4. N Emissions from Manure Management

In this section, N emissions from livestock housing, farmyard, and manure storage are calculated. N emissions during field application of manure, and during grazing period are calculated in 10. N Losses from Soil when they are added to the soil.

Emissions of N are calculated separately for each type of animal, and for both solid and liquid forms, in each MMS. Unless otherwise specified, the units for all N terms are kg N ha^–1 yr^–1. The following table summarises the pathways for N emissions and losses calculated in this section.

	Housing	Yard	Storage
NH₃	✅	✅	✅
N₂O			✅
NO_x	✅		✅
N₂			✅
Loss to water ^[1]			✅

Housing

Yard

Storage

NH₃

✅

N₂O

✅

NO_x

✅

N₂

✅

Loss to water ^[1]

✅

[1] Includes combined runoff and leaching during manure storage.

NH₃-N emissions are calculated on the basis of total ammoniacal N (TAN), following the approach by the EMEP/EEA air pollutant emission inventory guidebook 2023 (hereafter “EMEP Guidebook”), with some simplification due to limitation on data availability. All the other gaseous N emissions are calculated based on total N.

The amounts of total N in solid and liquid forms of each type of animal manure in each stage are determined following the steps as described in 3.3. N content in livestock excretion.

	Solid	Liquid
Housing	N_{housing, solid}	N_{housing, liquid}
Farmyard	N_{yard, solid}	N_{yard, liquid}
Grazing	N_{grazing, solid}	N_{grazing, liquid}

Solid

Liquid

Housing

N_{housing, solid}

N_{housing, liquid}

Farmyard

N_{yard, solid}

N_{yard, liquid}

Grazing

N_{grazing, solid}

N_{grazing, liquid}

Next, the amounts of TAN deposited during housing, yard, and grazing period, are calculated by multiplying N content with TAN fraction:

Equation 4.1

where:

	is the TAN content in solid/liquid fraction of manure during the housing/yard/grazing period (kg N).
	is the total N content in solid/liquid fraction of manure during the housing/yard/grazing period (kg N). See Equation 3.1.
	is the fraction of TAN in total N (kg TAN kg^–1 total N). See Table 4.1.

Table 4.1: Emission factors and associated parameters for the calculation of NH₃-N emissions from manure management.
Livestock	Miterra Code ^[1]	Manure Type	f_TAN	E_housing	E_yard	E_storage	E_application	E_grazing
Dairy cattle	DAICOW	Liquid	0.6	0.24	0.30	0.25	0.55	0.14
Dairy cattle	DAICOW	Solid	0.6	0.08	0.30	0.32	0.68	0.14
Non-dairy cattle	OCOW	Liquid	0.6	0.24	0.53	0.25	0.55	0.14
Non-dairy cattle	OCOW	Solid	0.6	0.08	0.53	0.32	0.68	0.14
Finishing pigs	PIGS	Liquid	0.7	0.27	0.53	0.11	0.40	/
Finishing pigs	PIGS	Solid	0.7	0.23	0.53	0.29	0.45	/
Sows & piglets	/	Liquid	0.7	0.35	/	0.11	0.29	/
Sows & piglets	/	Solid	0.7	0.24	/	0.29	0.45	/
Sheep & goats ^[2]	SHEGOA	Solid	0.5	0.22	0.75	0.30	0.90	0.09
Horses	HORSES	Solid	0.6	0.22	/	0.35	0.90	0.35
Buffalo	/	Solid	0.5	0.20	/	0.17	0.55	0.14
Laying hens ^[3]	LAYHENS	Solid	0.7	0.20	/	0.08	0.45	/
Broilers	/	Solid	0.7	0.21	/	0.30	0.38	/
Other poultry ^[4]	OPOUL	Solid	0.7	0.39	/	0.21	0.51	/
Other animals	FURANI	Solid	0.6	0.27	/	0.09	/	/

[1] Corresponding livestock codes used in Miterra (see Livestock & manure codes in Appendix). Not all EMEP livestock categories are included in Miterra.
[2] Values are means of sheep, and goats (separate items) in the original table.
[3] Liquid slurry from laying hens is included in the EMEP Guidebook but not considered in Miterra.
[4] Values are means of turkeys, other poultry (ducks), and other poultry (geese) in the original table.
Reproduced from Table 3-9 of Chapter 3.B of the EMEP Guidebook.

