UNFCCC Guidance for GHG Inventories

The IPCC Guidelines for National Greenhouse Gas Inventories are the official guidance used by the Parties to the UNFCCC in preparing their National Communications and Biennial Update Reports. They were developed through a politically-oriented process to synthesize the best available science on greenhouse gas (GHG) estimation.

The first version of the guidelines was published in 1996 as the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories. The guidelines provide detailed instructions for the application of various methods for the estimation of GHG removals and emissions from sinks and sources across all sectors, and on reporting to the COP. Chapter 4 contains guidelines for agriculture and Chapter 5 for land-use change and forestry.

Two supplementary volumes provided additional guidance: Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories and Good Practice Guidance for Land Use, Land-Use Change and Forestry. These provide detailed guidance for procedures that may be used in characterizing activity data and selecting emission factors, in the quantification of uncertainty in GHG inventories and in the analysis of key GHG sources, and provides guidance on quality control and quality assurance in GHG inventories.

The most recent version of the guidelines was released in 2006: 2006 IPCC Guidelines for National Greenhouse Gas Inventories. The relevant volume for agriculture is Volume 4: Agriculture, Forestry and Other Land Use.

A supplement, published in 2013 (called the Wetlands Supplement) provides additional guidelines for inland organic soils and wetlands on mineral soils, coastal wetlands (including mangrove forests, tidal marshes and seagrass meadows) and constructed wetlands for wastewater treatment.

In 2019, the IPCC released a refinement of the 2006 guidelines, incorporating the latest science on greenhouse gas sinks and sources, called the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.

Who uses UNFCCC guidance?

Guidelines for the preparation of National Communications (NCs) advise developing countries to use the Revised 1996 IPCC Guidelines for National GHG Inventories to estimate and report their national GHG inventories and IPCC Good Practice Guidance and Uncertainty Management in National GHG Inventories. The Revised 1996 IPCC Guidelines provide detailed instructions for the application of various methods for estimating GHG removals and emissions from sinks and sources across all sectors, and on reporting to the Conference Of the Parties.

While there may be some evolution of GHG measurement requirements for developing countries under the Enhanced Transparency Framework established by the Paris Agreement (such as mandated use of the 2006 IPCC Guidelines), there have been no substantive negotiations on this issue to date (2021).

Guidelines for the preparation of BURs have considerable overlaps with the guidelines for NCs and explicitly reference the NC guidelines related to measurement in national GHG inventories. Some requirements for BURs represent updates to the NC reporting requirements (e.g., developing countries are encouraged to use reporting tables from the IPCC Good Practice Guidance for Land Use, Land Use Chance and Forestry in addition to other sectoral tables specified in the Revised 1996 Guidelines). Requirements are emphasized given the specific purpose of BURs (e.g., Parties are encouraged to provide a consistent time series back to the years reported in the previous National Communications). 

GHG inventories are usually prepared and submitted by the country’s meteorological institute or environment ministry. Other ministries and departments, such as those responsible for energy or agriculture, are often asked to prepare the relevant sector’s inventory or provide necessary information to the meteorological institute or environment ministry.

However, beyond official uses for reporting to the UNFCCC, the IPCC guidelines are the basis for many other tools and methodologies, such as GHG0 calculators, industry standards and carbon credit certifications. The “tier” language used in the IPCC guidelines is often used as a benchmark for a GHG estimation method’s complexity, even outside of UNFCCC reports and NCs. 

Methodological approaches

There are three tiers of methodological complexity in GHG inventories. Tier 1 is the most basic method, Tier 2 intermediate and Tier 3 most demanding in complexity and data requirements. Tiers 2 and 3 are sometimes referred to as “higher tier” methods and are generally considered more accurate and more suitable for MRV mitigation actions. For example, Tier 1 approaches for livestock emissions cannot reflect changes in animal production and productivity and are not suitable for measuring the effects of change in the livestock sector or specific mitigation actions on GHG emissions.

