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Denmark´s Second National Communication on Climate Change
4. Inventories of anthropogenic greenhouse gases and removals
In 1996, the Danish Environmental Protection Agency together with the National
Environmental Research Institute decided to use the software and the methodologies
developed by the EU and known as the CORINAIR - database system as the foundation for the
Danish national database system for air pollutants. This ensured the highest degree of
compatibility with other database systems for air pollutants and at the same time
facilitated updating and maintenance. The inventory presented below is based on the
CORINAIR system.
In general, the CORINAIR-inventory is transformed in accordance with the 1995-Guidelines for Communication of Information Under the Framework Convention on Climate Change (IPCC) into the IPCC-inventory. The Revised 1996-IPCC guidelines have supplementary been applied to N2O from agriculture and the pollutants not earlier included (SO2, HFCs, CFCs and SF6).
4.1 Inventory of anthropogenic emissions by source
4.1.1 Introduction
Pollutants
This section presents the results of the Danish inventory of emissions for the years 1990 - 1995 apportioned by source according to the IPCC guidelines as descibed above. In Annex A the inventory is shown in full IPCC reporting format. The pollutants reported here are the primary greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as the secondary substances nitrogen oxides (NOx), carbon monoxide(CO), non methane volatile organic substances (NMVOC) and sulphur dioxide (SO2,). Emission data for hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6) are presented in an condensed format. The figures for 1995 are preliminary data.
The secondary substances are important for different reasons. Thus CO can react with hydroxide (OH-) in the atmosphere, thereby preventing the oxidation of CH4, while NOx and NMVOC are precursors to the greenhouse gas ozone (O3).
Statistics and emission factors
The basis for the Danish emission inventory is activity data for the categories
described in detail in Fenhann et al., 1997, energy statistics from the Danish Energy
Agency shown in Table 4.1 and Annex B, agricultural livestock statistics from Statistics
Denmark shown in Annex C, and the emission factors for each source and each fuel or
livestock shown in Annex D. Other statistics and activity data used can be obtained at the
National Environmental Research Institute.
The emissions from the transport sector are calculated on the basis of fuel sales in Denmark. Emissions from international transports (aviation bunkers and marine bunkers), based on fuel sales in Denmark is calculated in the inventory for each pollutants. These emissions are shown in Tables 4.2 - 4.8 and Annex A, but are not included in the national totals. The emission factors for road transport are based on calculations with the COPERT - model for the transport sector, this being a background model for the CORINAIR work.
The emission factors for CO2 are based on the assumption that all the carbon content of the fuel is oxidised (complete combustion), albeit that this is seldom the case. Some carbon will be released as other compounds, e.g., CH4, CO or hydrocarbons (NMVOCs), and will eventually be transformed to CO2 in the atmosphere. The emission factors for CO2 is calculated from the low heat values and the carbon content of the fuels, as shown in Andersen et al., 1995.
Factors for CH4 emission from livestock are from the 1995-IPCC guidelines.
Dominant sources
The dominant source of Danish CO2, CO and NOx emissions is combustion of fossil fuel. Apart from combustion, the main source of N2O and CH4 emissions is agriculture while that of NMVOC emissions is solvent use.
Uncertainty
The uncertainty in the Danish emission inventories arises from two sources: Uncertainty in the statistics and uncertainty in the emission factors used. As mentioned above, the statistics are the official Danish statistics. The emission factors are based on either calculations, as is the case with CO2 (heat values and carbon content), or on measurements. The measurements originate from either existing Danish plants or from comparable European installations. Another uncertainty is whether all (major) sources of emissions are included in the inventory. It is assumed that the uncertainty is greatest for the inventories of NMVOC, CH4 and N2O, perhaps with an uncertainty factor of 2. With the CO and NOx inventories, the uncertainty is assumed to be less than 30 - 40%. With the CO2, the uncertainty may be as low as 1 - 2%.
Electricity exchange and temperature variations
In some years Denmark imports considerable electricity while in other years electricity is exported. The variation is due to changes in precipitation in Norway and Sweden leading to fluctuations in the availability of hydropower.
