[EN09]
Emissions of air pollutants from energy sources
Assessments published: [ 2009 2012 ]

This indicator shows past energy-related emissions of individual substances and total emissions of ozone precursors, acidifying substances and particulate matter.

Ozone precursors are substances that contribute to the formation of ground-level ozone. Ozone precursors are nitrogen oxides (NOx), carbon monoxide (CO), methane (CH4) and non-methane volatile organic compounds (NMVOC). Tropospheric or ground-level ozone has adverse effects on both human health and the ecosystem. High concentrations of ground-level ozone have been shown to adversely affect the human respiratory system, especially the lungs, while in the environment, high concentrations of ozone decrease yields, cause leaf damage and decrease disease resistance. Ozone is also capable of causing damage to plastics and rubbers.

Acidifying substances are sulphur dioxide (SO2), nitrogen oxides (NOx) and ammonia (NH3). Acidification causes substantial damage to the ecosystem, buildings and materials (corrosion). NOx and NH3 lead to eutrophication (excess nitrogen in soil and water).

Particulate matter emissions are classified into primary PM10 (particulate matter with a diameter of 10 μm or less, emitted directly into the atmosphere), and secondary PM10 or PM10 precursors (the fraction of NOx, SO2 and NH3 emissions which, as a result of photo-chemical reactions in the atmosphere, transform into particulate matter with a diameter of 10 μm or less). The inhalation of such particles may increase the frequency and severity of a number of respiratory problems, which may increase the risk of premature death. The smaller particles, which can go deeper into the lungs, are especially dangerous.

Image EN9-1: Changes in total SO2, NOx, NMVOC and NH3 emissions as regards the year 1990 and PM10 emissions as regards the year 2000 and 2010 targets for SO2, NOx, NMVOC and NH3 emissions

Source: Environmental Agency of the Republic of Slovenia, 2009.


Image EN9-2: Emissions of air pollutants by sector for 2007

Source: Environmental Agency of the Republic of Slovenia, 2009.


Image EN9-3: Changes in emissions of ozone precursors, acidifying substances and particulate matter

Source: Environmental Agency of the Republic of Slovenia; Jožef Stefan Institute, 2009.


Image EN9-4: Structure of total emissions of acidifying substances, ozone precursors and primary and secondary particulate matter in 2007

Source: Environmental Agency of the Republic of Slovenia; Jožef Stefan Institute, 2009.


Image EN9-5: Emissions of acidifying substances, ozone precursors and particulate matter in 2007

Source: Environmental Agency of the Republic of Slovenia; Jožef Stefan Institute, 2009.


Image EN9-6: Changes in emissions of acidifying substances, ozone precursors and particulate matter in the 2000-2007 period

Source: Environmental Agency of the Republic of Slovenia; Jožef Stefan Institute, 2009.


A reduction in emissions of air pollutants:
- reduction of SO2 emissions to target values of 27 thousand tonnes,
- reduction of NOx emissions to target values of 45 thousand tonnes,
- reduction of NMVOC emissions to target values of 40 thousand tonnes,
- reduction of NH3 emissions to target values of 20 thousand tonnes,
- reduction of CH4 emissions within the framework of an 8 percent reduction in greenhouse gas emissions in the 2008-2012 period or within the framework of a 20 % or 30 % reduction of greenhouse gas emissions by 2020 from the base year.

There is no quantified objective for CO and PM10 emissions. A revision of Directive 2001/81/EC on National Emission Ceilings for Certain Atmospheric Pollutants is being prepared. The amended Directive will set new targets for SO2, NOx, NMVOC, NH3 and PM2.5 emissions for the year 2020.

