Chapter 1: Introduction

CHAPTER 1

INTRODUCTION

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

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Volume 4: Agriculture, Forestry and Other Land Use

Authors
Stephen Michael Ogle (USA), Maria José Sanz Sanchez (Spain), Marcelo Theoto Rocha (Brazil), James Douglas
MacDonald (Canada), Hongmin Dong (China)

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Chapter 1: Introduction

Contents
1 Introduction4
1.1

Introduction ......................................................................................................................................... 1.4

1.2

Overview of greenhouse gas emissions and removals in the AFOLU Sector ..................................... 1.6
1.2.1 Science background ....................................................................................................................... 1.6
1.2.2 Carbon pool definitions and non-CO2 gases .................................................................................. 1.9

1.3

Overview of inventory preparation for the AFOLU Sector .............................................................. 1.10
1.3.1 Land-use and management categories ......................................................................................... 1.10
1.3.2 Tier definitions for methods in AFOLU ...................................................................................... 1.10
1.3.3 Identification of key categories ................................................................................................... 1.11
1.3.4 Steps in preparing inventory estimates ........................................................................................ 1.11

1.4

Organisation of Volume 4 in 2019 Refinement to the 2006 IPCC Guidelines.................................. 1.12

Annex 1A

Historical background on IPCC greenhouse gas inventory guidance for AFOLU Sector ..... 1.18

References............................................................................................................................................... 1.18

FiguresFigure 1.1

The main greenhouse gas emission sources/removals and processes in managed ecosystems 1.6

Figure 1.4

Structure of AFOLU Reporting ............................................................................................. 1.14

TablesTable 1.1 (Updated) Definitions for carbon pools used in AFOLU for each land-use category................................................................................................................................................. 1.9
Table 1.2 (Updated) Land-use categories, carbon pools and non-CO2 gases to be estimated under Tier 1, theirrelevance to AFOLU sections, and the reference to Revised 1996 IPCC Guidelines ............ 1.15

Box
Box 1.1

Framework of tier structure for AFOLU methods ................................................................. 1.11

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Volume 4: Agriculture, Forestry and Other Land Use1
1.1

INTRODUCTIONINTRODUCTION

Volume 4 provides guidance for preparing annual greenhouse gas inventories in the Agriculture, Forestry andOther Land Use (AFOLU) Sector. This volume integrates the previously separate guidance in the Revised 1996
IPCC Guidelines for National Greenhouse Gas Inventories for Agriculture (Chapter 4) and Land Use, Land-Use
Change and Forestry (Chapter 5). This integration recognizes that the processes underlying greenhouse gas
emissions and removals, as well as the different forms of terrestrial carbon stocks, can occur across all types ofland and that often the same practices influence both Agriculture and Land Use, Land Use Change and Forestry.
This approach is intended to improve consistency and completeness in the estimation and reporting of greenhousegas emissions and removals. The refinement builds on this objective by providing updates to the guidance in termsof improved emission factors, new methodologies, and examples for compilers to better understand the estimationof emissions and removals in the AFOLU sector.
The principal changes made in the 2006 IPCC Guidelines and 2019 Refinement to the 2006 IPCC Guidelines for
National Greenhouse Gas Inventories (2019 Refinment), as compared with the Revised 1996 IPCC Guidelines (forboth Agriculture, and Land-Use Change and Forestry, continue to reflect the elaborations of the Revised 1996
IPCC Guidelines introduced in the Good Practice Guidance and Uncertainty Management in National Greenhouse
Gas Inventories (GPG2000) and the Good Practice Guidance for Land Use, Land-Use Change and Forestry (GPGLULUCF). These include:• Adoption of the six land-use categories used in GPG-LULUCF (i.e., Forest Land, Cropland, Grassland,
Wetlands, Settlements, and Other Land – see Chapter 3). These land categories are further sub-divided into
land remaining in the same category and land converted from one category to another. The land-use categories
are designed to enable inclusion of all managed land area within a country;• Reporting on all emissions by sources and removals by sinks from managed lands, which are considered to beanthropogenic, while emissions and removals for unmanaged lands are not reported;• Additional reporting elements introduced in reporting all emissions and removals for managed lands, (see Table
1.2);• Generic methods for accounting of biomass, dead organic matter and soil C stock changes in all land-use
categories and generic methods for greenhouse gas emissions from biomass burning that can be applied in allland-use categories;• Incorporating methods for non-CO2 emissions from managed soils and biomass burning, and livestock
population characterization and manure management systems from Agriculture (Chapter 5 of the Revised 1996
IPCC Guidelines and GPG2000;• Adoption of three hierarchical tiers of methods that range from default emission factors and simple equations
to the use of country-specific data and models to accommodate national circumstances;• Description of alternative methods to estimate and report C stock changes associated with harvested wood
products;• Incorporation of key category analysis for land-use categories, C pools, and CO2 and non-CO2 greenhouse gas
emissions;• Adherence to principles of mass balance in computing carbon stock changes;• Greater consistency in land area classification for selecting appropriate emission and stock change factors andactivity data;• Improvements of default emissions and stock change factors, as well as development of an Emission Factor
Database (EFDB) that is a supplementary tool to the 2006 IPCC Guidelines, providing alternative emission
factors with associated documentation. The EFDB is described in Chapter 2 of Volume 1.
• Incorporation of methods to estimate CO2 and CH4 emissions from flooded land.
The AFOLU Sector has some unique characteristics with respect to developing inventory methods. There aremany processes leading to emissions and removals of greenhouse gases, which can be widely dispersed in spaceand highly variable in time. The factors governing emissions and removals can be both natural and anthropogenic

