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Emissions of ozone precursors

Indicator Assessmentexpired Created 10 Nov 2008 Published 19 Dec 2008 Last modified 04 Sep 2015, 06:59 PM
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Indicator codes: CSI 002

Key messages

  • The aggregated emissions of ground-level ozone precursor pollutants (nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOCs), carbon monoxide (CO) and methane (CH4)) have decreased by 37% across the EEA-32 region between 1990 and 2006.
  • This decrease has been achieved mainly as a result of the introduction of catalytic converters for vehicles and to a lesser extent by a switch from petrol-fuelled cars to more diesel cars. Together these changes have significantly reduced emissions of NOx and CO from the road transport sector, the main source of ozone precursor emissions.
  • The EU-27 is still some way from meeting its target to reduce emissions of two ozone precursors (NOx and NMVOC) for which emission limits exist under the NEC Directive. A number of individual Member States anticipate missing their ceilings for one or either of these two pollutants.

What progress is being made in reducing emissions of ozone precursors across Europe?

Emissions of ozone precursors

Note: The 'with measures' (WM) projections reported by Member States take into account currently implemented and adopted policies and measures

Data source:

EEA aggregated and gap-filled air emission dataset, based on 2008 officially reported national total and sectoral emissions to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution. 2010 NEC Directive projections data: EEA Directive status report 2007 (EEA Technical report No. 9/2008).

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Change in emissions of ozone precursors (NOx and NMVOC only) compared with the 2010 NECD and Gothenburg protocol targets

Note: Gothenburg protocol targets are shown for the non-EU countries

Data source:

EEA aggregated and gap-filled air emission dataset, based on 2008 officially reported national total and sectoral emissions to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution.

Downloads and more info

Distance-to-target for EEA member countries

Note: The 'distance to target' results are shown in light yellow (countries need to do more to be on track to meet their ceiling in 2010) and green (countries are on track to meet their ceiling in 2010)

Data source:

EEA aggregated and gap-filled air emission dataset, based on 2008 officially reported national total and sectoral emissions to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution.

Downloads and more info

Aggregated emissions of tropospheric (ground-level) ozone precursors have reduced by 37% across the EEA-32 region between 1990 and 2006 (Figure 1).  Emissions of these pollutants are weighted using a factor that reflects their specific ozone formation potential prior to aggregation - see the CSI 002 indicator specification for further details. Within most countries reductions have occurred for the aggregated emissions of the two ozone precursors for which emission limits exist under the NEC Directive and UNECE Gothenburg protocol (NOx and NMVOC) (Figure 2). The largest reductions have occurred in Luxembourg (-84%), Switzerland (-58%) and the Czech Republic (-52%), but the emissions of these two pollutants have increased in 7 countries (Bulgaria, Greece, Portugal, Spain, Cyprus, Romania and Hungary).

Emissions of NOx (51 % of the total aggregated emissions) and NMVOC (36 %) are the most important pollutants that contributed to the formation of tropospheric ozone in 2006. Carbon monoxide and methane contributed 13% and 1%, respectively. However emissions of both these pollutants have been significantly reduced since 1990 - NOx has contributed 38% and NMVOC 40% of the total observed reduction of precursor emissions (Figure 6). This reduction of emissions is mainly due to the introduction of three way catalytic converters for cars and increased penetration of diesel-fuelled vehicles. The introduction of other European legislative measures has also contributed to the reduction, such as the implementation of the Solvent Emissions Directive in industrial processes. Some further reasons for the observed reductions in emissions are provided in the 'Specific assessment' section below.