4.1. N Emissions from livestock housing

Emissions of NH₃-N and NO_x-N are calculated during livestock housing.

The NH₃-N emissions during housing are calculated by multiplying TAN with corresponding emission factors:

Equation 4.2

where:

	is the NH₃-N emission from solid/liquid manure during the housing period (kg N).
	is the TAN content in solid/liquid fraction of manure during the housing period (kg N). See Equation 4.1.
	is the NH₃-N emission factor as specified in Table 4.1 (kg NH₃-N kg^–1 TAN).
	is the fraction of farms that adopted the i-th NH₃ abatement technique during housing in the region (unitless).
	is the fraction of emission reduction by applying the i-th NH₃ abatement technique during housing (unitless).
	is the set of NH₃ abatement techniques applied during housing in the region (i ∈ n).

The NO_x-N emissions during housing are calculated similarly to NH₃-N, but by multiplying total N with corresponding emission factors:

Equation 4.3

where:

	is the NO_x-N emission from solid/liquid manure during the housing period (kg N).
	is the total N content in solid/liquid fraction of manure during the housing period (kg N). See Equation 3.1.
	is the NO_x-N emission factor with a default value of 0.003 for all animal manure in all countries (kg NO_x-N kg^–1 total N).
	is the fraction of farms that adopted the the i-th NO_x abatement technique during housing in the region (unitless).
	is the fraction of emission reduction by applying the i-th NO_x abatement technique during housing (unitless).
	is the set of NO_x abatement techniques applied during housing in the region (i ∈ n).

By the end of the housing period (denoted by ex_housing), total N and TAN in solid/liquid manure are removed from livestock housing, and passed to storage system, subtracting the gaseous N emissions.

Equation 4.4

The next step is only relevant to solid manure deposited in livestock houses. It accounts for the addition of N in animal bedding in litter-based housing systems, and the consequent immobilisation of TAN in that bedding material.

where:

	is the TAN or total N content in solid/liquid manure by the end of the housing period (kg N).
	is the TAN or total N content in solid/liquid manure during the housing period (kg N). See Equation 3.1 and Equation 4.1.
	is the amount of NH₃-N or NO_x-N emission from solid/liquid manure during the housing period (kg N). See Equation 4.2 and Equation 4.3.
	is the mass of bedding straw added (kg fresh weight yr^–1).
	is the immobilization coefficient (kg N kg^–1 fresh straw) with a default value of 0.0067 ( Kirchmann & Witter, 1989; and Webb & Misselbrook, 2004).
	is the mass of N in that bedding straw (kg N yr^–1).

Default values for length of housing period, annual straw use in litter-based manure management systems, and the N content of straw are given below. If the actual housing period is longer or shorter than the days in the table, the amounts of straw and straw N added should be adjusted in proportion to the leangth of the actual housing days (e.g., if the housing period is 360 days for dairy cattle, then the amount of straw added should be 1500 / 180 × 360 = 3000 kg head^–1 yr^–1).

Livestock	Miterra Code ^[1]	Housing Period (day)	Straw (kg head^–1 yr^–1)	N Added in Straw (kg N head^–1 yr^–1)
Dairy cattle	DAICOW	180	1500	6.0
Non-dairy cattle	OCOW	180	500	2.0
Pigs	PIGS	365	200	0.8
Sheep & goats	SHEGOA	30	20	0.08
Horses	HORSES	180	500	2.0

[1] Corresponding livestock codes used in Miterra (see Livestock & manure codes in Appendix). Not all EMEP livestock categories are included in Miterra.
Reproduced from Table 3-7 of Chapter 3.B of the EMEP Guidebook.

4.2. N emissions from farmyard

Emissions of NH₃-N are calculated for farmyard.

Equation 4.5

where:

	is the NH₃-N emission from solid/liquid manure during the farmyard period (kg N).
	is the TAN content in solid/liquid fraction of manure during the farmyard period (kg N). See Equation 4.1.
	is the NH₃-N emission factor as specified in Table 4.1 (kg NH₃-N kg^–1 TAN).

By the end of the farmyard period (denoted by ex_yard), all yard manure are collected and passed to the storage system.

Equation 4.6

where:

	is the TAN or total N content in solid/liquid manure by the end of the farmyard period (kg N).
	is the TAN or total N content in solid/liquid manure during the farmyard period (kg N). See Equation 3.1 and Equation 4.1.
	is the amount of NH₃-N emitted from solid/liquid manure during the farmyard period (kg N). See Equation 4.5.

