Emissions of ozone precursors (version 1) (CSI 002) - Assessment published Mar 2008

Indicator definition

This indicator tracks trends since 1990 in anthropogenic emissions of ozone precursors: Nitrogen oxides, carbon monoxide, methane and non methane volatile organic compounds, each weighted by their tropospheric ozone-forming potential.

The indicator also provides information on emissions by 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

Emission ceiling targets for NO_x and NMVOCs are specified in both the EU National Emission Ceilings Directive (NECD) and the Gothenburg protocol under the United Nations Convention on Long-Range Transboundary Air Pollution (LRTAP Convention) (UNECE 1999). Emission reduction targets for the new EU-12 Member States have been specified in a consolidated version of the NECD for the EU-25 [1] which was adopted by the European Community after the accession of the EU-10 Member States. In addition, the consolidated NECD also includes emission ceilings for Bulgaria and Romania whose targets have been defined in their respective Accession treaties [2].

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. For example, carbon monoxide is covered by the second daughter Directive under the Air Quality Directive. This gives a limit of 10 ug m-3 for ambient air quality to be met by 2005. Methane is included in the basket of six greenhouse gases under the Kyoto protocol (see CSI 10: Greenhouse gas emissions and removals).

[1] http://ec.europa.eu/environment/air/pdf/necd_consolidated.pdf

[2] http://ec.europa.eu/environment/air/pdf/eu27_nat_emission_ceilings_2010.pdf

3. UNECE (1999). Protocol to the 1979 Convention on Long-Range Transboundary air pollution (LRTAP Convention) to abate acidification, eutrophication and ground-level ozone, Gothenburg, Sweden, 1 December 1999.

4. NECD. Directive 2001/81/EC, on national emissions ceilings (NECD) for certain atmospheric pollutants.

Targets

Emissions of NO_x and NMVOCs 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.

Table 1. Percentage reduction required by 2010 from 1990 levels by country, for emissions of ozone precursors NO_x and NMVOCs (emission targets weighted by ozone formation potential).

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.
• 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

The dataset compiled by EEA/ETC-ACC for this indicator is based on national total and sectoral emissions of CO, NMVOC and NO_x (expressed as NO₂) officially reported to UNECE/EMEP Convention on Long-Range Transboundary Atmospheric Pollution (LRTAP Convention) and GHG Monitoring Mechanism.

Emissions data reported to the LRTAP Convention can be submitted in NFR format. A detailed discription of the difference reporting formats can be found in the EMEP/CORINAIR Emission Inventory Guidebook - 2006 (1).

Base data is available from http://webdab.emep.int/ and from the EEA dataservice.  Emission data for methane is obtained from the EEA Greenhouse Gas Inventory database. Base data, reported in NFR are converted into EEA sector codes to obtain a common reporting format across all countries and pollutants:

-          Energy industry: Emissions from public heat and electricity generation

-          Fugitive emissions: Emissions from extraction and distribution of solid fossil fuels and geothermal energy

-          Industry (Energy): relates to emissions from combustion processes used in the manufacturing industry including boilers, gas turbines and stationary engines

-          Industry (Processes): Emissions from production processes

-          Road transport: light and heavy duty vehicles, passenger cars and motorcycles;

-          Off-road transport: railways, domestic shipping, certain aircraft movements, and non-road mobile machinery used in agriculture, forestry;

-          Agriculture: manure management, fertiliser application, field-burning of agricultural wastes

-          Waste: incineration, waste-water management.

-          Other (energy-related) covers energy use principally in the services and household sectors

-          Other (Non Energy): Emissions from solvent and other product use.

The current LRTAP template Version 2004-1 includes 103 categories.

The following table shows the conversion of NFR sector codes into EEA sector codes:

Where reported data from countries is incomplete, simple gap-filling techniques are used in order to obtain a consistent time-series (see section on gap-filling).

To obtain emission values for the ozone precursors, the gap-filled emission values are multiplied by tropospheric ozone formation potential factors, de Leeuw (2002). The factors are NO_x 1.22, NMVOCs: 1, CO: 0.11 and CH₄: 0.014. Results are expressed in NMVOC equivalents (ktonnes).  For the main indicator trend graph, emissions are shown indexed to 1990 values (1990 emission =100). The sectoral shares are the share of the specific sector relative to the sum of all sectors for a given year. The 'unallocated' sector corresponds to the difference between the reported national total and the sum of the reported sectors for a given pollutant/country/year combination. This 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.

(1) http://reports.eea.europa.eu/EMEPCORINAIR4/en/BNPA_v3.1.pdf

Methodology for gap filling

Methodology references

• de Leeuw , F. (2002). A set of emission indicators for long-range transboundary air pollution. Environmental Science and Policy, Volume 5, Issue 2, p. 135-145 Abstract For assessing the progress made to mitigate the environmental problems related to long-range transboundary air pollution, emission indicators are developed for total potential acid, secondary PM 10 and ground-level ozone. The indicators are based on a weighted summation of emission data of the relevant precursors (SO 2 , NO x , NH 3 and VOC). By using comparable and reliable emissions data provided by the EU member states, the indicators provide clear information on the contribution of economic sectors and on the gap between current emissions and the emission targets set for 2010.
• EEA/ETC-ACC technical report describing the gap-filling methodologies used for the 2004 EEA/ETC-ACC LRTAP Convention and GHG (CRF) air emissions spreadsheet

Uncertainties

Methodology uncertainty

The use of ozone formation potential factors leads to some uncertainty. The factors are assumed to be representative for Europe as a whole; on the local scale uncertainties are larger and other factors are more relevant.  An extensive discussion on the uncertainties in these factors is available in de Leeuw (2002).

Data sets uncertainty

EEA uses data officially submitted by EU Member States and other EEA member countries which follow common guidelines on the calculation and reporting of emissions (EMEP/EEA 2006) for the air pollutants NO_x, NMVOC and CO, and IPCC (2006) for the greenhouse gas CH₄.

NO_x emission estimates in Europe are thought to have an uncertainty of about +/-30%, as the NO_x 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 1998). From these studies differences for individual monitoring stations of up to a factor of two have been found. This is consistent with an inventory of national annual emissions having an uncertainty of +/-30% (there are also uncertainties in the measurements and especially the modelling). Uncertainties in emissions of CO are likely to have a similar magnitude of uncertainty as for NO_x. NMVOC emissions data have been verified by EMEP and others by means of comparison between modelled and measured concentration throughout Europe. 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.      

EMEP/EEA (2006). Joint EMEP/CORINAIR Atmospheric Emission Inventory Guidebook (2006), 3^rd ed, EEA, Copenhagen. 

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.

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.

EEA (2004). European Community Greenhouse Gas Inventory 1990-2002 and Inventory Report 2004, Technical Report No 2/2004. European Environment Agency, Copenhagen.

Rationale uncertainty