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Toolkit for Identification and Quantification of Releases of Dioxins, Furans and Other Unintentional POPs PART III Annexes |
Annex 34 Complementary information to source category 3e Household Heating and Cooking with Fossil Fuels
Overview of recent revisions
Three new classes were added in this category:
- Coal/biomass co-fired stoves with waste, including domestic stoves using mixed solid fuels. In most cases this category applies to the co- firing of coal, biomass and waste. Nevertheless, co-firing of waste in residential appliances is an illegal practice in many countries.
- Peat fired stoves, including domestic stoves, ovens and boilers firing peat. The use of peat as a fuel in the residential sector is closely linked to its local availability.
- Coal/coke-fired simple stoves, including coal ore coke fired simple stoves for cooking with limited combustion control. The proposed dioxin emission factor for air is of 200 µg TEQ/ TJ. High chlorine coal fired stoves may show significantly higher emissions (Air: 1,500 µg TEQ/ TJ coal, Residue: 5,000 ng TEQ /kg ash).
Derivation of emission factors
Release to Air
Releases to air are the predominant vector for fossil fuel combustion. For coal, three classes of emission factors are proposed since there are distinct ranges of PCDD/PCDF emissions reported in the literature. The default emission factor for class 3 was derived from mean values reported between 1.6 and 50 μg TEQ/t of coal burned, which is reported from most European countries. It is important to note that the values reported for domestic coal combustion are fairly consistent between 1 and 7 μg TEQ/t of coal burned. Thus, an average value of 3 μg TEQ/t was chosen for typical coal. Based on an average heating value of 30 MJ/kg for coal, a default emission factor of about 100 μg TEQ/TJ can be calculated. On the other hand, an Austrian study reported a much higher value of 0.91 mg TEQ/t as well as the Swiss value of 230 ng TEQ/GJ also seems to be somewhat on the high side (LUA 1997). However, emission factors in the same range were recently reported for small residential stoves when coal or briquettes from Poland were burned resulting in an emission factor as high as 200 µg TEQ/TJ (Grochowalski and Konieczynski 2008). Kubica et al. (2004) reported emission factors between 108.5 μg TEQ/t and 663.9 μg I-TEQ/t of coal burned. These high values may be explained by the high chlorine content – ranges from traces to 0.4% and maxima up to 1.5% of chlorine - in the coal from Poland. For an average of 400 μg I-TEQ/t of coal burned and with an average heating value of 25 MJ/kg for bituminous coal from Poland (and coals from other regions with similar specifications), a class 1 default emission factor of 1,700 μg TEQ/TJ (Pandelova 2005). However, the role of chlorine concentration in the reaction gases from hard coal firing in combustion processes is not yet clearly explained. There are many processes inhibiting PCDD/PCDF formation as well. The NaCl content in coal seems to be less important in light of data obtained from recent measurements. These results indicate that even for 0,5 - 1% of NaCl (high chlorine coal) in coal fired in modern CFB boilers, PCDD/PCDF emissions are less than previously expected.
The new emission factor for peat fired stoves (class 4) was derived from McGettigan (2009).
The default emission factor for class 5 was derived from values reported between 0.04 and 2 μg TEQ/t. The value of 0.04 mg TEQ/t as reported in the Austrian study seems to be extraordinarily high whereas the Swiss value of 0.5 ng TEQ/GJ is extremely low. Thus, an average value of 0.5 μg TEQ/t was chosen for oil. Based on an average heating value of 44–46 MJ/kg for heating oil, a default emission factor of 10 μg TEQ/TJ was calculated.
The default emission factor for class 6 was derived from values reported between 0.04 and 0.07 ng TEQ/m³. An average value of 0.05 ng TEQ/m³ was chosen for natural gas. Based on an average heating value of 32–35 MJ/m³ for natural gas, a default emission factor of 1.5 μg TEQ/TJ was calculated (LUA 1997, IFEU 1998, Environment Canada 1999).
Release to Water
No release to water is expected.
Release to Land
No release to land is expected.
Release in Products
The process has no product; thus no release to product occurs.
Release in Residues
PCDD/PCDF in the fly ash residue of coal combustion has been analyzed and concentrations between 4 and 42,000 ng TEQ/kg ash were detected (Dumler-Gradl et al. 1995). For a first estimate, an emission factor of 5,000 ng TEQ/kg ash should be used in the Toolkit. For the high chlorine coal from Poland, no emission factor was found. However, for a first approximation the upper values of the measured data from Dumler-Gradl et al. (1995) could be used for class 1 residues.
