Solid Waste Disposal Sites constitutes a sub-sector in the waste sector. In the Danish emission inventory system CH₄ emissions from solid waste disposal sites are calculated with use of a first order decay model. Such an approach is recommended by the IPCC in their guidelines and is based on the fact that waste being deposited over time will be degraded and in this process the organic part of the waste emits CH₄. In the model used it is - with reference to the IPCC - assumed that half of the potential CH₄ generated in a given part of the waste deposited is emitted within 14 years after the year of deposition.

CH₄ from solid waste disposal is in 2009 contributing with 1.7 % to the national emission of CO₂-equivalents (excluding LULUCF) and is the dominant source in the Waste sector with contributions in the time-series 1990-2009 varying from 76.5 % (2008) to 83.1 % (1992) of the total emission, given in CO2-equivalents, originating from the waste sector. The contribution in 2009 is 77.3 %. Throughout the time-series, the emissions are decreasing due to a reduction in the amount of waste deposited. Comparing 1990 and 2009 the decrease is 6.4 %.

In general, the amount of deposited waste has decreased markedly throughout the time-series. The general development for solid waste is a result of action plans by the Danish government called the "Action plan for Waste and Recycling 1993-1997" and "Waste 21 1998-2004". The latter plan had, inter alia, the goal to recycle 64 %, incinerate 24 % and deposit 12 % of all waste. The goal for deposited waste was met in 2000. Further, in 1996 a municipal obligation to assign combustible waste to incineration was introduced. In 2003, the Danish Government set up targets for the year 2008 for waste handling in a “Waste Strategy 2004-2008” report. According to this strategy, the target for 2008 is a maximum of 9 % of the total waste to be deposited. In the waste statistics report for the year 2004, data shows that this target was met, since 7.7 % of total waste was deposited in 2004. Further in 2005 the amount decreased compared to 2004 and was only 6.9 % of the total waste amount. In 2009 the contribution was 5.6%. The Danish Government in 2009 set up targets for 2012 according to which a maximum of 6 % the total waste produced is to be deposited.

The information and the data for disposal of waste are provided by the Danish Environmental Protection Agency, who registers more than hundred sites for disposal. The organic part of the deposited waste at these sites generates CH₄ gas, of which some is collected and used as biogas in energy-producing installations at around 26 sites. The Danish Energy Agency registers the gas amounts recovered at disposal sites.

The data used for the amounts of municipal solid waste deposited at managed disposal sites are according to the official registration worked out by the Danish Environmental Protection Agency in the so-called ISAG database The registration of the amounts of waste deposited takes place in the ISAG database in the following waste categories, domestic, bulky, garden, commercial & office, industrial, building & construction, sludge, and ash & slag. However, for CH₄ emission estimation, a division of waste types is needed in categories with data for the degradable organic carbon (DOC) content. For the following categories, investigations of DOC content etc. have been carried out for Danish conditions: waste food, cardboard, paper, wet cardboard and paper, plastics, other combustible, glass and Other, not combustible.

The decrease in the emission throughout the time-series is much less than the general decrease in the amount of waste deposited. This is due to the time involved in the processes generating the CH₄, which is reflected in the model used for emission calculation, see the figures below.

Time-series for waste deposited for the years 1990-2009.

Time-series for potential, collected and actual emissions of CH₄ from solid waste disposal for the years 1990-2009. The potential emission refers to waste deposited in the previous year assuming the emission starts the year after the waste is deposited and that the emission is completed within a year, while the actual emission estimated by a decay-model with a half-life time of 14 years reflects the fact that emission from waste occurs for several years after deposition.