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

Chapter 1: Introduction(direct and indirect) and it can be difficult to clearly distinguish between causal factors 1. While recognizing thiscomplexity, inventory methods need to be practical and operational.
The 2006 IPCC Guidelines and this 2019 Refinement are designed to assist in estimating and reporting national
inventories of anthropogenic greenhouse gas emissions and removals. For the AFOLU Sector, anthropogenic
greenhouse gas emissions and removals by sinks are defined as all those occurring on ‘managed land’. Managed
land is land where human interventions and practices have been applied to perform production, ecological or social
functions. All land definitions and classifications should be specified at the national level, described in atransparent manner, and be applied consistently over time. Emissions/removals of greenhouse gases do not need
to be reported for unmanaged land. However, it is good practice for countries to quantify, and track over time, thearea of unmanaged land so that consistency in area accounting is maintained as land-use change occurs. The IPCC
describes the Managed Land Proxy (MLP) as an approach to approximate estimates of anthropogenic emissions
and removals, but this proxy estimate also contains emissions and removals resulting from natural disturbances.
This approach, i.e., the use of managed land as a proxy for anthropogenic effects, was adopted in the GPGLULUCF and that use is maintained in the 2019 Refinement. The key rationale for this approach is that the
preponderance of anthropogenic effects occurs on managed lands. By definition, all direct human-induced effects
on greenhouse gas emissions and removals occur on managed lands only. While it is recognized that no area of
the Earth’s surface is entirely free of human influence (e.g., CO2 fertilization), many indirect human influences ongreenhouse gases (e.g., increased N deposition, accidental fire) will be manifested predominately on managed
lands, where human activities are concentrated. Finally, while local and short-term variability in emissions andremovals due to natural causes can be substantial (e.g., emissions from fire, see footnote 1), the natural‘background’ of greenhouse gas emissions and removals by sinks tends to average out over time and space. This
leaves the greenhouse gas emissions and removals from managed lands as the dominant result of human activity.
However, some of the emissions and removals from managed land are characterised by high interannual variability.
Interannual variability (IAV) refers to the variability in the annual emissions and removals estimates between years
within a time series. In the AFOLU sector, the application of the MLP means that IAV can be caused by bothanthropogenic and natural causes. The three main causes of IAV in GHG emissions and removals in the AFOLU
sector are (1) natural disturbances (such as wildfires, insects, windthrow, and ice storms), which can cause large
immediate and delayed emissions and kill trees; (2) climate variability (e.g. temperature, precipitation, anddrought), which affects photosynthesis and respiration; and (3) variation in the rate of human activities, including
land use (such as forest harvesting), and land-use change.
When the MLP is used and the interannual variability in emissions and removals due to natural disturbance is large,
it is difficult to gain a quantitative understanding of the role of human activities compared to the impacts of naturaleffects. In such situations disaggregating 2 MLP emissions and removals into human and natural effects may
provide increased understanding and refined estimates of the emissions and removals that are due to humanactivities such, land use (including harvesting) and land-use change. In this way, disaggregation can contribute toimproved quantification of the trends in emissions and removals due to human activities and mitigation actions
that are taken to reduce anthropogenic emissions and preserve and enhance carbon stocks.
Guidance and methods for estimating greenhouse gas emissions and removals for the AFOLU Sector now include:• CO2 emissions and removals resulting from C stock changes in biomass, dead organic matter and mineral soils,
for all managed lands;• CO2 and non-CO2 emissions from fire on all managed land;• Optional guidance that may be used by countries that choose to disaggregate their reported MLP emissions andremovals (i.e. all emissions and removals on managed land) into those that are considered to result from humanactivities and those that are considered to result from natural disturbances;• N2O emissions from all managed soils;• CO2 emissions associated with liming and urea application to managed soils;• CH4 emissions from rice cultivation;

1

This general observation was made in the IPCC Report on Current Scientific Understanding of the Processes Affecting
Terrestrial Carbon Stocks and Human Influences upon Them (July 2003, Geneva, Switzerland). As a specific example,
emissions from wildfires on managed (and unmanaged) land can exhibit large interannual variations that may be driven byeither natural causes (e.g. climate cycles, random variation in lightning ignitions), or indirect and direct human causes (e.g.
historical fire suppression and past forest harvest activities) or a combination of all three causes, the effects of which cannot
be readily separated.

2

Disaggregating means that an estimate is separated into its component parts.

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Volume 4: Agriculture, Forestry and Other Land Use• CO2 and N2O emissions from cultivated organic soils;• CO2 and N2O emissions from managed wetlands, and CH4 emissions from flooded land;• CH4 emission from livestock (enteric fermentation);• CH4 and N2O emissions from manure management systems; and• C stock change associated with harvested wood products.
The scientific background and rationale for these inventory components are given in the next section.

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OVERVIEW OF GREENHOUSE GASEMISSIONS AND REMOVALS IN THE AFOLU
SECTOR

1.2.1

Science background

Land use and management influence a variety of ecosystem processes that affect greenhouse gas fluxes (Figure1.1), such as photosynthesis, respiration, decomposition, nitrification/denitrification, enteric fermentation, andcombustion. These processes involve transformations of carbon and nitrogen that are driven by the biological(activity of microorganisms, plants, and animals) and physical processes (combustion, leaching, and run-off).

Greenhouse Gases in AFOLUThe key greenhouse gases of concern are CO2, N2O and CH4. CO2 fluxes between the atmosphere and ecosystems
are primarily controlled by uptake through plant photosynthesis and releases via respiration, decomposition andcombustion of organic matter. N2O is primarily emitted from ecosystems as a by-product of nitrification anddenitrification, while CH4 is emitted through methanogenesis under anaerobic conditions in soils and manurestorage, through enteric fermentation, and during incomplete combustion while burning organic
Figure 1.1

The main greenhouse gas emission sources/removals and processes inmanaged ecosystems.

matter. Other gases of interest (from combustion and from soils) are NOx, NH3, NMVOC and CO, because they
are precursors for the formation of greenhouse gases in the atmosphere. Formation of greenhouse gases fromprecursor gases is considered an indirect emission. Indirect emissions are also associated with leaching or run-off

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Chapter 1: Introductionof nitrogen compounds, particularly NO3- losses from soils, some of which can be subsequently converted to N2O
through denitrification.

