Chapter 4: Methodological Choice and Identification of Key Categories

CHAPTER 4

METHODOLOGICAL CHOICE AND
IDENTIFICATION OF KEY
CATEGORIES2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

4.1

Volume 1: General Guidance and Reporting

Authors
Justin Goodwin (UK)
Newton Paciornik (Brazil), Michael Gillenwater (USA)Contributing Author
Timo Kareinen (Finland)

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Chapter 4: Methodological Choice and Identification of Key Categories

Contents
4

Methodological Choice and Identification of Key Categories ...................................................................... 4.5
4.1

Introduction ............................................................................................................................................ 4.5

4.1.1

Definition ........................................................................................................................................ 4.5

4.1.2

Purpose of the key category analysis .............................................................................................. 4.5

4.1.3

General approach to identify key categories ................................................................................... 4.7

4.2

General rules for identification of key categories .................................................................................. 4.7

4.3

Methodological approaches to identify key categories ........................................................................ 4.16

4.3.1

Approach 1 to identify key categories ........................................................................................... 4.16

4.3.2

Approach 2 to identify key categories ........................................................................................... 4.20

4.3.3

Qualitative criteria to identify key categories ............................................................................... 4.20

4.4

Reporting and Documentation ............................................................................................................. 4.20

4.5

Examples of key category analysis ...................................................................................................... 4.21

References………………………………………………………………………………………………………4.32

Equations
Equation 4.1 (Updated)

Level Assessment (Approach 1) .............................................................................. 4.16

Equation 4.2 (Updated)

Trend Assessment (Approach 1) .............................................................................. 4.18

FiguresFigure 4.1

Decision Tree to choose a Good Practice method...................................................... 4.6

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TablesTable 4.1 (Updated)

Suggested aggregation level of analysis for Approach 1 ............................................... 4.9

Table 4.2 (Updated)

Spreadsheet for the Approach 1 analysis – Level Assessment ..................................... 4.17

Table 4.3 (Updated)

Spreadsheet for the Approach 1 analysis – Trend Assessment .................................... 4.18

Table 4.4 (Updated)

Summary of key category analysis ............................................................................... 4.21

Table 4.4a (New)Key categories ranks .................................................................................................... 4.21

Table 4.5 (Updated)

Example of Approach 1 Level Assessment for Finland’s GHG Inventory for 2016 .... 4.22

Table 4.6 (Updated)

Example of Approach 1 Trend Assessment for Finland's GHG inventory for 2016 .... 4.24

Table 4.9 (Updated)

Example of Approach 2 Level Assessment for Finland’s GHG Inventory for 2016 .... 4.27

Table 4.10 (Updated) Example of Approach 2 Trend Assessment for Finland’s GHG Inventory for 2016 ... 4.28
Table 4.11 (Updated) Example of Summary of Key Category Analysis for Finland's GHG inventoryfor 2016 ........................................................................................................................ 4.30

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Chapter 4: Methodological Choice and Identification of Key Categories

4 METHODOLOGICAL CHOICE AND
IDENTIFICATION OF KEY CATEGORIES
Users are expected to go to Mapping Tables in Annex 1, before reading this chapter. This is required to correctly
understand both the refinements made and how the elements in this chapter relate to the corresponding chapter
in the 2006 IPCC Guidelines.

4.1

INTRODUCTION

This chapter addresses how to decide on methods to apply and in using key category analysis 1 to inform this choice.
Methodological choice for individual source and sink categories is important in managing and where possible
reducing the overall inventory uncertainty. Generally, inventory uncertainty is lower when emissions and removals
are estimated using the most rigorous methods provided for each category or subcategory in the sectoral volumesof the 2006 IPCC Guidelines and its 2019 Refinement. However, these methods generally require more extensive
resources for data collection, so it may not be feasible to use more rigorous method for every category of emissions
and removals. It is therefore good practice to identify those categories that have the greatest contribution to overall
inventory uncertainty in order to make the most efficient use of available resources. It is also important to identify
categories that contribute significantly to the national totals to ensure that they are compiled accurately and thatthe data needed to update their estimates is sufficiently maintained. It is good practice for each country to identify
its national key categories in a systematic and objective manner. By identifying these key categories in the national
inventory, inventory compilers can prioritise their efforts and improve their overall estimates.

4.1.1

Definition

Key categories are inventory categories which individually, or as a group of categories (for which a common
method, emission factor and activity data are applied) are prioritised within the national inventory system because
their estimates have a significant influence on a country’s total inventory of greenhouse gases in terms of theabsolute level, the trend, or the level of uncertainty in emissions or removals. Whenever the term key category isused, it includes both source and sink categories.

4.1.2

Purpose of the key category analysis

Within the National Inventory Arrangements (see Section 1.4a of Chapter 1, Volume 1), application of a key
category analysis will help identifying the priority categories for which methods, activity data, emission factors
and other parameters should be considered for regular update, more rigorously checked and reviewed and, where
necessary or possible, improved as elaborated below:•

Regular update: Making sure the methods, data flows and country-specific emission factors are kept up todate and available for important regular estimate updates.

•

More focussed checking and review: Making sure that specific quality assurance and quality control(QA/QC) activities are implemented for key categories. It is good practice to give additional attention to key
categories with respect to QA/QC as described in Chapter 6, Quality Assurance/Quality Control andVerification, and in the sectoral volumes.

•

Improvement: Improving accuracy of estimates and reducing overall uncertainty using higher tiered (moreaccurate) methods. In general, more detailed higher tier methods should be selected for key categories.
Inventory compilers should use the category-specific methods presented in sectoral decision trees in Volumes
2-5. For most sources/sinks, higher tier (Tier 2 and 3) methods are suggested for key categories, although thisis not always the case. For guidance on the specific application of this principle to key categories, it is goodpractice to refer to the decision trees and sector-specific guidance for the respective category and additional
good practice guidance in chapters in sectoral volumes. In some cases, inventory compilers may be unable toadopt a higher tier method due to lack of resources. This may mean that they are unable to collect the required
data for a higher tier or are unable to determine country specific emission factors and other data needed forTier 2 and 3 methods. In these cases, although this is not accommodated in the category-specific decision trees,a Tier 1 approach can be used, and this possibility is identified in Figure 4.1. It should in these cases be clearly

1 In Good Practice Guidance for National Greenhouse Gas Inventories (GPG2000, IPCC, 2000), the concept was named ‘key

source categories’ and dealt with the inventory excluding the LULUCF Sector.

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documented why the methodological choice was not in line with the sectoral decision tree. Any key categories
where the good practice method cannot be used should have priority for future improvements.
It is good practice for each country to identify and communicate its national key categories in a systematic andobjective manner as presented in this chapter. Such a process will help countries to prioritise available resourcesfor (key) category methods, data sources and assumptions and will lead to improved inventory quality, as well as
greater confidence in the estimates that are developed.
Figure 4.1 Decision Tree to choose a Good Practice methodStart

Is thesource or sink category
considered as key
category?

No

Choose a method presented
in Volumes 2-5 appropriate
to available data.
Box 1

Yes

Are the data
available to follow
category-specific good practiceguidance for the key
categories?

Yes

Estimate emissions or
removals following guidance
for key categories presented
in the decision trees in the
sectoral Volumes 2-5.
Box 2

No

Can data
be collected without
significantly jeopardizing theresources for other key
categories?

Yes

No

Make arrangements tocollect data.

Choose a method presented
in Volumes 2-5 appropriate toavailable data, and document
why category-specificguidance cannot be followed.
Box 3

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Chapter 4: Methodological Choice and Identification of Key Categories

4.1.3

General approach to identify key categories

Key category analysis should be applied in all circumstances of inventory compilation no matter how simple orbasic the inventory is. A category can be identified as a key for different reasons. These include:•

Level: Their absolute level of emissions/removals for a particular year of interest.

•

Trend: Their change across a time series. Particularly important for categories that are showing increasing or
decreasing emissions or removal trends across a time series.

•

Uncertainty: If a category’s contribution to the GHG inventory total or trend uncertainty is high for relevant
years or year spans, then the category should be identified as key.

•

In addition to making a quantitative determination of key categories, it is good practice to consider thequalitative criteria for identifying categories that are likely to need prioritised attention (e.g. expectedsignificant trends, categories not estimated or with suspected high uncertainty) as described in more detail in
Section 4.3.3.