For all air pollutants, energy-related emissions decreased in the treated period. This is especially true for SO2 emissions that were 93 % lower in 2007 than in 1990, whereby approximately half of this reduction was achieved by the year 2000. The reason was the installation of desulphurisation devices on thermal power plants and the use of fuel with a lower sulphur content. In 2007, the emissions of the Šoštanj Thermal Power Plant reduced by 18 % due to flue gas exhausts from units 1-3 being connected to the desulphurisation device of unit 4. In 2007, energy sources contributed 92 % of total SO2 emissions. Emissions of non-methane volatile organic compounds substantially reduced as well, being 51 % lower in 2007 than in 1990. This reduction was predominantly caused by the use of catalytic converters for the after-treatment of motor vehicle exhaust gases and a substantial increase in the share of diesel fuel in total motor fuel consumption. In 2007, emissions reduced by 4 % due to reductions in industry and transport-related emissions. In 2007, the share of energy-related emissions amounted to 59 %. The smallest reduction was evident in NOx emissions (by 21 %). With regard to the year 2000, these emissions reduced by 9 %. This reduction was caused by European standards defining the permissible content of substances in the exhaust gases that are met by using catalysts and implementing primary measures in thermal power plants. On the other hand, industry-related emissions increased (due to including emissions from the construction sector – construction machinery, in the year 2000 and economic growth in 2005 and 2006) as well as emissions in the household sector that increased due to a growth in the use of liquid fuels (until 1999). In 2007, a 5 % reduction in emissions was noted due to reductions in energy consumption in the industrial sector (natural gas) and in wider use (fuel oil). All NOx emissions are energy-related. In 2007, 96 % of ammonia emissions (NH3) originated in agriculture and the remainder in transport. Transport emissions have been increasing due to a higher number of cars with catalytic converters. Since the year 2000, these emissions increased by 11 % and by 0.4 % since 2007.

Particulate matter with a diameter of 10 μm or less is also an atmospheric pollutant but its records were set up only in the year 2000 so there is no quantified objective for its reduction. Following a chequered trend until 2003, energy-related emissions slowly reduced between 2004 and 2006 (at an average annual rate of 2.3 %), while a more substantial reduction was evident in 2007 (7 %). In 2007, energy-related emissions represented 83 % of total emissions that stood at 7.4 kt.

Carbon monoxide (CO) emissions, which are fully energy-related, were substantially lower in 2007 than in 1990 (61 %). This was due to swift reductions in transport emissions after 1996 (due to European standards), as transport is by far the largest source (almost 70 %). In 2007, they amounted to 99.3 kt.

In 2007, total emissions (non-energy related and energy-related) amounted to, for SO2, 14.2 kt, which is almost 13 kt less than the 2010 target; NOx 44.6 kt (0.9 % lower than target emissions); NMVOC 39.3 kt (1.7 % less than the 2010 target) and NH3 18.5 kt (7.5 % less than target emissions). The year 2007 was the first year when emissions of all substances in Slovenia were below 2010 target values. We need to be aware however, that targets for NOx emissions can still be jeopardised, as the consumption of liquid fuel in transport is rapidly growing, while liquid fuel consumption in wide use increased in 2008, which means that growth in transport will no longer be offset by reductions in wide use.

Detrimental environmental effects of air pollutants can be classified into three groups: acidification and eutrophication that have a detrimental effect on the ecosystem and therefore an indirect effect on human health and ground-level ozone and dust particles that have direct detrimental effects on human health. The impact of emissions of individual air pollutants on these environmental impacts can be estimated by using weighting factors.

If we compared data to the year 1990, emissions of acidifying substances and ozone precursors decreased by 38 % and 20 % respectively by the year 2000. This reduction in emissions continued after the year 2000 with emissions of acidifying substances reducing by 54 % and emissions of ozone precursors by 19 % by the year 2007 compared to the year 2000 (Figure 3). Particulate matter emissions (primary and secondary particulate matter) were 45 % lower in 2007 compared to the year 2000.

In 2007, ammonia contributed the largest share to total emissions of acidifying substances (over 95 % coming from non-energy related sectors – agriculture), followed by NOx, in Slovenia generated only by the combustion of fuel, and SO2 (16 %). Energy sources contributed 57 % of total emissions. The weighted total emissions of acidifying substances indicate that the highest factor is that of NH3, followed by SO2 and NOx. This helps us to understand the high share of non-energy related sectors in total emissions (43 %). In the 2000-2007 period, the reduction in emissions was mostly influenced by reductions of SO2 emissions from large thermal power plants and from wider use (Figure 5).

In 2007, more than half of the emissions of ozone precursors related to NOx emissions, followed by NMVOC, CO and a minimum contribution by CH4 (Figure 4). Energy sources contributed 84 % of total emissions. The highest weight in calculating total emissions is that of NOx, followed by NMVOC, with CO and CH4 weights being substantially lower (9 and 70 times lower respectively). It is for this reason that changes in total emissions are similar to changes in NOx and NMVOC emissions. The main source is transport.

Contributing pollutants to particulate matter or dust particles emissions are SO2, NOx and NH3 that are the source of secondary particulate matter and PM10. The same as is the case with ozone precursors, the highest share in total emissions is held by NOx followed by NH3, SO2 and PM10 (Figure 4). Again, the majority of emissions relate to transport. In 2007, energy sources contributed 80 % of total emissions. The reduction in emissions is predominantly due to reductions in SO2 emissions.

