Indicator Assessment

Energy-related emissions of acidifying substances

Indicator Assessment
Prod-ID: IND-130-en
  Also known as: ENER 006
Published 30 Apr 2012 Last modified 11 May 2021
19 min read
This page was archived on 12 Nov 2013 with reason: Content not regularly updated

Energy-related emissions account for only 2% of NH3 emissions but 96% of NOx and 94% of SO2 emissions in the EEA-32 in 2009. They fell by 17%, 13% and 21% respectively between 2005 and 2009 in EEA-32 countries. Since 1990, these energy related emissions declined by 40% and 78% for NOx and SO2 respectively but increased by 88% for NH3 in the EU-27 and declined by 37% (NOx) and 74% (SO2) and increased by 92% (NH3) in EEA-32 member countries. However as noted earlier the percentage of energy related NH3 emissions are insignificant compare do the non-energy related NH3 emissions. Most of the total reduction in pollutants contributing to acid deposition since 1990 is accounted for by lower SO2 emissions from the energy-producing sector and lower NOx emissions from the transport sector. The EU-27 is broadly on track to meet its overall targets set under the NEC Directive (NECD)[1], however further reductions are needed to improve remaining local and transboundary air pollution issues, and for ensuring that individual countries meet emissions ceiling targets under the NECD and the UNECE Gothenburg Protocol.

[1] See Pollutant Specific Factsheet NOx

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Contribution of different sectors (energy and non-energy) to total emissions of SO2, NOx, NH3, 2009, EEA-32

Note: The figue shows the contribution of different sectors (energy and non-energy) to total emissions of SO2, NOx and NH3

Emissions intensity of electricity & heat production and public conventional thermal power production, EEA-32

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Emissions intensity from public conventional thermal power production, EEA32

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In the EEA-32, energy related emissions declined by 13% (NOx), 21% (SO2) and 17% (NH3) between 2005 and 2009. NOx, SO2 and NH3 emissions declined by 13%, 27% and 17% respectively in the EU-27 within the same period.

Energy-related emissions are the predominant sources of total NOx and SOx emissions in 2009 in the EEA-32, accounting for 96% of NOx and 94% of SO2 emissions, underlining the large contribution that energy production and use make to both local and transboundary air pollution. The non-energy related agriculture sector is the most important source of NH3, releasing the vast majority of NH3 (over 94%) in 2009 in the EEA-32. Emission reductions from agriculture have been much lower than from energy-related sources since 1990 (see Figure 1). 

For NOx, all sources except for Household & services (+15%), Other transport (+2%), and Waste (+8%) have decreased I the EEA_32 countries since 2005. Combustion modification and flue-gas treatment have been used to reduce NOx emissions. One of the most common forms of combustion modification is to use low NOx burners, which typically can reduce NOx emissions by up to 40 %. Flue gas treatment such as selective catalytic reduction can also be used to remove NOx from the flue gases.

Total SO2 emissions decreased significantly across all sectors in the EEA-32 (30%) and EU-27 (37%) countries since 2005 (see Figure 1). Energy related SO2 emissions decreased significantly in most EEA32 member countries since 2005, with the highest overall reductions in Slovenia (71%), Spain (67%) and Portugal (58%) (see Figure 3 and 4). Similarly, energy related NOx emissions decreased in 29 out of 30[1] countries since 2005, with the highest reduction occurring in the United Kingdom (30%) and Ireland (29%). However, NH3 emissions increased in 10 out of 29[2] EEA member countries in the same time period with large increases in Bulgaria (more than 25 times the 2005 value).  The large increase was primarily a result of an increase in road transport[3].

Many of the reductions reported here are a result of actions implemented as a result of various European policies and measures, including the Industrial Emissions Directive, IPPC Directive, the Large Combustion Plant Directive, vehicle EURO standards, and the EU NECD and Gothenburg Protocol. The EU-27 as a whole is on track to meet its NECD target to reduce emissions from SO2, NH3 and NOx.

However, many individual countries currently anticipate missing their respective emission ceilings for NOx[4].

The emissions and emissions intensity o sulphur dioxide (SO2) and nitrogen oxides (NOx) from public conventional thermal power plants has decreased substantially since 2005 (Figure 4). During the period 2005 to 2009, the emissions intensity of NOx from public conventional thermal plants in the EEA-32 decreased by 7% (see Figures 4 and 5). This was due to the increased use of end-of-pipe abatement techniques. NOx intensities fell in the majority of Member States (except Switzerland, Germany, Finland, Turkey and Hungary), with the largest decreases of over 50 % occurring in Italy and the Ireland.

