Example Inventory 7 Source Group 6 Open Burning Processes

In country X, open burning processes releasing PCDD/PCDF mainly include biomass burning to clean the fields and domestic waste burning. The baseline inventory of country X is developed in 2006 based on data collected for the reference year 2004. The developer of the inventory found only limited data on activity levels for this sector. Data on forest fires was collected for instance from the Ministry of Agriculture and Forestry. Nevertheless, expert judgment was an essential tool to calculate releases from open burning.

6a Biomass burning

According to the statistics provided by the Ministry of Agriculture and Forestry of country X, three major fire incidents have occurred in 2004, affecting a total of 20’000 hectares of forest. Data from a national forest inventory and analysis program and a number of studies estimating forest biomass in country X using remote sensing and satellite products show that forest biomass density across the country is on average 150 tons/ha. The baseline activity rate for this source class is thus estimated at 3’000’000 tons burnt annually.

Secondly, the extent of crop residue burning is very difficult to estimate. The actual amount varies dramatically from year to year, depending upon amounts of rainfall, cropping patterns and weather conditions during and after the harvest season. Some years, burning may take place over quite a long fall season, or even be delayed to the following spring. As such, it is very difficult to estimate the extent of burning in a given year, or to analyze trends.

Assumptions are thus needed to quantify the quantity of agricultural residues that are burnt annually. Two assumptions are made by the developer of the inventory, according to a similar study:

1. that the amount of agricultural residue able to be burned was equal to the total crop production, and
2. that 80% of residues were burned in the developing world and 50% of residues were burned in the developed world for any given year.

Based on these assumptions, activity rates for agricultural residue burning were estimated at 500’000 tons of material burnt in 2004. Dioxin and furan releases from these sources were calculated according to the Toolkit (2005) methodology and the corresponding results are presented below.

Source category	Source class	Activity rate (t/year)	Annual Release (g TEQ/a)					Total
			Air	Water	Land	Product	Residue
Biomass burning	Forest fires	3,000,000	15		12			27
	Agricultural residue burning, poor combustion conditions	500,000	15		5			20

6b Waste burning and accidental fires

The only relevant source contributing to dioxin and furan releases from this category is domestic waste burning. Data on domestic waste burning are not readily available in country X. The developer of the inventory therefore needs to estimate activity rates for this sector based on assumptions and expert judgment. The average amount of waste produced in urban areas is of 0.7 kg per capita per day and of 0.5 kg per capita per day in rural areas. From the total amount of waste generated in urban areas, 70% are collected for reuse, incineration or disposal, leaving 30% that can be burned in backyard fires. From the total amount of waste generated in rural areas, it is considered that 20% are burnt in the open, since a greater fraction is used for composting.

The estimated amount of domestic waste burnt annually is of 60,000 tons in 2004. The total annual releases are calculated by multiplying this activity rate with the corresponding emission factor. The results are shown in the table below:

Source category	Source class	Activity rate (t/year)	Annual Release (g TEQ/a)					Total
			Air	Water	Land	Product	Residue
Waste burning and accidental fires	Open burning of domestic waste	60,000	18		36			54

Country X implements measures to reduce releases from open burning as part of the action plan within its National Implementation Plan. The measures are based on providing incentives to avoid open burning and manage waste in a more appropriate manner: through education and awareness raising programmes, better infrastructure and enforcement. In 2013, country X initiates an update of the inventory to assess the success of these measures. The activity data used for updating release estimates are collected for the reference year 2010, while the inventory is developed according to the Toolkit methodology as revised in 2013.

6a Biomass burning

The 2010 activity data are estimated according to the same approach and using the same expert judgment and assumptions as in the baseline inventory. Only two fire incidents were registered in 2010, totaling 2’000’000 tons of forest material burnt annually.

