4

AGRICULTURE

CHAPTER

4

AGRICULTURE

IPCC Guidelines for National Greenhouse Gas Inventories:

Reference Manual

4

AGRICULTURE

4. A G R I C U L T U R E
4.1

Overview
Agricultural activities contribute directly to emissions of greenhouse gases through avariety of different processes. This chapter discusses four greenhouse gas-emitting
activities:••

CH4 and N2O emissions from domestic livestock (enteric fermentationand manure management)−

CH4 emissions from enteric fermentation in domestic livestock
Methane is produced in herbivores as a by-product of enteric fermentation, adigestive process by which carbohydrates are broken down by micro-organisms
into simple molecules for absorption into the bloodstream. Both ruminantanimals (e.g., cattle, sheep) and some non-ruminant animals (e.g., pigs, horses)
produce CH4, although ruminants are the largest source since they are able todigest cellulose, a type of carbohydrate, due to the presence of specific microorganisms in their digestive tracts. The amount of CH4 that is released
depends on the type, age, and weight of the animal, the quality and quantity of
the feed, and the energy expenditure of the animal.

−

CH4 emissions from manure management
CH4 is produced from the decomposition of manure under anaerobic
conditions. These conditions often occur when large numbers of animals aremanaged in a confined area (e.g., dairy farms, beef feedlots, and swine andpoultry farms), where manure is typically stored in large piles or disposed of inlagoons.

−

N2O emissions from manure management
During storage of manure, some manure nitrogen is converted to N2O.
Emissions of N2O related to manure handling before the manure is added tosoils are included in this source category. (Manure-related N2O emissions
from soils are considered agricultural soil emissions).

CH4 emissions from rice cultivation
Anaerobic decomposition of organic material in flooded rice fields produces
methane, which escapes to the atmosphere primarily by transport through therice plants. The amount emitted is believed to be a function of rice species,
number and duration of harvests, soil type and temperature, irrigation
practices, and fertiliser use. The seasonally integrated CH4 flux depends upon
the input of organic carbon, water regimes, time and duration of drainage, soil
type etc.

•

CH4, CO, N2O, and NOX emissions from agricultural burning (savanna
and agricultural burning)–

CH4, CO, N2O, and NOX emissions from the prescribed burning ofsavannas
The burning of savannas – areas in tropical and subtropical formations with
continuous grass coverage – results in the instantaneous emissions of carbon

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.1

AGRICULTURE

dioxide, but because the vegetation regrows between burning cycles, thecarbon dioxide released into the atmosphere is reabsorbed during the next
vegetation growth period. Net CO2 emissions are therefore assumed to be
zero. However, savanna burning also releases gases other than CO2, including
methane, carbon monoxide, nitrous oxide and oxides of nitrogen. Unlike CO2
emissions, these are net emissions.
–•

CH4, CO, N2O, and NOX emissions from the burning of agriculturalresidues
The burning of crop residues is not thought to be a net source of carbon
dioxide because the carbon released to the atmosphere is reabsorbed during
the next growing season. However, this burning is a significant source ofemissions of methane, carbon monoxide, nitrous oxide, and nitrogen oxides. It
is important to note that some crop residues are removed from the fields andburned as a source of energy, especially in developing countries. Non-CO2
emissions from this type of burning are dealt with in the Energy module of thismanual. Crop residue burning must be properly allocated to these twocomponents in order to avoid double counting.

CH4, CO2, and N2O emissions from agricultural soils
Emissions of N2O from agricultural soils are primarily due to the microbial
processes of nitrification and denitrification in the soil. Three types of emission
can be distinguished: direct soils emissions, direct soil emissions of N2O fromanimal production (including stable emissions to be reported under Manure
Management) and indirect emissions. Increases in the amount of nitrogen
added to the soil generally result in higher N2O emissions (Bouwman, 1990).
Direct soil emissions may result from the following nitrogen input to soils: (1)synthetic fertilisers, (2) nitrogen from animal waste, (3) biological nitrogen
fixation, (4) reutilised nitrogen from crop residues, and (5) sewage sludge
application. In addition, cultivation of organic soils may increase soil organic
matter mineralisation and, in effect, N2O emissions. Direct soil emissions ofN2O from animal production include those induced by grazing animals.
Emissions from other animal waste management systems are reported under“Manure Management’’. Indirect N2O emissions take place after nitrogen islost from the field as NOx, NH3 or after leaching or runoff. Agricultural soils
may also emit or remove CO2 and/or CH4. For example, peat compost used
as a soil amendment in agriculture and gardening may result in CO2 emissions
or removals. Carbon emissions from organic, mineral and limed soils are
discussed in Chapter 5.

4.2

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

4.2

Methane And Nitrous Oxide Emissions
From Domestic Livestock EntericFermentation And Manure Management
4.2.1

Overview of Methane and Nitrous Oxide
Emissions from LivestockThis section covers methane and nitrous oxide emissions from enteric fermentation andthe management of manure from domestic livestock. Cattle are the most importantsource of methane from enteric fermentation in most countries because of their highnumbers, large size, and ruminant digestive system. Methane emissions from manure
management are usually smaller than enteric fermentation emissions, and are principally
associated with confined animal management facilities where manure is handled as a liquid.
This section presents a brief overview of the key factors affecting methane and nitrous
oxide emissions from these sources. The methods for estimating methane emissions arethen presented.1 The method for estimating nitrous oxide emissions from manure
management is presented in Section 4.5.3.
Enteric Fermentation
Methane is produced during the normal digestive processes of animals. The amount ofmethane produced and excreted by an individual animal is dependent primarily on thefollowing:•

Digestive System
The type of digestive system has a significant influence on the rate of methane
emission. Ruminant animals have the highest emissions because a significant amountof methane-producing fermentation occurs within the rumen. The main ruminantanimals are cattle, buffalo, goats, sheep and camels. Pseudo-ruminant animals (horses,
mules, asses) and monogastric animals (swine) have relatively lower methane
emissions because much less methane-producing fermentation takes place in theirdigestive systems.