Section 4.3 presents the detailed methodology for the above cases of key category analysis under two approaches.
Approach 1 where key category analysis is done without incorporating uncertainties and approach 2 where
information on uncertainties is included.
As explained in Section 4.1.2 above, the main objective of key category analysis is to identify and prioritise key
categories within the inventory management system. Therefore, it is helpful to consolidate the different analysisof the level and trend into a single summary list of key categories. This makes engagement with key stakeholders
easier and communication of the key categories priorities possible.
Guidance on reporting and documentation of the key category analysis is provided in Section 4.4. Section 4.5 gives
examples for key category identification.

4.2

GENERAL RULES FOR IDENTIFICATION OF
KEY CATEGORIESThe following guidance describes good practice in determining the appropriate level of disaggregation of GHG
estimates to identify key categories, additional to those presented in the 2006 IPCC Guidelines. The results of the
key category analysis will be most useful for prioritising data gathering and estimation activities if the analysis isdone at a level of aggregation aligned with countries' use of methods, data sources and assumptions.
Disaggregation to very low levels of subcategories that are all covered by a single method and use of emission
factor should be avoided since it will split an important aggregated category into many small subcategories that
may be no longer considered as key. Countries should establish their own aggregations or disaggregation of
categories accordingly and considering the guidance provided below. Countries using Approach 2 will need toalign the level of aggregation with that used for the uncertainty analysis. This will be facilitated by an approach
which is aggregated/disaggregated based on methodology and in particular uncertainties. The following principles
can be followed in designing the analysis and in choosing the level of aggregation or disaggregation for key
categories:•

IPCC categories: All relevant sectors and categories that contribute to the GHG inventory totals should be
included in the key category analysis. Countries should also consider the relative importance of memo items
such as international transportation and biomass burning to ensure that the calculations for these items areadequately addressed when designing improvement activities. The analysis should be performed at the levelof categories or subcategories at which the IPCC methods are applied in the inventory. Over time, as estimates
are updated/refined and higher tier approaches applied to categories and/or subcategories, the aggregationsfor key category analysis may change. Countries can consider the disaggregation of categories andsubcategories by fuel or other relevant activity differentiators (e.g. livestock/management types etc.) where
activity data, assumptions and/or emission factors are from different sources and/or uncertainties are likely to
be significantly different. For Approach 2, possible cross-correlations between categories and/or subcategories
should be taken into account when considering category aggregation 2 . When using Approach 2, theassumptions about such correlations should be the same when assessing uncertainties and identifying key
categories (see Chapter 3, Uncertainties).

2 In practice, the effect of correlations for key category analysis should be taken into account in the disaggregation level used

for the Approach 2 assessment (for more advice on correlations in uncertainty analysis, see Chapter 3).

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Regional disaggregation: Countries may want to subdivide by region in exceptional cases where regional
differences in methods applied are significant. Where this is needed, a regional tag can be added to the IPCC
category group column (see Tables 4.2 and 4.3).

•

Individual gas level: All direct GHGs should be included in the key category analysis. Generally, eachgreenhouse gas emitted from each category should be considered separately, unless the same method, data
sources and assumptions are applied and uncertainties are similar across gases or linked. For example, carbon
dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from road transport using a Tier 1 default methodology
would all be treated separately due to the different levels of uncertainty in the default EFs. However, where a
Tier 2 method is applied to estimate emissions for CH4 and N2O using country-specific measurement data theCO2 equivalent 3 estimates for CH4 and N2O could be aggregated in the key category analysis. This aggregation
helps to promote the importance of the combined impacts of CH4 and N2O with the new Tier 2 methodology.
In cases where a common model and assumptions are applied for analysis of all chemical species ofhydrofluorocarbons (HFCs) from refrigeration or air conditioning, these gases could be aggregated as HFC
CO2 equivalent emissions. If precursor gases for CO2 (e.g. CO and Non-methane volatile organic compound(NMVOC)) are included in the national totals as CO2 equivalent emissions they should also be included in the
KCA as with any other gas. Precursor gases that cannot be converted to CO2 equivalent emissions cannot be
included in the quantitative key category analysis but could be included in the qualitative analysis. It is notpossible to include gases, which cannot be converted to CO2 equivalent since the analysis is performed using
CO2 equivalent emissions.

•

Emissions and removals: If data are available, the key category analysis should be performed for emissions
and removals separately within a given category or for different pools. For example, the land use categories
and the pool estimates can include emissions and removals that may cancel or almost cancel at the aggregatedlevel for the category resulting in an aggregated net estimate that does not qualify as a key category despite
the components (emissions and removals separately) being significant. This separation of emissions andremovals is also important where methods, data sources and assumptions are different for estimating emissions
and removals for a category or for different pools. Similar considerations may apply in the Energy and IPPU
(Industrial Processes and Product Use) Sectors, for example, in a situation where CO2 is being captured forstorage.

•

Indirect N2O emissions from deposition of NOx and other nitrogen compounds from categories other thanAgriculture, Forestry and Other Land Use (AFOLU) Sector are included in the key category analysis in
category 5A, Indirect N2O emissions from the atmospheric deposition of nitrogen in NOx and NH3.

Once the level of aggregation has been resolved, the inventory compiler should determine if certain components(e.g. subcategories/gases/pools/sinks/sources) are particularly significant and should be further disaggregated, if
appropriate. Usually, for this purpose, the components can be ranked according to their contribution to theaggregate key category. As a general rule, those subcategories that contribute together more than 60 percent to the
key category should be treated as particularly significant and possibly disaggregated from the category where they
were included. For those categories where subcategories need to be identified, it is clearly mentioned in theappropriate decision trees in Volumes 2-5. Table 4.1 provides suggested aggregation levels with subdivisions that
relate to methods, data sources and assumptions based on guidance in the sectoral volumes.

3 The methodology is also applicable for other weighting scheme, but for the derivation of threshold for Approach 1 and 2 CO2equivalent values were calculated using the global warming potentials (GWP) over a 100-year horizon of the different
greenhouse gases, provided by the IPCC in its Second Assessment Report (SAR). For the examples in Section 4.5, CO2
equivalent values were calculated using the GWPs provided by the IPCC in its Fourth Assessment Report.

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.1 (UPDATED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1A
Source and Sink Categories to be assessed in Key
Category Analysis
Category Codes b

Category Names b

Gases to beassessed
separately cCategory aggregation/disaggregationconsiderations 4

CO2, CH4, N2O

These categories should be disaggregatedaccording to methods, data sources,
assumptions applied and known or likely
differences in uncertainty. Estimatescompiled from a common set of activity
data and emission factors (e.g. energybalances and default or average country
specific emission factors) with similar
uncertainties can be aggregated. Common
reasons for disaggregation can include
differences in uncertainty for estimates ofemissions for different fuels(disaggregation by main fuel type) or theapplication of Tier 2 or 3 methods for
categories or sub-categories.

CO2, CH4, N2O

Disaggregation could be considered wheredata for different fuels is sourced fromdifferent data providers and different
methods are used for small and major
airports.

Energy1A1 & 1A2

Energy and Manufacturing Industry
Fuel Combustion Activities

1A3a

Fuel Combustion Activities Transport - Civil Aviation

1A3b

Fuel Combustion Activities Transport - Road transportation

1A3c

1A3d

CO2, CH4, N2O

Disaggregate by fuel if fuel data issourced from different data providers andlikely to have different levels of accuracy.

CO2, CH4, N2O

Disaggregation could be considered wheredata (e.g. on fuels) is sourced fromdifferent data providers and different
methods are used for different types oftransport.

CO2, CH4, N2O

Disaggregation could be considered wheredata (e.g. on fuels) is sourced fromdifferent data providers and different
methods are used for different types oftransport.

CO2, CH4, N2O

Disaggregation could be considered wheredata (e.g. on fuels) is sourced fromdifferent data providers and different
methods are used for different types oftransport.

Fuel Combustion Activities Transport - Railways

Fuel Combustion Activities Transport - Water-borne Navigation

1A3e

Fuel Combustion Activities Transport - Other Transportation

1A4

Fuel Combustion Activities - Other
Sectors

CO2, CH4, N2O

1A5

Fuel Combustion Activities - NonSpecified

CO2, CH4, N2O

4 Only disaggregate further by subcategory, fuel and/or gas where activity data and emission factors are from different sources

and/or uncertainties are significantly different.