Climate variation imply not only a variation in electricity exchange but also inter-annual fluctuations in domestic energy consumption due to variation in outside temperature. Consequently, correction for the impact of outside temperature variation has been applied as well.
In Table 4.1 and in the energy balances in Annex B these corrections are shown.
Both corrections are only significant for CO2 and are given separately together with the corrected values in Table 4.2. These values should be used in assessing the inter-annual variation in CO2 emissions corresponding to the energy consumption. The corrected values should also be used in connection with evaluation of compliance with emission reduction commitments.
The calculation method is futher described in Annex E.
4.1.2 CO2
CO2
As mentioned above the emission factors used for the CO2 emission inventory are based on the assumption that all the carbon in the fuel is oxidised during combustion. This is in accordance with the recommendations in the IPCC-guidelines.
Emissions from biomass fuels are not included in the inventory. Biomass fuels here include wood, straw, biogas and refuse. It should be noted that not all of the refuse used as fuel is renewable and hence a biomass fuel, but it has not yet been possible to divide the refuse burned in Denmark into different fractions.
Danish emissions of CO2 amounted to 59,500 Gg in 1995 (Table 4.2 and Annex A). The main part - 58,000 Gg - derived from the combustion sector. The remaining 1,500 Gg derived from industrial processes, with cement production being the main source.
The development in total Danish CO2 emissions corrected for electricity exchange and outside temperature variation is shown in Table 4.2, and as it can be seen from Figure 4.1, this development indicates a slight negative trend from 1991.
Table 4.2. CO2 emissions to air by
sources and removals by sinks and correction for electricity exchange and outside
temperature variation in
Gg 1990 - 95.
CO2 emissions to air by
sources and removals by sinks and correction for electricity exchange and outside
temperature variation in
Gg 1990 - 95. CO2 emissions to air by
sources and removals by sinks and correction for electricity exchange and outside
temperature variation in
Gg 1990 - 95.
The corrected figures reflect CO2 emissions corresponding to Danish energy consumption under normal meteorological conditions. Thus, when comparing Danish emission figures from year to year to get an impression of the effect of the implemented measures to reduce CO2 emissions it is necessary to use the corrected figures. These should also be applied when assessing the compliance with emission reduction targets under the UNFCCC, etc.
CO2 uptake by sequestration in existing and new forests is given separately in Table 4.2 and Annex A.
4.1.3 CH4
CH4
Total Danish anthropogenic emissions of CH4 amounted to 430 Gg in 1995 (Table 4.3 and Annex A). The dominant sources were animal waste and enteric fermentation in the agricultural sector, which accounted for 327 Gg in 1995. A new calculation has been used applying the emission factors recommended in the 1995-IPCC guidelines.
Table 4.3. CH4 emissions to air by sources in Gg 1990 - 95.
The second most important source was waste, with CH4 emissions from landfills being dominant (74 Gg in 1995). Only a minor part (28 Gg in 1995) derived from fuel combustion and fugitive sources. The inventory takes into account animal waste treatment in biogas plants.
From January 1997 the disposal of any kind of combustible waste at landfills is prohibited. CH4 gas emissions from landfills are consequently expected to drop in the future.
At present there are no rules in Denmark for gas collection at landfills. In the EU Commission's proposal for a Council Directive on landfilling of waste it is proposed that landfill gas should be collected from all landfills receiving biodegradable waste and thereafter treated and used, or alternatively flared. Thirteen Danish landfills currently generate electricity by extracting methane gas with an aggregated heating value of 550 TJ per year.
CH4 emissions in the period 1990 - 95 ranged from 421 to 445 Gg per year with no clear trend.
4.1.4 N2O
N2O
Total estimated emissions to air of N2O from Danish sources amounted to 33 - 34 Gg in the period 1990 - 95 (Table 4.4 and Annex A).
Table 4.4. N2O emissions to air by
sources in Gg 1990 - 95.
N2O emissions to air by
sources in Gg 1990 - 95.
N2O emissions to air by
sources in Gg 1990 - 95.
Using the Revised 1996-IPCC guidelines, five major sources have been identified: Direct emissions from fertiliser and nitrogen fixation, emissions from nitrogen deposition, emissions from nitrogen leaching, emissions from livestock and emissions from histosols. IPCC emission factors have been applied for each source.