•

Feed Intake
Methane is produced by the fermentation of feed within the animal's digestivesystem. Generally, the higher the feed intake, the higher the methane emission.
Feed intake is positively related to animal size, growth rate, and production (e.g.,
milk production, wool growth, or pregnancy).

The amount of methane emitted by a population of animals is calculated by multiplying theemission rate per animal by the number of animals. To reflect the variation in emission
rates among animal types, the population of animals is divided into subgroups, and anemission rate per animal is estimated for each subgroup. Types of population subgroupare recommended in the method2.

1 All GHG emissions from the burning of animal waste are estimated in Section 1.4;

Greenhouse Gas Emissions from Burning Traditional Biomass Fuels. CO2 from theburning of animal waste is part of a closed cycle and is not counted as net CO2.
2 Countries are encouraged to carry out emissions inventory calculations at a finerlevel of detail if possible. Many countries have available more detailed information than

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.3

AGRICULTURE

Human management of wildlife can affect the total number of animals and therefore theiremissions, though the associated emissions are believed to be small. The key issue isdistinguishing those emissions resulting from human interventions from those emissions
that would have occurred naturally. No methodology for estimating these emissions ispresented here, though they may be estimated if national experts can fully document theirapproach, including all assumptions and methods. If these emissions are estimated, theyshould be reported in the “Other” subcategories of the Enteric Fermentation and Animal
Wastes Tables (4 A & B) of Volume 1: Reporting Instructions.
Manure Management
Livestock manure is principally composed of organic material. When this organic material
decomposes in an anaerobic environment (i.e., in the absence of oxygen), methanogenic
bacteria, as part of an interrelated population of micro-organisms, produce methane.
The principal factors affecting methane emission from animal manure are the amount ofmanure produced and the portion of the manure that decomposes anaerobically. The
amount of manure that is produced is dependent on the amount produced per animal andthe number of animals. The portion of the manure that decomposes anaerobicallydepends on how the manure is managed. When manure is stored or treated as a liquid(e.g., in lagoons, ponds, tanks, or pits), it tends to decompose anaerobically and produce asignificant quantity of methane. When manure is handled as a solid (e.g., in stacks or pits)
or when it is deposited on pastures and rangelands, it tends to decompose aerobically andlittle or no methane is produced.
To estimate methane emission, the animal population must be divided into subgroups toreflect the varying amounts of manure produced per animal, and the manner in which themanure is handled. Population subgroups are recommended in the method.
Nitrous oxide is formed when manure nitrogen is nitrified or denitrified. The amount of
N2O released depends on the system and duration of waste management. Emissions of
N2O taking place during storage or handling of manure (i.e., before the manure is added
to soils) are reported under “ Manure Management”. Manure-induced N2O emissions
from soils are considered soil emissions ( See Section 4.5 of this Reference Manual).

was used in constructing default values here. Countries may wish to calculate emissions
estimates at a finer level of detail by subcategory – further disaggregating recommended
activity categories and subcategories – or they may choose to subdivide the categories onsome other basis which they feel is appropriate to their particular national circumstances.
Working at finer levels of disaggregation does not change the basic nature of thecalculations. Once emissions have been calculated at whatever is determined by thenational experts to be the most appropriate level of detail, results should also be
aggregated up to the minimum standard level of information requested in the IPCC
proposed methodology. This will allow for comparability of results among all participating
countries. The data and assumptions used for finer levels of detail should also bereported to the IPCC to ensure transparency and replicability of methods. Volume 1:
Reporting Instructions discusses these issues in more detail.

4.4

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

BOX 1
HUMAN WASTE USED AS FERTILISER

Human waste is sometimes used as fertiliser, and can result in emissions or
removals of CH4, N2O or CO2. At present, no methodology can berecommended for estimating CH4 and CO2 emissions. N2O emissions from
Human waste are described in Chapters 4 & 6. The development of amethodology specifically for this source has been identified as an area for
future work. Countries are nevertheless encouraged to estimate emissions
from this source if they are able to do so. CH4 emissions from this source
can be estimated in one of at least two ways:•

Emissions from human waste used as fertiliser may be estimated in thepresent section by adapting the methodology for estimating emissions
from livestock manure to use the data provided below. In this case,the estimate should be reported in the “Other” line in Tables 4 A & B
in Volume 1: Reporting Instructions.
Bhattacharya et al. (1993) has reported these characteristics of humanwaste:
Dry waste per day
Fractional carbon content==

0.107 kg/head/day
0.375

And Thomas (1994, in press) reports the following values:
Volatile solid production
Dry matter production
Fractional carbon content
•

=
=
=

0.06 kg/head/day
0.09 kg/head/day
4.46% of dry matter

These emissions can also be estimated using the methodology for
sewage treatment in the Waste section. In this case, the emissions
should then be treated as wastewater disposed of in aerobic (shallow)
ponds, and should be reported in Table 6 B.

In any case, care should be taken to avoid double counting emissions fromthis source.

4.2.2 Inventory Method for Methane – Overview
The method for estimating methane emission from enteric fermentation and manure
management requires three basic steps:
Step 1: Divide the livestock population into subgroups and characterise each subgroup. It
is recommended that national experts use three year averages of activity data if available.
This is to help prevent bias in the event that the base year of the inventory was an
exceptional year not representative of the country’s normal activity level.
Step 2: Estimate emission factors for each subgroup in terms of kilograms of methane per
animal per year – separate emission factors are required for enteric fermentation andmanure.
Step 3: Multiply the subgroup emission factors by the subgroup populations to estimate
subgroup emission, and sum across the subgroups to estimate total emission.
These three steps can be performed at varying levels of detail and complexity. This
chapter presents the following two approaches:

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.5

AGRICULTURE•

Tier 1
A simplified approach that relies on default emission factors drawn from previous
studies. The Tier 1 approach is likely to be sufficient for most animal types in mostcountries.