The National Emission Ceilings Directive (NECD) sets for each of the EU-27 Member States ceilings (i.e. limits) for two ozone precursors, NOx and NMVOC, that must be met by 2010 [1]. The reported data shows that as of 2006, slightly more than half of the 27 Member States are not on track towards meeting their combined target for the two ozone precursor pollutants (Figure 3). Similarly, the EU-27 as a whole is also not on track to achieve its aggregated ceiling for these pollutants. On an individual pollutant basis, other EEA analysis [2] indicates that many Member States anticipate that, without implementing additional measures to reduce emissions, they will miss one or either of their respective 2010 NECD ceilings. The 2010 emission ceiling for NOx is the most difficult ceiling for many Member States to meet. Thirteen Member States have reported that they anticipate missing their NOx ceiling (Austria, Belgium, Denmark, France, Germany, Hungary, Ireland, Italy, the Netherlands, Slovenia, Spain, Sweden and the United Kingdom). Five Member States report they anticipate missing their NMVOC ceiling (Denmark, France, Poland, Portugal and Spain).

Several of the non-EU countries also have 2010 emissions ceilings defined under the Gothenburg protocol of the UNECE Convention on Long-range Transboundary Air Pollution. Of these countries, Norway alone has reported emissions that lie above a linear target path to its aggregated NOx and NMVOC ceiling for 2010 - in contrast both Liechtenstein and Switzerland appear on track to meet their respective aggregated Gothenburg ceilings [3].

Further details concerning emissions of the main ozone precursor pollutants may be found in the following indicator fact sheets:

[1] The NECD and Gothenburg protocol also set emission ceilings for two other pollutants ammonia (NH3) and sulphur dioxide (SO2) that contribute to acidification and particulate matter formation.
[2] NEC Directive Status report (EEA Technical report No 9/2008).
[3] Lichtenstein has signed, but not yet ratified, the Gothenburg protocol.

How do different sectors and processes contribute to emissions of ozone precursors?

Emissions by sector of ozone precursors

Note: Due to numerical rounding, values may not add exactly to 100%

Data source:

EEA aggregated and gap-filled air emission dataset, based on 2008 officially reported national total and sectoral emissions to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution.

Downloads and more info

Change in ozone precursors emissions for each sector and pollutant between 1990 and 2006

Note: No data available for Iceland.

Data source:

EEA aggregated and gap-filled air emission dataset, based on 2008 officially reported national total and sectoral emissions to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution.

Downloads and more info

Contribution to total change in ozone precursors emissions for each sector and pollutant

Note: 'Contribution to change' plots show the contribution to the total emission change between 1990-2006 made by a specified sector/ pollutant

Data source:

EEA aggregated and gap-filled air emission dataset, based on 2008 officially reported national total and sectoral emissions to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution.

Downloads and more info

In 2006, the most significant sources of ozone precursor pollutants in the EEA-32 region were the 'road transport' (31% of total emissions), and the 'other non-energy' sectors (e.g. solvent use - 13% of total emissions) (Figure 4). Emissions in virtually all sectors have decreased since 1990 (Figure 5).

Within the EEA-32 transport is clearly the dominant source of ozone precursor pollutants. In addition to 'road transport', a further 11% of total emissions are emitted by 'other transport' modes (including aviation, rail and shipping). Since 1990, the vast majority of the reduction of ozone precursor pollutants has occurred in the road transport sector, despite the general increase in activity within this sector over the period. This sector alone has contributed 62% of the total reduction of emissions (Figure 6). The emission reductions have primarily been achieved as a result of fitting three way catalytic converters for petrol-fuelled cars (driven by the legislative 'Euro' standards) coupled with an increased penetration of diesel-fuelled vehicles.

Emissions of ozone precursors from the fuel-combustion related sectors 'energy industries' and 'industry (energy)' have also decreased significantly, together contributing 17% of the total reduction of emissions since 1990. In this instance the reduction has been driven by reduced NOx emissions which have been achieved as a result of measures including the introduction of combustion modification technologies (such as use of low NOx burners), implementation of flue-gas abatement techniques (e.g. NOx scrubbers and selective (SCR) and non-selective (SNCR) catalytic reduction techniques) and fuel-switching from coal to gas (which has led e.g. to increases in energy efficiency and lower rates of NOx emissions).

Significant reductions have also been achieved in the 'other (non-energy)' sector, reflecting amongst other measures, the introduction and implementation of the Solvent Emissions and Paints Directives.