In Denmark's first national communication only the first source category was taken into account. This implied an underestimation of total N2O emissions from the agricultural sector by a factor of 3 - 4.
Due to the impact of the Danish Action Plan for a Sustainable Agricultural Development, the consumption of commercial fertiliser decreased by 25% from 1990 to 1996. This decrease is reflected in the emission figures for the period 1990 - 95.
4.1.5 NOx
NOx
Total emissions to air of NOx from Danish sources amounted to 253 Gg in 1995 (Table 4.5 and Annex A). Fuel combustion was practically the only source of Danish NOx emissions.
Table 4.5. NOx emissions to air by sources in Gg 1990 - 95.
The NOx emissions tended to decrease over the period, from 280 Gg in 1990 to 253 Gg in 1995.
4.1.6 CO
CO
Total anthropogenic emissions of CO from Danish sources amounted to 702 - 726 Gg in 1995 (Table 4.6 and Annex A).
The main source was combustion processes, accounting for 656 Gg in 1995. The second most important source was fugitive emissions from coal stores, accounting for 45 Gg in 1995. This is calculated using an emission factor of 0.0000034 Gg CO per tonne of stored coal.
Table 4.6. CO emissions to air by sources in
Gg 1990 - 95.
CO emissions to air by sources in
Gg 1990 - 95.
CO emissions to air by sources in
Gg 1990 - 95.
The CO emissions tended to decrease over the period, from 785 Gg in 1990 to 702 Gg in 1995.
4.1.7 NMVOC
NMVOC
Total Danish anthropogenic NMVOC emissions amounted to 162 Gg in 1995 (Table 4.7 and Annex A). The main part - 93 Gg - came from combustion processes. 40 Gg came from solvent use, where paint application were the most important sub-category.
NMVOC emissions also tended to decrease over the period, from 179 Gg in 1990 to 162 Gg in 1995.
Table 4.7. NMVOC emissions to air by sources
in Gg 1990 - 95.
NMVOC emissions to air by sources
in Gg 1990 - 95.
NMVOC emissions to air by sources
in Gg 1990 - 95.
4.1.8 SO2
SO2
Danish SO2 emissions were computed using the emission factors in Annex D and
the corresponding consumption of sulphur-containing fuel. Since most Danish power plants
are equipped with desulphurisation units, emissions from this source are based on direct
measurements. Total Danish anthropogenic SO2 emissions amounted to 150 Gg in
1995 (Table 4.8 and Annex A). The main part - 106 Gg - came from the source category public power, CHP and district heating.
Table 4.8. SO2 emissions to air by sources in Gg 1990 - 95.
4.1.9 HFCs, PFCs and SF6
HFCs, PFCs and SF6
The consumption of HFCs in the period 1990 - 95 increased in line with the replacement of CFCs, while the consumption of SF6 remained largely unchanged (Table 4.9 and Annex A). The consumption of PFCs in the period was negligible.
Table 4.9. Consumption of HFCs, PFCs and SF6
in Gg, 1990 - 95.
Consumption of HFCs, PFCs and SF6
in Gg, 1990 - 95. Consumption of HFCs, PFCs and SF6
in Gg, 1990 - 95.
The Danish consumption figures, estimated actual emission figures and GWP-weighted emissions from industrial non-energy processes in 1995 are shown for HFCs, PFCs and SF6 in Table 4.10.
Table 4.10. HFCs, PFCs and SF6 , consumption, emissions to air and the related GWP in Gg, 1995.
The estimated actual emissions are computed from the consumption figures by applying the method recommended in the Revised 1996-IPCC guidelines.
Total GWP-weighted emissions of HFCs, PFCs and SF6 was 419 Gg CO2 equivalents in 1995, of which was accounted for by HFCs (52%) and SF6 (48%).
HFCs
HFCs are mainly emitted during the blowing of sealing foams (63%). A further 15 % is emitted in the manufacture of refrigerator/freezer insolation foam and 12% during the blowing of miscellaneous foams, e.g. open cell foam.
PFCs
Consumption and emissions of PFCs are insignificant, only perfluoropropane being used in Denmark. PFCs are not produced in Denmark.