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TABLE 4.1 (UPDATED) (CONTINUED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1A
Source and Sink Categories to be assessed in Key
Category Analysis

Gases to beassessed
separately cCategory aggregation/disaggregationconsiderations

Category Codes b

Category Names b

1B1a and 1B1b

Fugitive emissions from mining,processing, storage, andtransportation of coal, andspontaneous combustion and burning
coal dumps

CO2, CH4

1B1c

Fugitive Emissions from Fuel
Transformation

CO2, CH4

1B2a

Fugitive Emissions from Oil Systems

CO2, CH4

1B2b

Fugitive Emissions from Natural Gas
Systems

CO2, CH4

1C

Carbon Dioxide Transport andStorageCO2

See note e

CO2, CH4, N2O

Assess whether other sources in the
Energy Sector not listed above should be
included. Key category analysis has tocover all emission sources in theinventory. Therefore, all categories notpresented above should be either
aggregated with some other category,where relevant, or assessed separately.

1

Miscellaneous

Industrial Processes and Product Use
2A1

2A2

Mineral Industry - Cement
Production

Mineral Industry - Lime Production

CO2

CO2

Estimates compiled from a common set of
activity data and emission factors withsimilar uncertainties can be aggregated.
Common reasons for disaggregation can
include the application of Tier 2 or 3
methods for categories or sub-categories.

2A3

Mineral Industry - Glass Production

CO2

Estimates compiled from a common set of
activity data and emission factors withsimilar uncertainties can be aggregated.
Common reasons for disaggregation can
include the application of Tier 2 or 3
methods for categories or sub-categories.

2A4

Mineral Industry - Other Process
Uses of Carbonates

CO2

See note e

2B1

Chemical Industry - Ammonia
Production

CO2

2B2

Chemical Industry - Nitric Acid
Production

N2O

2B3

Chemical Industry - Adipic Acid
Production

N2O

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.1 (UPDATED) (CONTINUED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1A
Source and Sink Categories to be assessed in Key
Category Analysis

Gases to beassessed
separately cCategory aggregation/disaggregationconsiderations

See note e

Category Codes b

Category Names b

2B4

Chemical Industry - Caprolactam,
Glyoxal and Glyoxylic Acid
Production

N2O

2B5

Chemical Industry - Carbide
Production

CO2, CH4

2B6

Chemical Industry - Titanium
Dioxide Production

CO2

2B7

Chemical Industry - Soda Ash
Production

CO2

2B8

Chemical Industry - Petrochemicaland Carbon Black Production

CO2, CH4

See note e

2B9Chemical Industry - Fluorochemical
Production

HFCs, PFCs, SF6,
NF3 and otherhalogenatedgases should be
aggregated

If aggregated gases are key,
disaggregating by gas should beconsidered where methods, data sources
and assumptions are different to identify
gases that are may be individually key.

2B10

Chemical Industry – Hydrogen
Production

CO2

2C1

Metal Industry - Iron and Steel
Production

CO2, CH4, N2O

2C2

Metal Industry - Ferroalloys
Production

CO2, CH4

2C3

Metal Industry - Aluminium
Production

PFCs should be
aggregated, CO2

PFCs should be assessed jointly. CO2
should be assessed separately.

2C4

Metal Industry - Magnesium
Production

CO2
SF6, PFCs, HFCs,
other halogenatedgases should be
aggregatedMethods for HFCs, PFCs and otherhalogenated gases are only provided atTier 3 level. If they are not included in theinventory it is good practice to use
qualitative considerations (see Section
4.3.3).

2C5

Metal Industry - Lead Production

CO2

2C6

Metal Industry - Zinc Production

CO2

2C7

Metal Industry – Rare Earths

CO2, PFCs

PFCs should be assessed jointly. CO2
should be assessed separately.

2D

Non-Energy Products from Fuels andSolvent Use

CO2

See note eElectronics Industry

SF6, PFCs, HCFs,
NF3 and otherhalogenatedgases can be
aggregated

If aggregated gases are key,
disaggregating by gas should beconsidered where methods, data sources
and assumptions are different to identify
gases that are may be individually key.

2E

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TABLE 4.1 (UPDATED) (CONTINUED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1A
Source and Sink Categories to be assessed in Key
Category Analysis

Gases to beassessed
separately cCategory aggregation/disaggregationconsiderations

Category Names b

Category Names b

2F1

Product Uses as Substitutes for
Ozone Depleting Substances Refrigeration and Air Conditioning

HFCs and PFCs
See note e
can be aggregated

2F2

Product Uses as Substitutes for
Ozone Depleting Substances - Foam
Blowing Agents

HFCs can be
aggregated

2F3

Product Uses as Substitutes for
Ozone Depleting Substances - Fire
Protection

HFCs, PFCs canbe aggregated

2F4

Product Uses as Substitutes for
Ozone Depleting Substances Aerosols

HFCs, PFCs canbe aggregated

2F5

Product Uses as Substitutes for
Ozone Depleting Substances Solvents

HFCs, PFCs canbe aggregated

2F6

Product Uses as Substitutes for
Ozone Depleting Substances - Other
Applications

HFCs, PFCs canbe aggregated

Other Product Manufacture and Use

SF6 and PFCs canbe aggregated.
N2O treatedseparately

If aggregated gases are key,
disaggregating by gas should beconsidered where methods, data sources
and assumptions are different to identify
gases that are may be individually key.
N2O should be assessed separately.

Miscellaneous

CO2, CH4, N2O
should beassessed
separately.
HFCs, PFCs andSF6, otherhalogenatedgases can be
aggregated

Assess whether other sources in the IPPU
Sector not listed above should be
included. Key category analysis should
cover all emission sources in theinventory. Therefore, all categories notpresented above should be either
aggregated with some other category,where relevant, or assessed separately.

CH4

If there are differences in the data sources,
assumptions applied and uncertainties forthe different animal types and or
management/feed practices or if a subcategory accounts for more than 25
percent of the emissions of the category
then these should also be disaggregated.

CH4, N2O

If there are also differences in the data
sources, assumptions applied anduncertainties for the different animal types
and or management practices or if a subcategory accounts for more than 25
percent of the emissions of the category
then these should also be disaggregated.

2G

2Agriculture, Forestry and Other Land Use

3A1

3A2

4.12

Livestock: Enteric Fermentation

Livestock: Manure Management

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.1 (UPDATED) (CONTINUED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1A
Source and Sink Categories to be assessed in Key
Category Analysis
Category Names b

Category Names b

Gases to beassessed
separately c

3B1a

Forest Land Remaining Forest Land

CO2

See note f

3B1b

Land Converted to Forest Land

CO2

See note f

3B2a

Cropland Remaining CroplandCO2

See note f

3B2b

Land Converted to CroplandCO2

See note f

3B3a

Grassland Remaining Grassland

CO2

See note f

3B3bLand Converted to Grassland

CO2

See note f

3B4ai

Peatlands Remaining Peatlands

CO2, N2O

See note f

3B4aiiFlooded land remaining Flooded land

CO2, CH4

See note f

3B4bLand Converted to Wetlands

CO2

See note f

3B5a

Settlements Remaining Settlements

CO2

See note f

3B5b

Land Converted to Settlements

CO2

See note f
Where countries estimate CO2 emissions
from biomass burning separately fromthose associated to carbon stock change,
they may wish to separate CO2 emissions
from biomass burning under a key
category 3C1.

3C1

Biomass Burning

CH4, N2O

3C2Liming

CO2

3C3

Urea Application

CO2

3C4

Direct N2O Emissions from Managed
soils

Category aggregation/disaggregationconsiderations

N2O

If there are differences in the data sources,
assumptions applied and uncertainties fordifferent pools (mineral soils, organicsoils), or if a sub-category accounts formore than 25 percent of the emissions of
the category, then these should beassessed separately.
If there are differences in the data sources,
assumptions applied and uncertainties fordifferent pools (mineral soils, organicsoils) or if a sub-category accounts formore than 25 percent of the emissions of
the category, then these should beassessed separately.

