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Denmark's Greenhouse Gas Projections until 2012, an update including a preliminary projection until 2017

7 Waste

7.1 Solid Waste Disposal on Land

The former Danish Government published the last waste disposal plan "Waste 21: The Government's Waste Management Plan for the period 1998 to 2004", in May 1999 [45]. "Waste 21" puts the future waste disposal on the agenda and the plan set as a goal to stabilise the amount of waste and to improve the quality of waste treatment. This shall be obtained by reducing the influence from environmental pollutants by a higher degree of recycling of the resources in the waste. The plan has the target that 64% of the waste should be recycled in 2004, 24% incinerated and 12% landfilled (see Table 25). However, "Waste 21" does not project the production of waste in the year 2004, but with the optimistic assumption of constant total amounts from 1997, the result is that 1.5 million tonnes will be landfilled in 2004 [42] (see Table 25).

Table 25.
Treatment of solid waste in Denmark 1985-2004.

The amount of solid waste being landfilled in Denmark according to source is shown in Table 27, the information is from the following sources: The first complete estimate of the solid waste was made for the year 1985 by the Danish Municipalities and Counties [40]. In 1993, the new ISAG-data system started to operate in the Ministry of Environment. According to public regulations, waste management facilities have to report the amount of waste received to the Danish Environmental Protection Agency. The data in ISAG includes the amount of waste grouped according to sources, types (like domestic waste, garden waste, industrial waste etc.), and waste management. However, only ISAG data from 1994 to 2000 [41] is used in the calculation, due to the incompleteness of the 1993 data.

From January 1, 1997 the Danish Government introduced a stop for landfilling of combustible waste [45]. Due to lack of incineration capacity part of the combustible waste will be stored temporarily before it is treated. However, it is assumed that no methane is emitted from these interim storages due to the dry conditions prevailing there.

The source of the historical data-point for the amount of waste landfilled in 1970 in Table 27, is Figure 2.16 in [43], which shows that the total amount of waste being landfilled in 1970 was 42% of the 1994 value, increasing linearly in the period 1970-1985 with the same disaggregation on source categories. A linear interpolation is also used in the periods 1985-1994 and 2000-2003 for each source category.

The disaggregation of the total amount of waste in 2004 on source categories were done using the following assumptions [42]: the amount of domestic-, bulky-, garden- and commercial waste in 2004 were assumed to be 50% of the 1997 values, the amount of industrial waste and building & construction waste in 2004 were assumed to be 75% of the 1997 values [42], the amount of sludge waste were assumed to be constant after 1999, and the small amount of ash & slag to disappear after 2004. For the period 2004-2012 the amounts of waste landfilled are kept constant for all source categories.

Since the carbon content in different fractions in the landfilled waste varies, it is necessary to make assumptions about the composition of the waste in the source categories. The assumptions are shown in Table 26 (the sum of all the fractions in each line of the table is one). All these fractions are from reference [40] except for the composition of sludge. The weight of the landfilled sludge in Table 27 includes 71% water [42], so only 29% of the sludge landfilled is in the category "other combustible".

The assumptions of the carbon content in the different fractions are shown at the bottom of Table 26. The carbon content of the fraction "other combustible" varies among the source categories from 20% in domestic waste to 57% in sludge [42]. The resulting CH₄ emission factors are also shown. They are based on the following assumption: 50% of the carbon in the landfill is emitted as a gas containing 45% CH₄, 10% of the CH₄ is oxidised in the topsoil layer [44]. The calorific value used for biogas is therefore 18 MJ/ m³ (45% of the calorific value of CH₄, which is 40 MJ/m³).

Table 26.
Composition of landfilled waste

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To the right in Table 27 the calculated CH₄ emissions from Danish landfilled are shown in the column " Potential emissions". Here the emissions in a given year are calculated, using the IPCC tier 2 method, as a sum of the emissions from the waste landfilled the years before, based on the assumption of a half-life of the carbon of 10 years (e.g. ten years later always half of the carbon is converted to CH₄). Due to this calculation method there is a time-delay between the year with maximum waste landfilled (1985) and the year with the maximum potential CH₄ emissions of 68.8 kt CH₄ (1996).

In order to calculate the "actual emission" of CH₄ from landfills in Table 27, the CH₄ collection by landfill gas plants must be subtracted from then "potential emission". According to Willumsen [44] the first landfill gas plant started operating in the end of 1985. The data from this source were used until the year 1994. In the period from 1994 until 1999 the production increases from 0.333 PJ to 0.58 PJ (10.3 kt CH₄) according to the Danish Energy Agency [28]. It increases to 0.66 in 2004 and thereafter no new plants are included. From 2004 the production decreases slowly due to ageing of the plants. Table 27 shows that due to the decrease in the potential emissions and the increase in the CH₄ collected the actual emissions in 2012 will have decreased to 38.5 kt CH₄ from the 62.4 kt CH₄ in 1990.

Table 27.
Time-series for the amount of landfilled waste and annual CH₄ emissions

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7.2 Wastewater Handling

Since all wastewater in Denmark is treated aerobically, there are no emissions of CH₄ from this source.

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