Toolkit for Identification and Quantification of Releases of Dioxins, Furans and Other Unintentional POPs
PART I General Guidance
Chapter 2 Identifying Sources and Estimating Releases of PCDD/PCDF
The PCDD/PCDF inventory includes these five steps:
- Identify sources;
- Select emission factors for the sources;
- Assign activity rates for each of the sources;
- Multiply the emission factor with the activity rate;
- Compile the inventory.
To assist Parties in identifying PCDD/PCDF sources at the national level, the Toolkit includes source categories as described in Annex C of the Stockholm Convention, Parts II and III. Since the list in Part III is indicative and open for additions, the Toolkit also contains further source categories that have been identified in existing inventories, national assessments, scientific studies, etc. In addition, it provides a simple screening process for identifying other sources not yet listed in the Toolkit.
A country or region can begin identifying its PCDD/PCDF sources by determining the presence or absence within its borders of the PCDD/PCDF sources currently listed in the Toolkit. The Toolkit lists the source categories identified in Annex C as well as those identified by other means, such as national PCDD/PCDF inventories, scientific studies and reports. The source categories listed in the Toolkit are divided into ten source groups. Table I.2.1 presents these ten source groups and the source categories currently listed in the Toolkit.
When an activity or process is identified but not described or not exactly matching the description provided in the Toolkit, the respective estimate of PCDD/PCDF releases can be included in the national inventory. The additional source will be inserted into the national inventory by adding extra lines into the respective source group (in the EXCEL spreadsheet). Such additions should be highlighted accordingly.
To identify PCDD/PCDF sources not currently listed in the Toolkit, it is necessary to determine whether chlorine (in elemental, organic or inorganic forms) is or was present in the processes or activities of interest. PCDD/PCDF formation is influenced by many factors. However, when chlorine is not present, PCDD/PCDF formation cannot occur; when chlorine is present, even as a trace element, PCDD/PCDF formation may occur.
When Parties have identified processes or activities that are potential PCDD/PCDF sources due to the presence or use of chlorine in some form, those potential sources should be thoroughly evaluated. Evaluations can begin by investigating existing inventories, the scientific literature, government reports, etc., to determine if the processes of interest or very similar processes have already been reported to release PCDD/PCDF. Additional guidance, including lists of processes and activities for which evidence of PCDD/PCDF formation and/or release exists but which are not addressed elsewhere in the Toolkit, is given in Annex 2.
For each source category and/or source, it is necessary to obtain basic information about the design, operation, and other related factors that can substantially influence the magnitude of PCDD/PCDF releases. Based on this information, each source will be classified and placed in one of the several classes to which default emission factors are assigned.
Example questionnaires provided in Annex 3 may be useful in obtaining the information needed to classify source categories and so select appropriate emission factors. More specific suggestions on the information needed and potential avenues for obtaining such information for a source category may be found in Part II, in the chapters concerning source groups 1 through 10.
The default emission factors presented in the Toolkit are drawn from a variety of data sources, ranging from laboratory experiments, peer reviewed literature, dedicated experimental projects, to governmental or institutional reports. The emission factors for each class are best estimates based where possible on data measured at well-documented sources taking into account technology, process characteristics and operating practices, or otherwise estimates based on expert judgment. For the purpose of defining a default emission factor, results/processes with similar characteristics are aggregated into one emission factor. As such, the Toolkit’s default emission factors are approximations intended to represent order of magnitude release estimates. They are suitable to derive national release inventories, set priorities, develop action plans and evaluate their efficacy; however, they should not be taken as accurately describing releases from individual plants/facilities.
The Toolkit methodology is designed so that both country-derived emission factors and the default emission factors presented in the Toolkit can be used. Default emission factors are recommended to be used for comparison or in cases where country-specific emission factors are not available.
Activity rates are values in unit per year of product manufactured ( e.g., steel, sinter, cement, pulp, compost, etc.) or feed material processed (e.g., municipal waste, hazardous waste, coal, diesel fuel, bodies cremated, etc.), or annual quantities of material released (e.g., m³ of flue gas, liters of wastewater, kilograms or tons of sludge generated, etc.).
Values for activity rates may be found in centralized statistical information assembled by state, provincial, national or international agencies, and they may be obtained from trade associations and owner/operators of facilities. Potential sources of information on activity rates include the following:
When the activity rate for an industrial source category is not available but the nameplate capacity is known, an activity rate can be estimated by multiplying capacity by the domestic capacity utilization factor (CUF). If no domestic CUF is available, a regional or global CUF may be used and, if neither regional nor global CUF is available, the Toolkit Expert Group may provide an appropriate value.
Activity rates for diffuse source categories, such as traffic, open burning of domestic waste, agricultural residues, etc., are best characterized by drawing from centrally available data.
Once PCDD/PCDF sources are identified and classified, emission factors selected and national or regional activity rates determined, the estimation of the total annual releases by source group, source category and class is relatively simple and straightforward.
For a source class, PCDD/PCDF releases per year are calculated according to the equation below. The activity rate is multiplied by each of the five emission factors and the sum of the five resulting values represents the quantity of PCDD/PCDF released annually from the source class.
|PCDD/PCDF released, grams TEQ/year =||Activity Rate x Emission FactorAir|
|+ Activity Rate x Emission FactorWater|
|+ Activity Rate x Emission FactorLand|
|+ Activity Rate x Emission FactorProduct|
|+ Activity Rate x Emission FactorResidue|
For a source category, the annual PCDD/PCDF release is calculated as the sum of the total annual releases for each class within the category.
For each source group, the annual PCDD/PCDF release is the sum of the annual releases calculated for each source category in the source group.
For a country or region, the total annual PCDD/PCDF release is the sum of the annual releases from all source groups.
The spreadsheet will be used to determine annual releases according to source groups and the year of reporting.
The Toolkit simplifies and expedites the calculations described above by providing an Excel spreadsheet that includes a list of the source categories addressed in the Toolkit, along with their associated classes and accompanying default emission factors. Once the activity rates for all classes within the source categories that have been determined to be present within a country or region are entered into the spreadsheet, annual PCDD/PCDF releases are automatically calculated for each source category. A summarizing worksheet provides an overview of all releases according to vectors (air, water, land, product, residue) and source groups.
Newly identified sources can also be included in the spreadsheet, along with their associated emission factors and activity rates. Their releases are also automatically calculated and included in the final results. If desired, a country can replace the Toolkit’s default emission factors with their own emission factors that have been otherwise derived.
These and other issues related to the preparation of inventories and reporting of releases are discussed in greater detail in Chapter 3 Reporting of Releases.