Toolkit for Identification and Quantification of Releases of Dioxins, Furans and Other Unintentional POPs
PART III Example Inventories
Example Inventory 1 Updating and Revising an Inventory
This example illustrates the inventory updating and revision for a single source class – open burning of domestic waste - which is triggered by the revision of the emission factor in the Toolkit methodology.
Let’s consider a hypothetical inventory of country X. The baseline inventory is developed in 2005, based on data collected for the reference year 2003 and by using the Toolkit 2005 methodology. The baseline inventory estimates that approximately 60,000 tons of domestic waste from rural and urban areas is burned in 2003. The total annual releases of the baseline year are calculated based on the Toolkit 2005 methodology, by applying an emission factor for air of 300 µg TEQ/t of material burnt. The baseline releases to air from open burning of domestic waste are thus estimated at 18 g TEQ/year.
|Baseline PCDD/PCDF released to air in 2003 (g TEQ/year) =||Quantity of waste burnt x EFAir =|
|60’000 t/yr x 300 µg TEQ/t =|
|18 g TEQ/year|
Country X implements measures to reduce releases from open burning as part of the action plan within the National Implementation Plan, and initiates an update of the PCDD/PCDF inventory to assess the success of these measures and report them as part of the national report under Article 15.
The updated inventory is developed in 2013, based on data collected for the reference year 2010 and the Toolkit methodology as revised in 2013. 2010 activity rates for this source were assessed at around 20,000 tons of domestic waste burned annually. The corresponding emission factor was revised since the first inventory and is much lower than the one used for the baseline inventory: EFAir is now 40 µg TEQ/t of material burned. The total annual releases are calculated based on the Toolkit 2013 methodology as below:
|Updated PCDD/PCDF released to air in 2010 (g TEQ/year) =||Quantity of waste burnt x EFAir =|
|20’000 t/yr x 40 µg TEQ/t =|
|0.8 g TEQ/year|
The total releases to air from open burning of domestic waste are thus estimated at 0.8 g TEQ/year in 2010. This translates into a significant reduction in releases to air from this source class from 2003 to 2010 (-95% decrease) as illustrated below:
This assessment is not correct as it does not consider that along with the decrease in the activity level from 2003 to 2010, the emission factor has also been revised downwards. Since the basis for the calculation is not the same in the updated inventory as in the baseline the estimations are not coherent and the initial inventory will have to be reassessed to allow for correct trends over time to be calculated.
The revised baseline estimate will be the product of the baseline activity levels that were assessed for 2003 (60,000 tons of domestic waste burned per year) and the revised emission factors taken from the Toolkit 2013 methodology which was used in the updated inventory: 40 µg TEQ/t for air. The revised baseline levels of releases are thus 2.4 g TEQ/yr.
|Revised PCDD/PCDF released to air in 2003 (g TEQ/year)=||Quantity of waste burnt x EFAir =|
|60’000 t/yr x 40 µg TEQ/t =|
|2.4 g TEQ/year|
The revision of the baseline inventory allowed country X to assess correct trends over time and see that indeed there was a decrease in releases from 2003 to 2010, but this amounted to only 66%.
Let’s now consider another source category in this hypothetical inventory, where the revision of the baseline inventory is triggered by an additional class included in the revised Toolkit methodology.
The initial/baseline inventory was performed in 2005, based on 2003 data and the Toolkit 2005 methodology. In 2003, country X estimates that 4’000’000 tons of agricultural residues are burnt in poor conditions. An emission factor for air of 30 µg TEQ/t is applied according to the Toolkit 2005 methodology, and the overall emissions to air from this source class are estimated at 120 g TEQ/yr.
|Baseline releases from agricultural residue burning in 2003 (g TEQ/year) =||Quantity of material burnt x EFAir =|
|4’000’000 t/yr x 30 µg TEQ/t =|
|120 g TEQ/year|
In 2013 country X updates the inventory based on 2010 data and by using the 2013 revised version of the Toolkit. The emission factor for agricultural residue burning in poor conditions is the same as in the 2005 methodology: 30 µg TEQ/t.
