Emission factors

• Janssens et al., 2015: HTAP_v2.2: a mosaic of regional and global emission grid maps for2008 and 2010 to study hemispheric transport of air pollution

The region-specific implied emission factors (EFs) present the emissions per 1000 head of animals for agricultural related activities, are defined for a substance x at year t (htap_8_AGRICULTURE) in a country C as follows:

The emissions of the htap_8_AGRICULTURE sector are weighted with the number of animals and not with the kton crops cultivated, because the crops serve for 85 % as animal food and are therefore considered a justified measure of agricultural activity.

Implied emissions factors (ton head−1) for the year 2010 for NH3.

For NH3 a relative difference of+17 % is acceptable because of the larger uncertainty in emission factors driven by lack of information about manure management practices and also by incomplete data on the agricultural activities

• Crippa et al., 2018: Gridded emissions of air pollutants for the period1970–2012 within EDGAR v4.3.2

Implied emission factors can be used as a metric of emission intensity of anthropogenic activities for each country,and they have been calculated following the methodology by Janssens-Maenhout et al. (2015)

The emission factors used in EDGAR are mainly based on the EMEP/EEA (2013) guidebook and partly on the latest available scientific knowledge (EMEP/EEA, 2016; see guidebook). When information on EFs is missing or very uncertain (e.g. for Africancountries), default emission factors are considered to keep the consistency and comparability of the emissions among countries.

The uncertainty of NH3 is the largest among all pollutants because of the high uncertainty of both agricultural statistics and emission factors (range of variation in 2012: 186 % and 294.4 %).

world median	2.4E-01
EU28 median	1.3E-01
USA	1.6E-01
China	8.3E-02
India	4.8E-01
Russia	8.0E-02
Japan	5.4E-04

Implied EFs (t/thousand heads) for agricultural sector for selected regions and the world in 2010.

• Hoesly et al.,2017: Historical (1750–2014): anthropogenic emissions of reactive gasesand aerosols from the Community Emissions Data System (CEDS)

EDGAR is used as the primary scaling inventory as well as gridding data proxies. Non combustion emissions estimates are taken from both EDGAR and the country inventories. Inventory values are gap filled and extended back to 1970 following EDGAR trends (most country inventories do not extend back to 1970, the starting point of the EDGAR data).

For agricultural emissions, the actual practices of managing livestock manures will affect true emissions; such practices vary significantly across the world but are not always well understood or reflected in the emission factors used in global inventories (Paulot et al., 2014).

• Riddick et al.,2015: Estimate of changes in agricultural terrestrial nitrogen pathways and ammonia emissions from 1850 to present in the Community Earth System Model

• Bouwman et al.,1997: global high-resolution emission inventory for ammonia

The uncertainty for the different sources depends on the uncertainty in the basic data and in the emission factors used. The basic data used for the different sources vary in quality.

Animal populations are quite well known, although there is some uncertainty caused by the season in which censuses are made. The overall uncertainty caused by the animal population is probably <10%. The uncertainty in the emission factor for animals stems from the assumptions on N in the feed and waste management. For developing countries, in particular, there are no data on waste management practices. Therefore the uncertainty is probably great in tropical countries and smallest in western Europe. The overall uncertainty for this source is estimated to be +50%.

The overall uncertainty in the gross NH3 loss from nitrogen fertilizers amounts to +50%. The greatest uncertainty stems from lack of measure- ments of NH3 emissions in tropical cropping systems.

• EDGAR inventory

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3.D Crop production and agricultural soils

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Tier 1 default approach

Emission

The Tier 1 approach for NH3 emissions from crop production and agricultural soils uses the general equation

E pollutant = AR fertiliser_applied · EF pollutant

where: E pollutant= amount of pollutant emitted (kg a -1 ),

AR fertiliser_applied = amount of N applied (kg a -1 ),

EF pollutant=EF of pollutant (kg kg -1 ).

This equation is applied at the national level, using annual national total fertiliser nitrogen use.

The Tier 1 default NH 3 EF has been derived as a mean of default EFs for individual N fertilisers weighted according to their use as reported by IFA for Europe in 2010.

