National Atmospheric Emissions Inventory

UK Emissions of Air Pollutants 1970 to 1996

J W L Goodwin A G Salway H S Eggleston T P Murrells J E Berry

January 1999

1. Introduction

The UK National Atmospheric Emission Inventory (NAEI) is compiled by the National Environmental Technology Centre on behalf of the Department of the Environment, Transport and the Regions' Air and Environmental Quality Research Programme. It is the standard reference inventory for the UK and includes emission estimates for a wide range of important pollutants including the greenhouse gases, regional pollutants leading to acid deposition and photochemical pollution, persistent organic pollutants and other toxic pollutants such as heavy metals. The full range of pollutants are summarised in Table 1.1 - go from this table to the sections detailing the findings for each pollutant.

Where possible, estimates are presented for 1970-1996. However, for some pollutants, e.g. ammonia, there is insufficient information to produce such a significant time series and estimates are presented from 1990-1996.

The NAEI provides the UK air emission data for submission to UNECE and UNFCCC. Under the Framework Convention on Climate Change, the UK is committed to developing, publishing and regularly updating national emission inventories of greenhouse gases using reporting guidelines from the Intergovernmental Panel on Climate Change (IPCC). The inventories for both direct (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride) and indirect greenhouse gases (nitrogen oxides, carbon monoxide and non-methane volatile organic compounds) are drawn from the UK NAEI emissions data included in this report. Likewise, NAEI estimates of emissions of nitrogen oxides, carbon monoxide, ammonia, sulphur dioxide, ??? persistent organic pollutants and heavy metals are submitted to UNECE. NAEI data are also provided to international emission inventory activities such as the CORINAIR, and EUROSTAT's inventories. The UK inventory team play an important role in the development of international guidelines by the European Environment Agency and the UNECE which aim to achieve a consistent set of good quality inventories for Europe. Within the UK the NAEI is a key database used to provide emissions data to UK Government, Local Authorities and private sector organisations. The 1x1km emission estimates for the UK are being used a starting point for many local emission inventories and emission factor data is fed into the UK's Emission Factor Database for Local Authorities.

1.1 Pollutants Covered by the Inventories

Pollutant   Range of Estimates Type of Pollutant*
Carbon Dioxide CO2 1970-1996 G
Methane CH4 1970-1996 G
Nitrous Oxide N2O 1990-1996 G
Nitrogen Oxides NOx (NO2 + NO) 1970-1996 NAQS, AC, IG, O
Sulphur Dioxide SO2 1970-1996 NAQS, AC, IG
Carbon Monoxide CO 1970-1996 NAQS
Non-Methane Volatile Organic Compounds NMVOC 1970-1996 NAQS, O
Black Smoke BS 1970-1996 NAQS
Particulates < 10 m m PM10 1970-1996 NAQS
Ammonia NH3 1990, 1996 AC
Hydrogen Chloride HCl 1970-1996 AC
Lead Pb 1970-1996 NAQS, TP
Cadmium Cd 1970-1996 TP
Mercury Hg 1970-1996 TP
Copper Cu 1970-1996 TP
Zinc Zn 1970-1996 TP
Nickel Ni 1970-1996 TP
Chromium Cr 1970-1996 TP
Arsenic As 1970-1996 TP
Selenium Se 1970-1996 TP
Vanadium V 1970-1996 TP
Polyaromatic Hydrocarbons PAH 1990-1996 TP
Dioxins PCDD/F 1990-1996 TP
Polychlorinated Biphenyls PCB 1990-1996 TP
Lindane (gamma-HCH) HCH 1990-1996 TP
Pentachlorophenol PCP 1990-1996 TP
Hexachlorobenzene HCB 1990-1996 TP
Hydrofluorocarbons HFC 1990-1996 G
Perfluorocarbons PFC 1990-1996 G
Sulphur Hexafluoride SF6 1990-1996 G

* G Greenhouse gas; AC Acid gas; IG Indirect greenhouse gas; NAQS National Air Quality Standard/Local Air Quality Management pollutant, TP toxic pollutant included in the heavy metals or POPs protocols, O Ozone precursor

The NAEI is compiled on an annual basis, each year the latest set of data are added to the inventory and the full time series are updated to take account of improved data and any changes in the methodology used to estimate the emissions. The new data are then reported to UNECE, UNFCCC and other international activities. This annual cycle of activity is represented schematically in Figure 1.1.

Figure 1.1 The Annual NAEI Cycle

This report presents the definitive 1996 data for the NAEI, it discusses the trends in the individual emission profiles, the accuracy of the emission estimates and in many cases the pattern of their spatial disaggregation within the UK. In addition, the report includes a detailed description of the methodology used in the compilation of the data (Appendix 1) and the recent methodological improvements that have been incorporated (Appendix 2). During 1996, particular emphasis has been placed on improving the inventories for PAHs and particulates due to the importance of these pollutants in the national air quality strategy and future international negotiations. This report is the latest in a series of annual reports on the NAEI (Eggleston, 1988; Eggleston and Munday, 1989; Munday, 1990; Leech, 1991; Gillham et al 1992; Gillham et al 1994; Salway et al 1996, 1996a, 1997). Summaries of these estimates are published annually in the Digest of Environmental Statistics (DETR, 1998) and on the internet.

Throughout the compilation of the inventory considerable effort has been made to ensure both consistency with other national statistics and that all available data sources are considered. Hence, the source data are drawn from a wide range of sources. Of particular importance is the provision by the Environmen t Agency of emissions data, since 1988, on SO2 and NOx emissions from large combustion plant, and more recently the emissions data for Part A Processes in the Chemical Release Inventory. Where point source data is unavailable, emissions are estimated from other activity data such as fuel combustion, distance travelled, production or some other statistical data related to the emissions. Estimates are calculated by applying an emission factor to an appropriate activity statistic.

That is:

      Emission = Factor × Activity

The emission factors have been derived from measurements on a number of typical sources and the resulting factor is assumed to apply to all such sources. The inventories presented here are a combination of estimated emissions and emissions measured on point sources.

For many of the pollutants, the major source of primary emissions is the combustion of fossil fuels, consequently fuel consumption statistics feature prominently in the calculation of these emission estimates. It is important to consider the difference between consumption and deliveries when making use of fuel statistics. Most readily available statistics refer to deliveries which for many source categories relate closely to actual consumption of fuel. However, where fuel can be stockpiled, deliveries and consumption may differ significantly.

Emissions from sources such as industrial processes, farm animals and motor spirit evaporation require different statistics; in these cases data on process output, population and motor spirit sales are appropriate. In other cases, where emissions are more complex, an alternative methodology is required, for example emissions from vehicles.

The following sections of the report present the NAEI emission estimates for the UK. They have been divided into five groups, reflecting the national and international activity relating to atmospheric pollution, namely greenhouse gases, National Air Quality Strategy pollutants, stratospheric ozone depletors, acidifying gases and tropospheric ozone and other toxic air pollutants. Each section includes a discussion of the importance of the pollutants concerned, presents time series emission data, and a discussion of the data trends and the accuracy of the emission estimates.