GpgGood Practice Guidance: Time Series Consistency

Category / Methological Choice
Version / 3 (draft 0)[TP1] / Guidebook Revision, 2007/2008
Major change since earlier versions / This chapter presents an outline for a chapter on Methological Choice

Methological Choice

Based on IPCC 2006 Cross Cutting Chapter on Methodological Choice.

Contents

Methological Choice......

1INTRODUCTION

2Definition

2.1Key Categories

2.2Method Tiers

2.3Purpose of the key category analysis

2.4General approach to identify key categories

3General rules for identification of key categories......

4Methodological approaches to identify key categories......

4.1Stage 1 pollutant specific key category analysis......

4.1.1Approach 1 to identify key categories......

Trend Assessment

4.1.2Approach 2 to identify key categories......

Application of Uncertainty Estimates to Identify Key Categories

Level assessment

Trend assessment

Incorporating Monte Carlo Analysis

4.1.3Qualitative criteria to identify key categories......

4.2Stage 2: Combining Air Pollutant Specific Key Categories......

4.3Reporting and Documentation......

5References......

6Annexes......

1INTRODUCTION

This chapter addresses how to identify key categories[1] in a national inventory. Methodological choice for individual source and sink categories is important in managing 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 volumes of this Guidebook. 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. By identifying these key categories in the national inventory, inventory compilers can prioritise their efforts and improve their overall estimates. It is good practice for each country to identify its national key categories in a systematic and objective manner as presented in this chapter. Consequently, it is good practice to use results of key category analysis as a basis for methodological choice. Such a process will lead to improved inventory quality, as well as greater confidence in the estimates that are developed.

2Definition

2.1Key Categories

The IPCC Definition of a Key Category that will be used for this Guidebook is as follows:

“A key category is one that is prioritised within the national inventory system because its estimate has a significant influence on a country’s total inventory of greenhouse gases in terms of the absolute level, the trend, or the uncertainty in emissions and removals. Whenever the term key category is used, it includes both source and sink categories”.

2.2 Method Tiers

Emissions can be estimated at different levels of complexity. Within the IPCC Guidelines these are expressed in terms of three Tiers:

Tier 1: / a method using readily available statistical data on the intensity of processes (“activity rates”) and default emission factors. These emission factors assume a linear relation between the intensity of the process and the resulting emissions. The Tier 1 default emission factors also assume an average or typical process description.
Tier 2: / is similar to Tier 1 but uses more specific emission factors developed on the basis of knowledge of the types of processes and specific process conditions that apply in the country for which the inventory is being developed.
Tier 3: / is any method that goes beyond the above methods. These might include the use of more detailed activity information, specific abatement strategies or other relevant technical information.

In other words: the ”Tier 1” method is a “quick and dirty” method, using default emission factors only. To upgrade a Tier 1 to a Tier 2 method, the default emission factors should be replaced by country specific or technology specific emission factors. This might also require a further split of the activity data over a range of different technologies, implicitly aggregated in the Tier 1 method. A Tier 3 method could be regarded as a method that uses the latest scientific knowledge in more sophisticated approaches and models.

The present Guidebook structure is less clear in this respect, but provides a ”Simpler Methodology” and a ”Detailed Methodology” in all technical chapters.

2.3 Purpose of the key category analysis

As far as possible, key categories should receive special consideration in terms of three important inventory aspects. Firstly, identification of key categories in national inventories enables limited resources available for preparing inventories to be prioritised. It is good practice to focus the available resources for the improvement in data and methods onto categories identified as key. Secondly, 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 xxx (see Figure x.1). For most sources/sinks, higher tier (Tier 2 and 3) methods are suggested for key categories, although this is not always the case. For guidance on the specific application of this principle to key categories, it is good practice 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 to adopt 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 for Tier 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 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. Thirdly, it is good practice to give additional attention to key categories with respect to quality assurance and quality control (QA/QC) as described in Chapter 6, Quality Assurance/Quality Control and Verification, and in the sectoral volumes.

Figure x.1 Decision Tree to choose a Good Practice method

2.4 General approach to identify key categories

Any inventory compiler who has prepared a national greenhouse gas inventory will be able to identify key categories in terms of their contribution to the absolute level of national emissions and removals. For those inventory compilers who have prepared a time series, the quantitative determination of key categories should include an evaluation of both the absolute level and the trend of emissions and removals. Some key categories may be identified only when their influence on the trend of the national inventory is taken into account.