The Tier 1 emission factors for NH3 = 0.081 kg kg-1 fertilizer-N applied

Activity data

Information is required on the annual consumption national of total N-fertiliser. Annual fertiliser consumption data may be collected from official country statistics, often recorded as fertiliser sales and/or as domestic production and imports. If country-specific data are not available, data from the International Fertiliser Industry Association (www.fertilizer.org/ ) on total fertiliser use by type and by crop, or from the Food and Agriculture Organisation of the United Nations (FAO, ​http://faostat.fao.org/) on mineral fertiliser consumption, can be used.

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Tier 2 technology-specific approach

Emission

Noting the interdependence of direct fertiliser emissions and subsequent emissions from foliage and decomposing residues from fertilised vegetation, the emissions are treated here as a single integrated term. These are estimated as proportional losses of the fertiliser-N use for each of the main fertiliser categories. Emissions from unfertilised crops are considered to be zero.

Tier 2 EFi , kg NH3 kg N-1 Fertiliser type Low soil pH High soil pH

Ammonium nitrate (AN) 0.037 0.037

Anhydrous ammonia 0.011 0.011

Ammonium phosphate (MAP and DAP) 0.113 0.293

Ammonium sulphate (AS) 0.013 0.270

Calcium ammonium nitrate (CAN) 0.022 0.022

Calcium nitrate (CN) 0.009 0.009

Ammonium solutions (AN) 0.037 0.037

Ammonium solutions (Urea AN) 0.125 0.125

Urea ammonium sulphate (UAS) 0.195 0.195

Urea 0.243 0.243

Other NK and NPK 0.037 0.037

Activity data

Information is required on the annual national consumption of the N-fertiliser types shown in Table 3–2. Annual fertiliser consumption data may be collected from official country statistics, often recorded as fertiliser sales and/or as domestic production and imports. If country-specific data are not available, data from the International Fertiliser Industry Association (www.fertilizer.org) on total fertiliser use by type and by crop, or from the Food and Agriculture Organisation of the United Nations (FAO, ​http://faostat.fao.org/) on mineral fertiliser consumption, can be used. Fertiliser use also needs to be disaggregated by fertiliser type. In addition, if ammonium sulphate or diammonium phosphate are significant sources, then information will be needed on the amounts of those fertilisers applied to soils of < and > pH 7.0

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Tier 3 emission modelling and use of facility data

Emission

Tier 3 methodologies are those that result in more accurate estimates of emissions than would be achieved using the Tier 2 methodology. This could include the use of alternative EFs, based on local measurement, the use of more detailed activity data and EFs or the use of process-based models. Users are encouraged to use Tier 3 methodologies wherever possible.

Activity data

Data will typically be required on type of N fertiliser applied, soil pH, land use, application rate, rainfall and temperature. Activity data for model input can be gathered from country-specific databases, trade associations (preferred) or, where these data are unavailable, can be found in different international databases.

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Uncertainty

The main uncertainty lies in the generalization of EF, rather than the areas of crops under cultivation which is probably accurate in most countries to better than ± 10 %. The standard deviation in the NH 3 measurements from mineral fertiliser are at the same level as the average measured emission in percent. The overall emissions are probably no better than ± 50 %.

Application of fertiliser-N may be estimated with an accuracy of ± 10 %; other factors such as returns of N in manures may be estimated to within ± 25 %. With respect to national data on crop areas, an uncertainty of < 5 % is assumed, with a normal distribution.

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3.B Manure management

There are five main sources of emissions from animal husbandry and manure management:

• livestock feeding
• livestock housing and holding areas
• manure storage
• field-applied manure )
• manure deposited during grazing

Ammonia emissions from livestock production depend on many factors including:

• the amount and N content of feed consumed;
• the efficiency of conversion of N in feed to N in meat, milk and eggs and, hence, the amount of N deposited in excreta;
• the proportion of time spent by animals indoors and outside, e.g. at pasture or on yards or, buildings and on animal behaviour;
• whether livestock excreta are handled as slurry, or solid;
• the housing system of the animal (especially the floor area per animal) and whether manure is stored inside the building;
• climatic conditions in the building (e.g. temperature and humidity) and the ventilation system; the storage system of the manure outside the building: open or covered slurry tank, loose or packed heap of solid manure, any treatment applied to the manure such as aeration, separation or composting..

