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Energy-related emissions of ozone precursors (ENER 005) - Assessment published Aug 2011

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Generic metadata


Energy Energy (Primary topic)

Air pollution Air pollution

energy | emissions | ozone precursors
DPSIR: Pressure
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • ENER 005
Temporal coverage:
Geographic coverage:
Austria Belgium Bulgaria Cyprus Czech Republic Denmark Estonia Finland France Germany Greece Hungary Iceland Ireland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands Norway Poland Portugal Romania Slovakia Slovenia Spain Sweden Switzerland Turkey United Kingdom

Key policy question: Are energy-related emissions of ozone precursors decreasing?

Key messages

Energy-related emissions accounted for 87% of all Carbon Monoxide (CO) emissions, 44% of all Non-Methane Volatile Organic Compounds (NMVOC) emissions, 95% of all Nitrogen Oxide (NOx) emissions and 48% of all Methane (CH4) emissions from the EEA-32 in 2008. Energy related emissions of these pollutants in the EEA-32 fell by 4%, 3%, 5% and 1% respectively between 2007 and 2008, and since 1990, these emissions have declined by 53%, 59%, 30% and 44% 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 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, meet their limit values under Directive 2008/50/EC on ambient air quality and cleaner air for Europe and the Air Quality Framework Directive and its daughter directives.

Changes (%) in emissions of ozone precursors by source category, 1990-2008, EEA-32

Note: The figure shows the emissions methane CH4; carbon monoxide CO; non-methane volatile organic compounds NMVOCs; and nitrogen oxides NOx.

Data source:
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Contribution of different sectors (energy and non-energy) to total emissions of tropospheric ozone precursors, 2008, EEA-32

Note: The figure shows the emission of NOx, NMVOC, CO and CH4 in 2008

Data source:
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Key assessment

In the EEA-32, energy related emissions of pollutants contributing to tropospheric ozone formation have decreased by 53% (CO), 59% (NMVOC), 30% (NOX) and 44% (CH4) in EEA member countries between 1990 and 2008 (and by 55% (CO), 63% (NMVOC), 35% (NOX) and 46% (CH4) in the EU). All sources except international bunkers have decreased (see Figure 1). Energy-related emissions comprise the majority of Tropospheric Ozone Formation Precursors (TOFP) related emissions and accounted for 87% of all CO emissions, 44% of all NMVOC emissions, 95% of all NOX emissions and 48% of all CH4 emissions from the EEA-32 in 2008.

The road transport sector is the dominant source of NOX and CO and contributed 39% and 34% of total emissions in 2008 (see Figure 2) in the EEA countries. Road transport has decreased the most in absolute terms with a 73% (CO), 78% (NMVOC) and 40% (NOX) reduction seen in the EU-27 from 1990 to 2008 (see Figure 1). Decreases in emissions from the transport sector have occurred largely due to the continued introduction of catalytic converters, in line with Euro standard emission control legislation, which reduce emissions of CO and NOX.

Energy industries are a significant source of pollutants contributing to tropospheric ozone formation; accounting for 20% of NOX emissions (see Figure 2). This sector has reduced its emissions by over 13% (CO), 13% (NMVOC), 39% (NOX) and 38% of CH4 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 in the transport sector (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 in all electricity production and consumption sectors.

Concerning progress in individual countries, emissions of pollutants contributing to tropospheric ozone formation have decreased significantly in most EEA member countries; with the highest reductions reported by Malta (CO), Germany (NMVOC) and Czech Republic (NOX) and United Kingdom (CH4) (see Figure 3). Emissions of NOX increased by over 102% in Turkey.  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 the household sector across all pollutants and fugitive emissions despite significant decrease from road transport emissions. Emissions of CO and NMVOC in Romania have increased since 1990, due chiefly to sources categorised under the ‘Other (Energy)’ sector.

Emissions of NOx are responsible for much of the ozone formation occurring in rural areas. In more densely populated regions, in particular close to cities, ozone formation is enhanced by NMVOC emissions. NMVOCs are mainly released from road traffic and the use of products containing organic solvents. NOx and CO are mostly emitted from transport and combustion processes. After release, these precursors are dispersed by wind and atmospheric turbulence. The freshly emitted pollutants mix with other pollutants, including ozone, present in background air, and a complicated process of chemical reactions and continuous dilution takes place.[1]

[1] Tropospheric Ozone in EU - The consolidated report, Topic report No 8/1998

Data sources

More information about this indicator

See this indicator specification for more details.

Contacts and ownership

EEA Contact Info

Anca-Diana Barbu


EEA Management Plan

2010 2.8.1 (note: EEA internal system)



European Environment Agency (EEA)
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1050 Copenhagen K
Phone: +45 3336 7100