The most common, simple methodological approach used in the IPCC guidelines is to combine information on the extent to which a human activity takes place (called activity data, AD) with coefficients that quantify the emissions or removals per unit of activity (called emission factors, EF). The basic equation is:

Emissions = AD • EF

The guidelines also contain mass balance methods, for example, the stock change methods used in the agriculture, forestry and other land-use (AFOLU) sector estimates CO2 emissions from changes over time in the carbon content of living biomass and dead organic matter pools (IPCC 2006 Guidelines Volume 1).

The specific practices used in preparing inventories vary considerably, reflecting the flexibility in IPCC guidelines as well as national conditions, including the national situation, capacities and resources.

Livestock Example Case: Tier 1 vs. Tier 2 approaches to estimate GHG emissions from livestock

Tiered approaches to estimating GHG emissions

For the different GHG sources reported, the vast majority of Parties used a Tier 1 approach to estimate all GHG emissions from all types of livestock (Table 1). Appropriate to the tiered approach adopted, most countries used and presented livestock populations in a basic characterization. Only countries using a Tier 2 approach for some or all livestock types used an enhanced categorization of livestock populations.

Table 1. Use of tiered approaches in the estimation of livestock emissions by 140 non-Annex 1 Parties

Tier 1 for all livestock types Tier 1b for all livestock types Tier 2 for some livestock types Tier 2 for all livestock types
Enteric fermentation 118 0 19 2
Manure mgt 120 6 10 0
Agricultural soils 110 2 2 2

Using a Tier 2 approach for enteric fermentation

Twenty-one Parties have reported some or all livestock emissions using a Tier 2 approach. Most often this was applied only to cattle populations or certain types of cattle, while other livestock were reported using a Tier 1 approach. In some cases, a Tier 2 approach was also applied to some other livestock types (e.g., small ruminants in South Africa), and two Parties (Mongolia, Korea) reported applying a Tier 2 approach to estimate enteric fermentation emissions from all types of livestock.

The Tier 2 approach was implemented in different ways, depending on national circumstances, including the availability of data. These approaches included:

(a) IPCC model: The most commonly used approach was to populate the IPCC enteric fermentation model with available data. Countries structured this in different ways (see Box 1). For example, Bolivia stratified the livestock population by agro-ecological zone; Argentina stratified the population by agro-ecological zone and production system, and Georgia stratified the cattle population by breed. With each stratum, specific emission factors were developed for sub-categories of cattle.

(b) Use of other models: Considering the similarities between agro-ecological conditions and production systems in Australia and South Africa, South Africa developed Tier 2 emission factors for livestock based on equations produced under Australian conditions. India‘s national inventory uses Tier 2 emission factors for cattle developed through a country-specific methodology that relates the total digestible nutrients of national feeding standards to gross energy (Swamy & Bhattacharya, 2006).

(c) Use of the dry matter intake method: Bangladesh developed Tier 2 emission factors for cattle produced using a dry matter intake estimation method reported in an Indian research paper (see Box 2).

Box 1. Different ways used by selected countries to structure application of the IPCC Tier 2 equations
Argentina: The country was divided into eight regions, based on agro-ecological and climatic factors. In each region, a number of breeding and fattening systems were identified. Data to characterize production systems in terms of activity, diet, reproduction and production in each system were then procured from literature and entered into a model structured around regions and production systems. The resulting preliminary model was then refined using other data sources, and the aggregate results cross-checked against regional, census, and agricultural production data.

Bolivia: Cattle populations in three climatic regions (altiplano, valles and tropics) were identified according to the agro-ecological zonation of different departments (sub-regions) in the country. For cattle and sheep, the population was stratified into sub-classes (e.g., dairy cattle, non-dairy cattle, young cattle and oxen) based on consultations with livestock production experts in each region. In each region, data on feed rations and apparent digestibility of forage and feed was obtained from publications, and other production data (e.g., milk yields, live weights) were obtained from publications or government agencies.

