well as records of chemical transactions (e.g., sales,
imports, exports, and sector consumption allocation).

4.1.2

Inventory agency level activities

Inventory Agency Review (QA) of Plant or Company-Level Information: Before accepting consumption
data, the inventory agency should carry out an assessment of data quality. This type of review requires close
cooperation with company owners to obtain enough information to verify the reported consumption as discussed
above. The assessment should include sample calculations, an examination of the representativeness of the data,
an identification of potential bias in the methodology and recommendations for improvement.

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Figure 2

Key steps in the inventory QA/QC process
Plant/Company

Internal QC:

Plant-level measurement and calculations and/or company-level records ofchemical production, destruction, sales, exports, imports, and relatedtransactions (sufficient to establish consumption).

Documentation:

Plant-level information provided to the government agency, or company-level
information provided or made accessible to the government agency, andresults of internal QC.

Note: Workshop experts may want to discuss what level of data and documentation would be adequate and practical given
the number of chemicals and the amount of data required to support any of the methods.

Government Agency

Review/QA:

Plant or company-level inputs

Internal QC:

Compilation of chemical consumption by sector from plant or company-level
data and calculation of national inventory from chemical consumption.

Documentation:

Results of compilation and calculations, and results of QA/QC.

Reporting:

Official submission to UNFCCC

Note: This step assumes that the government agency, and not the reporting companies, will calculate emissions from
reported consumption.

External Review

External Review:

External audit; stakeholders, peer & public review of inventory results;
external verification against other data etc.

Documentation:

Results of external review.
UNFCCC Secretariat

External Review:

Requires standard format and transparency - ensure consistency with otherinventories and external data

Inventory Agency QC on Compiling National Emissions: In addition to a thorough quality assessment ofcompany-level data discussed above, the inventory agency should ensure that the process of aggregating company
data to develop the national inventory undergoes quality control. This should include, among other things:•

Ensuring all plants are included;•

Comparison with industry trends to identify anomalies and patterns, and•Cross-referencing production data with sectoral consumption information from chemical users.

Inventory Agency Documentation on Compiling National Emissions: The agency’s QA/QC management
plan should address the specific items needed to perform audits and reviews. When the consumption estimates
are provided by each company, the details should be documented at the company level to account for differencesin the procedures among companies. Examples of the types of information needed for documentation andexternal audit include:•

Proof of sales exports, imports, and related transactions;•

A detailed description of the inventory methodology;•

Identification of the input parameters that are needed and how they are obtained (measured or estimated);•

Results of determinations of accuracy and precision for the measurements;•

An estimate or discussion of uncertainty and variability for input parameters that are estimated instead of
measured, and•Enough data for the input parameters to reproduce the calculations.

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Background Paper

4.2

External inventory QA/QC systems

Several types of external reviews, or audits, may be appropriate for HFC/PFC inventories.
Third party audit by an accredited organisation, expert, independent third party: An audit of the
documentation and calculations ensures that each number is traceable to its origin. Given that much of theinformation with consumption of these gases may be proprietary, a third party audit that protects confidentiality
may be a necessary type of review.
Expert (peer) review: A detailed peer review would be appropriate when a new procedure for calculating
emissions, such as the implementation of new emission functions, is first adopted.
Stakeholder review: Review by HFC/PFC producing companies, industrial organisations, and air pollution
consultants can provide a forum for review of the methods used.
Public review: Some countries make their entire inventory available for public review and comment. This
process may result in a range of comments and issues broader than those from other review processes.

4.3

Examples of QA/QC systems

The ozone depleting substances tracking system implemented by the US EPA includes the submission ofpurchase, sales, export and import records in addition to consumption data from chemical producers. These
records provide US EPA with the ability to verify that the submitted consumption data is correct. An additional
tool available to the US EPA is its ability to audit the submitter. This system would be suitable for the Potential
Method and the submission of consumption data under the “top-down” approach.

5

CONCLUSIONS

The most important consideration in this sector is that, despite the high Global Warming Potentials of the gases
concerned, their current absolute contribution to global greenhouse gas forcing is comparatively small. It istherefore worthwhile for each Party to the Convention and Protocol to perform a preliminary scoping study toascertain the balance of efforts required to obtain the data (at the detail required) against the national contribution
to the global source strength. The essential first step is therefore to establish whether or not there are emissions
in this category. Hence, there are several options to estimate the importance of these emissions.
The Tier 1 methodologies to estimate potential emissions may be appropriate when the national contribution tothese greenhouse gases is very small. However, for significant emissions from many of the developed countries,
Tier 2 methodology should be used and actual emissions estimated.
Verification of these emissions is crucial, especially since many estimates will have been made from relatively
subjective information. Alternative sources of data should be examined, wherever possible and it may also beappropriate to attempt to balance the calculated emissions with atmospheric measurements using suitabledispersion modelling.

REFERENCES
Gamlen P.H., B.C. Lane, P.M. Midgley and J.M. Steed, The production and release to the atmosphere of CCl3F
and CCl2F2 (Chlorofluorocarbons CFC-11 and CFC-12), Atmos. Environ., 20(6), 1077-1085, 1986.
IPCC (Intergovernmental Panel on Climate Change), Second Assessment Report, IPCC, Geneva, 1996.
Junyi Chen, Valerie Young, and Hiromi Niki, Kinematic and Mechanistic Studies for Reaction of CF3CH2CHF2(HFC-245fa) Initiated by H-Atom Abstraction Using Atomic Chlorine, J. Phys. Chem. A 1997, 101, 26482653.
UNFCCC Secretariat Methodological Issues Identified While Processing Second National Communications(UNFCCC/SBSTA/1998/7)
WMO (World Meteorological Organization), Scientific Assessment of Stratospheric Ozone: 1998, Global Ozone
Research and Monitoring Project Report No 44., WMO, Geneva, 1998.

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