•

Tier 2A more complex approach that requires country-specific information on livestock
characteristics and manure management practices.
The Tier 2 approach isrecommended when the data used to develop the default values do not correspondwell with the country's livestock and manure management conditions. Because
cattle characteristics vary significantly by country, it is recommended that countries
with large cattle populations consider using the Tier 2 approach for estimating
methane emissions from cattle and cattle manure. Similarly, because buffalo andswine manure management practices vary significantly by country, it is recommended
that countries with large buffalo and swine populations consider using the Tier 2
approach for estimating methane emissions for manure from these animals.

Some countries for which livestock emissions are particularly important may wish to go
beyond the Tier 2 method and incorporate additional country-specific information in theirestimates. Although countries are encouraged to go beyond the Tier 2 approachpresented below when data are available, these more complex analyses are only briefly
discussed here. Table 4-1 summarises the recommended approaches for the livestock
emissions included in this inventory.
TABLE 4-1
DOMESTIC LIVESTOCK INCLUDED IN THE METHODS
Livestock

Recommended Emissions Inventory Methods
Enteric Fermentation

Manure Management

Dairy Cattle

Tier 2aTier 2aNon-dairy Cattle

Tier 2aTier 2a

Buffalo

Tier 1

Tier 2a

Sheep

Tier 1

Tier 1

Goats

Tier 1

Tier 1

CamelsTier 1

Tier 1

HorsesTier 1

Tier 1

Mules and Asses

Tier 1

Tier 1

Swine

Tier 1

Tier 2a

Poultry(Not Estimated)

Tier 1a

The Tier 2 approach is recommended for countries with large livestock populations.
Implementing the Tier 2 approach for additional livestock subgroups may be desirable when thesubgroup emissions are a large portion of total methane emissions for the country.

4.6

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

4.2.3

Inventory
Approach

Methodfor

Methane– Tier 1

This Tier 1 method is simplified so that only readily-available animal population data areneeded to estimate emissions. Default emission factors are presented for each of therecommended population subgroups. Each step is discussed in turn.

TIER 1: STEP 1 – LIVESTOCK POPULATIONS
The average annual population of livestock is required for each of the livestock categories
listed in Table 4-1. In some cases the population fluctuates during the year. For example,
a census done before calving will give a much smaller number than a census done after
calving. A representative average of the population is therefore needed. In the case ofpoultry and swine, the number of animals produced each year exceeds the annual average
population because the animals live for less than 12 months. The population data can beobtained from the FAO Production Yearbook (FAO, 1990) or similar country-specificlivestock census reports.
The dairy cattle population is estimated separately from other cattle (see Table 4-2).
Dairy cattle are defined in this method as mature cows that are producing milk incommercial quantities for human consumption. This definition corresponds to the dairy
cow population reported in the FAO Production Yearbook.
In some countries the dairy cattle population is comprised of two well-defined segments:
high-producing "improved" breeds in commercial operations; and low-producing cows
managed with traditional methods. These two segments can be combined, or can beevaluated separately by defining two dairy cattle categories. However, the dairy cattle
category does not include cows kept principally to produce calves or to provide draft
power. Low productivity multi-purpose cows should be considered as non-dairy cattle.
Data on the average milk production of dairy cattle is also required. These data areexpressed in terms of kilograms of whole fresh milk produced per year per dairy cow,
and can be obtained from the FAO Production Yearbook or similar country-specificreports. If two or more dairy cattle categories are defined, the average milk production
per cow is required for each category.
Finally, the livestock populations must be described in terms of warm, temperate, or coolclimates for purposes of estimating emissions from livestock manure. Data on the annual
average temperature of the regions where livestock are managed should be used asfollows:•

Areas with annual average temperatures less than 15°C are defined as cool.

•

Areas with annual average temperatures from 15°C to 25°C inclusive are defined as
temperate.

•

Areas with annual average temperatures greater than 25°C are defined as warm.

For each livestock population, the fraction in each climate should be estimated. These
data can be developed from country-specific climate maps and livestock census reports.
To the extent possible, the temperature data should reflect the locations where thelivestock are managed. If necessary, data from nearby cities can be used. Table 4-2
summarises the animal population data that must be collected in Step 1.

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.7

AGRICULTURE

TABLE 4-2
ANIMAL POPULATION DATA COLLECTED IN TIER 1 STEP 1
Livestock

Data Collected
Population

Milk Production

Population By Climate (%)(# head)(kg/head/yr)

Cool

Temperate

Warm

Dairy Cattle

Average Annual
Population

Milk Production per
Head% Cool% Temp.

% WarmNon-dairy Cattle

Average Annual
Population

Not Applicable (NA)

% Cool% Temp.

% WarmBuffalo

Average Annual
Population(NA)% Cool% Temp.

% WarmSheep

Average Annual
Population(NA)% Cool% Temp.

% WarmGoats

Average Annual
Population(NA)% Cool% Temp.

% WarmCamelsAverage Annual
Population(NA)% Cool% Temp.

% WarmHorsesAverage Annual
Population(NA)% Cool% Temp.

% WarmMules and Asses

Average Annual
Population(NA)% Cool% Temp.

% WarmSwine

Average Annual
Population(NA)% Cool% Temp.

% WarmPoultry

Average Annual
Population(NA)% Cool% Temp.

% WarmData can be obtained from the FAO Production Yearbook and country-specific livestock census reports. Climates are defined in terms of
average annual temperature as follows: Cool = less than 15°C; Temperate = from 15°C to 25°C inclusive; Warm = greater than 25°C.

TIER 1: STEP 2 – EMISSION FACTORSThe purpose of this step is to select emission factors that are most appropriate for thecountry's livestock characteristics. Default emission factors for enteric fermentation andmanure management have been drawn from previous studies, and are organised by region
for ease of use. The basis for the emission factors, described more fully under Tier 2,
includes the following:•Enteric Fermentation:−

4.8

Feed Intake: Feed intake is estimated based on the energy intake required by
the animal for maintenance (the basic metabolic functions needed to stay alive)
and production (growth, lactation, work, and gestation). The livestock
characteristics required to estimate feed intake are taken from regional andcountry-specific studies and include: population structure (portion of adults andyoung), weight, rate of weight gain, amount of work performed, portion ofcows giving birth each year, and milk production per cow.