SF6
70% of the SF6 is emitted during the production of soundproof windows and 18% from magnesium foundries (used as cover gas). The rest is emitted from electrical equipment (insulation medium) in power plants, research institutions (e.g. air trace gas) and miscellaneous applications, e.g. low-noise proof car tyres.
4.2 Sinks
CO2-sequestration in existing forests.
The forest area is defined as closed canopy high forest. This means that open woodland and open areas within the forest are not included.
The assumption is that the Government's strategy of doubling the forest area within the next 80 - 100 years will be followed. Afforestation will gradually reach 40 km2 per year as the interest in private afforestation and appropriations for national afforestation increases. The peak afforestation rate will be around the year 2020.
The 1990 inventory on forests gives a total standing stock volume of 55,154,000 m3.
The standing stock volume is in average 13,200 m3 per km2 in 1990. Using the IPCC recommended conversion factors the amount of carbon stored in existing forests in 1990 was 23,600 Gg corresponding to 86,526 Gg CO2 as shown in Table 4.11.
Table 4.11. CO2 reservoir and
uptake in forests in Gg, 1990 - 95.
CO2 reservoir and
uptake in forests in Gg, 1990 - 95. CO2 reservoir and
uptake in forests in Gg, 1990 - 95.
Annual CO2 fixation in existing forests.
The annual net-increment (increment minus thinning removals) in the period 1990 - 2000 is estimated to be 600,000 m3 per year. Using the IPCC conversion factors this equals around 250 Gg carbon per year or 916 Gg CO2 per year. Annual felling / removal based on 1990 figures was 480 m3 per km2 per year or 0.110 Gg carbon per km2 per year.
Increasing carbon fixation through afforestation.
The total annual afforestation rate during the period 1990 - 95 is estimated to have been around 19 km2 per year. This includes both areas covered with trees and open areas in the forest. In connection with carbon fixation it is the tree-covered area that is the interesting factor. The annual afforestation rate is therefore estimated to be between 10 and 15 km2 per year. It is expected that the rate will increase gradually, as new afforestation incentives (adopted in 1996) takes effect, and peak with 40 km2 per year around the year 2020.
Assuming that the forest area doubles within the next 80 - 100 years, the following CO2 binding pattern can be expected. Over the next 30 years, CO2 binding will be small. 70 - 120 years after the forest is planted, CO2 binding will peak at approx. 3,500 Gg CO2 per year or approx. 5% of present annual anthropogenic emissions in Denmark.
Within the next 10 - 20 years, the quantity of wood for energy purposes is expected to rise while the quantity of wood for pulp and paper production will fall.
1990 - 95
The average afforestation rate over the period 1990 - 95 was 19.38 km2 per year. Danish CO2 uptake and growth models show an average CO2 binding rate of 0.41 Gg CO2 per km2 per year on average basis through the whole afforestation period of 150 years. This means that the 19.38 km2 per year equals 8 Gg CO2 per year. The total annual uptake over the period 1990 - 95 is shown in Table 4.11 and Annex A.
4.3 Agricultural sector
Agricultural Land use
In 1992 the total arable area was 27,600 km2, which is about 65% of the total area of Denmark. The distribution of agricultural area by crop type is shown in Table 4.12.
Since the 1930s the arable area has decreased by about 10%. Part of this land has been used for infrastructure and municipal development. More recently the area of agricultural land has also decreased due to afforestation and environmental measures.
Permanent grassland has also decreased by about 10% during this period, whereas annual crops have increased.
Due to the EU Agricultural Policy reform, 2,000 km2 of arable land has been set aside every year in order to reduce food production. This land may be used for nonfood production, however.
According to the Action Plan for Sustainable Agricultural Development, the arable area is expected to decrease by a further 2,500 to 4,500 km2 over the next 15 years. Land is needed for municipal development and infrastructure, and marginal land will be set aside or taken out for other environmental reasons. It is not expected that the use of the arable land will change considerably.
Biomass in agricultural ecosystems
During the last 30 years, there has been a considerable increase in the biomass production of in the agricultural ecosystem due to a change in agricultural practice. In concert with this there has been an increase in the use of fertiliser, especially nitrogen.