4.3. N losses from manure storage

Emissions of NH₃-N, N₂O-N, NO_x-N, N₂-N, and NO₃^–-N losses to water are calculated for manure storage.

In the first step, the amounts of total N and TAN that are passed to storage system from housing and farmyard periods are calculated. It is assumed that all yard manure (both solid and liquid forms) are collected into the liquid storage system.

This step simplifies the method in EMEP Guidebook by assuming that all manure are stored before application. Manures applied to fields directly from livestock housing, and manures (mainly slurries) used as feedstocks for digestion, are not considered due to lack of reliable estimation.

Equation 4.7

The next step is only applied to liquid slurries. It adds a fraction of the organic N that is mineralized to TAN before the gaseous emissions are estimated.

where:

	is the TAN or total N content in solid/liquid manure during the storage period (kg N).
	is the TAN or total N content in solid/liquid manure by the end of the housing period (kg N). See Equation 4.4.
	is the TAN or total N content in solid/liquid manure by the end of the farmyard period (kg N). See Equation 4.6.
	is the mineralization coefficient (kg TAN mineralized kg^–1 total N) with a default value of 0.1 ( Dämmgen et al., 2007).

The NH₃-N emissions from storage are calculated by applying emission factors on TAN.

Equation 4.8

where:

	is the NH₃-N emission from solid/liquid manure during the storage period (kg N).
	is the NH₃-N emission factor as specified in Table 4.1 (kg NH₃-N kg^–1 TAN).
	is the fraction of farms that adopted the the i-th NH₃ abatement technique during storage in the region (unitless).
	is the fraction of emission reduction by applying the i-th NH₃ abatement technique during storage (unitless).
	is the set of NH₃ abatement techniques applied during storage in the region (i ∈ n).

All other gaseous N emissions are calculated by applying emission factors on total N.

Equation 4.9

where:

	is the N₂O/NO_x/N₂-N emission from solid/liquid manure during the storage period (kg N).
	is the N₂O/NO_x/N₂-N emission factor (kg N₂O/NO_x/N₂-N kg^–1 total N).
	is the fraction of farms that adopted the the i-th N₂O/NO_x/N₂ abatement technique during storage in the region (unitless).
	is the fraction of emission reduction by applying the i-th N₂O/NO_x/N₂ abatement technique during storage (unitless).
	is the set of N₂O/NO_x/N₂ abatement techniques applied during storage in the region (i ∈ n).

Part of the N may also be lost to water as NO₃^– during storage. This can take place via seepage through the bottom of the storage tank, or via overflow during precipitation.

Equation 4.10

where:

is the NO₃^–-N leached from solid/liquid manure during the storage period (kg N).

is the total N content in solid/liquid manure during the storage period (kg N). See Equation 4.7.

is the leaching factor of NO₃^– during storage (kg NO₃^–-N kg^–1 total N), which is specific to the type of manure and storage system.

Manure Type

Storage System

Concrete Floor

Cover

Liquid slurry

❌

0.2

❌

✅

0.15

✅

0.0

Solid manure

❌

0.1

❌

✅

0.02

✅

❌

0.05 ^[1]

✅

0.0

[1] Assuming that some manure may be washed from the concrete floor to the surrounding soil.

Finally, the amounts of total N and TAN remaining by the end of storage (denoted by ex_storage subscript) are calculated. Total N and TAN in solid and liquid forms may be combined at this step.

Equation 4.11

Total N and TAN from solid and liquid fractions of manure are further aggregated.

where:

	is the aggregated TAN or total N content in both solid and liquid manure by the end of the storage period (kg N).
	is the TAN or total N content in solid/liquid manure by the end of the storage period (kg N).
	is the TAN or total N content in solid/liquid manure during the storage period (kg N). See Equation 4.7.
	is the amount of N emitted in gaseous forms from solid/liquid manure during the storage period (kg N). See Equation 4.8 and Equation 4.9.
	is the amount of NO₃^–-N lost via leaching from solid/liquid manure during the storage period (kg N). See Equation 4.10.
	i ∈ {NH₃, N₂O, NO_x, N₂}.

Total N and TAN remaining after storage (N_{ex_storage} and TAN_{ex_storage}) is applicable to the fields as organic fertilisers. The distribution of applicable manure N to different crops are described in 7. Fertilization.