Atmospheric Environment 46 (2012) 248e255
Contents lists available at SciVerse ScienceDirect
Atmospheric Environment
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A model for inventory of ammonia emissions from agriculture in the Netherlands
G.L. Velthof a, *, C. van Bruggen b, C.M. Groenestein c, B.J. de Haan d, M.W. Hoogeveen e, J.F.M. Huijsmans f
a
Alterra, Part of Wageningen UR, P.O. Box 47, 6700 AA Wageningen, The Netherlands
Statistics Netherlands (CBS), Postbus 24500, 2490 HA Den Haag, The Netherlands
c
Wageningen UR Livestock Research, P.O. Box 135, 6700 AC Wageningen, The Netherlands
d
PBL Netherlands Environmental Assessment Agency, PO Box 303, 3720 AH Bilthoven, The Netherlands
e
LEI, Part of Wageningen UR, PO Box 29703, 2502 LS The Hague, The Netherlands
f
Plant Research International, Part of Wageningen UR, P.O. Box 616, 6700 AP Wageningen, The Netherlands
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 May 2011
Received in revised form
16 September 2011
Accepted 28 September 2011
Agriculture is the major source of ammonia (NH3). Methodologies are needed to quantify national NH3
emissions and to identify the most effective options to mitigate NH3 emissions. Generally, NH3 emissions
from agriculture are quantified using a nitrogen (N) flow approach, in which the NH3 emission is
calculated from the N flows and NH3 emission factors. Because of the direct dependency between NH3
volatilization and Total Ammoniacal N (TAN; ammoniumeN þ N compounds readily broken down to
ammonium) an approach based on TAN is preferred to calculate NH3 emission instead of an approach
based on total N. A TAN-based NH3-inventory model was developed, called NEMA (National Emission
Model for Ammonia). The total N excretion and the fraction of TAN in the excreted N are calculated from
the feed composition and N digestibility of the components. TAN-based emission factors were derived or
updated for housing systems, manure storage outside housing, manure application techniques, N
fertilizer types, and grazing. The NEMA results show that the total NH3 emission from agriculture in the
Netherlands in 2009 was 88.8 Gg NH3eN, of which 50% from housing, 37% from manure application, 9%
from mineral N fertilizer, 3% from outside manure storage, and 1% from grazing. Cattle farming was the
dominant source of NH3 in the Netherlands (about 50% of the total NH3 emission). The NH3 emission
expressed as percentage of the excreted N was 22% of the excreted N for poultry, 20% for pigs, 15% for
cattle, and 12% for other livestock, which is mainly related to differences in emissions from housing
systems. The calculated ammonia emission was most sensitive to changes in the fraction of TAN in the
excreted manure and to the emission factor of manure application. From 2011, NEMA will be used as
official methodology to calculate the national NH3 emission from agriculture in the Netherlands.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Ammonia
Agriculture
Inventory
Manure
Total ammoniacal nitrogen (TAN)
Netherlands
1. Introduction
Agriculture contributes to about 80% of the total ammonia
emission in Europe (http://www.emep.int). The major NH3 sources
from agriculture are related to the excretion of urine by livestock,
i.e. livestock housing (Groenestein, 2006; Monteny, 2000), manure
storage, grazing (Bussink, 1994), and application of manure
(Huijsmans et al., submitted for publication). Moreover, application
of urea containing fertilizers and application of ammonium (NHþ
4)
based mineral N fertilizers on calcareous soils are sources of NH3
* Corresponding author. Tel.: þ31 317 486503; fax: þ31 317 419000.
E-mail addresses: [email protected] (G.L. Velthof), [email protected]
(C. van Bruggen), [email protected] (C.M. Groenestein), bronno.deHaan@
pbl.nl (B.J. de Haan), [email protected] (M.W. Hoogeveen), jan.
[email protected] (J.F.M. Huijsmans).
1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.atmosenv.2011.09.075
(Bouwman et al., 2002). Ammonia may form secondary particulate
matter in the atmosphere (Erisman and Schaap, 2003), which may
have adverse effects on human health (Moldanová et al., 2011).
When NH3 is deposited to soil, it can cause soil acidification (Van
Breemen et al., 1983) and eutrophication of natural aquatic and
terrestrial ecosystems. This results in loss of plant biodiversity
(Bobbink et al., 1998). Moreover, NH3 is a so-called indirect source
of the greenhouse gas nitrous oxide (N2O; IPCC, 1996).
The Gothenburg Protocol of the UN Convention on Long-range
Transboundary Air Pollution (UNECE, 1999) and the EU National
Emission Ceiling Directive (European Commission, 2001) have set
limits to NH3 emissions. Therefore countries have to report their
NH3 emissions to the UNECE and/or the European Commission.