3C5

Indirect N2O Emissions fromManaged soils

Indirect N2O

3C6

Indirect N2O Emissions from Manure
Management

Indirect N2O

3C7

Rice Cultivation

CH4

3D1

Harvested Wood Products

CO2

Use of key category analysis is optional.

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TABLE 4.1 (UPDATED) (CONTINUED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1A
Source and Sink Categories to be assessed in Key
Category Analysis
Category Names b

Category Names b

3

Miscellaneous e.g. non-CO2
emissions from biomass burning inforestland, cropland, grassland andwetlands, CH4 and N2O from theburning of drained organic soils, theCH4 and N2O from rewetting oforganic soils and N2O fromaquaculture

Gases to beassessed
separately cCategory aggregation/disaggregationconsiderations

CO2, CH4, N2O

Assess whether other sources or sinks in
the AFOLU Sector not listed above
should be aggregated or included
separately. Key category analysis has tocover all emission sources and sinks in theinventory. Therefore, all categories notpresented above should be either
aggregated with some other category,where relevant, or assessed separately.

This category should be disaggregatedaccording to methods, data sources,
assumptions applied and known or likely
differences in uncertainty. Estimatescompiled from a common set of activity
data and emission factors with similar
uncertainties can be aggregated. E.g. if
there are significant differences inmethodology and uncertainty for different
types of solid waste disposal (managed
and unmanaged sites) these should bedisaggregated.

Waste

4A

Solid Waste Disposal

CH4

4B

Biological Treatment of Solid Waste

CH4, N2O

4C

Incineration and Open Burning of
Waste

CO2, CH4, N2O

4D

Wastewater Treatment and Discharge

CH4, N2O

If there are differences in data sources,
assumptions applied and uncertainties fordifferent types of wastewater treatment(domestic or industrial wastewater and ordifferent discharge routes) these should bedisaggregated. Estimates compiled from acommon set of activity data and emission
factors with similar uncertainties can be
aggregated.
Assess whether other sources in the Waste
Sector not listed above should be
included. Key category analysis has tocover all emission sources in theinventory. Therefore, all categories notpresented above should be either
aggregated with some other category,where relevant, or assessed separately.

4

Miscellaneous

CO2, CH4, N2O

5A

Indirect N2O Emissions from theatmospheric deposition of nitrogen in
NOx and NH3

Indirect N2O

5B

4.14

Other

CO2, CH4, N2O,
SF6, PFCs, HFCs

Include sources and sinks reported under
5B. Key category assessment has to cover
all emission sources in the inventory.
Therefore, all categories not presented
above should be either aggregated withsome other category, where relevant, orassessed separately.

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.1 (UPDATED) (CONTINUED)SUGGESTED AGGREGATION LEVEL OF ANALYSIS FOR APPROACH 1Aa

In some cases, inventory compilers may modify this list of IPCC categories to reflect particular national circumstances.

b

The categories should include the respective codes and be consistent with the IPCC terminology.

c

All the gases in this column are to be assessed separately unless stated otherwise where gases can be assessed jointly. There may also besome new gases other than those listed here, and those should be assessed separately.
d

In the quantitative key category analysis, conversion of forest (deforestation) is spread out under the different land-use change categories.
Countries should identify and sum up the emission estimates associated with forest conversion to any other land category and compare themagnitude to the smallest category identified as key. If its size is larger than the smallest category identified as key, it should be consideredkey.

eCategories should be disaggregated if methods, data sources and/or assumptions applied are different and/or there is a difference inuncertainties between them. Estimates compiled from a common set of activity data and emission factors with similar uncertainties can be
aggregated.
f

Where possible, assess emissions, removal and carbon stock change separately. If there are differences in the data sources, assumptions
applied and uncertainties for different pools (biomass, DOM, mineral soils, organic soils) then these should be also assessed separately.

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Volume 1: General Guidance and Reporting

4.3

METHODOLOGICAL APPROACHES TO
IDENTIFY KEY CATEGORIESNo refinement.

4.3.1

Approach 1 to identify key categories

Approach 1 to identify key categories assesses the influence of various categories of sources and sinks on the level,and possibly the trend, of the national greenhouse gas inventory. When the inventory estimates are available forseveral years, it is good practice to assess the contribution of each category to both the level and trend of thenational inventory. If only a single year’s inventory is available, a level assessment should be performed.
Approach 1 can readily be accomplished using a spreadsheet analysis. Tables 4.2 and 4.3 in the following sections
illustrate the format of the analysis. Separate tables are suggested for the level and trend assessments because it isnecessary to sort the results of the analysis according to two different columns. It is more difficult to track theprocess if the analyses are combined in the same table. In Table 4.2, columns A through C and Table 4.3 A throughD, are inputs of the national inventory data. Section 4.5 illustrates the application of the Approach 1 to the Finnish
inventory.

LEVEL ASSESSMENT
The contribution of each source or sink category to the total national inventory level is calculated according toEquation 4.1:
EQUATION 4.1 (UPDATED)LEVEL ASSESSMENT (APPROACH 1)
Key category level assessment = source or sink category estimate/ total contribution

Lx ,t =

E x ,t∑Eii ,tWhere:

Lx ,t= level assessment for source or sink x in latest inventory year (year t)

E x ,t= absolute value of emission or removal estimate of source or sink category x in year t

∑E
i

i ,t

= total contribution, which is the sum of the absolute values of emissions and removals for all n
categories (i=1, …. x, n) in year t calculated using the aggregation level chosen by the country
for key category analysis. Because both emissions and removals are entered with positive sign 5,
the total contribution/level can be larger than a country’s total emissions less removals 6

Key categories according to Equation 4.1 are those that, when summed together in descending order of magnitude,
add up to 95 percent of the sum of all Lx,t..
Table 4.2 presents a spreadsheet that can be used for the level assessment. An example of the use of the spreadsheet
is given in Section 4.5.

5 Removals are entered as absolute values to avoid an oscillating cumulative value L as could be the case if removals werex,tentered with negative signs, and thus to facilitate straightforward interpretation of the quantitative analysis.

6 This equation can be used in any situation, regardless of whether the national greenhouse gas inventory is a net source (as ismost common) or a net sink.

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.2 (UPDATED)SPREADSHEET FOR THE APPROACH 1 ANALYSIS – LEVEL ASSESSMENT
A

B

C

D

E

F

G

Category
Codes and
Names

Greenhouse
Gas

Latest Year
Estimate[in CO2 eq.
units]

Absolute
Value of
Latest Year
Estimate

Level
Assessment

Cumulative
Total of
Column E

E x ,tE x ,tRank of
Absolute
Value of
Latest Year
Estimate
Column D

∑E

Total

i

i ,t

Lx ,t

1

Where:
Column A:= description of category (see Section 4.2 above)

Column B:= greenhouse gas from the category

Column C:= value of emission or removal estimate of category 𝑥𝑥 in latest inventory year (year t)
in CO2 equivalent units

Column D:= absolute value of emission or removal estimate of category x in year t

Column E:= level assessment following Equation 4.1

Column F:= cumulative total of Column E

Column G:= rank of absolute value of latest year estimate Column D

Inputs to Columns A-C will be available from the inventory. The total of Column C presents the net emissions andremovals unless emissions and removals are presented separately. In Column D, absolute values are taken fromeach value in Column C. The sum of all entries in Column D is entered in the total line of Column D (note that
this total may not be the same as the total net emissions and removals). In Column E, the level assessment iscomputed according to Equation 4.1. Once the entries in Column E are computed, the categories in the table should
be sorted in descending order of magnitude according to Column E. After this step, the cumulative total summedin Column E can be calculated into Column F. Key categories are those that, when summed together in descendingorder of magnitude, add up to 95 percent of the total in Column F. Where the method is applied correctly, the sumof entries in Column E must be 1. The rationale for the choice of the 95 percent threshold for the Approach 1
builds on Rypdal and Flugsrud (2001) and is presented in GPG2000, Section 7.2.1.1 in Chapter 7.
It is also good practice to examine categories identified between threshold of 95 percent and 97 percent carefully
with respect to the qualitative criteria (see Section 4.3.3).
The level assessment should be performed for the base year of the inventory and for the latest inventory year (yeart). If estimates for the base year have changed or been recalculated, the base year analysis should be updated. Key
category analysis can also be updated for other recalculated years. In many cases, however, it is sufficient to derive
conclusions regarding methodological choice, resource prioritisation or QA/QC procedures without an updated
key category analysis for the entire inventory time series. Any category that meets the threshold for the base yearor the most recent year should be identified as key. However, key category analysis can also take other years into
account to identify key categories if key category analyses are available for these years. This is because somecategories may have emissions/removals that fluctuate from year to year above and below the key category
threshold. Therefore, for categories between threshold of 95 and 97 percent, it is suggested to assess three or more
previous years identifying if these categories were key categories in these years except in cases where a clear
explanation can be provided why a category may no longer be key in any future years. These additional categories
should be addressed in the reporting table for key categories by using a column for comments (see Table 4.4 andreporting table for key categories in Section 4.4 for more information). The qualitative criteria presented in Section
4.3.3 may also help to identify which categories with fluctuating emissions or removals should be considered as
key categories.

