Choice of method

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Open-Cell Foam: Since HFCs used for open-cell foam blowing are released immediately, the emissions in almost all cases will occur in the country of manufacture. The only exception may be in the case of OCF (One Component Foams) where the filled container may be manufactured in one country but the emissions occur in another country because the containers are easily traded. Emissions are calculated according to the following equation:14

Equation 7.8

Generic calculation method for emissions from open-celled foams

Emissionst = Mt

Where:

Emissionst = emissions from open-cell foam in year t, tonnes

Mt = total HFC used in manufacturing new open-cell foam in year t, tonnes

This equation must be applied for each chemical used in open-celled foam applications. Although, there is little variation in emission factor across the open-cell sub-applications, it may still be advantageous to use a disaggregated Tier 2a method in order to make it easier to accurately assess net consumption activity data. Such an approach will naturally address the trade in one-component foams. Where there is little use of one-component foam, it could be logical to revert to a Tier 1a method where Equation 7.8 is applied at the application level.

Closed-Cell Foam: Emissions from closed-cell foam occur at three distinct points, which have already been highlighted in Equation 7.7:

(i) First Year Losses from Foam Manufacture and Installation: These emissions occur where the product is manufactured or installed.

(ii) Annual Losses (in-situ losses from foam use): Closed-cell foam will lose a fraction of its initial charge each year until decommissioning. These emissions occur where the product is used.

(iii) Decommissioning Losses: Emissions upon decommissioning also occur where the product is used.

To implement an approach which captures these three phases it is necessary to collect current and historical data on annual chemical sales to the foam industry for the full length of time HFCs have been used in this application period up to and including the average lifetime of closed-cell foam (as long as 50 years). The import or export of foam formulations which already include HFCs should be also taken into account. Similarly, there should be adjustments made for articles such as domestic or commercial refrigerators and freezers or of construction sector applications such as sandwich panels, boards, blocks and insulated pipes which are produced in one country but may be used in another country.

14 For these applications, actual emissions of each chemical are equal to potential emissions.

In earlier assessments the calculation of decommissioning losses has been based on the premise that all blowing agent remaining in a foam at end-of-life will be lost at the decommissioning stage. From an emissions standpoint, this is a worst case scenario, even for disposal methods which are not targeted at recovery and destruction (see footnote 13). In practice, recovery and destruction of blowing agent or direct destruction (e.g., incineration) will further alleviate these losses. Hence Equation 7.7 carries a fourth component to allow for HFC emissions prevented in this way. The UNEP TEAP Task Force Report on Foams End-of-Life (UNEP-TEAP, 2005) addresses the many of the potential ways in which foam blowing agent emissions can be avoided and introduces the concept of Recovery and Destruction Efficiency (RDE) to assess the effectiveness of such methods.

Even where active recovery and destruction methods are not practised, it is still unlikely that all blowing agent will be released at end of life, particularly when foams are typically left in tact during disposal (e.g. during land-filling). Under these circumstances, a considerable proportion of the blowing agent will remain in the waste stream and an additional banked emission source will be established. Since the emission rates from such a bank will be lower than 100 percent, Equation 7.7 will over-estimate emissions where a significant proportion of the foam containing HFCs used in the country has already been decommissioned. Although it would be possible to envisage a fifth component to Equation 7.7 to address this element of emission, it is not deemed of sufficient relevance to warrant such an approach for the global phase of HFC use being covered by these Guidelines. However, some of the more sophisticated globally or regionally-derived assessments may address this issue.

If it is not possible to collect data for potential losses upon decommissioning, it should be assumed that all chemical not emitted in manufacturing is emitted over the lifetime of the foam. However, particular care should be taken to check whether articles such as domestic or commercial refrigerators and freezers are exported to another country for re-use. Where the foam application cannot be disaggregated to the sub-application level and no globally or regionally derived activity data is available, a Tier 1a method needs to be followed. Good practice in the choice of a Tier 1 method is to assume that all closed cell foam emissions follow the Gamlen model (see Table 7.5)

Table 7.5

Default emission factors for HFC from closed-cell foam

Emission Factor

Default Values

Product Lifetime

n = 20 years

First Year Losses

10% of the original HFC charge/year, although the value could drop to 5% if significant recycling takes place during manufacturing.

Annual Losses

4.5% of the original HFC charge/year

Source: Gamlen et al. (1986).

If both historical and current country-specific activity data is available for closed cell foams at the application level, it is possible to apply the Gamlen model to this information. However, the primary challenge for inventory compilers is usually in the characterisation of historic activity data at a country level. If such difficulties exist, it is usually possible to estimate activity data at a country level from the application of geo-economic factors provided that regional, globally or regionally-validated activity data are known. This approach is covered further in Section 7.4.2.3.

Where net consumption activity data is available at the sub-application level, either from sources of country-specific data or from globally or regionally derived activity datasets, it is good practice to use Tier 2 methods that reflect the level of disaggregation. This is particularly important for foams because of the heterogeneous nature of the various sub-applications involved. The decision tree in Figure 7.4 describes good practice in selecting methods for estimating emissions.

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