What is an Emission Inventory?

Roles of an emission inventory
Given the current rapid rate of economic development in East Asia and the degradation of air
quality in the future likely to result from this, it becomes necessary to make use of all thescientific tools available for the management of the atmospheric environment. One of thesetools is the air pollutant emission inventory.
What quantities of air pollutants are emitted and where do they come from? The best way toanswer these questions is to prepare an air pollutant emission inventory. Emission inventories
are now regarded as indispensable tools for a wide range of environmental measures such as
management of chemicals as well as the prevention of air pollution.

Fig. 1 Roles of the emission inventory for air quality management
An emission inventory can be utilized for the following purposes.

◎ Quantitative understanding of actual emissions
The quantitative emissions estimates provided by an inventory promote a better understanding of the actualemissions and help to raise the awareness of both policy makers and the general public. Through this process, themajor emission sources can be identified, priorities for emission reduction defined and any data gaps requiring
further work are revealed.

02

What is anEmission Inventory?

Fig. 2 Examples of application of an emission inventory◎ Use for modeling activity
Emissions data allocated geographically and temporally can be used as input data for atmospheric transport anddeposition models. The resulting air concentration and deposition estimates obtained by modeling, after verification
with monitoring data on the ground and/or data from satellite observations, will be important information for air
quality management decision-making. Further useful information can be provided by estimates of the likely adverse
impacts (to humans, animals, crops and natural ecosystems), which may be assessed from the modeled depositionand concentration of pollutants.

◎ Use for future projections and setting of targets
A current emission inventory can be used as the basis for estimating future emissions according to projected
likely changes in socio-economic indices (e.g. population growth, economic growth, changes in energy use per unit
activity), lower emission factors (e.g. by introduction of better control measures), fuel switching and so forth.
Estimated future emissions provide important information for setting emissions targets.

◎ Use for the consideration of possible reduction measures
An emission inventory enables the likely effects of introducing various prevention and control measures withindifferent source sectors to be assessed and compared, both now and in the future. Combined with knowledge ofcosts of the different options, this also enables the most cost-effective emission reduction measures to be identified.

◎ Use for planning of policy and measures and their follow-up
Emission inventory data can be regarded as an index similar to the various indices used for gauging changes in
economic activity. The trend of such an index allows us to judge whether we should introduce or reinforce
regulations, economic measures or technical measures to control air pollutant emissions.

◎ Cooperation in preparing inventories in East Asia
Analyses based on emission inventories and atmospheric transport modeling are crucial when dealing with longrange transport of air pollutants. Such analyses would be made easier and more fruitful if the methodologies usedwere harmonized across all countries in a region. Cooperation in preparing inventories also could promote capacity
building in the measurement of emissions, developing emission factors and on the use of inventories and models.
The resulting increased capacity will contribute to the development of pollution control strategies in each country
leading to a reduction in transboundary air pollution.

What is anEmission Inventory?

03

Emission sources of air pollutants in inventories
The emission sources of air pollutants are divided into anthropogenic (human-made) andnatural sources.

Anthropogenic sources

Natural sources
OceanEnergy○Power plants○Vehicles,ship,airplanes etc.
○Commercial / Instituional○Residential

Industrial process

Forest fire○Industrial boilers

Lightning
Volcanic activities

etc.

AgricultureWaste etc.

Examples of air pollutants considered in inventories: SO2, NOx, VOCs, NH3, CO, BC, OC, PM10, Hg, etc.

Fig. 3 Conceptual scheme showing emission sources of air pollutants

Burning of fossil fuels is often the most important emission source. On the other hand, in Asia
sources such as the domestic use of biomass fuel and incineration of agricultural residues arealso very important. Emissions from vehicles are also increasingly important since vehicle use
is growing rapidly in most Asian countries.

04

What is anEmission Inventory?

Method for developing inventories
In general, anthropogenic emissions of air pollutants are estimated by the following basic
formula for each source, when it is difficult to measure it directly.

Emission = Emission Factor x Activity Data
Examples:・SOx emission per the amount of fuel burnt, calculated based on thesulfur content of fuel, the sulfur retained in the ash and the reduction
achieved by emission control technology (fuel combustion)

・NOx emission per distance (exhaust gas emissions from vehicles)・SOx emission per the amount of copper smelted (copper smelting)・the amount of fuel burnt (fuel combustion)・the distance of vehicle travelled (exhaust gas
emissions from vehicles)
・the rates of the production of the commodity(industrial process without combustion)◎ Emission factors
Emission factors are the average rate of emission of a pollutant per unit of activity data for a given sector.
When there is no emission factor reflecting the actual local situation, default values in manuals are used.
However, if the default factor is considered to be inappropriate, it is preferable to obtain an emission factor thatreflects the real situation by direct measurement.
The rates of reduction and propagation of technical measures have to be reflected in the factor or the formula,because introduction of countermeasures reduces the emission.

◎ Activity Data
Activity data give a measure of the scale of activity causing the emissions.
The necessary data basically can be collected from statistics and surveys

Inventory Manuals
EMEP/CORINAIR
Atmospheric Emission Inventory
Guidebook

This manual provides suggested methods for estimating emissions of air pollutants such as
SO2, NOx, NMVOC, CH4, NH3 and CO. It is applied for reporting the national inventory
under the Convention on Long-range Transboundary Air Pollution (CLRTAP).

IPCC（Intergovernmental Panel on
Climate Change）
Guidelines

This manual provides suggested methods for estimating emissions of the 6 direct
greenhouse gases (CO2, CH4, N2O, HFCs, PFCs, SF6) as well as the precursors, NOx, CO,
NMVOC and SO2. It is applied for reporting national inventories under the UNFCCC andKyoto Protocol.