Indicator specification and metadata

Indicator definition

This indicator tracks trends since 1990 in anthropogenic emissions of ozone precursor pollutants: nitrogen oxides (NOx), carbon monoxide (CO), methane (CH4) and non methane volatile organic compounds (NMVOCs), each weighted by their respective tropospheric ozone-forming potential.

The indicator also provides information on the sources of emissions from a number of sectors: Energy industries; road and other transport; industry (processes and energy); other (energy); fugitive emissions; waste; agriculture and other (non energy).

Units

ktonnes (NMVOC-equivalent)


Policy context and targets

Context description

Within the European Union, the National Emission Ceilings Directive (NEC Directive) imposes emission ceilings (or limits) for emissions of NOx and NMVOCs (the NEC Directive also sets emissions ceilings for ammonia NH3 and sulphur dioxide SO2). There are no specific EU emission targets set for either carbon monoxide (CO) or methane (CH4). However, there are several Directives and Protocols that affect the emissions of CO and CH4. Methane is included in the basket of six greenhouse gases under the Kyoto protocol (see CSI 10: Greenhouse gas emissions and removals).

The European Commission is expected to propose a revised NEC Directive in 2009.

 

Internationally, the issue of air pollution emissions is also being addressed by the UNECE Convention on Long-range Transboundary Air Pollution (the LRTAP Convention) and its protocols. The Gothenburg 'multi-pollutant' protocol under the LRTAP Convention also contains national emission ceilings for NOx and NMVOCs that are either equal to or slightly less ambitious than those in the EU NEC Directive. 

 

References

Directive 2001/81/EC, on national emissions ceilings (NECD) for certain atmospheric pollutants. http://ec.europa.eu/environment/air/pdf/necd_consolidated.pdf

UNECE (1999). Protocol to the 1979 Convention on Long-Range Transboundary air pollution (LRTAP Convention) to abate acidification, eutrophication and ground-level ozone. http://www.unece.org/env/lrtap/multi_h1.htm

Targets

Emissions of NOx and NMVOCs are covered by the EU National Emission Ceilings Directive (NECD) and the Gothenburg Protocol to the UNECE LRTAP Convention (UNECE 1999). Both instruments contain emission ceilings (limits) that countries must meet by 2010.

Table 1. Percentage reduction required by 2010 compared to 1990 levels by country, for aggregated emissions of ozone precursors NOx and NMVOCs (individual pollutant emission ceilings weighted by ozone formation potential factors prior to aggregation).

 

Country

1990 - 1990 - 2010 NECD target

1990-2005 Gothenburg

Austria

-44%

-43%

Belgium

-54%

-53%

Denmark

-53%

-53%

Finland

-43%

-43%

France

-60%

-58%

Germany

-69%

-68%

Greece

5%

5%

Ireland

-42%

-42%

Italy

-46%

-46%

Luxembourg

-47%

-47%

Netherlands

-55%

-54%

Portugal

-17%

-11%

Spain

-35%

-35%

Sweden

-41%

-41%

United Kingdom

-56%

-56%

Bulgaria

15%

23%

Cyprus

33%

-

Czech Republic

-53%

-53%

Estonia

-23%

-

Hungary

-24%

-24%

Latvia

22%

39%

Lithuania

-18%

-18%

Malta

23%

-100%

Poland

-22%

-22%

Romania

18%

18%

Slovakia

-28%

-28%

Slovenia

-34%

-34%

EU-27

-51%

-47%

Liechtenstein

-

109%

Norway

-

-30%

Switzerland

-

-49%

Iceland

-

-

Turkey

-

-

Related policy documents

  • 1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone
    Convention on Long-range Transboundary Air Pollution 1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone, amended on 4 May 2012.
  • 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.

Methodology

Methodology for indicator calculation

This indicator factsheet uses emissions data from the EEA dataservice dataset 'EEA aggregated and gap-filled air emission data'. The 2010 projection estimates reported by the EU-27 Member States under the requirements of the NEC Directive are also included in the analysis http://www.eea.europa.eu/themes/air/datasets).

