Choice of emission factors

The emission factor EF represents the fraction of chemical emitted from solvents in year t. The product lifetime is assumed to be two years, and thus any amount not emitted during the first year is assumed by definition to be emitted during the second and possibly final year. A decision tree for estimating actual emissions is included in Figure 7.2, Decision Tree for Actual Emissions from the Solvents application. The data collection process is described in Section 7.2.2.3.

In the absence of country-specific data, it is good practice to use a default emission factor of 50 percent of the initial charge/year for solvent applications.9 In certain applications with new equipment incorporating low emission design features, it is very possible that much lower loss rates will be achieved and that emissions will occur over a period of more than two years. Alternative emission factors can be developed in such situations, using data on the use of such equipment and empirical evidence regarding alternative emission factors.10 Such country-specific emission factors should be documented thoroughly (Tier 2a). The 'mix' of hand operated batch cleaning systems and automated conveyorised systems within a country or region may result in very different emissions. Attention to proper work practices, setup of the work area and proper training of the workers will significantly lower solvent emissions. Within such groups (batch or conveyorised), there is a wide range of equipment age, low emission design sophistication, workpiece design, workpiece load size and maintenance diligence. All of these factors will affect emissions from a particular piece of equipment or region.

Modifications for the recovery and recycling of solvents can be applied if an appropriate estimate of retrofitted equipment can be obtained. While HFC and PFC solvents may be recovered and recycled multiple times during their use owing to their high costs, in most emissive end uses (sub-applications) these chemicals will be released considerably more quickly after being placed in use than those in sealed refrigeration applications.

9 Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories (IPCC, 2000).

10 As guidance, for sales to new equipment, approximately 10-20 percent may be emitted with the rest of the solvent used to fill the equipment. In subsequent years sales are for replenishment and can eventually be considered 100 percent emitted.

Figure 7.2 Decision tree for actual emissions from the solvents application

Figure 7.2 Decision tree for actual emissions from the solvents application

What Are The Factors 176

Box 1: Tier 1a

Note:

1. See Volume 1 Chapter 4, Methodological Choice and Identification of Key Categories (noting Section 4.1.2 on limited resources), for discussion of key categories and use of decision trees.

Box 1: Tier 1a

Note:

1. See Volume 1 Chapter 4, Methodological Choice and Identification of Key Categories (noting Section 4.1.2 on limited resources), for discussion of key categories and use of decision trees.

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