As regards environmental impacts, the common point for all emission groups is NOx. It holds the largest share in emissions of ozone precursors and particulate matter emissions (51 % and 59 % respectively) and is only slightly behind NH3 (by 3 percentage points) in emissions of acidifying substances. This allows us to conclude that a reduction of NOx emissions efficiently reduces all of the above mentioned adverse environmental impacts. The continued reduction of these emissions in 2007 is therefore very positive, the question however remains about trends for 2008, as statistical data on energy consumption for 2008 indicate a substantial growth in the sale of motor fuels in transport as well as the sale of fuel oil in wider use. In order to continue improving air quality, measures determined by both the Operational Programme for Complying with National Emission Ceilings for Atmospheric Pollutants as well as the Operational Programme for Limiting Greenhouse Gas Emissions by 2012 will have to be implemented, especially in the field of transport. An analysis of the implementation of the Operational Programme for Limiting Greenhouse Gas Emissions by 2012 has shown that the implementation of measures is unsatisfactory especially in the area of transport.

Data for Slovenia

Objectives summarised by: Resolucija o Nacionalnem programu varstva okolja 2005-2012 (Resolution on the National Environmental Action Plan 2005-2012, Official Gazette of the Republic of Slovenia, No. 2/06), the proposal of the climate and energy package, Protocol to the 1979 Convention on long-range transboundary air pollution to abate acidification, eutrophication and ground-level ozone and Directive 2001/81/EC of 23 October 2001 on national emission ceilings for certain atmospheric pollutants (the NEC directive).
Source database or source: Official data on emissions of air pollutants were used as sent on 19 February 2009 to the United Nations and as located in the Central Data Repository (CDR) under Slovenia/United Nations/UNECE – CLRTAP air emission inventories/2009 Report: CLRTAP SLO 1980–2007/CLRTAP SLO 2009 Submission (1st submission), and GHG emissions as sent on 15 April 2009 to UNFCCC and as located in the Central Data Repository (CDR) under Slovenia/United Nations/UNFCCC – UN Framework Convention on Climate Change data/UNFCCC – GHG Report 2008 (1986–2007 data). Upon preparing new records, data for previous years are often corrected.
Data administrator: The Environmental Agency of the Republic of Slovenia, the Environment Office, Air Quality Sector, contact person: Bojan Rode, Tajda Mekinda-Majaron.
Data acquisition date for the indicator: 8 December 2009
Methodology and frequency of data collection for the indicator: Data are prepared on an annual basis and on the basis of data on activities (the use of fuels, number of animals, quantity of waste, industrial manufacturing, etc.), calorific value of fuels and emission factors. For air pollutants, the recommended methodology has been prepared by the UNECE/EMEP task force on emissions inventories and projections and for GHG emissions by the Intergovernmental Panel on Climate Change (IPCC).
Energy-related emissions or emissions from energy sources (CRF 1, NRF 1) include emissions arising from fuel combustion activities (CRF 1.A, NFR 1.A) that are further divided into emissions from energy and heat production – transformations (CRF 1.A.1, NFR 1.A.1), emissions from manufacturing industries and construction (CRF 1.A.2, NFR 1.A.2), transport emissions (CRF 1.A.3, NFR 1.A.3) and emissions from other sectors (CRF 1.A.4, NFR 1.A.4) that include emissions from households, the services sector and fuel combustion in agriculture and forestry. In addition to emissions arising from fuel combustion activities, energy-related emissions also include fugitive emissions from fuels (CRF 1.B, NFR 1.B) that are further classified into fugitive emissions from solid fuels (CRF 1.B.1, NFR 1.B.1) and fugitive emissions from oil and natural gas (CRF 1.B.2., NFR 1.B.2) that originate in the production of fuels (coal mines) or the transmission and distribution of oil and natural gas. Transmissions or the production of electricity and heat in the text includes emissions from energy industries and fugitive emissions.
Non-energy related GHG emissions include emissions from industry (CRF 2, NFR 2) (i.e. processes in manufacturing industries and construction without fossil fuel combustion including the production and consumption of fluorinated gases), agriculture (CRF 4, NFR 4) (i.e. domestic livestock (manure management and enteric fermentation) and emissions from the use of fertilisers), emissions from waste (CRF 6, NFR 6) (i.e. emissions from landfill sites and incineration plants and waste water treatment) and emissions from the use of solvents and other products (CRF 3, NFR 3).