Emission and Removal Processes
Greenhouse gas fluxes in the AFOLU Sector can be estimated in two ways: 1) as net changes in C stocks overtime (used for most CO2 fluxes) and 2) directly as gas flux rates to and from the atmosphere (used for estimating
non-CO2 emissions and some CO2 emissions and removals). The use of C stock changes to estimate CO2 emissions
and removals, is based on the fact that changes in ecosystem C stocks are predominately (but not exclusively)
through CO2 exchange between the land surface and the atmosphere (i.e. other C transfer process such as leaching
are assumed to be negligible). Hence, increases in total C stocks over time are equated with a net removal of CO2
from the atmosphere and decreases in total C stocks (less transfers to other pools such as harvested wood products)
are equated with net emission of CO2. Non-CO2 emissions are largely a product of microbiological processes (i.e.,
within soils, animal digestive tracts and manure) and combustion of organic materials. Below, emission andremoval processes in the AFOLU Sector are described for the major ecosystem stocks and processes, organizedby ecosystem components, i.e., 1) biomass, 2) dead organic matter, 3) soils and 4) livestock.

Biomass
Plant biomass, including above-ground and below-ground parts, is the main conduit for CO2 removal from theatmosphere. Large amounts of CO2 are transferred between the atmosphere and terrestrial ecosystems, primarily
through photosynthesis and respiration. The uptake of CO2 through photosynthesis is referred to as gross primary
production (GPP). About half of the GPP is respired by plants, and returned to the atmosphere, with the remainder
constituting net primary production (NPP), which is the total production of biomass and dead organic matter in ayear. NPP minus losses from heterotrophic respiration (decomposition of organic matter in litter, dead wood andsoils) is equal to the net carbon stock change in an ecosystem and, in the absence of disturbance losses, is referred
to as net ecosystem production (NEP).
Net Ecosystem Production (NEP) = Net Primary Production (NPP) – Heterotrophic respiration
NEP minus additional C losses from disturbance (e.g., fire), harvesting and land clearing during land-use change,
is often referred to as net biome production (NBP). The carbon stock change that is reported in national greenhousegas inventories for land-use categories is equal to NBP 3.
Net Biome Production (NBP) = NEP – Carbon Losses from Disturbance/Land-Clearing/Harvest
NPP is influenced by land use and management through a variety of anthropogenic actions such as deforestation,afforestation, fertilization, irrigation, harvest, and species choice. For example, tree harvesting reduces biomass
stocks on the land. However, harvested wood requires additional consideration because some of the carbon may
be stored in wood products in use and in landfills for years to centuries. Thus, some of the carbon removed fromthe ecosystem is rapidly emitted to the atmosphere while some carbon is transferred to other stocks in which theemissions are delayed. In non-forest ecosystems (i.e., Cropland, Grassland), biomass is predominantly non-woody
perennial and annual vegetation, which makes up a much smaller part of total ecosystem carbon stocks than inForest Land. The non-woody biomass turns over annually or within a few years and hence net biomass carbon
stocks may remain roughly constant, although stocks may diminish over time if land degradation is occurring.
Land managers may use fire as a management tool in grasslands and forests or wild fires may inadvertently burnthrough managed lands, particularly Forest Land, leading to significant losses of biomass carbon. Fires not only
return CO2 to the atmosphere through combustion of biomass, but also emit other greenhouse gases, directly or
indirectly, including CH4, N2O, NMVOC, NOx and CO.

Dead Organic Matter
The bulk of biomass production (NPP) contained in living plant material is eventually transferred to dead organic
matter (DOM) pools (i.e., dead wood and litter – see Table 1.1 for definitions). Some DOM decomposes quickly,
returning carbon to the atmosphere, but a portion is retained for months to years to decades. Land use andmanagement influence C stocks of dead organic matter by affecting the decomposition rates and input of fresh
detritus. Losses due to burning dead organic matter include emissions of CO2, N2O, CH4, NOx, NMVOC, and CO.

3

Harvested wood or other durable products derived from biomass (e.g., clothing) products are not included in NBP; harvested
wood products (HWP) are dealt with in Chapter 12.