Section 3 sets out general rules for identification of key categories including the sectoral level to which the categories should be split. As indicated in figure x.2 the methodological approaches for determination of key categories follows 2 key stages and is described in Section 4. The methodology follows the principals of that developed by the IPCC (IPCC’s good Practice Guide 2006) as described in section 4.1 but is expanded in section 4.2 to accommodate the wide diversity of pollutants and the lack of GWP equivilent approaches to aggregate pollutants. in two stages

Figure x.2: Illustration of methods and approaches for identifying key categories for air pollutant inventories.


3General rules for identification of key categories

The results of the key category identification will be most useful if the analysis is done at the appropriate disaggregation level of categories. Table x.1, Suggested aggregation level of analysis for Approach 1, lists the source categories that are recommended and identifies special considerations related to the disaggregation of the analysis, where relevant. For example, the combustion of fossil fuels is a large emission source category that can be broken down into subcategories of 1st, 2nd or 3rd order, and even to the level of individual plants or boilers. Countries may adapt the recommended level of analysis in Table x.1 to their national circumstances. In particular countries using Approach 2 will probably choose the same level of aggregation that was used for the uncertainty analysis. In some cases, disaggregation to very low levels should be avoided since it may split an important aggregated category into many small subcategories that are no longer key. The following guidance describes good practice in determining the appropriate level of disaggregation of categories to identify key categories:

  • The analysis should be performed at the level of NFR categories or subcategories at which the Guidebook methods and decision trees are generally provided in the sectoral volumes.
  • Each Air Pollutant emitted from each category should be considered separately. For example, carbon monoxide (CO), Oxides of Nitrogen (NOx) and Particlualte Matter (PM10) are emitted from each of the detailed road transport classes.The key category analysis for this source should be performed for each of these gases separately because the methods, emission factors and related uncertainties differ for each gas. In contrast, a collective analysis of all chemical species of Non Methane Volatile Organic Compounds (NMVOC) is appropriate for this category.
  • Table x.1 shows the recommended level of analysis.[2] Countries may choose to perform the quantitative analysis at a more disaggregated level than suggested in this table. In this case, possible cross-correlations between categories and/or subcategories should be taken into account when performing the key category analysis. When using Approach 2, the assumptions about such correlations should be the same when assessing uncertainties and identifying key categories (see Chapter 3, Uncertainties).
  • The categories included in Table x.1 are those for which estimation methods are provided in the sectoral volumes. If countries develop estimates for new categories or gases, these should be added to the analysis under Miscellaneous for the appropriate sector.

For each key category where relevant (see Table x.1 below), the inventory compiler should determine if certain subcategories are particularly significant. Usually, for this purpose, the subcategories should be ranked according to their contribution to the aggregate key category. Those subcategories that contribute together more than 60 percent to the key category should be treated as particularly significant. It may be appropriate to focus efforts towards methodological improvements of these most significant subcategories. For those categories where subcategories need to be identified it is clearly mentioned in the appropriate decision trees in Volumes 2-5. In some cases and alternative method to identify these subcategories is used.