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE−•

Conversion of Feed Energy to Methane: The rate at which feed energy isconverted to methane is estimated based on the quality of the feed consumed– low quality feed has a slightly higher methane conversion rate. Feed quality isassessed in terms of digestibility on a regional basis.

Manure Management:−

Manure Production: Manure production is estimated based on feed intake anddigestibility, both of which are used to develop the enteric fermentation
emission factors.

−

Methane Producing Potential: Methane producing potential (referred to as Bo) is
the maximum amount of methane that can be produced from a given quantityof manure. The methane producing potential varies by animal type and thequality of the feed consumed. Reported measurements for selected animals
are used.

−

Methane Conversion Factor (MCF): The MCF defines the portion of the methane
producing potential (Bo) that is achieved. The MCF varies with the manner inwhich the manure is managed and the climate, and can theoretically range from0 to 100 per cent. Manure managed as a liquid under hot conditions promotes
methane formation and emissions. These manure management conditions havehigh MCFs, of 65 to 90 per cent. Manure managed as dry material in cold
climates does not readily produce methane, and consequently has an MCF of
about 1 per cent. Laboratory measurements were used to estimate MCFs forthe major manure management techniques.

−

Manure Management Practices: Regional assessments of manure management
practices are used to estimate the portion of the manure that is handled witheach manure management technique.

The data used to estimate the default emission factors for enteric fermentation andmanure management are presented in Appendix A and Appendix B respectively, at theend of this section.
Table 4-3 shows the enteric fermentation emission factors for each of the animal types
except cattle. As shown in the table, emission factors for sheep and swine vary fordeveloped and developing countries. The differences in the emission factors are driven bydifferences in feed intake and feed characteristic assumptions (see Appendix A).
Although point estimates are given for the emission factors, an uncertainty of about +20
per cent exists due to variations in animal management and feeding. Deviations from theemission factors can be larger than 20 per cent under specialised feeding or management
conditions.
Table 4-4 presents the enteric fermentation emission factors for cattle. A range ofemission factors is shown for typical regional conditions. As shown in the table, theemission factors vary by over a factor of four on a per head basis.
While the default emission factors shown in Table 4-4 are broadly representative of theemission rates within each of the regions described, emission factors vary among
countries within regions. Also, as with the emission factors shown in Table 4-3, an
uncertainty of about +20 per cent exists due to variations in animal management andfeeding. Animal size and milk production are important determinants of emission rates
for dairy cows. Relatively smaller dairy cows with low levels of production are found in
Asia, Africa, and the Indian subcontinent. Relatively larger dairy cows with high levels of
production are found in North America and Western Europe.

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.9

AGRICULTURE

TABLE 4-3
ENTERIC FERMENTATION EMISSION FACTORS(KG PER HEAD PER YR)

Livestock

Developed Countries

Developing Countries

Buffalo

55

55

Sheep

8

5

Goats

5

5

Camels46

46

Horses18

18

Mules and Asses

10

10

Swine

1.5

1.0

Poultry

Not Estimated

Not EstimatedAll estimates are ± 20 %Sources: Emission factors for buffalo and camels from Gibbs and Johnson (1993). Emission factors for otherlivestock from Crutzen et al. (1986).

Animal size and population structure are important determinants of emission rates fornon-dairy cattle. Relatively smaller non-dairy cattle are found in Asia, Africa, and theIndian subcontinent. Also, many of the non-dairy cattle in these regions are young. Nondairy cattle in North America, Western Europe and Oceania are larger, and young cattle
constitute a smaller portion of the population3.
Select emission factors from Tables 4-3 and 4-4 by identifying the region most applicableto the country being evaluated. The data collected on the average annual milk production
by dairy cows should be used to help select a dairy cow emission factor. If necessary,interpolate between dairy cow emission factors shown in the table using the datacollected on average annual milk production per head.
Table 4-5 shows the default manure management emission factors for each animal type
except cattle, buffalo, and swine. Separate emission factors are shown for developed anddeveloping countries, reflecting the general differences in feed intake and feedcharacteristics of the animals in the two regions. These emission factors reflect the factthat virtually all the manure from these animals is managed in dry manure management
systems, including pastures and ranges, drylots, and daily spreading on fields (Woodbury
and Hashimoto, 1993).

3 For each animal category, it is important to use the average weight of the animal

during the year for estimating emissions. Because the weights of mature animals may
fluctuate seasonally, a representative weight should be selected that considers conditions
throughout the year. For growing animals, the average weight is generally less than the
final (or end) weight of the animal at the end of the year. Growth rate statistics should be
used to estimate the average weight during the year for purposes of estimating emissions.

4 . 10

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

TABLE 4-4
ENTERIC FERMENTATION EMISSION FACTORS FOR CATTLE
Regional Characteristics

Cattle Type

Emission
Comments
Factor(kg/head/yr)

North America: Highly productive commercialised Dairy
dairy sector feeding high quality forage and grain.
Separate beef cow herd, primarily grazing with feed
Non-dairy
supplements seasonally. Fast-growing beefsteers/heifers finished in feedlots on grain. Dairy
cows are a small part of the population.

118

Average milk production of
6,700 kg/head/yr

47

Includes beef cows, bulls, calves,
growing steers/heifers, and feedlot
cattle.

Western Europe: Highly productive commercialised Dairy
dairy sector feeding high quality forage and grain.
Dairy cows also used for beef calf production. Very
Non-dairysmall dedicated beef cow herd. Minor amount offeedlot feeding with grains.

100

Average milk production of
4,200 kg/head/yr.

48

Includes bulls, calves, and growing
steers/heifers.

Eastern Europe: Commercialised dairy sector
feeding mostly forages. Separate beef cow herd,
primarily grazing. Minor amount of feedlot feedingwith grains.

Dairy

81

Average milk production of
2,550 kg/head/yr.