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Volume 1: General Guidance and Reporting

TREND ASSESSMENT
The purpose of the trend assessment is to identify categories that may not be large enough to be identified by thelevel assessment, but whose trend contributes significantly to the trend of the overall inventory and should
therefore receive particular attention. The Trend Assessment can be calculated according to Equation 4.2 if morethan one year of inventory data are available.
EQUATION 4.2 (UPDATED)TREND ASSESSMENT (APPROACH 1)

Tx ,t =

Ex ,t − Ex ,0∑E −∑E
i

i ,t

i

i ,0

Where:

Tx ,t = trend assessment of source or sink category x in year t as compared to the base year (year 0)
Ex ,0 and Ex ,t= value of emission or removal estimate of source or sink category x in year 0 andyear t∑ E and ∑ E
i

i ,t

i

i ,0

= total inventory estimates in years t and 0, respectively

for i = 1, ..., nThe trend assessment of a category refers to the change in the source or sink category emissions or removals overtime compared to the total trend. This is computed as an absolute value for source or sink category x by subtracting
the value of the base year (year 0) estimate from the value of the latest inventory year (year t) estimate and dividing
this by the overall difference between the target year (year t) and the base year (year 0) total inventories (theinventory trend). The percentage contribution of category x for year t to the trend is then calculated by dividing
Tx,t by the sum of the trend assessment of all categories of the inventory.
The trend assessment then sorts categories by magnitude (highest to lowest) of their contribution to the trend,
regardless whether category trend is increasing or decreasing, or a category is a sink or source. Categories whose
cumulative percentage contribution is greater than 95 percent should be identified as key.
Table 4.3 outlines a spreadsheet that can be used for the Approach 1 Trend Assessment.
TABLE 4.3 (UPDATED)SPREADSHEET FOR THE APPROACH 1 ANALYSIS – TREND ASSESSMENT
A

B

C

D

E

F

G

H

Category
Codes
and
Names

Greenhouse
Gas

Base
Year
Estimate

LatestYear
Estimate

Trend
Assessment

Contribution
to Trend

Cumulative
Total of
Column F

Ex ,0E x ,tRank oftrend
assessment
Column E

Tx ,t

Tx ,t

∑T
i

∑E

Total

i

i ,0

∑E
i

i ,t

i ,t

∑T
i

i ,t

Where:

4.18

Column A := description of category (see Section 4.2 above)

Column B:= greenhouse gas from the category

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Chapter 4: Methodological Choice and Identification of Key Categories

Column C:= base year estimate of emissions or removals from the national inventory data,
in CO2 equivalent units. Sources and sinks are entered as real values (positive or
negative values, respectively)

Column D:= latest year estimate of emissions or removals from the most recent national inventory
data, in CO2 equivalent units. Sources and sinks are entered as real values (positive or
negative values, respectively)

Column E:= trend assessment from Equation 4.2

Column F:= contribution of the category to the total of trend assessments in last row of Column
E, i.e., Tx ,t ∑ Ti ,ti

Column G:= cumulative total of Column F, calculated after sorting the entries in descending orderof magnitude according to Column F

Column H:= rank of the trend assessment value (column E)

The entries in Columns A, B and D should be identical to those in Columns A, B and C in the Table 4.2, for the
Approach 1 analysis - Level Assessment. The base year estimate in Column C is always entered, while the latest
year estimate in Column D will depend on the year of analysis. The value of Tx,t (which is always positive) should
be entered in Column E for each category of sources and sinks, following Equation 4.2, and the sum of all theentries entered in the total line of the table. The percentage contribution of each category to the total of Column Eshould be computed and entered in Column F. The categories (i.e., the rows of the table) should be sorted indescending order of magnitude, based on Column F. The cumulative total of Column F should then be computedin Column G. Key categories are those that, when summed together in descending order of magnitude, add up to
more than 95 percent of the total of Column F. An example of Approach 1 analysis for the level and trend is given
in Section 4.5.
The trend assessment treats increasing and decreasing trends similarly. However, for the prioritisation of resources,
there may be specific circumstances where countries may not want to invest additional resources in the estimationof key categories with decreasing trends. Underlying reasons why a category showing strong decreasing trend
could be key include activity decrease, mitigation measures leading to reduced emission factors or abatement
measures (e.g., F-gases, chemical production) changing the production processes. In particular, for a long-term
decline of activities (not volatile economic trends) and when the category is not key from the level assessment, it
is not always necessary to implement higher tier methods or to collect additional country-specific data if
appropriate explanations can be provided why a category may not become more relevant again in the future. This
could be the case e.g., for emissions from coal mining in some countries where considerable number of mines areclosed or where certain production facilities are shut down. Regardless of the method chosen, countries should
endeavour to use the same method for all years in a time series, and therefore it may be more appropriate tocontinue using a higher tier method if it had been used for previous years.
For other reasons of declining trends such as the introduction of abatement measures or other emission reduction
measures, it is important to prioritise resources for the estimation of such categories that were identified as key inthe trend assessment. Irrespective of the methodological choice, inventory compilers should clearly and precisely
explain and document categories with strongly decreasing trends and should apply appropriate QA/QC procedures.

KEY CATEGORY ANALYSIS FOR A SUBSET OF INVENTORY ESTIMATES
Good Practice Guidance for Land Use, Land-Use Change and Forestry (GPG-LULUCF, IPCC 2003) provided
guidance on how to conduct a key category analysis using a stepwise approach, identifying first the key (source)
categories for the inventory excluding Land Use, Land-Use Change and Forestry (LULUCF), and secondly
repeating the key category analysis for the full inventory including the LULUCF categories to identify additional
key categories. This two-step approach is now integrated into one general approach. However, inventory compilers
may still want to conduct a key category analysis using a subset of inventory estimates. For example, inventory
compilers may choose to include only emission sources in order to exclude the effects of removals from the levelassessment or in order to exclude the influence of different trends for carbon fluxes from the other emission trends.
It is good practice to document the subsets the analysis was performed for and the differences in results comparing
with an integrated analysis.

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Volume 1: General Guidance and Reporting

4.3.2

Approach 2 to identify key categories

No refinement.

4.3.3

Qualitative criteria to identify key categories

In some cases, the results of the Approach 1 or Approach 2 analysis of key categories may not identify all
categories that should be prioritised in the inventory system. If quantitative key category analysis has not been
carried out due to lack of completeness in the inventory, it is good practice to use qualitative criteria to identify
key categories. The criteria below address specific circumstances that may not be readily reflected in thequantitative assessment. These criteria should be applied to categories not identified in the quantitative analysis,
and if additional categories are identified they should be added to the list of key categories. It is particularly
important to consider these criteria if the trend assessment has not been compiled. Although it is important toimplement a trend assessment as part of good practice if data are available, early identification using qualitative
criteria could be used until such assessment is available. Followings are the examples of points in qualitative
criteria.
•

Mitigation techniques and technologies: If emissions from a category have decreased or removals haveincreased through the use of climate change mitigation techniques, it is good practice to identify such
categories as key. This will ensure that such categories are prioritised within the inventory and that better
quality estimates are prepared to reflect the mitigation effects as closely as possible. It will also ensure thatthe methods used are transparent with respect to mitigation which is important for assessing inventory quality.

•

Expected growth: The inventory compiler should assess which categories should be designated as key because
they are likely to show substantial increase of emissions or decrease of removals in the future. The inventory
compiler may use expert judgement to make this determination. It is encouraged to identify such categories as
key.