Table x.1
Suggested aggregation level of analysis for Approach 1 a
Source and Sink Categories to be Assessed in Key Category Analysis / Special Considerations
Category Code b / Category Title b
1 A 1 a / 1 A 1 a Public Electricity and Heat Production / Disaggregate to main fuel types.
1 A 1 b / 1 A 1 b Petroleum refining / Disaggregate to main fuel types.
1 A 1 c / 1 A 1 c Manufacture of Solid Fuels and Other Energy Industries / Disaggregate to main fuel types.
1 A 2 a / 1 A 2 a Stationary Combustion in Manufacturing Industries and Construction: Iron and Steel / Disaggregate to main fuel types.
1 A 2 b / 1 A 2 b Stationary Combustion in Manufacturing Industries and Construction: Non-ferrous Metals / Disaggregate to main fuel types.
1 A 2 c / 1 A 2 c Stationary Combustion in Manufacturing Industries and Construction: Chemicals / Disaggregate to main fuel types.
1 A 2 d / 1 A 2 d Stationary Combustion in Manufacturing Industries and Construction: Pulp, Paper and Print / Disaggregate to main fuel types.
1 A 2 e / 1 A 2 e Stationary Combustion in Manufacturing Industries and Construction: Food Processing, Beverages and Tobacco / Disaggregate to main fuel types.
1 A 2 f i / 1 A 2 f i Stationary Combustion in Manufacturing Industries and Construction: Other (Please specify in your IIR) / Disaggregate to main fuel types.
1 A 2 f ii / 1 A 2 f ii Mobile Combustion in Manufacturing Industries and Construction: (Please specify in your IIR) / Disaggregate to main fuel types.
1 A 3 a ii (i) / 1 A 3 a ii (i) Civil Aviation (Domestic, LTO)
1 A 3 a ii (ii) / 1 A 3 a ii (ii) Civil Aviation (Domestic, Cruise)
1 A 3 b i / 1 A 3 b i Road Transport:, Passenger cars
1 A 3 b ii / 1 A 3 b ii Road Transport:, Light duty vehicles
1 A 3 b iii / 1 A 3 b iii Road Transport:, Heavy duty vehicles
1 A 3 b iv / 1 A 3 b iv Road Transport:, Mopeds & Motorcycles
1 A 3 b v / 1 A 3 b v Road Transport:, Gasoline evaporation
1 A 3 b vi / 1 A 3 b vi Road Transport:, Automobile tyre and brake wear
1 A 3 b vii / 1 A 3 b vii Road Transport:, Automobile road abrasion
1 A 3 c / 1 A 3 c Railways
1 A 3 d ii / 1 A 3 d ii National Navigation (Shipping) / Disaggregate to main fuel types.
1 A 3 e / 1 A 3 e i Pipeline compressors / Disaggregate to main fuel types.
1 A 4 a i / 1 A 4 a i Commercial / Institutional: Stationary / Disaggregate to main fuel types.
1 A 4 a ii / 1 A 4 a ii Commercial / Institutional: Mobile / Disaggregate to main fuel types.
1 A 4 b i / 1 A 4 b i Residential: Stationary plants / Disaggregate to main fuel types.
1 A 4 b ii / 1 A 4 b ii Residential: Household and gardening (mobile) / Disaggregate to main fuel types.
1 A 4 c i / 1 A 4 c i Agriculture/Forestry/Fishing: Stationary / Disaggregate to main fuel types.
1 A 4 c ii / 1 A 4 c ii Agriculture/Forestry/Fishing: Off-road Vehicles and Other Machinery / Disaggregate to main fuel types.
1A 4 c iii / 1A 4 c iii Agriculture/Forestry/Fishing: National Fishing / Disaggregate to main fuel types.
1 A 5 a / 1 A 5 a Other, Stationary (including Military)
1 A 5 b / 1 A 5 b Other, Mobile (Including military, land based and recreational boats)
1 B 1 a / 1 B 1 a Fugitive emission from Solid Fuels: Coal Mining and Handling
1 B 1 b / 1 B 1 b Fugitive emission from Solid Fuels:Solid fuel transformation
1 B 1 c / 1 B 1 c Other fugitive emissions from solid fuels
1 B 2 a i / 1 B 2 a i Exploration Production, Transport
1 B 2 a iv / 1 B 2 a iv Refining / Storage
1 B 2 a v / 1 B 2 a v Distribution of oil products
1 B 2 a vi / 1 B 2 a vi Geothermal energy extraction
1 B 2 b / 1 B 2 b Natural gas
1 B 2 c / 1 B 2 c Venting and flaring / If this category is key, the inventory compiler should determine which subcategories are significant.
2 A 1 / 2 A 1 Cement Production
2 A 2 / 2 A 2 Lime Production
2 A 3 / 2 A 3 Limestone and Dolomite Use
2 A 4 / 2 A 4 Soda Ash Production and use
2 A 5 / 2 A 5 Asphalt Roofing
2 A 6 / 2 A 6 Road Paving with Asphalt
2 A 7 a / 2 A 7 a Quarrying and mining of minerals other than coal
2 A 7 b / 2 A 7 b Construction and demolition