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Soils
As dead organic matter is fragmented and decomposed, it is transformed into soil organic matter (SOM). Soilorganic matter includes a wide variety of materials that differ greatly in their residence time in soil. Some of thismaterial is composed of labile compounds that are easily decomposed by microbial organisms, returning carbon
to the atmosphere. Some of the soil organic carbon, however, is converted into recalcitrant compounds or boundin organic-mineral complexes that are very slowly decomposed and thus can be retained in the soil for decades tocenturies or more. Following fires, small amounts of so-called ‘black carbon’ are produced, which constitute anearly inert carbon fraction with turnover times that may span millennia. Biochar C 4 may be produced throughpyrolysis and amended to soils with a long turnover time.
Soil organic carbon stocks are influenced by land-use and management activities that affect litter input rates andsoil organic matter loss rates. Although the dominant processes governing the balance of soil organic carbon stocks
are C inputs from plant residues and C emissions from decomposition, losses as particulate or dissolved carbon
can be significant in some ecosystems. Inputs are primarily controlled by decisions impacting NPP and/or theretention of dead organic matter, such as how much harvested biomass is removed as products and how much isleft as residues. Outputs are mostly influenced by management decisions that affect microbial and physicaldecomposition of soil organic matter, such as tillage intensity. Depending on interactions with previous land use,
climate and soil properties, changes in management practices may induce increases or decreases in soil C stocks.
Generally, management-induced C stock changes are manifested over a period of several years to a few decades,
until soil C stocks approach a new equilibrium. In addition to the influence of human activities, climate variability
and other environmental factors affect soil C dynamics (as well as biomass and DOM).
In flooded conditions, such as wetland environments and paddy rice production, a significant fraction of thedecomposing dead organic matter and soil organic matter is returned to the atmosphere as CH4. This can be amajor source of emissions in countries with a considerable amount of land dedicated to paddy rice production or
are flooded land (e.g., reservoirs created by constructing dams on rivers). Although virtually all flooded soils emit
methane, net soil C stocks may either increase, decrease or remain constant over time, depending on management
and environmental controls on the overall carbon balance. In well-drained soils, small amounts of CH4 areconsumed (oxidized) by methanotrophic bacteria although this impact on CH4 removals is not addressed in thecurrent guidance due to limited studies for quantifying the impact. 5
Soils also contain inorganic C pools, either as primary minerals in the parent material from which the soil wasformed (e.g., limestone), or as secondary minerals (i.e., pedogenic carbonates) that arise during soil formation.
Inorganic soil C stocks can be affected by management, although typically not to the extent of organic C pools.
Some soil management practices impact greenhouse gas emissions beyond simply changing the C stock. For
example, liming is used to reduce soil acidity and improve plant productivity, but it is also a direct source of CO2
emissions. Specifically, liming transfers C from the earth’s crust to the atmosphere by removing calcium carbonate
from limestone and dolomite deposits and applying it to soils where the carbonate ion evolves into CO2.
Nitrogen additions are a common practice for increasing NPP and crop yields, including application of synthetic
N fertilizers and organic amendments (e.g., manure), particularly to cropland and grassland. This increase in soil
N availability increases N2O emissions from soils as a by-product of nitrification and denitrification. Nitrogen
additions (in dung and urine) by grazing animals can also stimulate N2O emissions. Similarly, land-use changeenhances N2O emissions if associated with heightened decomposition of soil organic matter and subsequent N
mineralization, such as initiating cultivation on wetlands, forests or grasslands.

Livestock
Animal production systems, particularly those with ruminant animals, can be significant sources of greenhousegas emissions. For example, enteric fermentation in the digestive systems of ruminants leads to production andemission of CH4. Management decisions about manure disposal and storage affect emissions of CH4 and N2O,
4 Biochar is a solid carbonised product from thermochemical conversion through pyrolysis (heating with limited air). The

termbiochar is used herein only to refer to materials that have been produced under process conditions in which relatively easily
mineralisable organic materials are converted to more persistent forms by heating to above 350°C with limited air through agasification or pyrolysis process. No default methodology is provided for biochar C amendments, but guidance is provided
for Tier 2 and 3 methods. However, this guidance does not deal with pyrolytic organic materials that result from wild fires
or open fires, and is only applicable for biochar added to mineral soils.

5

No default methodology exists for estimation of CH4 removals in aerobic soils because of limited studies addressing landuse and management impacts on methane oxidation. However, there is evidence that disturbance through land-use change
and addition of nitrogen (i.e., as fertilizer) may reduce rates of methane oxidation. Countries that wish to estimate and report
CH4 removals should develop, validate and document an appropriate national methodology for estimating CH4 removals,
including analysis of uncertainty. It is good practice for countries reporting CH4 removals to also ensure symmetry byincluding all emissions of CH4 on lands were CH4 removals are reported.

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Chapter 1: Introduction

which occur result from methanogenesis in decomposing manures and as a by-product nitrification/ denitrification.
Furthermore, volatilization losses of NH3 and NOx and losses of N in leaching and runoff from manure
management systems and soils leads to indirect greenhouse gas emissions.

1.2.2

Carbon pool definitions and non-CO2 gases

Within each land-use category, C stock changes and emission/removal estimations can involve the five carbon
pools that are defined in Table 1.1. For some land-use categories and estimation methods, C stock changes may
be based on the three aggregate carbon pools (i.e., biomass, DOM and soils). National circumstances may require
modifications of the pool definitions introduced here. Where modified definitions are used, it is good practice toreport and document them clearly, to ensure that modified definitions are used consistently over time, and todemonstrate that pools are neither omitted nor double counted. Carbon stock changes associated with harvested
wood products are normally reported at the national scale (see Chapter 12).
The non-CO2 gases of primary concern for the AFOLU Sector are methane (CH4) and nitrous oxide (N2O).
Emissions of other nitrogenous gases including NOx and NH3, which can serve as a source of subsequent N2Oemissions (and hence referred to as indirect emission sources), are also considered (see Chapters 10 and 11).
TABLE 1.1 (UPDATED)DEFINITIONS FOR CARBON POOLS USED IN AFOLU FOR EACH LAND-USE CATEGORY

Pool
Biomass

Dead organic
matterSoils

Description
Abovegroundbiomass

All biomass of living vegetation, both woody and herbaceous, above the soil
including stems, stumps, branches, bark, seeds, and foliage.
Note: In cases where forest understory is a relatively small component of theabove-ground biomass carbon pool, it is acceptable for the methodologies andassociated data used in some tiers to exclude it, provided the tiers are used in aconsistent manner throughout the inventory time series.

Belowgroundbiomass

All biomass of live roots. Fine roots of less than (suggested) 2mm diameter areoften excluded because these often cannot be distinguished empirically from soilorganic matter or litter.

Dead wood

Includes all non-living woody biomass not contained in the litter, either standing,lying on the ground, or in the soil. Dead wood includes wood lying on the surface,dead roots, and stumps, larger than or equal to 10 cm in diameter (or the diameter
specified by the country).

LitterIncludes all non-living biomass with a size greater than the limit for soil organic
matter (suggested 2 mm) and less than the minimum diameter chosen for dead wood(e.g. 10 cm), lying dead, in various states of decomposition above or within themineral or organic soil. This includes the litter layer as usually defined in soil
typologies. Live fine roots above the mineral or organic soil (of less than theminimum diameter limit chosen for below-ground biomass) are included in litter
where they cannot be distinguished from it empirically.

