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Indicator Assessment
Energy-related emissions account for 75% of all emissions of ozone precursors (CH4, CO, NMVOC, NOX) emissions from the EEA-32 in 2007. These emissions fell by 4.1% between 2006 and 2007 (and by 5.2% in the EU-27). Since 1990, these emissions have declined by 45% in the EU and 41% in EEA member countries. The largest reductions in emissions occurred in the road transport sector, largely as a result of the continued introduction of catalytic converters in new vehicles during this period. Energy production and use still remains a significant source of emissions for all these precursor pollutants. Reducing energy-related emissions of ozone precursors therefore is a key priority for reducing local and transboundary air pollution and in ensuring that the EU and individual countries meet emission ceiling targets under the National Emissions Ceilings Directive (NECD) and the UNECE Gothenburg Protocol.
Sectoral shares of tropospheric ozone precursors (energy and non-energy components) in total emissions, EU-27.
Note: The emissions of ozone precursors (NOx, NMVOC, CO and CH4) are each weighted by an ozone formation factor prior to aggregation to represent their respective ozone forming potentials. The relative impact of the combined contribution of NOx, NMVOC, CO and CH4 to ozone formation can be assessed based on their tropospheric ozone forming potentials (TOFP): nitrogen oxides 1.22, non-methane volatile organic compounds 1.0, carbon monoxide 0.11 and methane 0.014.
Overall change in emissions of ozone precursors by country, 1990-2007
Note: The graph shows the change in energy-related emissions of ozone precursors (NOx, NMVOC, CO and CH4) each weighted by an ozone formation factor prior to aggregation to represent their respective ozone forming potentials. The relative impact of the combined contribution of NOx, NMVOC, CO and CH4 to ozone formation can be assessed based on their tropospheric ozone forming potentials (TOFP): nitrogen oxides 1.22, non-methane volatile organic compounds 1.0, carbon monoxide 0.11 and methane 0.014 (de Leeuw 2002).
Changes (%) in emissions of ozone precursors by source category, 1990-2007, EEA-32 (weighted by tropospheric ozone forming potential)
Note: The graph above shows the emissions of ozone precursors (methane CH4; carbon monoxide CO; non-methane volatile organic compounds NMVOCs; and nitrogen oxides NOx) each weighted by a factor prior to aggregation to represent their respective tropospheric ozone formation potential (TOFP). The TOFP factors are: NOx 1.22, NMVOC 1, CO 0.11 and CH4 0.014 (de Leeuw 2002). Results are expressed in NMVOC equivalents (kilotonnes - kt). Data not available for Iceland (emissions of CO, NMVOC, NOx were not reported) and Malta (CO). 'Energy combustion' includes all energy-related emissions minus fugitive.
In the EEA-32, total trophospheric ozone forming potentials (TOFP) emissions have decreased by 39% between 1990 and 2007 (and by 43% in the EU). All sources except international bunkers have decreased (see Figure 1). Energy-related emissions comprise the majority of TOFP emissions and accounted for 75 % of all TOFP emissions in 2007.
The transport sector is the dominant source of ozone precursors and contributed 38% of total ozone precursor emissions in 2007 (see Figure 2). Road transport has decreased the most with a 57% reduction seen in the EU-27 from 1990 to 2007 (see Figure 1). Decreases in emissions from the transport sector have occurred largely due to the continued introduction of catalytic converters in passenger cars, which reduces emissions of CO and NOx.
Energy industries are a significant source of TOFP emissions, accounting for 11 %, of total TOFP emissions in 2007 (see Figure 2). This sector has reduced its emissions by over 35% in EEA-32 since 1990 (see Figure 1). The decreases in emissions from this sector (primarily NOx) can be attributed to a range of measures, including the increased use of abatement technologies (e.g. selective catalytic reduction (SCR), exhaust gas recirculation (EGR), 3-way catalytic converters), fuel-switching from coal to gas prompted by the liberalisation of the energy market, the requirements of the IPPC and Large Combustion Plant Directives and improved technology efficiencies.
Concerning progress in individual countries, emissions of ozone precursors have decreased significantly in most EEA member countries, with the top reductions measured in Germany, Switzerland and the UK (see Figure 3). Emissions of ozone precursors increased by over 40% in Turkey, Finland and Liechtenstein between 1990 and 2007. In Turkey nearly half the increase in emissions was from non-road transport, with significant emissions increases also seen from energy industries and manufacturing and construction. Total emissions from Liechtenstein remained small across the period, but increases were seen in from household and services and fugitive emissions despite significant decrease from road transport emissions. Increases in emissions in Finland were primarily from road transport and manufacturing and construction.
Emissions of TOFP in terms of NMVOC Equivalent. TOFP is the Tropospheric Ozone Forming Potential of each of the air pollutants that contribute to ozone formation in the troposphere i.e. ‘ground-level’ ozone.
Emissions of TOFP in ktonnes
This indicator monitors the trend in emissions of energy-related ozone precursors. Emissions of NOx and NMVOCs are both 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). Both these instruments contain emission ceilings targets that EU Member States and other countries must meet by 2010. Emission reduction targets for the new Member States have been specified in the Treaties of Accession to the European Union (2003 and 2005 -The Treaty of Accession 2003 of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovakia and Slovenia. AA2003/ACT/Annex II/en 2072 / 2005 European Union Consolidated Versions of the Treaty on European Union and of the Treaty Establishing the European Community C 321 E/1) in order that they can comply with the National Emission Ceilings Directive. In addition, the Treaty of Accession for Bulgaria and Romania (2005 - http://ec.europa.eu/environment/air/pdf/eu27_nat_emission_ceilings_2010.pdf) also includes a new target for the EU-27 region as a whole. Targets for the new Member States are temporary and are without prejudice to the review of the NECD. A proposal for a revised NEC Directive (which will set 2020 emission ceiling targets for these ozone precursors pollutants), is expected in spring 2008. Targets for Bulgaria and Romania are provisional and not binding. Hence, the existing EU25 NECD Target has been used in the following analysis.
The NECD generally involves slightly stricter emission reduction targets than the Gothenburg Protocol. For example, during the period 1990-2010 the EU-15 has NOx emission reduction targets of 52 % and 51% under the NECD and Gothenburg Protocol respectively. For NMVOC, the EU-15 reduction required under the NECD is 55 %, under the Gothenburg reduction target the reduction required is 54 %.
In September 2005 the European Commission released a thematic strategy on air pollution. This strategy sets interim objectives for reducing air pollution impacts across Europe by 2020. Other directives influencing emissions of ozone precursors include:
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. See also CSI002
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 transmissions of air pollutants in Europe) Convention on Long-range Transboundary Air Pollution (CLRTAP), submission 2007. CO2 emissions are from officially reported national total and sectoral emissions, reported to UNFCCC and EU Monitoring Mechanism, submission 2007 (National Annual Greenhouse Gas Inventories).Recommended methodologies for emission inventory data collection are compiled in the Joint EMEP/CORINAIR Atmospheric Emission Inventory Guidebook 3rd edition EEA Copenhagen EEA (2006) and Revised 2006 IPCC Guidelines for National Greenhouse Gas Inventories IPCC (2006).
The relative impact of the combined
contribution of NOx, NMVOC, CO and CH4 to ozone formation can be
assessed based on their tropospheric ozone forming potentials (TOFP):
nitrogen oxides 1.22, non-methane volatile organic compounds 1.0, carbon
monoxide 0.11 and methane 0.014 (de Leeuw 2002).
Thus, total acid equivalent emission = w(SO2)*Em(SO2) + w(NOx)*Em(NOx) + w(NH3)*Em(NH3) where weight factors are given by:
w(SO2) = 2/64 acid eq/g = 31.25 acid eq/kg
w(NOx) = 1/46 acid eq/g = 21.74 acid eq/kg
w(NH3) = 1/17 acid eq/g = 58.82 acid eq/kg
Results are in NMVOC equivalents (kilotonnes - kt), except where
specified. These factors are assumed to be representative for Europe as a
whole; on the (very) local scale different factors might be estimated;
see de Leeuw (2002) for a more extensive discussion on the uncertainties
in these factors. Due to the variation in potential TOFP factors that
might be determined on a local scale, the use such factors does not
always have wide support or recognition in EU Member States. The energy
supply sector includes public electricity and heat production, oil
refining, production of solid fuels and fugitive emissions from fuels.
The transport sector includes emissions from road and off-road sources
(e.g. railways and vehicles used for agriculture and forestry). Industry
(energy) relates to emissions from combustion processes used in the
manufacturing industry including boilers, gas turbines and stationary
engines. ‘Other (energy-related)’ covers energy use principally in the
services and household sectors.
Base data, reported in SNAP, draft NFR or 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 following table shows the conversion of NFR sector codes into EEA sector codes (EEA, 2006):
EEA classification Non-GHGs (NFR) GHGs (CRF)
| 0 | National totals | National Total | National totals without LUCF (sector |
| 1 | Energy industries | 1A1 | 1A1 |
| 3 | Industry (Energy) | 1A2 | 1A2 |
| 2 | Fugitive emissions | 1B | 1B |
| 11 | Transport n.a. | n.a. | n.a. |
| 7 | Road transport | 1A3b | 1A3b |
| 8 | transport (non-road mobile machinery) | 1A3 (excl 1A3b) + sector mapped to 8 in table below | 1A3a, 1A3c, 1A3d, 1A3e |
| 9 | Industry (Processes) | 2 | 2 |
| 4 | Agriculture | 4 + 5B | 4 |
| 5 | Waste | 6 | 6 |
| 6 | Other (Energy) | 1A4a, 1A4b, 1A4b(i), 1A4c(i), 1A5a | 1A4+1A5 |
| 10 | Other (non-energy) | 3+7 | 3+7 |
| 14 | Unallocated | difference between NT and sum of sectors (1-12) | |
| 12 | Energy Industries (Power Production 1A1a) | 1A1a | 1A1a |
| 15 | residential | n.a. | 1A4 b |
| 16 | services, agriculture and other sectors | n.a. | 1A4a + 1A4c + 1A5 |
EEA-ETC/ACC gap-filling methodology. To allow trend analysis, where countries have not reported data for one, or several years, data has been interpolated to derive annual emissions. If the reported data is missing either at the beginning or at the end of the time series period, the emission value has been considered to equal the first (or last) reported emission value. It is recognised that the use of gap-filling 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. The gap-filled spreadsheet containing the data used in this indicator is available on the EEA dataservice website.
No methodology references available.
The individual uncertainties of the estimates for individual gases are discussed in the respective EEA Air Pollution fact sheets for these gases. The trend is likely to be much more accurate than to individual absolute annual values - the annual values are not independent of each other.NOx emission estimates in Europe are thought to have an uncertainty of about +/-30%, 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 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 NOx. 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).
Available datasets do not include full time series for all years and/or sectors. Reporting to LRTAP Convention/EMEP and UNFCCC can be inconsistent for some countries in terms of precise sector definitions, missing data etc. Incomplete reporting and resulting intra- and extrapolation may obscure some trends.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/energy-related-emissions-of-ozone-precursors-2/assessment or scan the QR code.
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