The updated inventory assesses the activity rate as 2’000’000 t material burnt annually. In addition, the developer of the inventory discovers that a new class was added to this source category, which is of major relevance for the country: this is sugarcane burning. The new emission factor for sugarcane burning included in the 2013 methodology is of 4 µg TEQ/t, while the activity rate for this source class is estimated at 2’000’000 tons residues burnt annually. The release estimates are calculated as below, by multiplying the activity rate with the respective emission factors:
|Updated releases from agricultural residue burning in 2010 (g TEQ/year) =||Quantity of material burnt x EFAir =|
|2’000’000 t/yr x 30 µg TEQ/t =|
|60 g TEQ/year|
|Updated releases from sugarcane burning in 2010 (g TEQ/year) =||Quantity of material burnt x EFAir =|
|2’000’000 t/yr x 4 µg TEQ/t =|
|8 g TEQ/year|
Further to the updating of the inventory, the immediate conclusion would be a 50% reduction in air emissions from agricultural residue burning and a significant increase from 0 to 8 g TEQ in air emissions from sugarcane burning.
This conclusion is wrong, because the new class has to be assessed separately in the baseline inventory, similarly as in the updated inventory. At the time the baseline inventory was developed, emission factors were not yet specifically developed and available to assess releases from sugarcane burning, and this source class had to be assessed together with other types of agricultural residues. There is a need to go back to the previous inventory and revise the calculations therein to include this new class. Only after this revision, the comparison between the situation in 2003 and the one in 2010 can be done.
In the revised baseline inventory, activity rates for the two source classes (agricultural residue burning and sugarcane burning) need to be retrospectively estimated for the baseline year. In 2003, from the initially estimated 4’000’000 t agricultural residues burnt annually, only 3’000’000 t actually corresponded to this source class; the remaining 1’000’000 tons were actually sugarcane residues that were burnt in the open. Therefore, in the baseline year, emissions to air from agricultural residue burning were of 90 g TEQ/yr, while the emissions from sugarcane burning were of 4 g per year.
|Revised releases from agricultural residue burning in 2010 (g TEQ/year) =||Quantity of material burnt x EFAir =|
|3’000’000 t/yr x 30 µg TEQ/t =|
|90 g TEQ/year|
|Revised releases from sugarcane burning in 2010 (g TEQ/year) =||Quantity of material burnt x EFAir =|
|1’000’000 t/yr x 4 µg TEQ/t =|
|4 g TEQ/year|
The revision of the baseline inventory shows that the actual reduction in air emissions from agricultural residue burning is of only 33%, while the increase in air emissions from sugarcane burning is only of 4 g TEQ:
This example illustrates a different type of situation, where the revision of the baseline inventory is not triggered by the changes in the methodology, but rather by better information becoming available at the country level during the inventory updating process.
We’ll take the example of another source group: waste incineration.
The baseline inventory of country X mentions that the incineration of animal carcasses is rarely applied in the country and information for this source category is not available. It is thus considered that releases from this source category are negligible in 2003.
With the updating of the inventory in 2013, country X discovers that one old facility exists that is specialized in thermal destruction of carcasses. The activity rate for 2010 (the reference year in the updated inventory) is estimated at 1’000 t carcasses destroyed. The emission factor applied is of 500 µg TEQ/t, corresponding to old facilities without air pollution control system. The overall emissions to air from this source category amount to 0,5 g TEQ/year.
|Updated PCDD/PCDF released to air in 2010 (g TEQ/year) =||Quantity of carcasses x EFAir =|
|1’000 t/yr x 500 µg TEQ/t =|
|0.5 g TEQ/year|
This would mean that an increase in emissions from this source took place from 2003 to 2010.
Nevertheless, the facility was operational in the baseline year as well, releasing dioxins and furans in the environment. A revision of the baseline inventory is thus necessary to ensure coherent trends over time. The revised baseline inventory estimates that the activity rate of this facility in 2003 was of 2’000 t of carcasses destroyed, double the amount in 2010. The corresponding emission level is of 1 g TEQ/yr.
|Revised PCDD/PCDF released to air in 2010 (g TEQ/year) =||Quantity of carcasses x EFAir =|
|2’000 t/yr x 500 µg TEQ/t =|
|1 g TEQ/year|
The revision of the inventory enabled thus country X to observe an actual decrease in emissions from this category. If the revision was not performed, the incorrect conclusion would have been, on the opposite, an increase in emissions.