 

The dataset 'EEA aggregated and gap-filled air emission data' is consistent with the annual 'European Community LRTAP Convention emission inventory' compiled by EEA. This inventory is based on the officially reported emissions data from countries submitted to the UNECE LRTAP Convention and supplemented with additional data reported under the NEC Directive and the EU GHG Monitoring Mechanism/UNFCCC.   

 

Air pollutant emissions data are reported by countries using the Nomenclature For Reporting (NFR) sectroal classification system developed by UNECE/EMEP.  For the purposes of the 'EEA aggregated and gap-filled air emission dataset', the numerous NFR sectors reported by countries are combined into the following EEA aggregated sectors to allow a simpler analysis: 

  • 'Energy industries': emissions from public heat and electricity generation
  • 'Fugitive emissions': emissions from extraction and distribution of solid fossil fuels and geothermal energy
  • 'Industry (Energy)': emissions from combustion processes used in the manufacturing industry including boilers, gas turbines and stationary engines
  • 'Industry (Processes)': emissions from production processes
  • 'Road transport': emissions from light and heavy duty vehicles, passenger cars and motorcycles;
  • 'Off-road transport': emissions from railways, domestic shipping, certain aircraft movements, and non-road mobile machinery used in agriculture, forestry;
  • 'Agriculture': emissions from manure management, fertiliser application, field-burning of agricultural wastes
  • 'Waste': emissions from incineration of waste, waste-water management.
  • 'Other (energy-related)': emissions from energy use principally in the services and household sectors
  • 'Other (Non Energy)': emissions from solvent and other product use.

 

The following table shows how the NFR categories used by countries to report their emissions are aggregated into the EEA aggregated sectors listed above:  

 EEA Code

EEA classification

Non-GHGs (NFR)

0

National totals

National Total

1

Energy industries

1A1

3

Industry (Energy)

1A2

2

Fugitive emissions

1B

7

Road transport

1A3b

8

Other transport (non-road mobile machinery)

1A3 (excl 1A3b) + sectors mapped to 8 in table below

9

Industry (Processes)

2

4

Agriculture

4 + 5B

5

Waste

6

6

Other (Energy)

1A4a, 1A4b, 1A4b(i), 1A4c(i), 1A5a

10

Other (non-energy)

3 + 7

14

Unallocated

Difference between NT and sum of sectors (1-12)

12

Energy Industries (Power Production 1A1a)

1A1a

 The 'unallocated' sector (14) corresponds to the difference between the reported national total and the sum of the reported sectors for a given pollutant/country/year combination. It can be either negative or positive. Inclusion of this additional sector means that the officially-reported national totals do not require adjustment to ensure they are consistent with the sum of the individual sectors reported by countries.

 

Where reported data from countries is incomplete, simple gap-filling techniques are used in the 'EEA aggregated and gap-filled air emission dataset' in order to obtain a consistent time-series (see following section).

 

To obtain an aggregated estimate of the total ozone precursor emissions, the emission values of the individual pollutants are multiplied by a troposheric ozone formation potential factor (de Leeuw, 2002) prior to aggregation. The factors are NOx 1.22, NMVOCs: 1, CO: 0.11 and CH4: 0.014. Results are expressed in terms of 'NMVOC equivalents' (ktonnes). 

 

In addition to historic emissions, Figure 1 of the indicator factsheet also shows the latest 2010 projection estimates reported by the EU-27 Member States under the requirements of the NEC Directive. The "with measures" (WM) projections reported by Member States take into account currently implemented and adopted policies and measures. Where countries have instead reported "business as usual" or "current legislation" projections, it is assumed for comparison purposes that these are equivalent to a WM projection. The "with additional measures" projections reported by Member States take into account additional future planned policies and measures but which are not yet implemented.