Georgia: Common cattle breeds in Georgia include late-maturing breeds (the Georgian Mountain and Red Mingrelian) characterized by low weight, low productivity, and high milk fat content, as well as several high-productive early-maturing breeds that were imported in the previous century. The IPCC equations were populated separately for early and late maturing breeds at different life stages using published data and expert opinion. Expert opinion was used to estimate the proportion of each breed in the total cattle population.

Mongolia: Although Mongolia has diverse indigenous breeds of livestock, a small number of breeds dominate the total population of each livestock type. Published breed characterization studies were referred to along with input from livestock experts and IPCC default factors to develop a single Tier 2 emission factor for each type of livestock in the country. Results were compared with Tier 2 factors from China.

Box 2. A dry matter intake method to estimate methane emissions
Singhal et al. (2005) present a method for estimating methane emissions from enteric fermentation based on estimated dry matter intake (DMI). The approach estimates DMI using data on the population of livestock of different classes (e.g., sex, age, breed), the weight of animals in each sub-class and estimates of DMI for animals of each sub-class. Published methane conversion factors developed on the basis of studies of in vitro dry matter digestibility are then applied to different types of feed. The national inventory of Bangladesh adjusts the published emission factors based on the difference in weight between cattle in India and Bangladesh.

Source: Singhal et al. 2005

Most countries have applied the IPCC Tier 2 methodology to produce ‘static‘ emission factors that are used to calculate livestock emissions in the current and subsequent inventories. In this sense, these emission factors are similar to but possibly more accurate than, Tier 1 emission factors. Of the 20 countries that described the methodology used in deriving a Tier 2 approach for enteric fermentation, 15 used a ‘static‘ emission factor, while five have updated the emission factor on the basis of subsequent statistical data or expert judgment:

  • Armenia updates dairy cattle emission factors using statistical data on milk yield;
  • Brazil updated emission factors considering a change in pregnancy rates and feed digestibility in some regions;
  • Georgia applies its Tier 2 emission factor within a model of herd reproduction and off-take (i.e., where different breeds reproduce at different rates and are culled at different ages), resulting in a changing average emission factor over time;
  • the Republic of Moldova updates cattle emission factors using statistical data on live weight, daily weight gain, milk yield, and pregnancy rates and expert judgment on feed digestibility in different historical periods;
  • Uruguay updated its cattle emission factors on the basis of recent data on cattle live weight.

From available descriptions of data sources and methodologies used, some other countries‘ Tier 2 emission factors could also be updated using subsequent data on livestock performance, but this has not yet been done. For example, Chile has reviewed its Tier 2 emission factors but decided that no update was needed as the emission factors still reflect prevailing management practices (see Box 3). South Africa’s national GHG inventory report recommends that “if sufficient data is available, annual emission factors incorporating changes in feed quality and milk production“ should be used.

Box 3. Constraints to developing a dynamic Tier 2 approach for enteric fermentation in Chile
Chile has relatively abundant data for the different regions of the country on livestock production systems, including livestock populations, type of cattle (dairy/beef), breed, age, feeds used and grass composition, and manure management. However, data is not regularly collected, and mainly derives from an agricultural census conducted every 10 years. This survey is undertaken by the National Institute of Statistics, but there is little coordination with the Institute for Agricultural Research, which is responsible for national inventory compilation. A key need is therefore for the Ministry of Environment to engage the National Statistics Institute to improve the utility of the agricultural survey for the national inventory. Improved funding for data collection to serve the national inventory would require stronger political support from the ministries of agriculture and the environment. In the absence of nationally representative data, information is collected through a variety of informal approaches and assessed using expert judgment.