Moreover, countries have to report their NH3 emissions as a basis
for their N2O emission calculation to the UNFCCC. Refinement of
the projections of NH3 emission are needed to find effective options
to mitigate NH3 emissions.
G.L. Velthof et al. / Atmospheric Environment 46 (2012) 248e255
A guidebook has been made for inventories of emissions of air
pollutants, including NH3 (EMEP/EEA, 2009). It has been designed
for countries that have to report NH3 emission to the UNECE and/or
European Commission. Generally, NH3 emissions from agriculture
are quantified using a nitrogen (N) flow approach. In such
approach, the NH3 emission is calculated from the N flows and
NH3-emission factors. Several studies describe models and emission factors used in different countries, e.g. Denmark (Hutchings
et al., 2001), France (Gac et al., 2007), Ireland (Hyde et al., 2003),
Germany (Dämmgen et al., 2006), Switzerland (Reidy et al., 2008b),
The Netherlands (Luesink and Kruseman, 2007), UK (Webb and
Misselbrook, 2004), and USA (Faulkner and Shaw, 2008).
Manure is a mixture of feces and urine. N in feces is mainly
organically bound. The urine of mammals consist mainly of urea N
and the urine of poultry of uric acid. Urea rapidly hydrolyses into
NHþ
4 through the enzyme urease, by which slurries do not contain
urea. The degradation of uric acid is much slower, especially in
dried manure in which microbial activity is low. Solid poultry
manure may still contain uric acid when applied to the soil
(Nicholson et al., 1996). AmmoniumeN and N compounds which
are readily broken down to NHþ
4 , such as urea and uric acid, are
referred to as Total Ammoniacal N (TAN; EMEP/EEA, 2009).
Accurate projections of NH3 emissions from agriculture require
methods that are closely linked to the processes controlling NH3
emission. An approach to calculate NH3 emission using emission
factors based on TAN instead of total N is a step closer to a processbased NH3-emission model and is preferred to calculate NH3
emission (EMEP/EEA, 2009; Reidy et al., 2008a). There are several
benefits of using a TAN-based approach instead of an approach
based on total N. Firstly, NH3 is produced from NHþ
4 (at high pH
levels) by which the relation between NH3 emission and TAN
content is more direct than between NH3 emission and total N
content (e.g. Elzing and Monteny, 1997; Velthof et al., 2005).
Secondly, changes in feed composition may not only change the
total N excretion, but also the portion of TAN in the total N excretion
(Canh et al., 1998; Valk, 1994). Thirdly, the emission factors for
manure application in the Netherlands are based on the TAN
content of the applied manure (Huijsmans et al., submitted for
publication). Effects of changes in feed composition and manure
management in housing may affect the TAN content of manure, and
thus affect the NH3 emission from manure applied to soil. These
effects can be quantified using a TAN-based flow model. A TANbased approach requires information on the N digestibility of the
N compounds in the feed to calculate the TAN excretion. Moreover,
the N mineralization of organic N into TAN and immobilization of
TAN into organic N during the storage of manure have to be
quantified.
This paper describes a TAN-based NH3-inventory model
(National Emission Model for Ammonia; NEMA), which will be
used for calculating NH3 emission from agriculture in the Netherlands (Van der Maas et al., 2011). In the current paper, the NEMA
model is described and the NH3 emissions from agriculture in the
Netherlands are quantified for the year 2009. Scenario analyses are
carried out to get quantitative insight in the effect of changes of
model parameters on the total NH3 emission, including changes in
the TAN excretion, types of housing systems, types of manure
application techniques, and emission factors for housing, manure
storage, grazing and manure application.
2. Materials and methods
2.1. Description of the NEMA model
The NEMA model is a deterministic TAN-based N flow model,
which calculates the total NH3 emission from agriculture in the
249
Netherlands on annual basis. It calculates NH3 emission from
housing, manure storage outside housing, manure application to
soil, grazing, and mineral N fertilizer, based on the flow of TAN
(Fig. 1) and TAN-based NH3-emission factors.
2.2. Excretion of total N and TAN
The total N and TAN excretion is calculated yearly for 35 livestock categories, using statistical data of the type and composition
of animal feed for the different livestock categories (CBS, 2009). The
N excreted is calculated as the difference between the intake of N
and retention of N in animal products, using standard N balance
calculation methods (e.g. Canh et al., 1998; Valk, 1994; Wilkerson
et al., 1997). The fraction of TAN in the N excretion is calculated
as the excretion of urine-N which is the digested part of the N in
feed not converted into animal products (Groenestein et al.,
submitted for publication). The undigested N is excreted as fecal
N. The content of crude protein of the feed is generally known.
However, the digestibility of N in the feed changes, because feeding
compounds in the feed change over time. Bikker et al. (2011)
developed an optimization model to calculate feed compositions
based on the crude protein content of the feed, season, prices of the
feed compounds of the specific year and market developments. The
calculated average N digestibility of the feed is then used to
calculate the TAN excretion of pigs, poultry, cattle, horses, sheep
and goats. For some small livestock categories, like rabbits, data of
feed composition are not available. For these animals, the TAN
fraction of the N excretion is estimated at 70%.
