Annex 53 Complementary information to source group 9 Disposal/Landfill

Overview of recent revisions

Emission factors were revised for source categories 9a Landfills, Waste Dumps and Landfill Mining, 9b Sewage and Sewage Treatment and 9d Composting. The information used to revise the emission factors is presented below, in the respective sections.

Derivation of emission factors

9a Landfills, Waste Dumps and Landfill Mining

Release to Air

On average, 1 ton of normal municipal waste in a landfill generates 150 m³ of landfill gas (European waste) during a period of 10-20 years (or even longer). The highest gas production normally takes place in the early years after disposal. Measurements of landfill gas have not produced any quantifiable PCDD/PCDF concentrations. However, PCDD/PCDF have been detected in flares and exhausts of gas-fired motors (see source category 3c Landfill and Biogas Combustion). No measurable PCDD/PCDF release to air is expected from this activity.

Release to Water

The leachate or seepage from landfills and dumps can contain PCDD/PCDF. From a Korean industrial waste landfill, Jin et al. (2007) reported a PCDD/PCDF concentration range of 0-31.17 µg TEQ/m³ in a leachate sample described as “water”, indicating analysis of the aqueous phase. In the U.S., Litten et al., (2003) reported an average PCDD/PCDF concentration of 0.32 pg/L in treated landfill leachate, which were analyzed in conjunction with numerous other aqueous samples. Hiraoka et al. (1993) found PCDD/PCDF concentrations ranging from 0.076 to 6.3 ng/l (> 0.05 ng TEQ/L) in landfill leachates that had undergone biological treatment, coagulation and sedimentation, sand filtration, and/or activated carbon adsorption. In a Spanish study leachate from eight different landfills contained 1.6- 1520 pg I- TEQ/ L (Casanova et al. 1994).

PCDD/PCDF are likely to be concentrated in any oily phase of the leachate (the oily phase can be found either above or below the aqueous phase). However, the solubility of PCDD/PCDF in water is enhanced by the presence of detergents, other surfactants and dissolved humic acids (Yoshikawa et al. 1999, Nishikawa et al. 1999, Schramm et al. 1995, Kim and Lee 2002).

Data from five landfills in New Zealand ranged from 7.5 to 221 pg I-TEQ/L. The New Zealand inventory subdivided the range into 14-48.3 pg I-TEQ/L for small and medium landfills and 7.5-221 pg I-TEQ/L for large landfills (New Zealand 2000). The highest concentration came from a landfill with significant portions of industrial and potentially hazardous wastes.

For the Toolkit, the releases via leachates from the deposited waste for the inventory year is calculated and the estimated content for the respective class.

Three classes are suggested: class 1 with an emission factor of 5 µ TEQ/t waste for landfills which contains industrial wastes from category 1 to 8, class 2 with an emission factor of 0.5 µg TEQ/t for landfills which may contain hazardous wastes and class 3, with an emission factor of 0.05 µg TEQ/t for landfills containing non-hazardous municipal wastes.

Release to Land

Contamination of land can result from poorly controlled dumps and landfills.

Release in Products

There is no product.

Release in Residues

There is no residue. However, with the presence of PCDD/PCDF, landfills may serve as a reservoir and a potential source in the future. PCDD/PCDF concentrations in municipal solid waste have been reported to range from less than 1 ng I-TEQ/kg to levels of 100 ng I-TEQ/kg, and peak concentrations several orders of magnitude higher (especially when dust fractions are present). In Germany, a mean concentration of 50 ng I-TEQ/kg was estimated from wastes sampled in the late 1980s (Wilken et al. 1992). In the UK, a mean concentration of 6 ng I-TEQ/kg was measured in the mid 1990s. In a recent study in Italy, PCDD/PCDF concentrations in MSW were ranging from 1.6 to 44 ng TEQ/kg (Grosso et al. 2012).

Since it is anticipated that hazardous waste is being generated within the productive sector and is being accounted therein as residue, the EFResidue is set to “not applicable” for class 9a. For classes 9b and 9c, the amount (in tons of solid waste) disposed of within the reference calendar year consistutes the activity for “residue”.

When landfills are excavated for mining purpose or due to remediation measures, the deposited PCDD/PCDF can become a relevant source if PCDD/PCDF contaminated wastes have been deposited (see Source Group 10). The amount of PCDD/PCDF present in landfills or waste dumps will be determined by the level of PCDD/PCDF sources in the country. For landfills having received specific wastes in the past, especially from the organochlorine industry or industries using elemental chlorine, site-specific PCDD/PCDF inventories need to be compiled (see Source Group 10).

9b Sewage and Sewage Treatment

Release to Air

There are almost no data describing PCDD/PCDF releases to air from sewage treatment facilities.