2 A 7 c / 2A 7 c Storage, handling and transport
2 A 7 d / 2 A 7 d Other Mineral products (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
2 B 1 / 2 B 1 Ammonia Production
2 B 2 / 2 B 2 Nitric Acid Production
2 B 3 / 2 B 3 Adipic Acid Production
2 B 4 / 2 B 4 Carbide Production
2 B 5 a / 2 B 5 a Other chemical industry (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
2 B 5 b / 2 B 5 b Storage, handling and transport (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
2 C 1 / 2 C 1 Iron and Steel Production
2 C 2 / 2 C 2 Ferroalloys Production
2 C 3 / 2 C 3 Aluminum Production
2 C 5 a / 2 C 5 a Copper Production
2 C 5 b / 2 C 5 b Lead Production
2 C 5 c / 2 C 5 c Nickel Production
2 C 5 d / 2 C 5 d Zinc Production
2 C 5 e / 2 C 5 e Other metal production (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
2 C 5 f / 2 C 5 f Storage, handling and transport (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
2 D 1 / 2 D 1 Pulp and Paper
2 D 2 / 2 D 2 Food and Drink
2 D 3 / 2 D 3 Wood processing
2 E / 2 E Production of POPs
2 F / 2 F Consumption of POPs and Heavy Metals (e.g. electricial and scientific equipment) / If this category is key, the inventory compiler should determine which subcategories are significant.
2 G / 2 G Other production, consumption, storage, transportation or handling of bulk products (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
3 A 1 / 3 A 1 Decorative coating application
3 A 2 / 3 A 2 Industrial coating application
3 A 3 / 3 A 3 Other coating application (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
3 B 1 / 3 B 1 Degreasing
3 B 2 / 3 B 2 Dry cleaning
3 C / 3 C Chemical products
3 D 1 / 3 D 1 Printing
3 D 2 / 3 D 2 Domestic solvent use including fungicides
3 D 3 / 3 D 3 Other product use
4 B 1 a / 4 B 1 a Cattle Dairy
4 B 1 b / 4 B 1 b Cattle Non-Dairy
4 B 2 / 4 B 2 Buffalo
4 B 3 / 4 B 3 Sheep
4 B 4 / 4 B 4 Goats
4 B 6 / 4 B 6 Horses
4 B 7 / 4 B 7 Mules and Asses
4 B 8 / 4 B 8 Swine
4 B 9 a / 4 B 9 a Laying Hens
4 B 9 b / 4 B 9 b Broilers
4 B 9 c / 4 B 9 c Turkeys
4 B 9 d / 4 B 9 d Other Poultry
4 B 13 / 4 B 13 Other
4 D 1 / 4 D 1 a Synthetic N-fertilizers
4 D 2 a / 4 D 2 a Farm-level agricultural operations including storage, handling and transport of agricultural products / If this category is key, the inventory compiler should determine which subcategories are significant.
4 D 2 b / 4 D 2 b Off-farm storage, handling and transport of bulk agricultural products / If this category is key, the inventory compiler should determine which subcategories are significant.
4 D 2 c / 4 D 2 c N-excretion on pasture range and paddock Unspesified (Please specify the sources included/excluded in the notes column to the right) / If this category is key, the inventory compiler should determine which subcategories are significant.
4 F / 4 F FIELD BURNING OF AGRICULTURAL WASTES
4 G / 4 G Agriculture OTHER (c) / If this category is key, the inventory compiler should determine which subcategories are significant.
6 A / 6 A SOLID WASTE DISPOSAL ON LAND
6 B / 6 B WASTE-WATER HANDLING
6 C a / 6 C a Clinical Waste Incineration (d)
6 C b / 6 C b Industrial Waste Incineration (d)
6 C c / 6 C c Municipal Waste Incineration (d)
6 C d / 6 C d Cremation
6 C e / 6 C e Small Scale Waste Burning
6 D / 6 D OTHER WASTE (e) / If this category is key, the inventory compiler should determine which subcategories are significant.
7 A / 7 A OTHER (included in National Total for Entire Territory)
aIn 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, except ‘Miscellaneous’ category, where gases can be assessed jointly. There may also be some new gases other than those listed here, and those should also be assessed separately.

4Methodological approaches to identify key categories

It is good practice for each country to identify its national key categories in a systematic and objective manner, by performing a quantitative analysis of the relationships between the level and the trend of each category’s emissions and total national emissions.