•

No quantitative assessment of Uncertainties performed: Where Approach 2 including uncertainties in the key
category analysis is not used, inventory compilers are still encouraged to identify categories that are assumed
to contribute most to the overall uncertainty as key, because the largest reductions in overall inventory
uncertainty can be achieved by improving estimates of categories having higher uncertainties. The qualitative
consideration should take into account whether any methodological improvements could reduce uncertainties
significantly. This could, for example, be applied to a small net flux results from the subtraction of large
emissions and removals, which can imply a very high uncertainty.

•

Completeness: Neither the Approach 1 nor the Approach 2 gives correct results if the inventory is not complete.
The analysis can still be performed, but there may be key categories among those are not estimated. In thesecases, it is good practice to examine qualitatively potential key categories that are not yet estimatedquantitatively by applying the qualitative considerations above. The inventory of a country with similar
national circumstances can also often give good indications on potential key categories. Chapter 2, Approaches
to Data Collection, gives suggestions for methods to approximate activity data that can be used to compile
preliminary estimates of emissions/removals from a category. This preliminary analysis can be used toconclude whether a category potentially can be key and prioritise data collection of this category.

4.4

REPORTING AND DOCUMENTATION

It is good practice to clearly document the results of the key category analysis in the inventory report. This
information is essential for explaining the choice of method for each category. In addition, inventory compilers
should list the criteria by which each category was identified as key (e.g., level, trend, or qualitative), and themethod used to conduct the quantitative key category analysis (e.g., Approach 1 or Approach 2). Tables 4.2 and4.3 should be used to record the results of the key category analysis. Table 4.4 should be used to present a summaryof the key category analysis. The notation keys: L = key category according to level assessment; T = key category
according to trend assessment; and Q = key category according to qualitative criteria; should be used to describe
the assessment method used. The Approach used to identify the key category should be included as L1, L2, T1 or
T2. In the column for comments, reasons for a qualitative assessment can be provided.

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.4 (UPDATED)SUMMARY OF KEY CATEGORY ANALYSIS
Quantitative method used: Approach 1/Approach 1 and Approach 2
A
Category
Codes

B

C

Category Names

Greenhouse Gas

D
Identification
criteria

E
Comments

Key category analysis is designed to inform the functions of the National Inventory Arrangements and various
stakeholders on the priorities for regular update and improvement of the inventory. Therefore, the detailed analysis
can be aggregated into a single informative list of the categories identified as key and why as suggested above inTable 4.4. In addition, inventory compilers could consider a means of prioritisation using category rankings acrossthe different analysis. Ideally, this summary should also highlight the tier at which the estimates are estimated togive an indication of the scope for further improvement (see Table 4.4a).
TABLE 4.4A (NEW)KEY CATEGORIES RANKS
A

B

C

D

E

F

Category
Codes and
Names

Greenhouse
Gas

Method(Tier)

Latest Year
Estimate[in CO2 eq.
units]

Level Assessment
Rank(If Key category)

Trend Assessment
Rank(If Key category)

4.5

EXAMPLES OF KEY CATEGORY ANALYSISThe application of the Approach 1 and Approach 2 to Finland's greenhouse gas inventory for the reporting year
2016 is shown in the following tables. Both the level and the trend assessment were conducted using estimates ofemissions, removals and uncertainties from the official national inventory of Finland (Statistics Finland, 2018).
The category code and the category name (column A in Tables 4.5, 4.6, 4.9-4.11) are presented as reported in thenational inventory of Finland. That is why they may not be identical to IPCC category code and name provided inVolume 1, Chapter 8, Table 8.2.

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Volume 1: General Guidance and Reporting

TABLE 4.5 (UPDATED)EXAMPLE OF APPROACH 1 LEVEL ASSESSMENT FOR FINLAND’S GHG INVENTORY FOR 2016
(only key categories are presented)
A

Category Codes and Names

B

C

GHG

Emissions/removals(2016)D

E

F

G

Absolute
value ofemissions /removalsLevel
assessment

Lx,t

Cumulative
sum oflevel
assessment

Rank of Level
Assessment|Ex,t|Gg CO2equivalent

Gg CO2equivalent

4.A.1, Forest Land remaining Forest
Land

CO2

-35 773.5

35 773.5

0.322

0.322

1

1.A.1, Energy Industries, SolidCO2

8 952.1

8 952.1

0.081

0.402

2

1.A.3b, Road transportation, Diesel
oil

CO2

7 796.6

7 796.6

0.070

0.472

3

1.A.1, Energy Industries, Peat

CO2

4 797.5

4 797.5

0.043

0.516

4

4.B.1, Cropland remaining Cropland

CO2

4 742.3

4 742.3

0.043

0.558

5

1.A.3b, Road transportation, Motor
gasoline

CO2

4 047.8

4 047.8

0.036

0.595

6

4.G, Harvested Wood Products

CO2-3 642.4

3 642.4

0.033

0.627

7

1.A.4, Other sectors, Liquid

CO23 293.5

3 293.5

0.030

0.657

8

1.A.2, Manufacturing industries andconstruction, Liquid

CO2

3 182.0

3 182.0

0.029

0.686

9

3.D.1, Direct soil emissions

N2O

3 031.3

3 031.3

0.027

0.713

10

4.B.2, Land converted to Cropland

CO2

2 416.2

2 416.2

0.022

0.735

11

1.A.1, Energy Industries, GaseousCO2

2 315.5

2 315.5

0.021

0.755

12

1.A.1, Energy Industries, Liquid

CO22 256.0

2 256.0

0.020

0.776

13

2.C.1, Iron and steel production

CO2

2 171.0

2 171.0

0.020

0.795

14

3.A, Enteric fermentation

CH4

2 104.6

2 104.6

0.019

0.814

15

4.D.1, Wetlands remaining Wetlands

CO2

1 961.9

1 961.9

0.018

0.832

16

5.A, Solid Waste Disposal

CH4

1 639.6

1 639.6

0.015

0.847

17

2.F.1, Refrigeration and air
conditioning

HFCs

1 340.1

1 340.1

0.012

0.859

18

1.A.2, Manufacturing industries andconstruction, GaseousCO2

1 326.3

1 326.3

0.012

0.871

19

4(ii), Drainage, rewetting and othermanagement soils

N2O

1 212.4

1 212.4

0.011

0.882

20

1.A.2, Manufacturing industries andconstruction, Solid

CO2

1 176.6

1 176.6

0.011

0.892

21

1.A.2, Manufacturing industries andconstruction, Peat

CO2

940.3

940.3

0.008

0.901

22

2.B.10b, Hydrogen production

CO2

937.8

937.8

0.008

0.909

23

4(ii), Drainage, rewetting and othermanagement soils

CH4

918.8

918.8

0.008

0.917

24

1.A.5, Other energy, Liquid

CO2

850.0

850.0

0.008

0.925

25

4.E.2, Land converted to Settlements

CO2

570.7

570.7

0.005

0.930

26

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.5 (UPDATED) (CONTINUED)
EXAMPLE OF APPROACH 1 LEVEL ASSESSMENT FOR FINLAND’S GHG INVENTORY FOR 2016
(only key categories are presented)
A

Category Codes and Names

B

C

GHG

Emissions/removals(2016)D

E

F

G

Absolute
value ofemissions /removalsLevel
assessment

Lx,t

Cumulative
sum oflevel
assessment

Rank of Level
Assessment|Ex,t|Gg CO2equivalent

Gg CO2equivalent

2.A.1, Cement production

CO2

553.2

553.2

0.005

0.935

27

1.A.1, Energy Industries, Other fossil

CO2

507.2

507.2

0.005

0.940

28

3.B, Manure management

CH4

460.9

460.9

0.004

0.944

29

4.C.1, Grassland remaining Grassland

CO2

433.1

433.1

0.004

0.948

30

1.A.3d, Domestic navigation, Liquid

CO2

403.2

403.2

0.004

0.951

31

31 733.1

111 229.7

1.0

Total

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Volume 1: General Guidance and Reporting

TABLE 4.6 (UPDATED)EXAMPLE OF APPROACH 1 TREND ASSESSMENT FOR FINLAND'S GHG INVENTORY FOR 2016
(only key categories are presented)
A