The emissions intensity of SO2 from public conventional thermal power plants decreased by 23 % from 2005 to 2009, a significantly larger reduction than occurred for NOx emissions intensities from public conventional thermal power plants (see Figures 4 and 5). All member states apart form Switzerland, Slovakia and Romania show a reduction in SO2 emissions with 11 member states showing reductions of over 50% in emissions intensity. In particular Spain and Belgium decreased their emissions intensity the most.


[1] No data available for Luxemburg and Poland for 2005

[2] No data available for Iceland, Turkey and Poland  for 2005

[3] Bulgaria did not report any emissions for certain sector in 2005 compared to 2009, household and services and manufacturing, making the 2005 total emissions values artificially smaller than the 2009 value.

[4] NOx Pollutant specific fact sheet

Emissions intensity of electricity & heat production and public conventional thermal power production, EEA-32

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Estimated impact of different factors on the reduction in emissions of SO2 from public electricity and heat production between 1990 and 2009, EEA-32

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Estimated impact of different factors on the reduction in emissions of NOx from public electricity and heat production between 1990 and 2009, EEA-32

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Energy industries (such as public heat and electricity production) contribute over half of all SO2 (66%) and account for a quarter of total NOx (22%) emissions in 2009, and emissions have decreased by nearly 24% and 10% respectively since 2005 (see Figures 1 and 2). The emissions intensity of NOx from public conventional thermal plants in the EEA-32 decreased by 54% since 1990 (see Figures 5). This was due to the increased use of catalytic reduction, low-NOx burners and the use of less polluting fuels in public conventional thermal power production in many Member States.

Much of this reduction of energy-related emissions (except transport) of acidifying substances is due to a decrease in SO2 emissions. This was mainly due to abatement techniques, use of low-sulphur fuels, to fossil fuel switching and the economic downturn (Figure 5 and 6). The increased utilisation of coal plants has in recent years meant that the decline in SO2 emissions has slowed, although the significant specific reductions being achieved by flue gas desulphurisation mean that SO2 emissions have continued to fall in absolute terms (Figure 5 and 6). In the absence of any changes to the generation mix since 1990 SO2 would have increased by 25% by 2009 (Figure 6).

If the structure of power production had remained unchanged from 1990 then by 2009 emissions of NOx would have increased by 25% above their 1990 levels (Figure 7). NOx emissions stayed broadly stable since 2000. This trend is linked to an increased use of coal and lignite for electricity and heat production from 1999/2000 onwards.

NOx emissions from the transport sector are the largest source of energy-combustion emissions and reductions in this sector are largely due to the introduction of catalytic converters on new cars since the early 1990s. However, emission controls on vehicles, and in particular certain catalyst technologies in road vehicles, can increase the rate of N2O generation and thus of greenhouse gases. The Transport White Paper published by the European Council in 2010 proposes a vast number of measures to develop a more sustainable transport sector through tightening of regulations and controls and promotion of biofuels and electric vehicles.

Supporting information

Indicator definition

Emissions of SO2 and NOx (also NH3 where applicable) in 1000 tonnes.


Emissions kt


Policy context and targets

Context description

Several EU-wide emissions limits and targets exist for the reduction of total SO2, NOx and NH3 emissions, including the National Emissions Ceiling Directive (NECD; 2001/81/EC) and the UNECE LRTAP Convention Gothenburg Protocol under UNECE LRTAP Convention (UNECE 1999). This indicator provides relevant information for assessing the achievement of these targets and also for analyses performed within the European Commission’s Clean Air for Europe programme (CAFE). This thematic strategy on air quality was released in September 2005 (The CAFE Programme/implementation of the Thematic Strategy on Air Pollution, and due to be reviewed by 2013.
The NEC Directive includes emission reduction targets that are slightly stricter than the targets set in the Gothenburg Protocol and requires the introduction of national emission ceilings for emissions of SO2, NOx and NH3 (and also for NMVOCs) in each Member State, as well as setting interim environmental objectives for reducing the exposure of ecosystems and human populations to damaging levels of the acid pollutants. Targets for the new Member States are temporary and are without prejudice to the on-going review of the NECD.