Release to Water

Because PCDD/PCDF have very low solubility in water, treated effluents from sewage treatment facilities are expected also to be very low. However, the solubility of PCDD/PCDF in water is enhanced by the presence of detergents, other surfactants and dissolved humic acids (Yoshikawa et al. 1999, Nishikawa et al. 1999, Schramm et al. 1995, Kim and Lee 2002), all of these being commonly present in domestic and municipal wastewater. In addition, the use of chlorine for disinfection of treated effluents can increase PCDD/PCDF concentrations by as much as 50-fold: a PCDD/PCDF concentration of 0.006 pg TEQ/L was measured in treated effluent that had not been subject to chlorine disinfection, while a PCDD/PCDF content of 0.3 pg TEQ/L was determined in treated effluent that had undergone chlorine disinfection (Pujadas et al. 2001).

Release to Land

Sludge from sewage treatment may be applied to land to improve soil quality and as a management approach for sewage sludge. If so, the EFPRODUCT will be used for the EFLAND.

Release in Products

Sludge may be considered a product when it is applied to land as a soil improvement or is marketed for such use. In these cases it will be considered a release to land. Sludge otherwise disposed of will be accounted for as a release in residues. Here, sewage sludge is the product and there is no residue generated.

Release in Residues

PCDD/PCDF concentrations in sewage sludge have been measured since the late 1980s, when Hagenmaier found an average concentration of 200 ng TEQ/kg d.m. from 43 German sewage sludge treatment plants (Hagenmaier 1988). Subsequently, about 300 plants were analyzed to give an average of 50-60 ng TEQ/kg d.m. (Butzkamm-Erker and Mach 1990). In 30 Swiss sewage plants, Rappe et al. (1994) found concentrations between 6 and 4,100 ng I-TEQ/kg d.m., with four samples above 1,000 ng I-TEQ/kg d.m. During the last 25 years, the values of PCDD/PCDF have decreased considerably. Today, the average PCDD/PCDF values in Swiss sewage treatment plants are around 10 ng TEQ/kg (M. Zennegg, personal communication, 20 February 2012) and in Swedish sewage sludge below 3 ng I-TEQ/kg d.m. (Swedish Environmental Ministry 2010). These values are similar to the recent review of PCDD/PCDF levels in sewage sludge in Australia, registering a mean value of 6 ng I-TEQ/kg with most sludge samples around 2 and 3 ng I-TEQ and a two sludge samples between 10 and 20 ng TEQ/kg. In the Australian study, only a minor difference between the average for urban sludge (7 ng TEQ/kg) and rural sludge (5 ng TEQ/kg) was found (Clarke et al. 2008). In a Chinese survey, four sludge samples were between 3 and 7 ng TEQ/kg with two sludges at 33 and 88 ng TEQ/kg (Dai et al. 2007). In a Spanish survey, 24 of 31 samples collected were below 20 ng TEQ/kg, with only one sludge from an industrial area impacted by textile industries having relatively high levels (346 ng TEQ/kg) (Fuentes et al. 2007).

Based on these data, the following emission factors are included in the Toolkit:

  • 4 ng TEQ/kg for sewage treatment plants in remote areas and urban areas with only domestic inputs;
  • 20 ng TEQ for sewage treatment plants in urban environment with mixed input from households and industry without specific potential to contain PCDD/PCDF;
  • 200 ng TEQ/kg for sewage treatment plants with specific industrial impact with a potential to contain PCDD/PCDF as described for categories 1 to 8.

For the respective classes, emission factors are also given for releases into water depending if sludge is effectively removed or not in the respective plant.

9d Composting

Release to Air

Emissions to air are very low (few pg per m³) and may be considered negligible.

Release to Water

The composting process generates water, however, the concentrations are normally very low and the water is recycled into the compost during the process.

Release to Land

The most common use of finished compost is application on land or marketing for that purpose, therefore the EFProduct is the EFLand.

Release in Products

In a comprehensive study in Europe, PCDD/PCDF levels were measured in 185 composts. Average PCDD/PCDF levels in these composts were below 10 ng TEQ/kg dw (Brändli et al. 2005). Concentrations varied to a limited extent between compost containing organic household waste (9.6 ng I-TEQ/kg dry wt., n = 124) and containing green waste (8.5 ng I-TEQ/kg dry wt., n = 61); the differences were not significant (Brändli et al. 2005). A more recent study in Switzerland detected lower levels at 3.2 ng TEQ/kg dw (Brändli et al. 2008).

The levels of PCDD/PCDF in organic compost (separated at source) in Brazil were on average of 14 ng TEQ/kg. However compost made from mixed wastes, where organic fractions have been separated after the collection of the “grey compost”, had a higher average content of 57 ng TEQ/kg, with a maximum of 150 ng TEQ/kg in metropolitan areas; an average of 27 ng TEQ/kg was measured in small towns (Grossi et al. 1998). In addition, compost impacted by a pulp and paper sludge (Kraft process) had higher levels of 99 ng TEQ/kg (Grossi et al. 1998). Composts with PCDD/PCDF concentrations of 50 ng TEQ/kg and higher are not considered suitable for agriculture or horticulture.

An EFProduct of 5 ng TEQ/kg should be applied for compost produced from clean organics (separated at source) or green waste.

An EFProduct of 50 ng TEQ/kg should be applied for compost made from organics separated from mixed (household) waste “grey compost” or from industrial organic residues containing PCDD/PCDF.