Non-dairy

56

Includes beef cows, bulls, andyoung.

Oceania: Commercialised dairy sector based on
grazing. Separate beef cow herd, primarily grazing
rangelands of widely varying quality. Growing
amount of feedlot feeding with grains. Dairy cows
are a small part of the population.

Dairy

68

Average milk production of
1,700 kg/head/yr.

Non-dairy

53

Includes beef cows, bulls, andyoung.

Latin America: Commercialised dairy sector based Dairyon grazing. Separate beef cow herd grazing pasturesand rangelands. Minor amount of feedlot feeding
Non-dairy
with grains. Growing non-dairy cattle comprise alarge portion of the population.

57

Average milk production of
800 kg/head/yr.

49

Includes beef cows, bulls, andyoung.

Asia: Small commercialised dairy sector. Most cattle Dairy
are multi-purpose, providing draft power and somemilk within farming regions. Small grazing
Non-dairy
population. Cattle of all types are smaller thanthose found in most other regions.

56

Average milk production of
1,650 kg/head/yr.

44Includes multi-purpose cows, bulls,
and young

Africa and Middle East: Commercialised dairy
Dairy
sector based on grazing with low production per
cow. Most cattle are multi-purpose, providing draft
power and some milk within farming regions. Some Non-dairy
cattle graze over very large areas. Cattle of all types
are smaller than those found in most other regions.

36

Average milk production of
475 kg/head/yr.

32

Includes multi-purpose cows, bulls,
and youngIndian Subcontinent: Commercialised dairy sector Dairy
based on crop by-product feeding with low
production per cow. Most bullocks provide draft
Non-dairy
power and cows provide some milk in farming
regions. Small grazing population. Cattle in thisregion are the smallest compared to cattle found in
all other regions.

46

Average milk production of
900 kg/head/yr.

25

Includes cows, bulls, and young.
Young comprise a large portion of
the population

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.11

AGRICULTURE

TABLE 4-5
MANURE MANAGEMENT EMISSION FACTORS(KG PER HEAD PER YR)

Livestock

Developed Countries
Cool
Temp.aWarm

Developing Countries
Cool
Temp.a
Warm

Sheep

0.19

0.28

0.37

0.10

0.16

0.21

Goats

0.12

0.18

0.23

0.11

0.17

0.22

Camels

1.6

2.4

3.2

1.3

1.9

2.6

Horses

1.4

2.1

2.8

1.1

1.6

2.2

Mules and Asses
Poultryb

0.76

1.14

1.51

0.60

0.90

1.2

0.078

0.117

0.157

0.012

0.018

0.023

The range of estimates reflects cool to warm climates. Climate regions are defined in terms of annual average temperature as follows: Cool =less than 15°C; Temperate = 15°C to 25°C inclusive; and Warm = greater than 25°C. The Cool, Temperate and Warm regions are
estimated using MCFs of 1 %, 1.5 % and 2 %, respectively.
a Temp. = Temperate climate region.
b Chickens, ducks, and turkeys.
All estimates are +20 %.
Sources: Emission factors developed from: feed intake values and feed digestibilities used to develop the enteric fermentation emission
factors (see Appendix A); MCF, and Bo values reported in Woodbury and Hashimoto (1993). All manure is assumed to be managed in dry
systems, which is consistent with the manure management system usage reported in Woodbury and Hashimoto (1993).

The ranges of values shown in Table 4-5 reflect the range of Methane Conversion Factor
values of 1 to 2 per cent. The higher value is appropriate for manure managed in warm
climates, while the lower value is appropriate for manure managed in cooler and dryer
climates. A middle value is assigned to temperate conditions. The uncertainty in theemission factors remains substantial, however, because field measurements are required
to validate the laboratory measurements that form the basis for the MCFs used in theanalysis. Appendix B, at the end of this section, summarises the data used to estimate theemission factors shown in Table 4-6.
The climate data collected in Step 1 is used to select the emission factors from Table 4-6.
A weighted average emission factor for each animal type is computed by multiplying thepercentages of the animal populations in each climate region by the emission factor foreach climate region. For example, if sheep in a developing country were 25 per cent in atemperate region and 75 per cent in a warm region, the emission factor for sheep would
be estimated at about 0.2 kg/head/yr as follows:
Emission Factor = (25% x 0.16) + (75% x 0.21) = 0.1975 kg/head/yr.
An alternative way of handling these calculations is to sub-divide the category of sheep
into two populations: one in warm and one in temperate region. Calculations could thenbe done separately and summed.
Because the manure from cattle, buffalo, and swine is managed in a variety of ways,
including both dry and liquid systems, the variations in manure management practices
among regions and countries must be considered to develop emission factors for theseanimals. Table 4-6 presents emission factors based on regional manure management
practices described in Safley et al. (1992).

4 . 12

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

TABLE 4-6
MANURE MANAGEMENT EMISSION FACTORS FOR CATTLE, SWINE AND BUFFALO
Regional Characteristics

Emission Factor by Climate Regiona(kg/head/yr)

Livestock TypeCool

Temperate

Warm

North America: Liquid-based systems are commonly Dairy Cattle
used for dairy and swine manure. Non-dairy manure is Non-dairy Cattle
usually managed as a solid and deposited on pastures Swineor ranges.

36
1
10

54
2
14

76
3
18

Western Europe: Liquid/slurry and pit storage
systems are commonly used for cattle and swine
manure. Limited cropland is available for spreading
manure.

Dairy Cattle
Non-dairy Cattle
Swine
Buffalo

14
6
3
3

44
20
10
8

81
38
19
17

Eastern Europe: Solid based systems are used for
Dairy Cattle
the majority of manure. About one-third of livestock Non-dairy Cattle
Swine
manure is managed in liquid-based systems.
Buffalo

6
4
4
3

19
13
7
9

33
23
11
16

Oceania: Virtually all livestock manure is managed as a Dairy Cattle
solid on pastures and ranges. About half of the swine Non-dairy Cattle
Swine
manure is managed in anaerobic lagoons.