Methodology for gap filling

To allow trend analysis, where countries have not reported data for one or more years, data in the 'EEA aggregated and gap-filled air emission dataset' has been interpolated to derive the emissions for the missing year or years. If the reported data is missing either at the beginning or at the end of the period, the emission value is assumed to equal the first or last reported value. The use of gap-filling may lead to artificial trends, but it is considered necessary if a comprehensive and comparable set of emissions data for European countries is to be obtained. A spreadsheet containing a record of the gap-filled data is available from EEA's European Topic Centre on Air and Climate Change (ETC/ACC) (http://air-climate.eionet.europa.eu/)

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

The use of interpolation/extrapolation procedures to gap-fill the underlying emissions dataset and the application of tropospheric ozone formation potential factors both lead to uncertainties. With respect to the tropospheric ozone formation potential factors, these are assumed to be representative for Europe as a whole; on the local scale different factors might be estimated. An extensive discussion on the uncertainties in these factors is available in de Leeuw (2002).

Data sets uncertainty

The NOx, CO and NMVOC emissions data officially submitted by EU Member States and other EEA member countries follow common calculation (EMEP/EEA 2009) and reporting guidelines (UNECE 2003). CH4 emissions are estimated by countries following IPCC Guidelines (e.g. IPCC 2009).

Nitrogen oxide emission estimates in Europe are thought to have an uncertainty of about +/-20% (EMEP 2009), as the NOx emitted comes both from 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.

Uncertainties in emissions of CO are likely to have a similar magnitude of uncertainty as for NOx. NMVOC emissions data have been verified by EMEP and others by means of comparison between modelled and measured concentration throughout Europe (EMEP, 1998). From these studies total uncertainty ranges have been estimated to about +/-50%. Some main source categories are less uncertain.

CH4 estimates are reasonably reliable as they are based on a few well-known emission sources. The IPCC believes that the uncertainty in CH4 emission estimates from all sources, in Europe, is likely to be about +/-20 %. CH4 emissions from some sources, such as rice fields, are much larger (possibly an order of magnitude), but are a minor emission source in Europe. In 2004, EU Member States reported uncertainties in their estimates of CH4 emissions from enteric fermentation as ranging between 0.5 % (UK) and 2.8 % (Ireland) of the total national GHG emissions (EEA 2004).

Incomplete reporting and resulting intra- and extrapolation may obscure some trends.  

 References

  • EEA (2009). Annual European Community greenhouse gas inventory 1990-2007 and inventory report 2009, Technical report No 4/2009. European Environment Agency, Copenhagen.

  • EMEP/EEA 2009. EMEP/CORINAIR Emission Inventory Guidebook - 2009 (http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009)
  • EMEP (1998). Transboundary Acidifying Air Pollution in Europe, Part 1: Estimated dispersion of acidifying and eutrophying compounds and comparison with observations. EMEP/MSC-W Report 1/98, July 1998.
  • EMEP (2009). "Transboundary acidification, eutrophication and ground level ozone in Europe in 2007". EMEP August 2009 http://www.emep.int/publ/reports/2009/status_report_1_2009.pdf
  • IPCC (2006). Revised 2006 IPCC Guidelines for National Greenhouse Gas Inventories. JT Houghton, LG Meira Filho, B Lim, K Treanton, I Mamaty, Y Bonduki, DJ Griggs and BA Callender (Eds). IPCC/OECD/IEA. UK Meteorological Office, Bracknell.
  • UNECE (2003). Emission Reporting Guidelines: 'Guidelines for Estimating and Reporting Emission Data under the Convention on Long-range Transboundary Air Pollution', ECE/EB.AIR/80. Air Pollution studies No. 15, United Nations, New York and Geneva. http://www.unece.org/env/documents/2003/eb/air/ece.eb.air.80.E.pdf

Rationale uncertainty

This indicator on emissions of ozone precursors is updated annually by EEA and is used regularly in our reports on the state of the environment. It is therefore important to note the uncertainties related to methodology and data sets.

Data sources

Generic metadata

Topics:

Air pollution Air pollution (Primary topic)

Agriculture Agriculture

Environment and health Environment and health

Tags:
air emissions | ozone precursors
DPSIR: Pressure
Typology: Performance indicator (Type B - Does it matter?)
Indicator codes
  • CSI 002
Geographic coverage:
Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom

Contacts and ownership

EEA Contact Info

Martin Adams

Ownership

EEA Management Plan

2010 (note: EEA internal system)

Dates

European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100