B

C

D

E

Category Codes and
Names

GHG

Emissions/removals(1990)

Emissions/removals(2016)

Trend
assessment

Gg CO2equivalent

Gg CO2equivalent

Gg CO2equivalent

F

G

H

Contribution
to the trend

Cumulative
total ofcolumn F

Rank oftrend
assessment

4.A.1
Forest Landremaining Forest
Land

CO2

-22,636.0-35,773.5

0.516

0.287

0.287

1

1.A.4
Other sectors, Liquid

CO26,987.6

3,293.5

0.145

0.081

0.368

2

1.A.2
Manufacturingindustries andconstruction, Solid

CO24,841.6

1,176.6

0.144

0.080

0.448

3

1.A.3bRoad transportation,
Diesel oil

CO24,923.5

7,796.6

0.113

0.063

0.510

4

5.A
Solid Waste Disposal

CH44,327.7

1,639.6

0.106

0.059

0.569

5

1.A.3bRoad transportation,
Motor gasoline

CO25,884.3

4,047.8

0.072

0.040

0.609

6

1.A.2
Manufacturingindustries andconstruction, Liquid

CO24,861.6

3,182.0

0.066

0.037

0.646

7

4.B.2
Land converted to
Cropland

CO2

894.4

2,416.2

0.060

0.033

0.679

8

2.B.2
Nitric acidproduction

N2O

1,591.6

218.3

0.054

0.030

0.709

9

2.F.1
Refrigeration and air
conditioning

HFCs

0.0

1,340.1

0.053

0.029

0.738

10

1.A.2
Manufacturingindustries andconstruction,
GaseousCO2

2,198.6

1,326.3

0.034

0.019

0.757

11

1.A.1
Energy Industries,
Peat

CO2

3,949.5

4,797.5

0.033

0.019

0.776

12

2.B.10b
Hydrogen production

CO2

116.2

937.8

0.032

0.018

0.794

13

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Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.6 (UPDATED) (CONTINUED)
EXAMPLE OF APPROACH 1 TREND ASSESSMENT FOR FINLAND'S GHG INVENTORY FOR 2016
(only key categories are presented)
A

B

C

D

E

Category Codes and
Names

GHG

Emissions/removals(1990)

Emissions/removals(2016)

Trend
assessment

Gg CO2equivalent

Gg CO2equivalent

Gg CO2equivalent

F

G

H

Contribution
to the trend

Cumulative
total ofcolumn F

Rank oftrend
assessment

4.G
Harvested Wood
Products

CO2-2,951.6-3,642.4

0.027

0.015

0.809

14

1.A.1
Energy Industries,
Solid

CO2

9,640.1

8,952.1

0.027

0.015

0.824

15

4(ii)
Drainage, rewetting
and other
management soils

CH41,533.4

918.8

0.024

0.013

0.837

16

4.D.1
Wetlands remaining
Wetlands

CO2

1,357.8

1,961.9

0.024

0.013

0.850

17

1.A.2
Manufacturingindustries andconstruction, Peat

CO2

1,475.9

940.3

0,021

0.012

0.862

18

1.A.1
Energy Industries,
Other fossil

CO2

1.0

507.2

0.020

0.011

0.873

19

3.G
Liming

CO2

642.0

265.6

0.015

0.008

0.881

20

1.A.1
Energy Industries,
LiquidCO22,616.2

2,256.0

0.014

0.008

0.889

21

4.A.2
Land converted toForest Land

CO2

-1.3

-332.3

0.013

0.007

0.896

22

1.A.1
Energy Industries,
GaseousCO22,636.2

2,315.5

0.013

0.007

0.903

23

3.A
Enteric fermentation

CH42,423.0

2,104.6

0.013

0.007

0.910

24

4.E.2
Land converted toSettlements

CO2

870.5

570.7

0.012

0.007

0.917

25

1.A.2
Manufacturingindustries andconstruction, Other
fossil

CO2

100.6

387.1

0.011

0.006

0.923

26

3.D.1
Direct soil emissions

N2O

3,313.7

3,031.3

0.011

0.006

0.929

27

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 1: General Guidance and Reporting

TABLE 4.6 (UPDATED) (CONTINUED)
EXAMPLE OF APPROACH 1 TREND ASSESSMENT FOR FINLAND'S GHG INVENTORY FOR 2016
(only key categories are presented)
A

B

C

D

E

Category Codes and
Names

GHG

Emissions/removals(1990)

Emissions/removals(2016)

Trend
assessment

Gg CO2equivalent

Gg CO2equivalent

Gg CO2equivalent

F

G

H

Contribution
to the trend

Cumulative
total ofcolumn F

Rank oftrend
assessment

4.C.1
Grassland remaining
Grassland

CO2

682.8

433.1

0.010

0.005

0.935

28

2.C.1
Iron and steel
production

CO2

1,966.6

2,171.0

0.008

0.004

0.939

29

1.A.5
Other energy,
Gaseous

CO2

55.9

258.3

0.008

0.004

0.944

30

1.A.3aDomestic aviation,
Liquid

CO2

385.1

186.6

0.008

0.004

0.948

31

1.A.5
Other energy, Liquid

CO2

1,042.7

850.0

0.008

0.004

0.952

32

57 289.9

31 733.1

1.8

1.0

Total

4.26

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.9 (UPDATED)EXAMPLE OF APPROACH 2 LEVEL ASSESSMENT FOR FINLAND’S GHG INVENTORY FOR 2016

(only key categories are presented)
A

Category Codes and
Names

B

C

GHG

Emissions/removals(2016)

D

E

F

G

H

Uncertainty
in emissions

Absolute
value ofuncertain
emissions/ removals

Levelassessment

LUx,t

Cumulative
sum oflevel
assessment

Rank of
Approach 2
Level
Assessment

Ux,t

Ux,t|Ex,t|Gg CO2equivalent%

Gg CO2equivalent

4.A.1, Forest Landremaining Forest
Land

CO2

-35 773.530

10 604.7

0.286

0.286

1

4.B.1, Croplandremaining Cropland

CO2

4 742.3151

7 169.4

0.193

0.479

2

4.D.1, Wetlands
remaining Wetlands

CO2

1 961.9

153

2 992.2

0.081

0.560

3

4.B.2, Land
converted to
CroplandCO2

2 416.299

2 400.0

0.065

0.625

4

4.G, Harvested
Wood Products

CO2-3 642.4

50

1 829.2

0.049

0.674

5

3.D.1, Direct soil
emissions

N2O

3 031.3

56

1 706.6

0.046

0.720

6

4(ii), Drainage,
rewetting and othermanagement soils

N2O

1 212.4102

1 231.6

0.033

0.753

7

4.C.1, Grassland
remaining Grassland

CO2

433.1

254

1 098.8

0.030

0.783

8

3.D.2, Indirectemissions

N2O

381.4

273

1 039.9

0.028

0.811

9

4(ii), Drainage,
rewetting and othermanagement soils

CH4

918.8

101

927.6

0.025

0.836

10

5.A, Solid Waste
Disposal

CH4

1 639.6

34

557.1

0.015

0.851

11

4.E.2, Land
converted toSettlements

CO2

570.7

77

439.8

0.012

0.863

12

3.A, Entericfermentation

CH4

2 104.6

19

404.8

0.011

0.874

13

3.B, Manure
management

N2O

284.6

123

349.3

0.009

0.883

14

5.D, Wastewater
Treatment andDischarge

N2O

82.5

419

346.1

0.009

0.893

15

4.C.2, Land
converted to
Grassland

CO2

235.9

128

301.7

0.008

0.901

16

37 081.9

1.0

Total

31 733.1

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 1: General Guidance and Reporting

TABLE 4.10 (UPDATED)EXAMPLE OF APPROACH 2 TREND ASSESSMENT FOR FINLAND’S GHG INVENTORY FOR 2016

(only key categories are presented)
A
Category Codes
and Names

B

C

D

E

F

G

H

I

GHG

Emissions/removals(1990)

Emissions/removals(2016)