31
5
20

32
6
20

33
7
20

Latin America: Almost all livestock manure ismanaged as a solid on pastures and ranges. Buffalo
manure is deposited on pastures and ranges.

Dairy Cattle
Non-dairy Cattle
Swine
Buffalo

0
1
0
1

1
2
1
1

2
1
2
2

Africa: Almost all livestock manure is managed as asolid on pastures and ranges.

Dairy Cattle
Non-dairy Cattle
Swine

1
0
0

1
1
1

1
1
2

Middle East: Over two-thirds of cattle manure is
Dairy Cattle
deposited on pastures and ranges. About one-third of Non-Dairy Cattle
Swine
swine manure is managed in liquid-based systems.
Buffalo
Buffalo manure is burned for fuel or managed as asolid.

1
1
1
4

2
1
3
5

2
1
6
5

Asia: About half of cattle manure is used for fuel with Dairy Cattle
the remainder managed in dry systems. Almost 40% of Non-dairy Cattle
swine manure is managed as a liquid. Buffalo manure is Swine
Buffalomanaged in drylots and deposited in pastures andranges.

7
1
1
1

16
1
4
2

27
2
7
3

Indian Subcontinent: About half of cattle and buffalo Dairy Cattle
manure is used for fuel with the remainder managed in Non-dairy Cattle
Swine
dry systems. About one-third of swine manure is
Buffalomanaged as a liquid.

5
2
3
4

5
2
4
5

6
2
6
5

a Cool climates have an average temperature below 15°C; temperate climates have an average temperature from 15°C to 25°C inclusive; warm
climates have an average temperature above 25°C. All climate categories are not necessarily represented within every region. For example,
there are no significant warm areas in Eastern or Western Europe. Similarly, there are no significant cool areas in Africa and the Middle East.
See Appendix B for the derivation of these emission factors.
Note: Significant buffalo populations do not exist in North America, Oceania, or Africa.

As shown in the table, the emission factors for dairy cattle range between 81 kg/head/yr
in warm parts of Western Europe to 0 kg/head/yr in cool parts of Latin America. The

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.13

AGRICULTURE

emission factors for non-dairy cattle range between 38 kg/head/yr in warm parts ofWestern Europe to 1 kg/head/yr in cool parts of North America and Latin America. In
addition to climate, the range of emission factors is due to the manure management
practices used in each region. For example, the emission factors for North American
dairy cattle manure and European dairy and non-dairy cattle manure are relatively highbecause the manure is often managed using liquid systems that promote methane
production. The emission factors for North American non-dairy cattle and for all animals
in Africa and the Middle East are relatively low because their manure is generally managed
using dry systems that do not promote methane production.
To select emission factors from Table 4-6, first identify the appropriate region, such as
Latin America. Within that region, identify the animal type of interest. For that animal
type three values are given for the three climate regions. Compute a weighted average
emission factor for the animal type by multiplying the percentages of the animal
population in each climate region by the emission factor for each climate region.
Appendix B summarises the estimates of manure management system usage and MCFs
that underlie the emission factors in Table 4-6.
As with the other manure management emission factors, there is substantial uncertainty
in the estimates shown in Table 4-6 because field measurements are required to validate
the laboratory measurements that form the basis for the MCFs used in the analysis, andbecause there is uncertainty and variability in the manner in which manure is managed ineach region.

TIER 1: STEP 3 – TOTAL EMISSION
To estimate total emission the selected emission factors are multiplied by the associatedanimal population and summed. The emission estimates should be reported in gigagrams(Gg). Because the emission factors are reported in kilograms per head per year, the total
emissions in Gg is estimated as follows for each animal category:emission factor (kg/head/yr) x population (head) / (106 kg/Gg)= emissions Gg/yr.
As a point of reference, in 1990 total annual global methane emissions from domestic
livestock enteric fermentation were of the order of 0.060 to 0.100 Gg (Gibbs andJohnson, 1993). Enteric fermentation emissions from countries with large populations of
livestock may be on the order of 0.001 to 0.005 Gg per year. Countries with smaller
populations of livestock would likely have emissions of less than 0.001 Gg per year.
In 1990 total annual global methane emissions from manure management was on theorder of 0.010 to 0.018 Gg (Woodbury and Hashimoto, 1993). Manure management
emissions from countries where manure is managed in liquid-based systems may be on
the order of 0.001 to 0.002 Gg per year. Countries where manure is not managed inliquid-based systems would likely have emissions of much less than 0.001 Gg per year.

4.2.4

Tier 2 Approach for Methane
From Enteric Fermentation

Emissions

The Tier 2 approach is recommended for estimating methane emissions from entericfermentation from cattle for those countries with large cattle populations. As contrasted
with the Tier 1 method, this approach requires much more detailed information on the
cattle population. Using this detailed information, more precise estimates of the cattle

4 . 14

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

emission factors are developed. When the Tier 2 method is used the default emission
factors listed in Tier 1 for cattle are not used.
This Tier 2 approach is similar to the August 1991 OECD method (OECD, 1991), withsome modifications:•

The Blaxter and Clapperton (1965) equation is replaced with a recommended set ofmethane conversion rate "rules of thumb."•

Feed energy intake requirements for pregnancy have been added.

•

The energy requirements required for grazing have been reduced based on newly
available data from AAC (1990).

•

The equations used to relate gross energy intake to net energy used by the animal
have been made more general to fit a wider variety of feed conditions.

The three steps outlined for Tier 1 are also used here.