Source: Excerpted from Wilkes et al. (2017)

Table 2. The range and uncertainty of Tier 2 enteric fermentation emission factors (EF) for mature cattle used in national GHG inventories by selected countries

Country Tier 1 EF Tier 2 EF for mature animals (kg CH4 per head per year) Estimated uncertainty of Tier 2 EF

Dairy: 57
Non-dairy: 49
Dairy: 87.7-126.3
Non-dairy: 49.8 – 60.7
(range by region)
Armenia Dairy: 56
Non-dairy: 44
73.93 – 78.89 (range by year)
Bangladesh Dairy: 56
Non-dairy: 44
18.93-22.62 (range by physiological state)
Bolivia Dairy: 57 49.7-59 (range by climatic region) 10%
Brazil “Tier 2 EFs consistently higher than IPCC defaults”
Colombia Non-dairy: 49 Non-dairy: 50.0 – 60.78
(range by region)
Georgia Total cattle emissions 2.4%-3.3% higher using Tier 2 compared to Tier 1 emission factors 40%
India Dairy: 56 28 – 43 (range by breed type) 23-35%
Mongolia Dairy: 56
Non-dairy: 44
Dairy: 47.99-65.26
Non-dairy 32.09 – 43.56
(range by breed type)
South Africa DairyL 40
Non-dairy: 31
Dairy: 80-132
Non-Dairy: 72.56-112
(range by production system and physiological state)
Sources: NCs, BURs and NIRs available at the UNFCCC National Communication submissions from Non-Annex I Parties and Biennial Update Report submissions from Non-Annex I Parties

The IPCC Tier 1 default emission factors are given for mature animals in a limited number of classes (e.g., dairy cattle, non-dairy cattle). When implementing a Tier 2 estimation approach, most countries develop a more refined categorization of the livestock population, with a larger number of sub-classes of each type of livestock, or sub-classes identified in different regions or by breed. The range of emission factors identified in each country is large, so the weighted average implied Tier 2 emission factor will depend on the structure of the livestock population. Table 6 compares the IPCC default emission factors with recent implied Tier 2 emission factors for mature cattle categories reported in national inventories. In several cases, the Tier 2 emission factors are significantly higher than the Tier 1 default factor, due to differences in factors such as assumed productivity, pregnancy rates and digestible energy (e.g., GHG Inventory for South Africa). Some countries attempted to quantify the uncertainty associated with Tier 2 emission factors (Table 2). They mostly referred to an IPCC (2006) estimate that Tier 2 emission factors are likely to be associated with an uncertainty of ±20%, compared to between ±30% and ±50% for the Tier 1 emission factor. Other countries produced their own estimates of uncertainty on the basis of expert judgment. The uncertainty of resulting estimates of emissions from enteric fermentation will be highly dependent on the quality of activity data used.

Using higher tier approaches for manure management

Sixteen Parties used more advanced methods to estimate emissions of CH4 and/or N2O from manure management. Methane conversion factors (MCF) used in estimating methane emissions from manure management are sensitive to temperature, and the IPCC guidelines provide default values for methane emissions per head of livestock by temperature zone. Six Parties applied different Tier 1 default emission factors to livestock in different climate zones in the country, i.e., a T1b approach (see Box 4). Ten Parties applied a Tier 2 approach to the estimation of methane emissions from manure management for some types of livestock. Most Parties did this using the IPCC Tier 2 equations. In all cases, input data on gross energy intake and feed digestibility from Tier 2 estimates of enteric fermentation were used to estimate volatile solids produced. Most Parties used national data on the distribution of livestock between different manure management systems, although some used IPCC default estimates. Most Parties used IPCC default values for all other parameters in the IPCC calculations, although some used national data for parameters such as the ash content of dry matter feed intake. Very few Parties used a Tier 2 approach in estimating N2O emissions from manure management. Those that did refer to national studies on nitrogen excretion and crude protein content of diets.

Box 4. Tier1b approaches to estimating methane emissions from manure management
Sri Lanka was one of six Parties that used a Tier 1b approach to estimating methane emissions from manure management. Within Sri Lanka, one region located at high elevation is characterized as a temperate region (i.e., average annual temperatures 15-25°C), while others are characterized as warm regions (i.e., average annual temperatures >25°C). The numbers of each type of animal located in each region were estimated based on census data, to produce a more accurate estimate of national methane emissions from manure management.

Source: Sri Lanka (2012) Second National Communication on Climate Change.