Ammonia emissions from livestock manures during and after field application depend on:

• properties of the manure, including viscosity, TAN content, C content and pH;
• soil properties such as pH, cation exchange capacity, calcium content, water content, buffer capacity and porosity;
• meteorological conditions including precipitation, solar radiation, temperature, humidity and wind speed;
• the method and rate of application of livestock manures, including, for arable land, the time between application and incorporation, and method of incorporation;
• the height and density of any crop present.

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Tier 1 default approach

Emission

The pollutant emissions, E pollutant_animal for each livestock category, using the respective annual average population of each category, AAP animal and the relevant EF pollutant_animal : E pollutant_animal = AAP animal · EF pollutant_animal

where AAP animal=number of animals of a particular category that are present, on average, within the year. For a fuller explanation, see IPCC (2006).

Default Tier 1 EF (EF NH3 ) for calculation of NH 3 emissions from manure management.

Dairy cows slurry 39.3

Dairy cows solid 28.7

Other cattle (including young cattle, beef cattle and slurry suckling cows) 13.4

Other cattle solid 9.2

Fattening pigs slurry 6.7

Fattening pigs solid 6.5

Sows slurry 15.8

Sows solid 18.2

Sows outdoor 7.3

Sheep (and goats) solid 1.4

Horses (and mules, asses) solid 14.8

Laying hens (laying hens and parents) solid 0.48

Laying hens (laying hens and parents) slurry 0.48

Broilers (broilers and parents) litter 0.22

Other poultry (ducks) litter 0.68

Other poultry (geese) litter 0.35

Other poultry (turkeys) litter 0.95

Fur animals 0.02

Camels solid 10.5

Buffalo solid 9.0

Activity data

For Tier 1, data are required on animal numbers for each of the categories listed in the Table. An annual national agricultural census can supply these data. Otherwise, statistical information from Eurostat (​http://epp.eurostat.ec.europa.eu) or the Food and Agriculture Organization of the United Nations (FAO) Production Yearbook (FAO, 2005/2006) can be used.

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Tier 2 technology-specific approach

Emission

Tier 2 uses a mass flow approach based on the concept of a flow of TAN (total ammoniacal-N) through the manure management system.It should be noted that the calculations of a mass flow approach must be carried out on the basis of kg N. The resultant estimates of NH 3 -N emissions are then converted to NH 3 . When calculating emissions of NH 3 using a mass flow approach, a system based on TAN is preferred to one based on total N.

Activity data Activity data should be gathered from national farming statistics and farm practice surveys; of particular importance are estimates of the length of the grazing period for ruminants, how long manure is stored and the type of store and manure treatment used, and the method of manure application to land. For manures applied to tillage land, the interval before incorporation is also needed.

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Tier 3 emission modelling and use of facility data

Emission

There is no restriction on the form of Tier 3, provided it can supply estimates that can be demonstrated to be more accurate than Tier 2. If data are available, emission calculations may be made for a greater number of livestock categories than listed under Tier 2.

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Uncertainty

Uncertainties in NH 3 EFs vary considerably. A recent UK study indicated a range from ± 14 % for the EF for slurry spreading to ± 136 % for beef cattle grazing. In general, EFs for the larger sources tended to be based on a greater number of measurements than those for smaller sources and, in consequence, tended to be more certain. The exceptions were the EFs for buildings in which livestock were housed on straw and grazing EFs for beef and sheep. The uncertainties of partial EFs have yet to be discussed. The overall uncertainty for the UK ammonia emissions inventory, as calculated using a Tier 3 approach, was ± 21 % (Webb and Misselbrook, 2004), while that for the Netherlands, also using a Tier 3 approach, was ± 17 % (Van Gijlswijk et al., 2004). There is likely to be greater uncertainty in estimates of activity data, although for such data, a quantitative assessment of uncertainty is difficult to determine. Webb and Misselbrook (2004) reported that eight of the ten input data to which estimates of UK NH 3 emissions were the most sensitive were activity data.