ENTERIC FERMENTATIONTIER 2: STEP 1 – LIVESTOCK POPULATION
To develop precise estimates of emissions, cattle should be divided into categories ofrelatively homogeneous groups. For each category a representative animal is chosen andcharacterised for the purpose of estimating an emission factor. Table 4-7 presents a setof recommended representative cattle types. Three main categories, Mature Dairy
Cattle, Mature Non-dairy Cattle, and Young Cattle, are recommended as the minimum
set of representative types. The subcategories listed should be used when data are
available. In particular, the sub-population of cows providing milk to calves should be
identified among non-dairy cattle because the feed intake necessary to support milk
production can be substantial. In some countries the feedlot category is needed so thatthe implications of the high-grain diets can be incorporated.
TABLE 4-7
RECOMMENDED REPRESENTATIVE CATTLE TYPES
Main Categories

Subcategories

Mature Dairy Cattle

Dairy Cows used principally for commercial milk production

Mature Non-dairy Cattle

Mature Females:•Beef Cows: used principally for producing beef steers and heifers•Multiple-Use Cows: used for milk production, draft power, and otheruses

Mature Males:•Breeding Bulls: used principally for breeding purposes•Draft Bullocks: used principally for draft power

Young Cattle

Pre-Weaned Calves
Growing Heifers, Steers/Bullocks and Bulls
Feedlot-Fed Steers and Heifers on High-Grain Diets

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.15

AGRICULTURE

For each of the representative animal types defined, the following information is required:•annual average population (number of head);•average daily feed intake (megajoules (MJ) per day and kg per day of dry matter); and•methane conversion rate (percentage of feed energy converted to methane).

Generally, data on average daily feed intake are not available, particularly for grazing
animals. Consequently, the following data should be collected for estimating the feedintake for each representative animal type4:•

weight (kg);•average weight gain per day (kg);5•

feeding situation: confined animals; animals grazing good quality pasture; and animals
grazing over very large areas;•

milk production per day (kg/day);6•

average amount of work performed per day (hours/day);•percentage of cows that give birth in a year;7 and•feed digestibility (%).8

These data should be obtained from country-specific cattle evaluations. Some data, suchas weight, weight gain, and milk production, may be available from production statistics.
Care should be taken to use the live cattle weights, as contrasted with slaughter weights.
Appendix A, at the end of this section, lists the data used to develop the default emission
factors presented in Tier 1. Individual country data can be compared to the data
presented in Appendix A to ensure that the data collected are reasonable.
Data on methane conversion rates are also not generally available. The following rules of
thumb are recommended for the methane conversion rates:•

Developed Countries.
A 6 per cent conversion rate (±0.5 per cent) is
recommended for all cattle in developed countries except feedlot cattle consuming
diets with a large quantity of grain. For feedlot cattle on high grain diets a rate of
4 per cent (±0.5 per cent) is recommended. In circumstances where good feed isavailable (i.e., high digestibility and high energy value) the lower bounds of theseranges can be used. When poorer feed is available, the higher bounds are more
appropriate.

•

Developing Countries. Several recommendations are made for different animal
management situations in developing countries:
4 In many, if not most, cattle management circumstances, the principal driving factorsthat affect feed intake are: weight, milk production and feed digestibility.
5 This may be assumed to be zero for mature animals.
6 Milk production is required for dairy cows and non-dairy cows providing milk tocalves.
7 This is only relevant for mature cows.
8 Feed digestibility is defined as the proportion of energy in the feed that is not
excreted in the faeces. Digestibility is commonly expressed as a percentage (%).
Common ranges for feed digestibility for cattle are 50% to 60% for crop by-products andrangelands; 60% to 70% for good pastures, good preserved forages, and grainsupplemented forage-based diets; and 75% to 85% for grain-based diets fed in feedlots.

4 . 16

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE−−−

All dairy cows and young cattle are recommended to have a conversion rate of
6.0 per cent (±0.5 per cent). These cattle are generally the best-fed cattle inthese regions.
All non-dairy cattle, other than young stall-fed animals, consuming low-quality
crop by-products, are recommended to have a conversion rate of 7.0 per
cent (±0.5 per cent) because feed resources are particularly poor in manycases in these regions.
Grazing cattle are recommended to have a conversion rate of 6.0 per
cent (±0.5 per cent), except for grazing cattle in Africa, which arerecommended to have a rate of 7.0 per cent (±0.5 per cent) because of theforage characteristics found in many portions of tropical Africa.

These rules of thumb are a rough guide based on the general feed characteristics andproduction practices found in many developed and developing countries. Countryspecific exceptions to these general rules of thumb should be taken into consideration asnecessary based on detailed data from cattle experts.

ENTERIC FERMENTATIONTIER 2: STEP 2 – EMISSION FACTORSThe emission factors for each category of cattle are estimated based on the feed intake
and methane conversion rate for the category. Feed intake is estimated based on thefeed energy requirements of the representative animals, subject to feed-intake limitations.
The net energy system described in NRC (1984 and 1989) is recommended as thestarting point for the estimates. Because the NRC system was developed for feeding
conditions in temperate regions, several adjustments were made to avoid potential biases
when applied to evaluate feed-energy intakes for tropical cattle (see Appendix C).
Comparisons with alternative feeding systems (e.g., ARC, 1980) indicate that theemissions estimates are not sensitive to the feeding system used as the basis for making
the estimates.
The net energy system specifies the amount of feed energy required for the physiological
functions of cattle, including maintenance, growth and lactation.
Feed energy
requirements for work have also been estimated, and are included in this analysis for thedraft animals in developing countries. Energy requirements for pregnancy have also been
added for the portion of cows that give birth in each year. The following information isrequired to estimate feed energy intakes:•

Maintenance
Maintenance refers to the apparent feed energy required to keep the animal inenergy equilibrium, i.e., there is no gain or loss of energy in the body tissues(Jurgens, 1988). For cattle, net energy for maintenance (NEm) has been estimated to
be a function of the weight of the animal raised to the 0.75 power (NRC, 1984):
EQUATION 1
NEm (MJ/day) = 0.322 x (weight in kg)0.75
NRC (1989) recommends that lactating dairy cows be allowed a slightly
higher maintenance allowance:
NEm (MJ/day) = 0.335 x (weight in kg)0.75 dairy cows}

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.17

AGRICULTURE•

Feeding
Additional energy is required for animals to obtain their food. Grazing animals
require more energy for this activity than do stall-fed animals. The following energy
requirements are added for this activity based on their feeding situation:9
EQUATION 2
NEfeed =Confined animals (pens and stalls): no additional NEm;
Animals grazing good quality pasture: 17 % of NEm; andAnimals grazing over very large areas: 37 % of NEm.

