1 GENERAL INFORMATION
1.3 Key environmental issues
1.3.2 Emissions to air
1.3.2.6 Greenhouse gases (carbon dioxide and others)
Since the beginning of industrialisation, the energy balance of the earth has been changing due to the increasing emissions of anthropogenic greenhouse gases, mainly carbon dioxide (CO2).
Due to the accumulation of CO2 in the atmosphere over the last two centuries, the amount of infrared radiation trapped in the atmosphere has increased. At the same time, a considerable increase in the global mean temperature1 and CO2 concentrations in the atmosphere have been observed, as shown in Figure 1.5 and Figure 1.6.
Figure 1.5: Global mean temperature and amount of CO2 emitted over the past century [13, Verbund, 1998]
1 Between 1856 and 1998, the yearly deviations from the 1961 - 1990 global average and European temperature show an increase of 0.3 ºC to 0.6 ºC. 1998 was globally the warmest year on record, and 1997 the warmest before that. This is partly due to the 1997/1998 El Niño/Southern Oscillation (ENSO), which was the largest on record (Hadley Centre/The Met. Office, 1998a). The ENSO phenomenon is a cycle of natural fluctuations of Pacific ocean temperatures resulting in large-scale changes in tropical rainfall and wind patterns [11, EEA, 1999].
Figure 1.6: Change in CO2 concentrations in the atmosphere over time
It is thought that the rise in the global mean temperature due to the increased atmospheric concentration of greenhouse gases will change the earth’s climate if the emission of such gases (mainly CO2) is not reduced.
The only important greenhouse gases from the combustion of fossil fuels in large combustion plants are carbon dioxide (CO2) and nitrous oxide (N2O). Carbon dioxide (CO2) released by large combustion plants is responsible for approximately one third of the world’s global CO2
emissions. A number of scientists also expect natural influences such as sunspots/cosmic particles, geological things and, in particular, the increasing amount of water vapour in the atmosphere as additional reasons for global warming. Table 1.9 shows the estimated contribution of greenhouse gases to global warming (data have been taken from [14, EEA, 1999]).
Gas Concentration increase since about
1750
Contribution to
global warming 1 Main anthropogenic source Fossil fuel combustion (includes energy generation and transport)
Deforestation and land use
CO2 30 % 64 %
Cement production Use of fertilisers Land clearing
Adipic and nitric acid production Biomass burning
N2O 15 % 6 %
Fossil fuel combustion (FBC) Notes:
1 To compare the impact of different gases, the global warming potential (GWP) relative to CO2 is often used, with CO2 having the value of 1. GWP is a concept that takes into account the energy absorption capacity of the gas and its lifetime in the atmosphere. GWP should always be quoted for a specific time period. Examples of GWP values over a 100 year period are 21 for CH4, 310 for N2O and several thousands for a number of halogenated compounds. The emissions that take GWP values into account are called CO2 equivalents.
Table 1.9: Greenhouse gases: concentration changes, contribution to global warming and main sources
[12, IEA, 2001]
Carbon dioxide (CO2) is the main reaction product from the combustion of all fossil fuels. The CO2 emission is directly related to the carbon content of fuels, where gaseous fuels have significantly lower CO2 emissions than other fossil fuels. The content of carbon varies for coal and lignite (hard and brown coal) between 61 and 87 wt-%, for wood it is about 50 wt-%, and for gasoil and heavy fuel oil about 85 wt-% [1, Corinair, 1996]. Table 1.10 presents the specific CO2 emission factors for the main fuels burned in large combustion plants.
Fuel Specific CO2 emission factors as a range.
(t CO2/TJ (g/kWh))
Natural gas 55 (198)
Heavy fuel oil (HFO) 80 (288)
Light fuel oil (LFO) 77 (277)
Hard coal 95 (342)
Lignite 110 (396)
Table 1.10: Specific CO2 emission factors for the main fuels burned in large combustion plants [192, TWG, 2003]
Figure 1.7 presents the CO2 releases calculated as kg CO2/MWh electricity produced for different types of combustion plants [133, Strömberg, 2001].
0 200 400 600 800 1000 1200
Coal PP Coal C
HP
Gas com
bined c ycle
Gas C HP
Old coal P P
Old oil PP
Lig nite PP
Type of plant
kg/MWh
Figure 1.7: Examples of CO2 releases for different types of combustion plants Note: calculated as kg CO2/MWh electricity produced
[133, Strömberg, 2001]
EU CO2 emissions decreased by 1 % between 1990 and 1996, although the trend varies considerably between Member States. The decrease for the EU as a whole depends strongly on reductions in Germany and the United Kingdom. Germany has the largest national CO2
emission in the EU, with approximately 30 % of the EU total in 1995. Between 1990 and 1996 the largest absolute emission reduction took place in Germany, mainly caused by the economic restructuring of the former German Democratic Republic. The substantial reduction in emissions in the United Kingdom was mainly caused by the change-over of fuel switching from coal to natural gas [14, EEA, 1999]. Table 1.11 gives information about the greenhouse gas emissions and the removals/sinks for CO2 in the 15 European Member States (EU-15). For more detailed data about the emissions of greenhouse gases in the European Community consult the Annual European Community Greenhouse Gas Inventory 1990-1996 [14, EEA, 1999]
(http://www.eea.eu.int/).
CO2
(million tonnes) Member States
Emissions Removals/Sinks
CH4
(kt)
N2O (kt)
Austria 62 14 580 13
Belgium 129 2 591 35
Denmark 60 1 430 33
Finland 66 14 270 18
France 399 60 2844 174
Germany 910 30 4788 210
Greece 92 - 457 29
Ireland 35 6 800 26
Italy 448 36 2516 162
Luxembourg 7 0 24 1
Netherlands 185 2 1179 72
Portugal 51 1 834 14
Spain 248 29 2370 90
Sweden 63 32 297 10
United Kingdom 593 19 3712 189
EU-15 3347 247 21692 1076
Notes:
Estimates for 1996 were not available for Austria, Denmark, France, Italy, Portugal and Spain. For these countries 1994 and 1995 estimates have been used for a preliminary EU-15 1996 estimate. The CO2 estimates are not corrected for temperature or electricity trade. Some Member States use corrected CO2
estimates to better reflect national circumstances.
Table 1.11: Greenhouse gas emissions and removals/sinks in 1996 [14, EEA, 1999]