A proposal for a revised NEC Directive (which will set 2020 emission ceiling targets for these acidifying pollutants), is expected in 2013. Targets for Bulgaria and Romania are provisional and not binding. Hence, the existing EU25 NECD Target has been used in the following analysis.

In terms of the energy sector, the most relevant NEC Directive targets for the EU-25 (exclude Romania and Bulgaria) as a whole are:

  • SO2: emissions reduction of 74 % by 2010 from 1990 levels;
  • NOx: emissions reduction of 53 % by 2010 from 1990 levels.

NH3 emissions are also an important source of acid deposition and have an emissions target under NEC (emissions reduction target of 15 % by 2010 from 1990 levels), but energy-related emissions of ammonia are insignificant, accounting for only 2.5 % of total EU-27 ammonia emissions in 2005. Agriculture is by far the largest contributing sector to EU ammonia emissions.

    Other key policies that have contributed to the reduction of acidifying emissions across Europe include:

    • The Integrated Pollution Prevention and Control (IPPC) Directive (96/61/EC), which entered into force in 1999. It aims to prevent or minimise pollution of water, air and soil by industrial effluent and other waste from industrial installations, including energy industries, by defining basic obligations for operating licences or permits and by introducing targets, or benchmarks, for energy efficiency. It requires the application of Best Available Techniques in new installations (and for existing plants over 10 years, according to national legislation).
    • The Large Combustion Plant Directive (2001/80/EC) is important in reducing emissions of SO2, NOx and dust from combustion plants with a thermal capacity greater than 50 MW. The Directive sets emission limits for licensing of new plants and requires Member States to establish programmes for reducing total emissions. Emissions limits for all plants are also set under the IPPC Directive.


    Emissions of NOx, SO2 and NH3 are covered by the NECD and the Gothenburg Protocol to the UNECE LRTAP Convention. Both instruments contain emission ceilings (limits) that countries must meet by 2010. See CSI001

    Related policy documents

    • Council Directive 96/61/EC (IPPC)
      Council Directive 96/61/EC of 24 September 1996 concerning Integrated Pollution Prevention and Control (IPPC). Official Journal L 257.
    • Directive 2001/80/EC, large combustion plants
      Directive 2001/80/EC of the European Parliament and of the Council of 23 October 2001 on the limitation of emissions of certain pollutants into the air from large combustion plants
    • Directive 2001/81/EC, national emission ceilings
      Directive 2001/81/EC, on nation al emissions ceilings (NECD) for certain atmospheric pollutants. Emission reduction targets for the new EU10 Member States have been specified in the Treaty of Accession to the European Union 2003  [The Treaty of Accession 2003 of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia. AA2003/ACT/Annex II/en 2072] in order that they can comply with the NECD.
    • Directive 2010/75/EC on industrial emissions
      Directive 2010/75/EC on industrial emissions (integrated pollution prevention and control) The IED is the successor of the IPPC Directive and in essence, it is about minimising pollution from various industrial sources throughout the European Union. Operators of industrial installations operating activities covered by Annex I of the IED are required to obtain an integrated permit from the authorities in the EU countries. About 50.000 installations were covered by the IPPC Directive and the IED will cover some new activities which could mean the number of installations rising slightly.
    • UNECE Convention on Long-range Transboundary Air Pollution
      UNECE Convention on Long-range Transboundary Air Pollution.
    • WHITE PAPER European transport policy for 2010: time to decide
      The need for integration of transport in sustainable development


    Methodology for indicator calculation

    Indicator is based on officially reported national total and sectoral emissions to UNECE/EMEP (United Nations Economic Commission for Europe/Co-operative programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe) Convention on Long-range Transboundary Air Pollution (LRTAP Convention), submission 2010. Recommended methodologies for emission inventory estimation are compiled in the EMEP/CORINAIR Atmospheric Emission Inventory guidebook, EEA Copenhagen (EEA, 2009). Base data are available from the EEA Data Service ( and the EMEP web site ( Recalculations of Member States data may happen. These are fully documented in the EEA report

    Base data, reported in NFR are aggregated into the following EEA sector codes to obtain a common reporting format across all countries and pollutants:

    • Energy Industries: emissions from public heat and electricity generation, oil refining,  production of solid fuels, extraction and distribution of solid fossil fuels and geothermal energy;
    • Industrial processes: emissions derived from non-combustion related processes such as the production of minerals, chemicals and metal production;
    • Road transport: light and heavy duty vehicles, passenger cars and motorcycles;
    • Non-road (other) transport: railways, domestic shipping, certain aircraft movements, and non-road mobile machinery used in agriculture & forestry;
    • Household and services: emissions principally occurring from fuel combustion in the services and household sectors;
    • Manufacturing and Constructions: emissions from combustion processes used in the manufacturing industry including boilers, gas turbines and stationary engines;
    • Other non-energy (Solvent and product use): non-combustion related emissions mainly in the services and households sectors including activities such as paint application, dry-cleaning and other use of solvents;
    • Agriculture: manure management, fertiliser application, field-burning of agricultural wastes
    • Waste: incineration, waste-water management;

    The following table shows the conversion of Nomenclature for Reporting (NFR) sector codes used for reporting by countries into EEA sector codes:

    EEA classification

    Non-GHGs (NFR)

    GHG (CRF)

    National totals

    National total

    National totals without LUCF

    Energy Industries



    Fugitive emissions

    1B1, 1B2


    Road transport



    Non-road transport (non-road mobile machinery)

    1A3 (exl 1A3b)

    1A3a, 1A3c, 1A3d, 1A3e

    Industrial processes



    Other non-energy (Solvent and product use)

    3, 7A








    Household and services

    1A4ai, 1A4aii, 1A4bi, 1A5a

    1A4A, 1A4B

    Manufacturing / Construction



    Methodology for gap filling

    Methodology references

    • Methodology Reference EMEP/CORINAIR Emission Inventory Guidebook - 2009 This 2009 update of the emission inventory guidebook prepared by the UNECE/EMEP Task Force on Emissions Inventories and Projections provides a comprehensive guide to state-of-the-art atmospheric emissions inventory methodology. Its intention is to support reporting under the UNECE Convention on Long-range Transboundary Air Pollution and the EU National Emission Ceilings Directive.  
    • EMEP (2010). Transboundary, acidification, eutrophication and ground level ozone in Europe in 2008 This report has been prepared for the thirty-fourth session of the Steering Body to EMEP. It presents the progress of activities within EMEP in 2009 and 2010 in regard to acidification, eutrophication and ground level ozone. The status of transboundary depositions in Europe in 2008 is presented, and main differences with respect to other years are discussed. In addition, this year’s report describes preliminary studies on climate-chemistry couplings, as well as ongoing model development and evaluation efforts at MSC-W.


    Methodology uncertainty

    Officially reported data following agreed procedures and Emission Inventory Guidebook (EEA 2009), e.g. regarding source sector split.  The incomplete reporting and resultant extrapolation may obscure some trends.

    Data sets uncertainty

    The uncertainties of total sulphur dioxide emission estimates in Europe are relatively low, as the sulphur emitted mainly comes from the fuel burnt and therefore can be accurately estimated. However, because of the need for interpolation to account for missing data the complete dataset used here will have higher uncertainty. EMEP has compared modelled (which include emission data as one of the model parameters) and measured concentrations throughout Europe (EMEP 2005). From these studies the uncertainties associated with the modelled annual averages for a specific point in time have been estimated in the order of ± 30 %. This is consistent with an inventory uncertainty of ±10 % (with additional uncertainties arising from the other model parameters, modelling methodologies, and the air quality measurement data etc). In contrast, NOx emission estimates in Europe are thought to have higher uncertainty, as the NOx emitted comes both from the fuel burnt and the combustion air and so cannot be estimated accurately from fuel nitrogen alone. EMEP has compared modelled and measured concentrations throughout Europe (EMEP 2005). From these studies differences for individual monitoring stations of more than a factor of two have been found. This is consistent with an inventory of national annual emissions having an uncertainty of ±30% or greater (there are also uncertainties in the air quality measurements and especially the modelling). For some countries, reported time-series emissions data may be inconsistent. This may occur where for example different inventory reporting definitions have been used in different years and/or where changes made to estimation methodologies have not been applied back to 1990. For all emissions the trend is likely to be much more accurate than individual absolute annual values - the annual values are not independent of each other.

    Rationale uncertainty

    No uncertainty has been specified

    Data sources

    Other info

    DPSIR: Pressure
    Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
    Indicator codes
    • ENER 006
    EEA Contact Info


    Geographic coverage

    Temporal coverage



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