Uncertainty
in emissions

Trend
assessment
TUx,tContribution
to the Trend

Cumulative
sum oftrend
assessment

Rank of
Approach 2
Trend
Assessment

Gg CO2equivalent

Gg CO2equivalent

%

Ux,t

4.A.1, Forest Landremaining Forest
Land

CO2

-22 636.0-35 773.530

15.239

0.314

0.314

1

4.B.2, Land
converted to
Cropland

CO2

894.4

2 416.2

99

5.915

0.122

0.436

2

4.D.1, Wetlands
remaining Wetlands

CO2

1 357.8

1 961.9

153

3.605

0.074

0.510

3

5.A, Solid Waste
DisposalCH44 327.7

1 639.6

34

3.574

0.074

0.584

4

4.C.1, Grassland
remaining
Grassland

CO2

682.8

433.1

254

3.433

0.071

0.655

5

4(ii), Drainage,
rewetting and othermanagement soils

CH4

1 533.4

918.8

101

2.479

0.051

0.706

6

4.G, Harvested
Wood Products

CO2-2 951.6-3 642.4

50

1.357

0.028

0.734

7

3.D.2, Indirectemissions

N2O

482.7

381.4

273

1.080

0.022

0.756

8

2.F.1, Refrigeration
and air conditioning

HFCs

0.0

1 340.1

20

1.050

0.022

0.778

9

4.A.2, Land
converted to Forest
Land

CO2

-1.3

-332.3

76

0.990

0.020

0.798

10

1.A.4, Other
sectors, Liquid

CO2

6 987.6

3 293.5

7

0.977

0.020

0.818

11

4.E.2, Land
converted toSettlements

CO2

870.5

570.7

77

0.904

0.019

0.837

12

2.B.2, Nitric acidproduction

N2O

1 591.6

218.3

15

0.822

0.017

0.854

13

3.D.1, Direct soil
emissions

N2O

3 313.7

3 031.3

56

0.622

0.013

0.867

14

1.A.3b, Road
transportation,
Motor gasoline

N2O

88.3

13.6

148

0.431

0.009

0.875

15

1.A.1, Energy
Industries, Other
fossil

CO2

1.0

507.2

18

0.359

0.007

0.883

16

4.28

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.10 (UPDATED) (CONTINUED)
EXAMPLE OF APPROACH 2 TREND ASSESSMENT FOR FINLAND’S GHG INVENTORY FOR 2016
(only key categories are presented)
A
Category Codes
and Names

B

C

D

E

F

G

H

I

GHG

Emissions/removals(1990)

Emissions/removals(2016)

Uncertainty
in emissions

Trend
assessment
TUx,tContribution
to the Trend

Cumulative
sum oftrend
assessment

Rank of
Approach 2
Trend
Assessment

Gg CO2equivalent

Gg CO2equivalent

%

Ux,t

4.D.2, Land
converted to
Wetlands

CO2

65.5

137.8

121

0.342

0.007

0.890

17

1.A.2,
Manufacturingindustries andconstruction, SolidCO2

4 841.6

1 176.6

2

0.336

0.007

0.897

18

3.G, Liming

CO2

642.0

265.6

20

0.293

0.006

0.903

19

57 289.9

31 733.1

12 119.3

1.02019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 1: General Guidance and Reporting

TABLE 4.11 (UPDATED)EXAMPLE OF SUMMARY OF KEY CATEGORY ANALYSIS FOR FINLAND'S GHG INVENTORY FOR 2016
Category
Codes

Category Names

GHG

Identification
criteria

1.A.1

Energy Industries, Gaseous

CO2

L1, T1

1.A.1

Energy Industries, Liquid

CO2

L1, T1

1.A.1

Energy Industries, Other fossil

CO2

L1, T1

1.A.1

Energy Industries, Peat

CO2

L1, T1

1.A.1

Energy Industries, Solid

CO2

L1, T1

1.A.2

Manufacturing industries and construction, Gaseous

CO2

L1, T1

1.A.2

Manufacturing industries and construction, Liquid

CO2

L1, T1

1.A.2

Manufacturing industries and construction, Other fossil

CO2

T1

1.A.2

Manufacturing industries and construction, Peat

CO2

L1, T1

1.A.2

Manufacturing industries and construction, Solid

CO2

L1, T1, T2

1.A.3aDomestic aviation, Liquid

CO2

T1

1.A.3bRoad transportation, Diesel oil

CO2

L1, T1

1.A.3bRoad transportation, Motor gasoline

CO2

L1, T1, T2

1.A.3dDomestic navigation, Liquid

CO2

L1

1.A.4

Other sectors, Liquid

CO2

L1, T1, T2

1.A.5

Other energy, Gaseous

CO2

T1

1.A.5

Other energy, Liquid

CO2

L1, T1

2.A.1

Cement production

CO2

L1, T1

2.B.10b

Hydrogen production

CO2

L1, T1

2.B.2

Nitric acid production

N2O

T1, T2

2.C.1

Iron and steel production

CO2

L1, T1

2.F.1

Refrigeration and air conditioning

HFCs

L1, T1, T2

3.A

Enteric fermentation

CH4

L1, L2, T1

3.B

Manure management

CH4

L1

3.B

Manure management

N2O

L2

3.D.1

Direct soil emissions

N2O

L1, L2, T1, T2

3.D.2

Indirect emissions

N2O

L2, T2

3.G

Liming

CO2

T1, T24(ii)Drainage, rewetting and other management soils

CH4

L1, L2, T1, T2

4(ii)Drainage, rewetting and other management soils

N2O

L1, L2

4.A.1

Forest Land remaining Forest Land

CO2

L1, L2, T1, T2

4.A.2

Land converted to Forest Land

CO2

T1, T2

4.B.1

Cropland remaining Cropland

CO2

L1, L2

4.B.2

Land converted to Cropland

CO2

L1, L2, T1, T2

4.30

Comments

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Methodological Choice and Identification of Key Categories

TABLE 4.11 (UPDATED) (CONTINUED)
EXAMPLE OF SUMMARY OF KEY CATEGORY ANALYSIS FOR FINLAND'S GHG INVENTORY FOR 2016
Category
Codes

Category Names

GHG

Identification
criteria

4.C.1

Grassland remaining Grassland

CO2

L1, L2, T1, T2

4.C.2

Land converted to Grassland

CO2

L2

4.D.1

Wetlands remaining Wetlands

CO2

L1, L2, T1, T2

4.D.2

Land converted to Wetlands

CO2

T2

4.E.2

Land converted to Settlements

CO2

L1, L2, T1, T2

4.GHarvested Wood Products

CO2

L1, L2, T1, T2

5.A

Solid Waste Disposal

CH4

L1, L2, T1, T2

5.D

Wastewater Treatment and Discharge

N2O

L2

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Comments

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Volume 1: General Guidance and Reporting

References
References copied from the 2006 IPCC Guidelines
IPCC (2000). Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories.
Penman, J., Kruger, D., Galbally, I., Hiraishi, T., Nyenzi, B., Emmanuel, S., Buendia, L., Hoppaus, R.,
Martinsen, T., Meijer, J., Miwa, K., and Tanabe, K. (Eds). Intergovernmental Panel on Climate Change (IPCC),
IPCC/OECD/IEA/IGES, Hayama, Japan.
IPCC (2001). Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change, Houghton, J.T., Ding, Y., Griggs, D.J.,
Noguer, M., van der Linden, P.J., Dai, X., Maskell, K. and Johnson, C.A. (eds.), Intergovernmental Panel on
Climate Change (IPCC). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA,881pp.
IPCC (2003). Good Practice Guidance for Land Use, land-Use Change and Forestry, Penman, J., Gytarsky, M.,
Hiraishi, T., Kruger, D., Pipatti, R., Buendia, L., Miwa, K., Ngara, T. and Tanabe, K., Wagner, F. (Eds),
Intergovernmental Panel on Climate Change (IPCC), IPCC/IGES, Hayama, Japan.
Rypdal, K., and Flugsrud, K. (2001). Sensitivity Analysis as a Tool for Systematic Reductions in GHG Inventory
Uncertainties. Environmental Science and Policy. Vol 4 (2-3): pp. 117-135.
Statistics Finland (2005). Greenhouse gas emissions in Finland 1990-2003. National Inventory Report to the
UNFCCC, 27 May 2005.

References newly cited in the 2019 Refinement
Statistics Finland, 2018. Greenhouse gas emissions in Finland 1990-2016. National Inventory Report under the
UNFCCC and the Kyoto Protocol, 15 April 2018. (https://unfccc.int/documents/65334).

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2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories