Indicator Specification

Nitrogen oxides (NOx) emissions

Indicator Specification

Indicator codes: APE 002

Published 15 Oct 2010 Last modified 16 Nov 2020

14 min read

This page was archived on 22 Feb 2018 with reason: No more updates will be done

This indicator tracks trends since 1990 in anthropogenic emissions of nitrogen oxides. The indicator also provides information on emissions by sectors: energy production and distribution; energy use in industry; industrial processes; road transport; non-road transport; commercial, institutional and households; solvent and product use; agriculture; waste; other. Geographical coverage: EEA-32. The EEA-32 country grouping includes countries of the EU-27 (Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden and the United Kingdom) EFTA-4 (Iceland, Liechtenstein, Switzerland and Norway) and Turkey. Temporal coverage: 1990-2010

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This indicator is discontinued. No more assessments will be produced.

Assessment versions

Published (reviewed and quality assured)

No published assessments

Rationale

Justification for indicator selection

Nitric oxide (NO) and nitrogen dioxide (NO₂) are together referred to as nitrogen oxides (NO_X). Combustion of fossil fuels is by far the dominant source of NO_X emissions. The emissions are not dependent solely on the amount of nitrogen in the fuel but also on the air-fuel mix ratio. High temperatures and oxidation-rich conditions generally favour NO_X formation in combustion.

NO_X contributes to acid deposition and eutrophication which, in turn, can lead to potential changes occurring in soil and water quality. The subsequent impacts of acid deposition can be significant, including adverse effects on aquatic ecosystems in rivers and lakes and damage to forests, crops and other vegetation. Eutrophication can lead to severe reductions in water quality with subsequent impacts including decreased biodiversity, changes in species composition and dominance, and toxicity effects. In many cases, the deposition of acidifying and eutrophying substances still exceeds the critical loads of the ecosystems (see EEA indicator Core Set Indicator (CSI) 005 'Exposure of ecosystems to acidification, eutrophication and ozone'). Further details concerning emissions of acidifying pollutants are provided in EEA CSI 001 'Emissions of acidifying substances.

It is NO₂ that is associated with adverse affects on human health, as at high concentrations it can cause inflammation of the airways. NO₂ also contributes to the formation of secondary particulate aerosols and tropospheric ozone (O₃) in the atmosphere - both are important air pollutants due to their adverse impacts on human health. NO_x is therefore linked both directly and indirectly to effects on human health. Further details concerning the contribution of NO_X to emissions of tropospheric ozone precursors and particulate matter are contained in EEA CSI 002 'Emissions of ozone precursors' and CSI 003 'Emissions of primary particles and secondary particulate precursors'.

Scientific references

No rationale references available

Indicator definition

This indicator tracks trends since 1990 in anthropogenic emissions of nitrogen oxides.
The indicator also provides information on emissions by sectors: energy production and distribution; energy use in industry; industrial processes; road transport; non-road transport; commercial, institutional and households; solvent and product use; agriculture; waste; other.
Geographical coverage: EEA-32. The EEA-32 country grouping includes countries of the EU-27 (Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden and the United Kingdom) EFTA-4 (Iceland, Liechtenstein, Switzerland and Norway) and Turkey.
Temporal coverage: 1990-2010

Units

kilotonnes (1000 tonnes)

Policy context and targets

Context description

A number of policies have been implemented that directly or indirectly reduce the emissions of nitrogen oxides. These include: The National Emission Ceilings Directive 2001/81/EC (NECD), which entered into force in the European Community in 2001. The NECD sets emission ceilings for four important air pollutants (NO_x, sulphur dioxide (SO₂), ammonia (NH₃) and non-methane volatile organic compounds (NMVOCs)) to be achieved from 2010 onwards for each Member State. The ceilings are designed to improve the protection in the Community of the environment and human health against risks of adverse effects arising from acidification, eutrophication and ground level ozone. The NECD is presently under review, the European Commission may adopt a proposal for a revised Directive during 2010.

The Gothenburg Protocol (1999) to the United Nations Economic Commission for Europe's (UNECE) Convention on Long-Range Transboundary Air Pollution (LRTAP Convention) to abate acidification, eutrophication and ground-level ozone. A key objective of the protocol is to regulate emissions on a regional basis within Europe and to protect ecosystems from transboundary pollution by setting emission reduction ceilings to be reached by 2010 for the same four pollutants as addressed in the NECD (i.e. SO₂, NO_x,NH₃ and NMVOCs). Overall, for the EU Member States, the ceilings set within the Gothenburg protocol are generally either slightly less strict or the same as the emission ceilings specified in the NECD.

The Large Combustion Plant Directive (2001/80/EC) is important in reducing emissions of NO_x, SO₂ and dust from combustion plants having a thermal capacity equal to or greater than 50 MW. Installations within the scope of this Directive include power stations, petroleum refineries, steelworks and other industrial processes running on solid, liquid and gaseous fuels. "New" plant must meet the emission limit values (ELVs) given in the LCPD. However, Member States can choose to meet obligations for existing plant (i.e. those in operation pre-1987) by either complying with the ELVs or operating within a national emission reduction plan (NERP) that sets a ceiling for each pollutant. The interaction of the LCPD and the IPPC Directive (see below) is currently being examined as part of a review of the IPPC Directive.

The Directive on Integrated Pollution Prevention and Control (96/61/EC) entered into force in 1999. It aims to prevent or minimise pollution to air, water or land from various industrial sources throughout the European Union. Those installations covered by Annex I of the IPPC Directive are required to obtain authorisation from the authorities to operate. New and existing installations, which are subject to 'substantial changes', have been required to meet the requirements of the IPPC Directive since 30 October 1999. Other existing installations must have been brought into compliance by 30 October 2007. The emission limit values outlined in the permit conditions must be based on the best available techniques (BAT). The Commission has been undertaking a review of the IPPC Directive and related legislation on industrial emissions, and on 21 December 2007 adopted a proposal for a Directive on industrial emissions. The proposal recasts seven existing Directives relating to industrial emissions (including IPCC and the LCPD) into a single legislative instrument.

The aim of the Directive 96/62/EC on ambient air quality assessment and management (the 'Air Quality Framework Directive') is to maintain and improve air quality within the European Community by establishing objectives for ambient air, drawing up common methods and criteria for assessing air quality and obtaining and disseminating information. The first "Daughter" Directive 99/30/EC entered into force in 1999 and set limit values for hourly and annual average nitrogen dioxide concentrations to be achieved throughout the community by 1 January 2010.

Since the early 1990s, standards on NO_x emissions from new cars sold in Europe have been in place. This first came about with EU Directive 91/441/EC, which effectively mandated the fitting of three-way catalysts to all new petrol cars to significantly reduce emissions of CO, hydrocarbons and NO_x. Standards for this Directive, frequently referred to as Euro 1, were followed by Euro 2 standards implemented by Directive 94/12/EC during the mid 1990s. Yet more stringent EU Directives have been put in place to reduce NO_x emissions further, the most recent being (98/69/EC) setting emission limits for petrol cars sold after 2000 and then after 2005 (Euro 3 and 4 standards respectively).

NO_x emissions from diesel vehicles have also been regulated since the early 1990s (since 1988 for heavy duty vehicles) with a succession of more stringent EU Directives. The legislation currently in force for heavy duty vehicles is 2005/55/EC and 2005/78/EC (implementing provisions), which define the emission standards currently in force, Euro IV, as well as the next stage (Euro V) which entered into force in October 2008.

In parallel with vehicle technology developments, improvements in the quality of petrol and diesel fuels have been made as a result of the EU Directive on fuel quality (98/70/EC as amended by 2003/17/EC). Fuel quality has little effect on NO_x emissions directly, but improvements in fuel quality have allowed the fitting of exhaust after-treatment technologies and provided better catalyst performance, hence helping to reduce NO_x emissions further.

Directive 97/68/EC on the emissions of pollutants from internal combustion engines installed in non-road mobile machinery sets emission standards and type approval procedures for engines fitted to non-road mobile machinery.

Targets

Emissions of NO_X are covered by the EU National Emission Ceilings Directive (NECD) (2001/81/EC) and the Gothenburg protocol under the United Nations Convention on Long-Range Transboundary Air Pollution (LRTAP Convention) (UNECE 1999). The NECD generally involves slightly stricter emission reduction targets than the Gothenburg Protocol for EU-15 countries for the period 1990-2010. The Gothenburg Protocol entered into force on 17 May 2005, after ratification by 16 countries early in 2005. The 2012 revision to the Gothenburg protocol proposed emission reduction targets for 2020 relative to 2005 reported emissions for all EU-27 Member States and some EEA-32 non-EU member states.

Table: 2010 NO_X ceilings under the NEC Directive and the Gothenburg Protocol (kt)

Country	2010 NECD ceilings	2010 CLRTAP Gothenburg Protocol ceilings	2020 CLRTAP Gothenburg Protocol ceilings
Austria	103	107	149
Belgium	176	181	172
Bulgaria	247	266	91
Cyprus	23	N/A	12
Czech Republic	286	286	181
Denmark	127	127	80
Estonia	60	N/A	30
Finland	170	170	110
France	810	860	715
Germany	1051	1081	963
Greece	344	344	289
Hungary	198	198	134
Iceland^*	N/A	N/A	N/A
Ireland	65	65	65
Italy	990	1000	727
Latvia	61	84	25
Liechtenstein	N/A	0.37	N/A
Lithuania	110	110	29
Luxembourg	11	11	35
Malta	8	N/A	5
Netherlands	260	266	190
Norway	N/A	156	154
Poland	879	879	606
Portugal	250	260	167
Romania	437	437	170
Slovakia	130	130	65
Slovenia	45	45	28
Spain	847	847	827
Switzerland	N/A	79	55
Sweden	148	148	111
Turkey^*	N/A	N/A	N/A
United Kingdom	1167	1181	711

^* Iceland and Turkey do not have a ceiling under the NEC Directive or the Gothenburg protocol.

Methodology

Methodology for indicator calculation

This indicator is based on officially reported national total and sectoral emissions to the EEA and the 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 2011. For the EU-27 Member States, the data used is consistent with the emissions data reported by the EU in its annual submission to the LRTAP Convention.

Recommended methodologies for emission inventory estimation are compiled in the EMEP/EEA Air Pollutant Emission Inventory Guidebook, (EMEP/EEA, 2009). Base data are available from the EEA Data Service (http://dataservice.eea.europa.eu/dataservice/metadetails.asp?id=1096) and the EMEP web site (http://www.ceip.at/). Where necessary, gaps in reported data are filled by European Topic Centre/EEA using simple interpolation techniques (see below). The final gap-filled data used in this indicator are available from the EEA Data Service (http://dataservice.eea.europa.eu/PivotApp/pivot.aspx?pivotid=478)

Base data, reported in the UNECE/EMEP Nomenclature for Reporting (NFR) sector format are aggregated into the following EEA sector codes to obtain a consistent reporting format across all countries and pollutants:

Energy production and distribution: emissions from public heat and electricity generation, oil refining, production of solid fuels, extraction and distribution of solid fossil fuels and geothermal energy;
Energy use in industry: emissions from combustion processes used in the manufacturing industry including boilers, gas turbines and stationary engines;
Industrial processes: emissions derived from non-combustion related processes such as the production of minerals, chemicals and metals;
Road transport: light and heavy duty vehicles, passenger cars and motorcycles;
Non-road transport: railways, domestic shipping, certain aircraft movements, and non-road mobile machinery used in agriculture and forestry;
Commercial, institutional and households: emissions principally occurring from fuel combustion in the services and household sectors;
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;
Other: emissions included in national total for entire territory not allocated to any other sector.

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)
National totals	National total
Energy production and distribution	1A1, 1A3e, 1B
Energy use in industry	1A2
Road Transport	1A3b
Non-road transport (non-road mobile machinery)	1A3 (excl. 1A3b)
Industrial processes	2
Solvent and product use	3
Agriculture	4
Waste	6
Commercial, institutional and households	1A4ai, 1A4aii, 1A4bi, 1A4bii, 1A4ci, 1A4cii, 1A5a, 1A5b
Other	7

Methodology for gap filling

An improved gap-filling methodology was implemented in 2010 that enables a complete time series trend for the main air pollutants (eg NO_X, SO_X, NMVOC, NH₃ and CO) to be compiled. In cases where countries did not report emissions for any year, it meant that gap-filling could not be applied. For these pollutants, therefore, the aggregated data is not yet complete and is likely to underestimate true emissions. Further methodological details of the gap-filling procedure are provided in section 1.4.2 'Data gaps and gap-filling' of the European Union emission inventory report 1990–2009 under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP).

Methodology references

No methodology references available.

Data specifications

EEA data references

National emissions reported to the Convention on Long-range Transboundary Air Pollution (LRTAP Convention) provided by United Nations Economic Commission for Europe (UNECE)
National Emission Ceilings (NEC) Directive Inventory provided by Directorate-General for Environment (DG ENV)

Data sources in latest figures

Uncertainties

Methodology uncertainty

The use of gap-filling when countries have not reported emissions for one of more years can potentially lead to artificial trends, but it is considered unavoidable if a comprehensive and comparable set of emissions data for European countries is required for policy analysis purposes.

Data sets uncertainty

NO_X emissions estimates in Europe are thought to have an uncertainty of about ±20% (EMEP, 2010), as the NO_X emitted comes from both the fuel burnt and the combustion air and so cannot be estimated accurately from fuel nitrogen alone. However, because of the need for interpolation to account for missing data, the complete dataset used will have higher uncertainty. The trend is likely to be more accurate than the individual absolute annual values - the annual values are not independent of each other.

Overall scoring: (1-3, 1 = no major problems, 3 = major reservations)

Relevancy: 1
Accuracy: 2
Comparability over time: 2
Comparability over space: 2

Rationale uncertainty

This indicator is regularly updated by the EEA and is used in state of the environment assessments. The uncertainties related to methodology and datasets are therefore of importance. Any uncertainties involved in the calculation and in the datasets need to be accurately communicated in the assessment to prevent erroneous messages influencing policy actions or processes.