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The basic model for an
emission estimate is the product of (at least) two variables, for example:
·
An activity statistic
and a typical average emission factor
for the activity, or
·
An emission
measurement over a period of time and the number of such periods emissions
occurred in the required estimation period.
For example, to
estimate annual emissions of sulphur dioxide in tonnes per year from a power
plant oil-powered you should use, either:
·
Annual fuel
consumption (in tonnes fuel/year) and an emission factor (in tonnes SO2
emitted/tonne fuel consumed), or
·
Measured SO2
emissions (in grams per hour) and number of operating hours per year.
Another example is the
estimation of e.g. NOx emissions from vehicles in a
city. The basic emission factor here is the NOx
amount emitted per km driven, which is then multiplied by average driving
distance per year, for the vehicles in a city/country, and the number of
registered/counted vehicles.
In practice, the
calculations tend to be more complicated but the principles remain the same.
Emission estimates are
collected together into inventories or databases which usually also contain
supporting data on, for example: the locations of the sources of emissions;
emission measurements where available; emission factors; capacity, production
or activity rates in the various source sectors; operating conditions; methods
of measurement or estimation, etc.
Emission inventories
usually contain data on three categories of sources, namely point, area and
line. This separation is important, for instance since these source categories
are treated differently in dispersion models. The inventories should also
contain geographical information so that emissions can be separated on area
basis – e.g. region, country, province, urban air shed, city, department,
neighbourhood, etc.
Point sources - emission estimates are provided on an individual plant
or emission outlet (usually large), usually in conjunction with data on
location, capacity or throughput, operating conditions etc.
Area sources - smaller or more diffuse sources of pollution are
provided on an area basis either for administrative areas, such as counties,
regions etc, or for regular grids (for example the EMEP 50x50 km grid). Such
sources are e.g. indoor heating (offices, domestic), small-scale fuel
consumption for various activities/workshops etc., fuel
consumption for road traffic which is not accounted for by the traffic count
data which are usually available just for the main road network.
Line sources - in some inventories, vehicle emissions from road
transport are provided for sections along the road system in a city or a
country, based upon traffic data, and vehicle and technology type data. In
country-wise inventories, also railway-track, rivers and sea-lane could be
considered as line sources.
Emission inventories
usually provide:
·
The distribution of
emissions in relation to relevant technologies and socio-economic sectors;
·
The spatial
distribution of emissions and
·
Trends in emissions
over time.
When looking at
pollutant dispersion and air quality modelling in urban areas it is necessary
to have an accurate and high quality description of the emission sources in
terms of quantity and dynamic behaviour (especially on traffic sources). This
requires an emission inventory with a high resolution in space and time. For
example, in traffic and mobility planning in urban areas, the emission
inventory must be set up by a coherent and detailed description, at least, of
the road traffic distribution (see the Topics The role and prerequisites for Transport Emission Models in Urban Planning and Transport emission models at regional scale.).
Suggested background
and descriptive sources
Useful and informative
descriptive texts regarding emission inventories and their compilation are
provided by the following references:
·
By Rainer Friedrich
and Uwe-Bernd Schwarz, in Urban Air Pollution –
European Aspects, Chapter 6: Emission Inventories (Kluwer
Academic Publishers, Dordrecht, 1998, edited by Jes Fenger, Ole Hertel and Finn Palmgren)
·
By Peter J. Sturm, in Air
Quality in Cities (Final Report of the Eurotrac-2 Saturn Subproject),
Chapter 3: Air Pollutant Emissions in Cities:
http://aix.meng.auth.gr/saturn/finalreport/index.html
The EUROTRAC-2
Subproject GENEMIS, as well as the EU project IMPRESAREO (links provided in the
Additional Documents/web links section below) are useful references for
guidance on urban emission inventory work. The IMPRESAREO project looked
especially on using earth observations as a data source for improving urban
emissions inventories.
At EU level the most
important methodology to build an Emission Inventory is the CORINAIR
methodology. Council Decision 85/338/EEC (OJ, 1985) established a work
programme concerning an "experimental project for gathering, co-ordinating
and ensuring the consistency of information on the state of the environment and
natural resources in the Community". The work programme was given the name
CORINE - CO-oRdination d'INformation
Environnementale and included a project to
gather and organise information on emissions into the air relevant to acid
deposition - CORINAIR. This project started in 1986 with the objective of
compiling a co-ordinated inventory of atmospheric emissions from the 12 Member
States of the Community in 1985 (CORINAIR 1985).
CORINAIR uses a source
sector nomenclature:
·
NAPSEA, Nomenclature
for Air Pollution Socio-Economic Activity and
·
SNAP, Selected
Nomenclature for Air Pollution - for emission source sectors, sub-sectors and
activities.
To calculate emissions
from road transport, the COPERT III (Computer programme to calculate emissions
from road transport) has been implemented. The development of COPERT III was
financed by the European Environment Agency, in the framework of the activities
of the European Topic Centre on Air Emissions. It has been proposed to EEA
member countries for the compilation of CORINAIR emission inventories.
Links are provided below. |