Soil organic
matter1

Includes organic carbon in mineral soils to a specified depth chosen by the country
and applied consistently through the time series2,3. Live and dead fine roots andDOM within the soil that are less than the minimum diameter limit (suggested 2mm) for roots and DOM, are included with soil organic matter where they cannot be
distinguished from it empirically. The default for soil depth is 30 cm and guidanceon determining country-specific depths is given in Chapter 2.3.3.1.

1
Includes organic material (living and non-living) within the soil matrix, operationally defined as a specific size fraction (e.g.,
all matter passing through a 2 mm sieve). Soil C stock estimates may also include soil inorganic C if using a Tier 3 method. CO2
emissions from liming and urea applications to soils are estimated as fluxes using Tier 1 or Tier 2 methods.

Carbon stocks in organic soils are not explicitly computed using Tier 1 or Tier 2 methods, (which estimate only annual C flux
from organic soils), but C stocks in organic soils can be estimated in a Tier 3 method. Definition of organic soils for classification
purposes is provided in Chapter 3.

2

Biochar C amendments are estimated separately and includes all C added to soils without regard to depth for Tier 2 methods.
No default method is provided.

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1.3

OVERVIEW OF INVENTORY PREPARATIONFOR THE AFOLU SECTOR

To prepare inventories for the AFOLU Sector, emissions and removals of CO2 and non-CO2 greenhouse gases are
estimated separately for each of six land-use categories. Other CO2 emission and non-CO2 categories, such as
livestock related emissions, emissions from soil N management, soil liming emissions and harvested wood
products, may be estimated at the national scale, since often only aggregate data are available. However, they canbe broken out according to land-use category if data are available.

1.3.1

Land-use and management categories

A brief overview of how land area is categorized for inventory purposes is given here. Chapter 3 provides a detailed
description of land representation and categorization of land area by land-use and management systems as well as
stratification of land area by climate, soil and other environmental strata.
The six land-use categories (see definitions in Chapter 3) in the 2006 IPCC Guidelines are:•Forest Land;•

Cropland;•

Grassland;•

Wetlands;•

Settlements;•

Other Land.

Each land-use category is further subdivided into land remaining in that category (e.g., Forest Land Remaining
Forest Land) and land converted from one category to another (e.g., Forest Land converted to Cropland). Countries
may choose to further stratify land in each category by climatic or other ecological regions, depending on the
choice of the method and its requirements. Greenhouse gas emissions and removals determined for each specificland use includes CO2 (as carbon stock changes) from biomass, dead organic matter and soils, as well as non-CO2
emissions from burning and, depending on the land-use category, emissions from other specific sources (e.g. CH4emissions from rice and flooded land).
CH4 and N2O emissions from livestock management are estimated for major animal types, e.g., dairy cows, othercattle, poultry, sheep, swine and other livestock (buffalo, goats, llamas, alpacas, camels, etc). The animal waste
management systems include anaerobic lagoons, liquid systems, daily spread, solid storage, dry-lot, pasture/
range/paddock, and other miscellaneous systems.
Nitrous oxide emissions from managed soils are usually estimated from aggregate (national-level) data on N
supplied to soils, including N fertilizer usage or sales, crop residue management, organic amendments and landuse conversions that enhance mineralization of N in soil organic matter. Similarly, CO2 emissions from liming
and from urea application to managed soils are typically estimated using aggregate data (e.g., national-level).
Harvested wood products constitute a component of the carbon cycle for which carbon stock changes can be
estimated (guidance provided in Chapter 12), based on national-level data; however, estimation and reporting ofgreenhouse gas emissions for HWP is currently a matter of policy negotiations.

1.3.2

Tier definitions for methods in AFOLU

The concepts underpinning the three-tiered approach, as they relate to methods used in the AFOLU Sector, areoutlined here (see Box 1.1). In general, moving to higher tiers improves reduces uncertainty in the inventory, but
the complexity and resources required for conducting inventories also increases for higher tiers. If needed, acombination of tiers can be used, e.g., Tier 2 can be used for biomass and Tier 1 for soil carbon.
The methods and data presented focus on Tier 1 inventories. The methods will be generally applicable to Tier 2inventories, but the default data presented for Tier 1 will be partly or wholly replaced with national data as part ofa Tier 2 estimation. There are few exceptions with alternative methodologies to derive country-specific factors forTier 2 (e.g., gross energy intake calculations to estimate methane emissions from enteric fermentation). Tier 3
methods are not described in detail, but good practice in application is outlined and some examples are provided
in information boxes.

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Chapter 1: Introduction

BOX 1.1
FRAMEWORK OF TIER STRUCTURE FOR AFOLU METHODS

Tier 1 methods are designed to be the simplest to use, for which equations and default parametervalues (e.g., emission and stock change factors) are provided in this volume. Country-specificactivity data are needed, but for Tier 1 there are often globally available sources of activity data
estimates (e.g., deforestation rates, agricultural production statistics, global land cover maps,
fertilizer use, livestock population data, etc.), although these data are usually spatially coarse.
Tier 2 can use the same methodological approach as Tier 1 but applies emission and stock change
factors that are based on country- or region-specific data, for the most important land-use or livestockcategories. Country-defined emission factors are more appropriate for the climatic regions, land-use
systems and livestock categories in that country. Higher temporal and spatial resolution and moredisaggregated activity data are typically used in Tier 2 to correspond with country-definedcoefficients for specific regions and specialized land-use or livestock categories. For a few source
categories, methodologies are provided for estimating a country-specific emission and stock change
factors (e.g., CH4 emissions from enteric fermentation).
At Tier 3, higher order methods are used, such as process-based models and inventory measurement
systems tailored to address national circumstances, repeated over time, and driven by high-resolution
activity data and disaggregated at sub-national level. These higher order methods provide estimatesof greater certainty than lower tiers. Such systems may include comprehensive field sampling
repeated at regular time intervals and/or GIS-based systems of age, class/production data, soils data,
and land-use and management activity data, integrating several types of monitoring. Pieces of land
where a land-use change occurs can usually be tracked over time, at least statistically. In most cases
these systems have a climate dependency, and thus provide source estimates with interannual
variability. Detailed disaggregation of livestock population according to animal type, age, bodyweight etc., can be used. Models should undergo quality checks, audits, and validations and bethoroughly documented.