Furthermore, in addition to agricultural residue burning, a new class of major relevance for country X is included in the inventory – sugarcane burning. This class is newly added in the 2013 version of the Toolkit, and new emission factors were developed and are now available for this very specific source. Agricultural residues and sugarcane residues burnt in 2010 are estimated according to the same assumptions as in the baseline inventory and amount to 300’000 tons and 100’000 tons material burnt respectively. The resulting release estimates are shown below:

Source category	Source class	Activity rate (t/year)	Annual Release (g TEQ/a)					Total
			Air	Water	Land	Product	Residue
Biomass burning	Agricultural residue burning, poor combustion conditions	300,000	9		3			11
	Sugarcane burning	100,000	0.4		0.005			0.045
	Forest fires	2,000,000	2		0.3			2.3

The immediate conclusion after the updating of the inventory would be a drastic reduction in emissions to air from agricultural residue burning (-40%) and forest fires (-87%) and an increase from 0 to 2 g TEQ in emissions to air from sugarcane burning. This conclusion would not take into account the fact that the emission factors have equally been revised and are much lower in the 2013 edition of the Toolkit than in the 2005 edition. This has an impact on the resulting estimates of releases, contributing to lower emission values. In addition, the new class of sugarcane burning for which emission factors were not available in the 2005 edition of the Toolkit, will also have to be assessed separately in the baseline inventory, so that the same basis for calculation (and same emission factors) and the same scheme of classification of sources be used for both reference years.

6b Waste burning and accidental fires

2010 activity rates for open burning of domestic waste are calculated by extrapolating per capita waste production to population levels in urban and rural areas, and using the same assumptions concerning the fraction of waste that is burnt in the open in these areas. Approximately 70,000 tons of domestic waste are considered to be burnt annually. The total annual releases in 2010 are calculated as below, based on the Toolkit 2013 methodology:

Source category	Source class	Activity rate (t/year)	Annual Release (g TEQ/a)					Total
			Air	Water	Land	Product	Residue
Waste burning and accidental fires	Open burning of domestic waste	70,000	2.8		0.07			2.9

Despite the increase in the quantity of domestic waste burnt in the open, releases are shown to be much lower than in the baseline year (-85%). This is due to the revision of the respective emission factor e.g., for air, the emission factor was revised from 300 µg TEQ/t to 40 µg TEQ/t. To be able to assess the actual trend in releases over time, a revision of the baseline inventory is thus necessary use the same basis for calculation for both 2004 and 2010 estimates.

Two triggering factors come into play in this case prompting the need for revision: one is the revision of emission factors in the Toolkit, and the second one is the addition of new source classes to the Toolkit classification. To be able to compare release estimates in 2004 and 2010, the same methodology, the same basis for calculation (the same emission factors) need to be consistently used in the different inventories, along with the same source classification scheme.

There is a need to go back to the baseline release estimates for this source group and re-calculate those estimates according to the same methodology and approach as used in the updated inventory. The revised baseline estimate will be the product of the baseline activity levels and the revised emission factors taken from the Toolkit 2013 methodology.

6a Biomass burning

The baseline release estimates are re-calculated by applying the 2013 set of Toolkit emission factors and the classification of sources put forward in the 2013 version of the Toolkit. From the 400’000 tons of agricultural residues were considered to be burnt in the open in 2004 (the baseline year), 100’000 tons were actually sugarcane residues. As at the time the baseline inventory was developed there were no emission factors available for sugarcane burning, those residues were assessed together with the other agricultural crops. The releases are re-calculated by including this additional class and applying the emission factors proposed in the Toolkit 2013 methodology:

Source category	Source class	Activity rate (t/year)	Annual Release (g TEQ/a)					Total
			Air	Water	Land	Product	Residue
Biomass burning	Agricultural residue burning, poor combustion conditions	300,000	9		3			11
	Sugarcane burning	100,000	0.4		0.005			0.045
	Forest fires	3,000,000	3		0.45			3.45

The comparison between the updated and revised inventory accurately shows that the releases from agricultural residue burning and sugarcane burning are at a constant level since 2004. Only the forest fire emissions are down by one third, corresponding to an equivalent decrease in activity rates.

6a Waste burning and accidental fires

The re-calculation of release estimates from this source category is simply done by multiplying the baseline activity levels with the revised emission factors taken from the 2013 methodology. As no new or corrected information has become available that would influence activity level estimates, these are the same as in the 2004 inventory: 60’000 tons of domestic waste burnt annually. The revised baseline release estimates are shown in the table below:

Source category	Source class	Activity rate (t/year)	Annual Release (g TEQ/a)					Total
			Air	Water	Land	Product	Residue
Waste burning and accidental fires	Open burning of domestic waste	60,000	2.4		0.06			2.5

The results demonstrate that between 2004 and 2010 there was an actual increase in emissions from 2.5 to 2.9 g TEQ/year. If the baseline estimate was revised by using the same emission factors for the calculation, the conclusion of a reduction in releases from 2004 to 2010 would have been largely amiss.