•

GrowthThe energy requirements for growth can be estimated as a function of the weight of
the animal and the rate of weight gain. NRC (1989) presents formulae for largeand small-frame males and females, the estimates of which vary by about ± 25 percent. The equation for large-frame females is recommended, which is about the
average for the four types:
EQUATION 3
NEg (MJ/day) = 4.18 x {(0.035 W0.75 x WG1.119) + WG}
where:W
WG= animal weight in kilograms (kg); and= weight gain in kg per day.

The relationships for NEg were developed for temperate agriculture conditions, andmay over-estimate energy requirements for tropical conditions, particularly for draft
animals that may have a lower fat content in their weight gain (Graham, 1985).
However, no data are available for improving the estimates at this time.
•

Lactation
Net energy for lactation has been expressed as a function of the amount of milk
produced and its fat content (NRC, 1989):
EQUATION 4
NEl (MJ/day) = kg of milk/day x (1.47 + 0.40 x Fat %)At 4.0 per cent fat, the NEl in MJ/day is about 3.1 x kg of milk per day.

•

Draft Power
Various authors have summarised the energy intake requirements for providing draft
power (e.g., Lawrence, 1985; Bamualim and Kartiarso, 1985; and Ibrahim, 1985).
The strenuousness of the work performed by the animal influences the energy
requirements, and consequently a wide range of energy requirements have been
estimated. The values by Bamualim and Kartiarso show that about 10 per cent of

9 The original OECD method recommended slightly higher energy additions.

These

revised figures are based on newly-published information in AAC (1990).

4 . 18

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4

AGRICULTURE

NEm requirements are required per hour of typical work for draft animals. Thisvalue is used as follows:
EQUATION 5
NEdraft (MJ/day) = 0.10 x NEm x hours of work per day•

Pregnancy
Daily energy requirements for pregnancy are presented in NRC (1984). Integratingthese requirements over a 281-day gestation period yields the following equation:
EQUATION 6
NEpregnancy (MJ/281-day period) = 28 x calf birth weight in kg
The following equation can be used to estimate the approximate calf birth weight asa function of the cow's weight:10
EQUATION 7
Calf birth weight (kg) = 0.266 x (cow weight in kg)0.79
Manipulating Equations 6 and 7, in conjunction with Equation 1, shows that the NE
required for pregnancy is about 7.5 per cent of NEm for the range of cow sizes
considered in this analysis. Therefore, a factor of 7.5 per cent of NEm is added toaccount for the energy required for pregnancy for the portion of cows giving birtheach year.

Based on these equations, each of the net energy components for each of the cattle
categories can be estimated from the data collected in Step 1: weight in kilograms; feeding
situation; weight gain per day in kilograms; milk production in kilograms of 4 per cent fatcorrected milk; number of hours of work performed per day; and portion that give birth.
These net energy requirements must be translated into gross energy intakes. Also, by
estimating the gross energy intake, the net energy estimates can be checked forreasonableness against expected ranges of feed intake as a percentage of animal weight.
To estimate gross energy intake, the relationship between the net energy values andgross energy values of different feeds must be considered. This relationship can besummarised briefly as follows:
Digestible Energy=

Gross Energy - Faecal Losses

Metabolisable Energy=

Digestible Energy - Urinary and Combustible Gas
LossesNet Energy=

Metabolisable Energy - Heat Increment---------------------------------------------------------------------------------------------------------Net Energy=

Gross Energy - Faecal Losses - Urinary andCombustible Gas Losses - Heat Increment

10 This species-specific equation from Robbins and Robbins (1979) was adjusted to themean cow and calf weight of a typical beef breed of cattle. This adjustment increases thecoefficient in the equation from 0.214 to 0.266.

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual

4.19

AGRICULTURE

The quantitative relationship among these energy values varies among feed types.
Additionally, the values depend on how the feeds are prepared and fed, and the level atwhich they are fed. For the purposes of this method, simplifying assumptions are used toderive a relationship between net energy and digestible energy that is reasonably
representative for the range of diets typically fed to cattle. Gross energy intake is thenestimated using this relationship and the digestibility data collected in Step 1.
Given the digestibility of the feed (defined in Step 1), a general relationship between
digestible energy and metabolisable energy can be used as follows (NRC, 1984):
EQUATION 8Metabolisable Energy (ME) = 0.82 x Digestible Energy (DE)
Equation 8 is a simplified relationship; larger (smaller) methane conversion rates would
tend to reduce (increase) the coefficient to values below (above) 0.82.
NRC (1984) presents separate quantitative relationships between metabolisable energy
and net energy used for growth versus net energy used for other functions. Using
Equation 8, the NRC relationships can be re-arranged to quantify the ratio of NE to DE,
as follows:
EQUATION 9
NE/DE= 1.123 - (4.092 x 10-3 x DE%) + (1.126 x 10-5 x (DE%)2)- 25.4/DE%

EQUATION 10
NEg/DE

where:
NE/DE=

NEg/DE=DE%== 1.164 - (5.160 x 10-3 x DE%) + (1.308 x 10-5 x (DE%)2)- 37.4/DE%

the ratio of net energy consumed for maintenance, lactation, workand pregnancy to digestible energy consumed;
the ratio of net energy consumed for growth to digestible energy
consumed; anddigestible energy as percentage of gross energy, expressed in percent (e.g., 65%).

Because the NRC (1984) relationships were developed based on diets with relatively highdigestibilities (generally above 65 per cent), they may not be appropriate for the relatively
low digestibility diets that are commonly found in tropical livestock systems. In particular,
the non-linear nature of the relationships could appear to increase the estimates of feedintake for low-digestibility feeds. An apparent increase in feed intake would lead to an
apparent increase in emissions estimates.

4 . 20

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories:

Re fe r e n c e Manual