1.3.3

Identification of key categories

No refinement.

1.3.4

Steps in preparing inventory estimates

The following steps describe the compilation of the greenhouse gas inventory for the AFOLU Sector:
1. Divide all land into managed and unmanaged (Chapter 3).
2. Develop a national land classification system applicable to all six land-use categories (Forest Land, Cropland,
Grassland, Wetlands, Settlements and Other Land) and further subdivide by climate, soil type and/or ecologicalregions (i.e., strata) appropriate for the country, as described in Chapter 3.
3. Compile data on the area of land and the change in area of land in each land-use category (by category) if
available. Categorize land area by specific management systems defined for each land-use category (bycategory), which is based on combinations of management practices (e.g., tillage and fertiliser management in
Croplands). This categorization provides the basis for assigning emission factors and stock change factors,
required for a particular estimation approach (see Chapter 3).
4. Compile national-level statistics for livestock, manure management systems, soil N management, crop yields,
biochar C (Tier 2 and 3 only), liming and urea application (if land-use specific activity data are available forsoil fertilization and liming activities, these emissions categories can be stratified as in Step 2; biochar C
amendment data are stratified by Cropland and Grassland as in Step 2).
5. Estimate CO2 emissions and removals and non-CO2 emissions at the appropriate tier level in support of a key
category analysis. A preliminary inventory is likely to utilize a Tier 1 or Tier 2 approach. However, it may be
preferable to proceed with a Tier 3 approach if the methods have been previously developed and the supporting
activity and input data have been compiled (see Chapter 2 for general guidance on methods).
6. Re-estimate CO2 emissions and removals and non-CO2 emissions if a higher Tier is recommended, based on
the key category analysis (see Volume 1 Chapter 4 for methods to identify Key Categories).

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

1.11

Volume 4: Agriculture, Forestry and Other Land Use

7. Estimate uncertainties (see Volume 1 Chapter 3) and complete QA/QC procedures (which are initiated at Step
1) using the methods provided in Volume 1 Chapter 6, along with additional guidance provided in Chapters 2
to 12 of this Volume.
8. Sum CO2 emissions and removals and non-CO2 emissions over the inventory period for each source category
by land use and stratum, as well as emissions from livestock, manure, and N management (if not analysed
separately for each land-use category).
9. Transcribe summary information into reporting tables, converting C stock changes to emissions or removalsof CO2 and entering non-CO2 greenhouse gas emissions, by land-use categories, if available. Combine withany emission estimates that are based on national aggregate data (e.g. livestock, manure management and soil
management/amendment) to estimate the total emissions and removals for the AFOLU Sector (See Volume 1
Chapter 8, Reporting Guidance and Tables).
10. Document and archive all information used to produce an inventory, including activity and other input data,
emission factors, sources of data and metadata documentation, methods descriptions and model software orcode, QA/QC procedures and reports, in addition to the results for each source category.
11. Set priorities for future inventories in AFOLU Sector based on completeness of current inventories,
uncertainties, and issues arising during QA/QC. Revise key category analysis based on the newly completed
inventory to aid in decisions regarding future priorities.

1.4

ORGANISATION OF VOLUME 4 IN 2019
REFINEMENT TO THE 2006 IPCC GUIDELINES

The material in Volume 4 should be used as follows:• Chapter 2 describes generic methods for carbon pools and biomass burning that can be applied within each of
the six land-use categories, i.e., the methods are not specific to a particular land use. These consist of estimating
ecosystem C stock changes and CO2 and non-CO2 emissions from fires and biomass burning. To avoid
redundancy in the subsequent land-use specific chapters, Tier 1 equations are provided along with tables ofgeneric emission factors and other parameters. Chapter 2 also provides guidance on choice of method anddecision trees for tier selection including general guidance for Tier 2 emission factors on how to use allometricmodels and biomass maps; and guidance on how to parameterize and evaluate Tier 3 models, the integrationof data to models, estimating uncertainties and means to increase its transparency. Some case studies
demonstrating how parties have developed and worked with Tier 3 methods are presented in information boxes.
In addition, Chapter 2 provides an optional approach that may be used by countries that choose to disaggregate
their reported MLP emissions and removals (i.e. all emissions and removals (E/R) on managed land) into thosethat are considered to result from human activities and those that are considered to result from natural
disturbances (ND). In particular, the approach describes a generic method to reduce interannual variability of
E/R due to natural disturbances and increase the proportion of the anthropogenic contribution reported in the
MLP by disaggregating from the total flux the component which is attributed to ND. The remaining E/Rquantifies the anthropogenic component of E/R on managed land as the total minus that from ND. This estimate
may still be somewhat affected by ND and other natural effects, but less so compared to the total E/R estimatedusing the MLP. Because the goal of the national GHG Inventories is to estimate and report anthropogenic E/R,
the approach is proposed as a refined estimate of the anthropogenic E/R. The reason that the approach has
limited the disaggregation to E/R from ND is because scientific methods to quantify all-natural effects are
currently not available. Where a country choses to disaggregate E/R from ND from the remaining
anthropogenic E/R estimated using the MLP, it is good practice to report the total MLP E/R and the two
disaggregated components, and to document the methods and assumptions used.
• Chapter 3 deals with the consistent representation of land. In particular, the multiple approaches forclassification of land-use categories are presented in this chapter, along with the level of disaggregation. Users
will find this material helpful for understanding the general issues surrounding representation of systems, which
will be needed later in order to use the estimation methods that are specific to a particular land-use and/or
source category. After consulting Chapter 2 and Chapter 3, users should proceed to the appropriate chapter
addressing the issues specific to a particular land-use or source category.
• Chapters 4 to 9 provide information for specific land-use categories. These chapters contain information on theapplication of the generic methods described in Chapter 2 and they also contain full method descriptions andapplication for any land-use specific methods.