UNDP/UN DESA
ManualThis manual has been prepared by the Stockholm Environment Institute under a UNDP
and UN DESA project for transboundary air pollution for Northeast Asia. The types of air
pollutant emissions covered are SOx, NOx, NMVOCs, CO, NH3, PM10 and PM2.5.

The Global Atmospheric
Pollution Forum Air
Pollutant Emissions
Inventory Manual

The Forum manual was based on a similar manual being applied within theMaleDeclaration
countries of South Asia which, in turn, grew out of the above´
UNDP/UN DESA manual. The Forum manual also covers emissions of SOx, NOx,NMVOCs, CO, NH3, PM10 and PM2.5 and is suitable for use by developing countries
in any region of the world. An Excel-based workbook accompanies this manual.

What is anEmission Inventory?

05

Reporting of inventories
For instance, under the Convention on Long-range Transboundary Air Pollution, reporting ofemissions is implemented based on the emission reporting guidelines as shown below.

Principles○National emission inventories should be transparent, consistent, comparable, complete and accurate. (3)○Emission estimates should be prepared using the applicable methodologies agreed upon. (4)○Each Party must report on emissions for the base year and every year starting with the year of entry into force. (9)Scope○Parties should report projected activity data and projected national total emissions for the years 2010, 2015 and 2020. (10)○Parties should use the Guidebook to estimate emissions. (11)○It is preferable that each Party should use its own national emission factors. (13)Methods○The Task Force regularly updates the Guidebook. (14)○Where the methodology has changed, each Party should recalculate all inventory data to ensure consistency of the time series. (15)○For every fifth year, each Party should report total and sectoral emissions for the EMEP grid squares. (22)○For the year 2000 and every fifth year, Parties should provide the data on large point sources (type of source, latitude, longitude,Reporting

emission quantities and effective chimney height). (23)○Each Party should use the reporting format and submit the information preferably in electronic form. (34)○Parties are encouraged to submit an informative inventory report. (38)○Each Party should publish their emission data and inventory reports. (39)

Numbers in parentheses indicate the paragraph numbers.
Source: United Nations / Economic Commission for Europe (2003), Emission Reporting Guidelines

Emission inventories in Asia and the WorldRAINS・GAINSACESSThis database is developed by International Institute forApplied System Analysis (IIASA) to estimate emission ofair pollutants including greenhouse gases.

ACESS is developed by Argonne National Laboratory tosupport the Aerosol Characterization Experiments andTransport and Chemical evolution over the Pacific

EDGAR

Experiments.

EDGAR database is developed by National Institute for
Public Health and the Environment (RIVM) to estimate
emission of air pollutants and greenhouse gases.

GEIA
As part of International Geosphere - Biosphere
Programme (IGBP), GEIA has been developing
inventories of global gas and aerosol emissions.

LTP
LTP is a joint research program among China, Japanand Korea. Its purpose is the monitoring/modeling of Air
pollutants to improve understanding of transboundary air
pollutants in Northeast Asia.

06

What is anEmission Inventory?

REAS
REAS is developed by Frontier Research Center for
Global Change and National Institute for Environmental
Studies to understand the role of trace constituents in theatmosphere.

EA-Grid
EA-Grid is developed by the Ministry of theEnvironment in Japan to understand transboundary air
pollutants in Northeast Asia.

Although some countries in East Asia has prepared inventories, the detailed information they
contain is difficult to share in the region because 1) they are prepared only for a domestic use , 2)
the tasks are divided among different departments such as domestic affairs, international
cooperation, and human health-related departments and 3) there is no reporting system for suchinventories.

Substances targeted by inventories

ChinaJapan
R.of Korea

Main characteristics of inventories

What is anEmission Inventory?

07Conclusion
In Europe and North America, a methodology for preparing emission inventories of air pollutants
has been developed within the framework of the Convention on Long-range Transboundary Air
Pollution (CLRTAP). This methodology has also been used by many counties to compile theirgreenhouse gas emission inventories. Discussions on the hemispheric transport of air pollutants arealso starting to include the application of emission inventories and atmospheric transport models.
In East Asia, governments and researchers have prepared several emission inventories including
global ones. However, a harmonized system to compile inventories that are transparent andcomparable enough to be agreed among East Asian countries has not yet been established.
In order to deepen an understanding of the state of regional air pollution in East Asia and develop
capabilities of the countries on atmospheric environmental management, it will be necessary toestablish such a system in which inventories can be improved continuously in cooperation withadministrative agencies and inventory experts in East Asia.
Experience elsewhere has demonstrated the importance of cooperation for enhancing capacity inthe preparation of inventories within all countries of a region.
Understanding and awareness about the urgent need for good quality emission inventories alsoneed to be promoted in East Asia. It is intended that this pamphlet will assist in this process.

Web sites of relevant manuals and inventories◎Ministry of the Environment of Japan◎Cooperation: Acid Deposition and Oxidant Research Center (ADORC)
Mitsubishi-UFJ Research & Consulting
Tomoyuki Aizawa, National Institute for Environmental Studies (NIES)
Hajime Akimoto, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
Toshimasa Ohara, National Institute for Environmental Studies (NIES)
Akiyoshi Kannari, Independent Rseacher
Kiyoto Tanabe, Institute for Global Environmental Strategies (IGES)
Hideaki Nakane, National Institute for Environmental Studies (NIES)
Toshihiko Masui, National Institute for Environmental Studies (NIES)
Harry Vallack, Stockholm Environment Institute (SEI)
Printed on 100 percent recycled paper.

08

What is an

Printed by Prime Station Corp in March 2007

Emission Inventory?