emissions
2.2 Description and interpretation of emission trends by gas
Carbon dioxide
The largest source to the emission of CO2 is the energy sector, which includes combustion of fossil fuels like oil, coal and natural gas (Fig-ure 2.2). Public power and district heating plants contribute with al-most half of the emissions. About 24% come from the transport sec-tor. The CO2 emission decreased by approximately 9% from 2003 to 2004. The reason for this decrease was mainly due to decreasing ex-port of electricity. Also higher outdoor temperature in 2004 compared
with 2003 contributed to the decrease. If the CO2 emission is adjusted for climatic variations and electricity trade with other countries the CO2 emission from combustion of fossil fuels has decreased by 16%
since 1990. The decrease in CO2 emissions is observed despite an al-most constant gross energy consumption and an increase in the gross national product of 34%. This is due to change of fuel from coal to natural gas and renewable energy. As a result of the lower consump-tion of coal in recent years, the main part of the CO2 emission comes from oil combustion. In 2004, the actual CO2 emission was about 2%
higher than the emission in 1990.
Public power and district heating plants /
Refineries 47%
Residential and Commercial
plants 13%
Other 2%
Industrial processes
3%
Transport 24%
Industrial combustion
plants 11%
0 10000 20000 30000 40000 50000 60000 70000 80000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
CO2 emission (1000 tonnes
Public power and district heating plants / Refineries Industrial combustion plants Transport
Residential and Commercial plants Industrial processes
Other
Total
Total, adjusted
Figure 2.2 CO2 emissions. Distribution according to the main sectors (2004) and time-series for 1990 to 2004.
Nitrous oxide
Agriculture is the most important N2O emission source (Figure 2.3).
N2O is emitted as a result of microbial processes in the soil. Substan-tial emissions also come from drainage water and coastal waters where nitrogen is converted to N2O through bacterial processes.
However, the nitrogen converted in these processes originates mainly from the agricultural use of manure and fertilisers. The main reason for the drop in the emissions of approximately 25% from 1990 to 2004 is legislation to improve the utilisation of nitrogen in manure. The legislation has resulted in less nitrogen excreted per unit of livestock produced and a considerable reduction in the use of fertilisers. The basis for the N2O emission is then reduced. Approximately 10% of the emisison of N2O comes from combustion of fossil fuels, and transport accounts for around 6%. The N2O emission from transport has in-creased during the nineties because of the increase in the use of cata-lyst cars. Emissions of N2O from nitric acid production amount to approximately 7% of the total N2O emission.
Agriculture 83%
Energy
10% Industrial processes 7%
0 5 10 15 20 25 30 35 40
1990 1992 1994 1996 1998 2000 2002 2004
N2O emission (1000 tonnes)
Energy Industrial processes Agriculture Total
Figure 2.3 N2O emissions. Distribution according to the main sectors (2004) and time-series for 1990 to 2004.
Methane
The largest sources of anthropogenic CH4 emissions are agricultural activities, managed waste disposal on land, public power and district heating plants (Figure 2.4). The emission from agriculture derives from enteric fermentation and management of animal manure. The increasing CH4 emissions from public power and district heating plants are due to the increasing use of gas engines in the decentral-ised cogeneration plant sector. Approximately 3% of the natural gas in the gas engines is not combusted. From 1990, the emission of CH4
from enteric fermentation has decreased due to the decrease in the number of cattle. However, the emission from manure management has increased due to a change in traditional stable systems towards an increase in slurry-based stable systems. Altogether, the emission of CH4 for the agriculture sector has decreased by approximately 7%
from 1990 to 2004. The emission of CH4 from waste disposal has de-creased slightly due to increases in the incineration of waste.
Public power and district heating plants
/ Refineries 6%
Enteric fermentation 48%
Manure management 17%
Waste 23%
Other 6%
0 50 100 150 200 250 300 350
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
CH4 emission (1000 tonnes
Public power and district heating plants / Refineries
Enteric fermentation
Manure management
Waste
Other
Total
Figure 2.4 CH4 emissions. Distribution according to the main sectors (2004) and time-series for 1990 to 2004.
HFCs, PFCs and SF6
This part of the Danish inventory only comprises data for all sub-stances from 1995. From 1995 to 2000, there has been a continuous and substantial increase in the contribution from the range of F-gases as a whole, calculated as the sum of emissions in CO2 equivalents (Figure 2.5). This increase is simultaneous with the increase in the emission of HFCs. For the time-series 2000-2004, the increase has been much lower than for the years 1995 to 2000. SF contributed
con-siderably in earlier years, with 52% in 1993. Environmental aware-ness and regulation of this gas under Danish law has reduced its use in industry, with the result that the contribution in 2004 was ap-proximately 4%. The use of HFCs, and especially HFC-134a as a ma-jor contributor to HFCs, has increased several fold. HFCs have, there-fore, become dominant F-gases, comprising 48% in 1993, but 94% in 2004. HFC-134a is mainly used as a refrigerant. However, the use of HFC-134a as a refrigerant, as well as the use of other HFCs as refrig-erants, is stable or falling. This is due to Danish legislation, which, in 2007, forbids new HFC-based refrigerant stationary systems. On the other hand, the use of air conditioning in mobile systems is on the increase.
0 100 200 300 400 500 600 700 800 900
1990 1992 1994 1996 1998 2000 2002 2004
CO2-equ., F-gases (1000 tonnes
HFCs PFCs SF6 Total
Figure 2.5 F-gas emissions. Time-series for 1990 to 2004.