1.122019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 1: Introduction• Chapter 4 deals with estimation of emissions and removals from forest lands. Separate sections cover Forest
Land Remaining Forest Land and Land Converted to Forest Land. Harvested wood products are addressed
separately in Chapter 12.
• Chapter 5 deals with estimation of emissions and removals from cropland. Separate sections cover Cropland
Remaining Cropland and Land Converted to Cropland. CH4 production from rice cultivation, which is specificto cropland, is also addressed in this chapter.
• Chapter 6 deals with estimation of emissions and removals from the Grassland. Separate sections cover
Grassland Remaining Grassland and Land Converted to Grassland.
• Chapter 7 deals with estimation of emissions and removals from Wetlands, including peat extraction in natural
peatlands and flooded lands, including estimation of CO2 and CH4 emissions.
• Chapter 8 deals with estimation of emissions and removals from Settlements. Separate sections cover
Settlements Remaining Settlements and Land Converted to Settlements.
• Chapter 9 deals with ‘Other Land’, which includes areas with bare soil, rock, and ice, in addition to all land
areas that do not fall into the other five land-use categories treated in Chapters 4 to 8. Since greenhouse gas
emissions and removals are not reported for unmanaged lands, methods and guidance in this chapter apply onlyto ‘Land Converted to Other Land’, for example, from extreme degradation of forest, cropland or grassland tobarren land that is no longer managed for useful purposes.
• Chapter 10 provides guidance on livestock related emissions, including CH4 emissions from entericfermentation and CH4 and N2O (direct and indirect) emissions from manure management. The guidance
provides different options to adapt emission estimates to consider the productivity of the livestock systems andassures consistency among emission estimates for different sources of emissions resulting from livestock
production.
• Chapter 11 provides guidance for emissions sources from managed soils, associated primarily with applicationof fertilizer, crop residues, manure, lime, and urea to soils. Specifically, methods and guidance are provided
for estimating N2O emissions from managed soils and CO2 emissions from liming and urea applications.
Activity data for these sources are typically not broken out by individual land use, hence Tier 1 methods are
based on (national) aggregate data.
• Chapter 12 provides methodological guidance for estimation of C stock changes and emissions from harvested
wood products, and is neutral with regards to the multiple alternative approaches to inventory estimation thatare given.
Figure 1.4 presents the structure of AFOLU reporting with categories (including category codes) that are listed inTable 8.2 of Volume 1.
Annex 1 provides worksheets for each sub-category that can be used to estimate emissions based on Tier 1 methods
and appropriate emission/stock change factors and activity data. The Reporting Tables for the greenhouse gas
emissions/removals at sectoral and national levels are provided in Volume 1 Chapter 8 of the Guidelines.
Annex 2 is the summary of all equations in AFOLU that serves as quick reference for inventory compilers.
Table 1.2 provides the summary information as to what carbon pools and activities emitting non-CO2 gases in eachland-use category are treated under Tier 1 methods; in what section in AFOLU Volume the guidance is discussed,
and their reference to the Revised 1996 IPCC Guidelines.

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

1.13

Volume 4: Agriculture, Forestry and Other Land Use

Figure 1.4

1.14

Structure of AFOLU Reporting2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 1: Introduction

TABLE 1.2 (UPDATED)LAND-USE CATEGORIES, CARBON POOLS AND NON-CO2 GASES TO BE ESTIMATED UNDER TIER 1, THEIR RELEVANCE TO
AFOLU SECTIONS, AND THE REFERENCE TO REVISED 1996 IPCC GUIDELINES
Land-usecategory/
Chapter

Subcategory

Forest Land
Remaining
Forest Land (FF)Forest Land
(Chapter 4)

Land Converted
to Forest Land
(LF)

CroplandRemaining
Cropland (CC)
Cropland(Chapter 5)

Land Converted
to Cropland (LC)C pool & non-CO2
gases

Methods
Section

Chapter 2
MethodLinkage to
Revised1996 IPCC
Guidelines

Tier 1
MethodAbove-groundbiomass

4.2.1

2.3.1.1

5A⊕

Below-groundbiomass

4.2.1

2.3.1.1

NE⊕

Dead organic matter

4.2.2

2.3.2.1

NE

0

Soil carbon

4.2.3

2.3.3.1

5D⊕1

Non-CO2 frombiomass burning

4.2.4

2.4

NE

⊕

Above-groundbiomass

4.3.1

2.3.1.2

5A, 5C⊕

Below-groundbiomass

4.3.1

2.3.1.2

NE⊕

Dead organic matter

4.3.2

2.3.2.2

NE⊕

Soil carbon

4.3.3

2.3.3.1

5D⊕

Non-CO2 frombiomass burning

4.3.4

2.4

4E, 4F⊕

Above-groundbiomass

5.2.1

2.3.1.1

5A⊕3

Dead organic matter

5.2.2

2.3.2.1

NE

0

Soil carbon

5.2.3

2.3.3.1

5D⊕

Non-CO2 from crop
residue burning

5.2.4

2.4

4F

⊕

Methane emissions
from rice

5.5

-

4C

⊕

Above-groundbiomass

5.3.1

2.3.1.2

5B⊕

Dead organic matter

5.3.2

2.3.2.2

NE⊕

Soil carbon

5.3.3

2.3.3.1

5D⊕

Non-CO2 frombiomass (cropresidue) burning

5.3.4

2.4

4E, 5B⊕

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

1.15

Volume 4: Agriculture, Forestry and Other Land Use

TABLE 1.2 (UPDATED) (CONTINUED)
LAND-USE CATEGORIES, CARBON POOLS AND NON-CO2 GASES TO BE ESTIMATED UNDER TIER 1, THEIR RELEVANCE TO
AFOLU SECTIONS, AND THE REFERENCE TO REVISED 1996 IPCC GUIDELINES
Land-usecategory/
Chapter