Indicator EN09 – Emissions of Air Pollutants was introduced in 2009 and originates in the combination of three related indicators: EN02 – Energy-Related Emissions of Ozone Precursors, EN03 – Energy-Related Emissions of Acidifying Substances and EN04 – Energy-Related Particulate Matter Emissions.
Data processing methodology: Total emissions have been calculated as a weighted sum of individual emissions. We used the same weights as used by the European Environment Agency in its calculations. Ground-level ozone weights were calculated on the basis of the potential of each of the air pollutants to contribute to ozone formation in the troposphere (TOFP – Tropospheric Ozone Forming Potential).
Total emissions of ozone precursors have been calculated as a weighted sum of individual emissions (NOx, NMVOC, CO, CH4). The TOFP factors used are as follows: NOx – 1.22; NMVOC – 1.0; CO – 0.11; CH4 – 0.014. Results are expressed in NMVOC equivalents (ktonnes) (NMVOC eq.). Total emissions of acidifying substances are calculated using weighting factors that are calculated on the basis of acid equivalents (SO2, NOx, NH3). The weighting factors used are as follows: SO2 – 2/64 acid eq/g; NOx – 1/46 acid eq/g; NH3 – 1/17 acid eq/g. Results are expressed in kt equivalents of acidifying substances. The indicator for particulate matter emissions shows past emissions of particulate matter separately for primary and secondary particulate matter (SO2, NOx, NH3, PM10) (a weighted sum of individual emissions). The factors used in the estimation of emissions are based on assumptions about the deposition and reactions of the precursor pollutants – aerosol formation factors - and are as follows: SO2 – 0.54; NOx – 0.88; NH3 – 0.64; PM10 – 1.00. Results are expressed in PM10 equivalents (kt).
Average annual rate of growth is calculated as: [(last year / base year)(1 / number of years) –1] x 100.
Annual growth is occasionally shown in percentage points. A percentage point is a unit used in comparing different percentages. In percentage points, we are dealing with an absolute comparison calculated using the following formula: (nthis year)–(nlast year)=16 % – 15 % = 1 pp (e.g. if there was a 15 % growth last year and a 16 % growth this year, then this year growth is 1 percentage point higher). The difference in growth can also be expressed by relative comparison using the following formula: [(nthis year / nlast year) * 100] – 100 = [(16 % / 15 %) * 100] – 100 = 6.7 %. In this case, growth is expressed as a percentage.
Information concerning data quality:
- Advantages and disadvantages of the indicator: Officially reported data that are calculated using internationally confirmed methods have been used to calculate the indicator. Data on PM10 emissions have a higher uncertainty level than data on the emissions of other substances.
- Relevance, accuracy, robustness, uncertainty:
Reliability of the indicator (archival data): Data reliability for greenhouse gas emissions (CH4) was estimated for 1986, 2002 and 2003. For absolute data it stands at 16 %, 13.1 % and 12 % and for trends for 2002 and 2003 at 4 % and 3 % respectively. The reliability of emission factors and activity data is estimated on the basis of an expert assessment. It is possible for data reliability for emissions of air pollutants to differ for individual substances. SO2 emissions records have the highest reliability, as they relate directly to the fuel’s sulphur content and, with flue gas treatment, also the efficiency of desulphurisation units. Data on NOx emissions are much less reliable, as there are several emission origins. Emissions depend on the amount of nitrogen in the fuel, the ratio between oxygen and fuel and the combustion temperature, which is specific for each boiler making emission factors differ from one boiler to another. The reliability of data for NH3 emissions is high, as values were almost identical upon using two different methodologies.
Uncertainty of the indicator (scenarios/projections): scenarios and projections are not available.
- Overall assessment (1 = no major comments, 3 = data to be considered with reservation):
Relevance: 1
Accuracy: 2
Completeness over time: 2
Completeness over space: 1

Other sources and literature:

- EEA, 2008. EN05 Energy-Related Emissions of Ozone Precursors.
- EEA, 2008. EN06 Energy-Related Emissions Of Acidifying Substances.
- EEA, 2008. EN07 Energy-Related Particulate Matter Emissions.
- MOP, 2007. Operativni program doseganja nacionalnih zgornjih mej emisij onesnaževal zunanjega zraka /Revizija operativnega programa doseganja nacionalnih zgornjih mej emisij onesnaževal zunanjega zraka iz leta 2005/ (Operational Programme for Complying with National Emission Ceilings for Atmospheric Pollutants /Revision of Operational Programme for Complying with National Emission Ceilings for Atmospheric Pollutants from 2005/).

8 December 2009
Matjaž Česen, Jožef Stefan Institute