Emissions of acidifying substances

Indicator definition

• The indicator tracks trends since 1990 in anthropogenic emissions of the acidifying pollutants nitrogen oxides (NO_X) , ammonia (NH₃), and sulphur oxides (SO_X as SO₂).
• 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

ktonnes (1000 tonnes)

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 the acidifying pollutants nitrogen oxides, sulphur dioxide and ammonia that harm human health and the environment (the NEC Directive also sets emissions ceilings for a fourth pollutant - non-methane volatile organic compounds).

Other key EU legislation is targeted at reducing emissions of air pollutants from specific sources, for example:

• transport;
• industrial facilities and other stationary sources.

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. A key objective of the protocol is to regulate emissions on a regional basis within Europe and to protect eco-systems from transboundary pollution by setting emission reduction ceilings to be reached by 2010 for the same 4 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.

Targets

Emissions of SO₂, NO_X and NH₃ 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 Member States for 2010.

Table: 2010 Targets under the NEC Directive and the Gothenburg Protocol, in kt

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

Related policy documents

• 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.
• UNECE Convention on Long-range Transboundary Air Pollution
  UNECE Convention on Long-range Transboundary Air Pollution.

Methodology

Methodology for indicator calculation

This indicator is based on officially reported national total and sectoral emissions to EEA and 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 ETC/ACC 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 metal production;
• 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 & 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:

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 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

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 are not yet complete and are 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.

Uncertainties

Methodology uncertainty

The use of gap-filling for 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 emission estimates in Europe are thought to have an uncertainty of about ±20% (EMEP, 2010), 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.

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

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

SO_X emission estimates in Europe are thought to have an uncertainty of about +/-10% as the sulphur comes from the fuel burnt and therefore can be accurately estimated. However, because of the need for interpolation to account for missing data, the complete dataset used will have higher uncertainty. EMEP has compared modelled and measured concentrations throughout Europe (EMEP 2010). From these studies, differences in the annual averages have been estimated to be +/-30%, which is consistent with an inventory uncertainty of +/-10% (there are also uncertainties in the measurements and especially the modelling). The trend is likely to be much more accurate than individual absolute values

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

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

NH₃ emission estimates in Europe are more uncertain than those for NO_X, SO_X and NMVOCs due largely to the diverse nature of major agricultural sources. It is estimated that they are around +/- 30% (EMEP, 2009). 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 EEA and is used in state of the environment assessments. The uncertainties related to methodology and data sets are therefore of importance.