Methods
Section

Chapter 2
MethodLinkage to
Revised1996 IPCC
Guidelines

Tier 1
MethodAbove-groundbiomass

6.2.1

2.3.1.1

5A

0

Dead organic
matter

6.2.2

2.3.2.1

NE

0

Soil carbon

6.2.3

2.3.3.1

5D⊕

Non-CO2 frombiomass burning

6.2.4

2.4

4E

⊕

Above-groundbiomass

6.3.1

2.3.1.2

5B⊕

Dead organic
matter

6.3.2

2.3.2.2

NE⊕

Soil carbon

6.3.3

2.3.3.1

5D⊕

Non-CO2 frombiomass burning

6.3.4

2.4

4F, 5B⊕

CO2 emissions

7.2.1.1-

NE⊕

Non-CO2emissions7.2.1.2-

NE⊕

Land Being
Converted forPeat Extraction

CO2 emissions

7.2.2.1-

NE

NA

Non-CO2emissions7.2.2.2-

NE⊕

Flooded Land
Remaining
Flooded Land

CO2 emissions

7.3.1.1-

NE

0

Non-CO2emissions7.3.1.2-NE⊕

CO2 emissions

7.3.2.1-

NE⊕

Non-CO2emissions7.3.2.2-

NE⊕

Above-groundbiomass

8.2.1

2.3.1.1

5A

0

Dead organic
matter

8.2.2

2.3.2.1

NE

0

Soil carbon

8.2.3

2.3.3.1

NE⊕1

Above-groundbiomass

8.3.1

2.3.1.2

5B⊕

Dead Organic
Matter

8.3.2

2.3.2.2

NE⊕

Soil carbon

8.3.3

2.3.3.1

NE⊕

Above-groundbiomass

9.3.1

2.3.1.2

5B⊕

Dead Organic
Matter

9.3.2

2.3.2.2

NE

NA

Soil carbon

9.3.3

2.3.3.1

NE⊕

Subcategory

Grassland
Remaining
Grassland (GG)
Grassland(Chapter 6)
Land Converted
to Grassland(LG)

Peatlands
Remaining
Peatlands

Wetlands(Chapter 7)

Land Converted
to Flooded Land

Settlements
Remaining
Settlements (SS)Settlements(Chapter 8)Land Converted
to Settlements(LS)

Other Land
(Chapter 9)

1.16

Land Converted
to Other Land(LO)

C pool & non-CO2
gases2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 1: Introduction

TABLE 1.2 (UPDATED) (CONTINUED)
LAND-USE CATEGORIES, CARBON POOLS AND NON-CO2 GASES TO BE ESTIMATED UNDER TIER 1, THEIR RELEVANCE TO
AFOLU SECTIONS, AND THE REFERENCE TO REVISED 1996 IPCC GUIDELINES
Land-usecategory/
Chapter

Livestock(Chapter 10)

Managedsoils(Chapter 11)
Harvested
wood
products(Chapter 12)

Methods
Section

Chapter 2
MethodLinkage to
Revised1996 IPCC
Guidelines

Tier 1
MethodCH4 emissions

10.3

-

4A

⊕

CH4 emissions

10.4

-

4B

⊕

N2O emissions

10.5

-

4B

⊕

Soil
Management

N2O emissions

11.2

-

4D

⊕

Liming

CO2 emissions

11.3

-

_

⊕

Urea
Fertilization

CO2 emissions

11.4

-

NE

⊕

Wood Products

C stock changes

Chapter 12

-

NE

⊕2

Subcategory
Enteric
Fermentation
ManureManagement

C pool & nonCO2 gases

The Revised 1996 IPCC Guidelines cover the following categories: 5A Changes in Forest and Other Woody Biomass Stocks; 5B Forest
and Grassland Conversion; 5C Abandonment of Managed Lands; 5D Emissions and Removals from Soils, and 5E Other (Reporting
Instructions p. 1.14 - 1.16)
NE: not estimated under default method in the 1996 IPCC Guidelines
NG – no guidance provided in the Guidelines
Notes for column “Tier 1 Method”:⊕ - Tier 1 methods and default parameters are available in the Guidelines.
0 = Tier 1 (default) assumption is that emissions are zero or in equilibrium; no methods and parameters are provided in the Guidelines.
1 = Tier 1 and default factors available only for organic soils.
2 = Tier 1 method available to estimate HWP variables which may be used to compute HWP Contribution to AFOLU.
3 = Tier 1 and default factors only available for perennial woody vegetation
NA – not applicable2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

1.17

Volume 4: Agriculture, Forestry and Other Land Use

Annex 1A

Historical background on IPCC greenhouse gas
inventory guidance for AFOLU Sector

No refinement.

References
IPCC (1997). Revised 1996 IPCC Guidelines for National Greenhouse Inventories. Houghton J.T., Meira Filho
L.G., Lim B., Tréanton K., Mamaty I., Bonduki Y., Griggs D.J. Callander B.A. (Eds). Intergovernmental Panelon Climate Change (IPCC), IPCC/OECD/IEA, Paris, France.
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., Tanabe K. (Eds). Intergovernmental Panel on Climate Change (IPCC),
IPCC/OECD/IEA/IGES, Hayama, Japan.
IPCC (2003). Good Practice Guidance for Land Use, Land-Use Change and Forestry. Penman J., Gytarsky M.,
Hiraishi T., Krug, T., Kruger D., Pipatti R., Buendia L., Miwa K., Ngara T., Tanabe K., Wagner F.
(Eds).Intergovernmental Panel on Climate Change (IPCC), IPCC/IGES, Hayama, Japan.

1.18

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