Nielsen, M., Nielsen, O.-K., Plejdrup, M. & Hjelgaard, K., 2009: Danish Emission Inventories for Stationary Combustion Plants. Inventories until year 2007. National Environmental Research Institute, Aarhus University, Denmark. 216 pp. – NERI Technical Report no. 744.
Danish emission inventories are prepared on an annual basis and are reported to the United Nations Framework Convention on Climate Change (UNFCCC or Climate Convention) and to the Kyoto Protocol as well as to the United Nations Economic Commission for Europe (UNECE) Convention on Long-Range Transboundary Air Pollution (LRTAP Convention). Furthermore, a greenhouse gas emission inventory is reported to the European Union (EU), due to the EU – as well as the individual member states – being party to the Climate Convention. Four pollutants are estimated for reporting to the European Commissions National Emissions Ceiling Directive (NECD). The annual Danish emission inventories are prepared by the Danish National Environmental Research Institute (NERI), Aarhus University. The inventories include the following pollutants relevant to stationary combustion: CO2, CH4, N2O, SO2, NOx, NMVOC, CO, particulate matter, heavy metals, dioxins, PAH and HCB. In addition to annual national emissions, the report includes emission data for a number of source categories. Every five years the reporting includes data on the geographical distribution of the emissions, a projection of emissions data and details of the activity data – e.g. fuel consumption – on which the inventories are based.
The inventories for stationary combustion are based on the Danish energy statistics and on a set of emission factors for various source categories, technologies and fuels. Plant specific emissions for large combustion sources are incorporated into the inventories. This report provides detailed background information on the methodology and references for the input data in the inventory - energy statistics and emission factors.
The emission factors are based on either national references or on international guidebooks (EEA 2007 and IPCC 1997). The majority of the country-specific emission factors refer to: Danish legislation, Danish research reports or calculations based on plant-specific emission data from a considerable number of large point sources. The plant-specific emission factors are provided by plant operators, e.g. in annual environmental reports or in the EU ETS[1].
In the inventory for the year 2007, 71 stationary combustion plants are specified as large point sources. The point sources include large power plants, municipal waste incineration plants, industrial combustion plants and petroleum refining plants. The fuel consumption of these large point sources corresponds to 60 % of the overall fuel consumption of stationary combustion.
In 2007 the fuel consumption was 12 % higher than in 1990; the fossil fuel consumption, however, was 2 % lower than in 1990. The use of coal has decreased whereas the use of natural gas and biomass has increased. The fuel consumption for stationary combustion plants fluctuates due to variation in the import/export of electricity from year to year.
Stationary combustion plants account for more than 50 % of the national emission for the following pollutants: SO2, CO2, heavy metals (except Cu), TSP, PM10, PM2.5, dioxin, HCB and PAH. Furthermore, the emission from stationary combustion plants accounts for more than 10 % of the national emission for the following pollutants: NOx, CO, NMVOC and Cu. Stationary combustion plants account for less than 10 % of the national CH4 and N2O emission.
Public electricity and heat production are the most important stationary combustion emission source for CO2, N2O, SO2, NOx and heavy metals.
Lean-burn gas engines installed in decentralised combined heating and power (CHP) plants and combustion of biomass in residential plants are the two largest emission sources for CH4.
Residential plants represent the most important stationary combustion source for CO, NMVOC, particulate matter, PAH and dioxin. Wood combustion in residential plants is the predominant emission source.
The greenhouse gas emission (GHG) trend follows the CO2 emission trend closely. Both the CO2 and the total GHG emission were lower in 2007 than in 1990: CO2 by 10 % and GHG by 9 %. However, fluctuations in the GHG emission level are large. The fluctuations in the time-series are a result of electricity import/export and of outdoor temperature variations from year to year.
The CH4 emission from stationary combustion has increased by a factor of 3.6 since 1990. This is mainly a result of the considerable number of lean-burn gas engines installed in CHP plants in Denmark during the 1990s. In recent years the emission has declined. This is due to structural changes in the Danish electricity market, which means that the fuel consumption in gas engines has been decreasing. The CH4 emission from residential plants has increased since 1990 due to increased combustion of wood in residential plants.
The emission of N2O was 16 % higher in 2007 than in 1990. The fluctuations follows the fluctuations of the fuel consumption that is a result of import/export of electricity.
SO2 emission from stationary combustion plants has decreased by 95 % since 1980 and by 87 % since 1990. The considerable emission decrease is mainly a result of the reduced emission from electricity and heat production due to installation of desulphurisation technology and the use of fuels with lower sulphur content.
The NOx emission from stationary combustion plants has decreased by 58 % since 1985 and 46 % since 1990. The reduced emission is mainly a result of the reduced emission from electricity and heat production due to installation of low NOx burners and selective catalytic reduction (SCR) units. The fluctuations in the emission time-series follow fluctuations in electricity import/export.
In 2007 the wood consumption in residential plants was 4.1 times the 1990 level. A change of technology (installation of modern stoves) has, however, caused decreasing emission factors for several pollutants.
The CO emission has increased by 22 % from 1990 to 2007. The increase in CO emission from residential plants is less than the increase in wood consumption, because the CO emission factor for wood combustion in residential plants has decreased since 1990. Furthermore the emission from straw-fired farmhouse boilers has decreased considerably.
The NMVOC emission from stationary combustion plants has increased by 104 % from 1985 and 109 % from 1990. The increased NMVOC emission is mainly a result of the increasing wood combustion in residential plants and the increased use of lean-burn gas engines. The emission from straw-fired farmhouse boilers has decreased.
The emission of TSP, PM10 and PM2.5 has increased by 68-71 % since 2000 due to the increase of wood combustion in residential plants. The emission of PAHs has increased by 130-190 % since 1990, also a result of the increased combustion of wood in residential plants.
All the heavy metal emissions has decreased considerably since 1990 – between 34 % and 82[2]%. This is a result of the installation and improved performance of gas cleaning devices in municipal waste incineration plants and large power plants.
Dioxin emission has decreased 55 % since 1990 mainly due to installation of dioxin filters in municipal solid waste (MSW) incineration plants. However, the emission from residential plants is increasing due to the increasing wood combustion in the sector. This has caused a 23 % increase of dioxin emission from stationary combustion since 2004.
The uncertainty level of the Danish greenhouse gas emission from stationary combustion is estimated to be within a range of ±8.5 % and the trend in GHG emission (1990-2007) is -8.5 % ± 2.1 %-age points.
[1] EU Emission Trading Scheme.
[2] The estimated Zn emission in 2007 is 15% higher than in 1990. This is presumably due to insufficient emission factor update for recent years.
Full report in PDF-format (8.4 MB).