It is difficult to give an exact measure of production in the agricultural ecosystem as this is closely related to climate conditions. Average crop production over the four-year period 1989 - 92 is shown in Table 4.12.
Total annual dry matter crop production in Denmark is about 17,100 Gg.
Assuming that approx. 1/3 of crop biomass is accounted for by roots, straw etc. (left in field), total biomass production in the Danish agricultural ecosystem can be estimated at 23,000 Gg per year or 0.833 Gg/km2.
| Crop production in average 1989-92 | Freshweight (Gg) | Dry matter (Gg) |
| Total Crop Production Cereals Rape Pulses Straw Roots Tops Grass and green fodder |
41,704 8,647 645 437 3,535 10,854 2,258 15,328 |
17,106 7,350 587 371 3,005 2,388 339 3,066 |
Table 4.12. Average annual crop production in Gg for the last four-year period 1989 -1992.
CO2
In cultivated soils humus masses comprises 2 - 5% of the top soil, depending on the type of soil and crop.
It might be possible to increase the humus content slightly in some fields, though an increase will be very slow, and only be within the limits of the natural capacity of the soil. The most important factor for an increase is a constant high input of organic matter.
It is unlikely that a change in soil humus content can be of a sufficient magnitude to sequester significant amounts of CO2.
N2O
The emission rate of N2O from cultivated soil depends on a complex array of factors including soil structure, pH, climate, crop, soil carbon content, water status, and amount and kind of nitrogen fertilizer. The possible impact on N2O emissions of changing these factors is not well known.
Possibly the most effective way to influence emissions is to reduce nitrogen input to the soil and improve the use and handling of fertilizer, especially animal fertilizer.
In Denmark, several measures have been taken to improve the handling and utilisation of animal fertilizer and to decrease the total nitrogen input to the soil. The measures include compulsory crop rotation and fertilization planning at each farm, limits on the amount of animal fertilizer applied per hectare and improved utilisation of its nitrogen content. Nitrogen requirement norms for the different crops have been defined and the total application of nitrogen is not allowed to exceed the calculated requirement based on these norms. The consumption of nitrogen in commercial fertilizer has decreased by 25% from 1990 to 1996.
Methane, CH4
In the agricultural sector methane is produced by enteric fermentation in the digestive tract of ruminants. The methane production is dependent on the amount and quality of the ingested diet and the weight of the animal. Methane emission from cattle can be reduced by increasing digestibility of the diet, although the diet of a Danish dairy cow usually has a high digestibility.
Methane emission can also be reduced by reducing the number of cattle. During the last 10 years the number of cattle has been reduced by 24% and a further reduction is expected.
In Denmark, sheep are of no importance in relation to the methane emission due to their small number.
Manure
Manure from livestock also contributes to methane emissions, especially when kept under anaerobic conditions, e.q. liquid manure tanks. About 75% of the manure from Danish farms is stored in this way. Energy 21 foresees a gradual increase in the number of community biogas plants based on manure and other organic residues, which will contribute to the future reduction of CH4-emissions (compare table 6.3).
4.3.2 Biofuel production
Agriculturally produced raw material for liquid biofuel production is expected to have an important potential for the future. However, further investigation, research and development is needed before this potential can be determined and exploited fully.
The full utilisation of the potential is closely related to existing agricultural and energy policies. It is not presently attractive for farmers to engage in biofuel production due to existing price levels on products for other purposes and taxation on energy produced from biofuels. Recently, however, the production of biofuels has been made more attractive to farmers under the EU set-aside scheme.
The technological and economic issues are presently being reviewed by a joint task force from the Ministry of Environment and Energy and the Ministry of Food, Agriculture and Fisheries.
Energy 21 foresees a gradually increasing contribution from biofuels in the transport sector in the later half of the period until 2030.
4.3.3 Energy Crops
Surplus straw is already used for power and district heating production to a considerable degree. Existing agreements with power producers will expand this utilisation further in the near term.
In the longer term, solid biofuels from various energy crops from the agricultural sector is foreseen in Energy 21 to reach a level of about 50 PJ.