2.3. Emission from housing, manure storage, manure application,
grazing, and fertilizer
The NH3 emission from housing systems is calculated from the
number of livestock per category, the total N excretion during
housing, the fraction of TAN in the excreted N, the N nett mineralization and immobilization of manure during storage, and the
NH3-emission factor for housing systems. Most NH3-emission factors
for housing systems are based on measurements on commercial
farms or experimental stations (e.g. Aarnink, 1997; Groenestein,
2006; Groot Koerkamp, 1998; Ogink et al., 2008; and Monteny, 2000).
Groenestein et al. (submitted for publication) reason that based on
studies of Beline et al. (1998), Sommer et al. (2007), Sørensen et al.
(2003), 10% of organic N in slurry is mineralized during storage. In
solid manure, N may be immobilized, but quantification of immobilization is uncertain and studies show large variations in immobilization (Chadwick et al., 2000; Petersen et al., 1998; Kirchmann, 1991).
Therefore they assumed 25% of the TAN in solid manure to be
immobilized during storage, and that the N is not released during
a later stage of storage. For dried poultry manure they assume no net
mineralization or immobilization, because drying inhibits the hydrolysis of uric acid in poultry manure into ammonium. Part of the
produced manure is stored outside the livestock building. The total
amount of manure TAN stored outside was calculated for each manure
type from the TAN excretion, N mineralization in the housing and N
immobilization, multiplied with the fraction of manure stored outside.
In order to calculate the amount TAN applied to the field, the
gaseous emissions of other N compounds (N2, N2O, and NOx) during
housing and manure storage have to be calculated. The emission
factor for N2O is derived from IPCC (1996), that of NOx is set equal to
N2O, and that of N2 ranges from 1 to 10%. It was assumed that no N is
lost by leaching during manure storage, because in the Netherlands
slurries have to be stored in covered basins with concrete floors.
The total amount of TAN applied as slurry and solid manure to soil
is calculated from the TAN excreted and mineralized or immobilized
in housing and outside storage, corrected for the total gaseous N
250
G.L. Velthof et al. / Atmospheric Environment 46 (2012) 248e255
Excretion livestock
Total N (484 Gg N)
TAN (319 Gg TAN)
NH3: 46 Gg N
N2, N2O, NOx :12 Gg N
Grazing on
natural
grasslands
8 Gg TAN
Excretion in housing
269 Gg TAN
Housing + manure storage
Mineralisation: 8 Gg TAN
Export and treatment
of manure: 48Gg TAN
Mineral
fertilizer
238 Gg N
Slurry and solid manure
82 Gg TAN
NH3
11 Gg N
NH3
8 Gg N
Arable land
Slurry and solid manure
89 Gg TAN
NH3
22 Gg N
Grazing
43 Gg TAN
NH3
1 Gg N
Grassland
Fig. 1. General set-up of NEMA model. The arrows indicate the flows of TAN and N. The grey boxes with clouds the location and type of the gaseous N emissions and the boxes with
dotted lines the N sources. The numbers indicate the flows of TAN and N and the gaseous emissions in Gg N per year.
emissions in housing and outside storage. This amount is corrected
for the manure exported, imported, and processed (i.e. the N that is
removed from agriculture), and for changes in the amount of stored
manure between years. The total amount of manure is divided over
grassland and arable land, based on the N and P application standards
in the Netherlands. The implementation of the manure application
techniques were derived from statistics (CBS, 2009). The NH3-emission factors for manure application techniques were based on field
experiments, and ranged between 2% of the TAN applied for slurry
injection on arable land to 74% for broadcast surface spreading on
grassland (Huijsmans et al., submitted for publication).
The NH3-emission factor for grazing by cattle was based on the
results of studies of Bussink (1992, 1994), as described by
Huijsmans et al. (submitted for publication). The NH3-emission
factor for grazing in 2009 was 2.7% of the TAN excreted.
The NH3-emission factors for the different fertilizer types were
calculated using the regression equations of Bouwman et al. (2002).
Information about the fertilizer type, application method, soil pH,
soil Cation Exchange Capacity (CEC), and climate, were used to
derive the emission factors for the different N fertilizers (Huijsmans
et al., submitted for publication). The emission factors ranged from
0% for nitrate fertilizers to 14.3% for urea. The emission factor for
calcium ammonium nitrate, the most common mineral N fertilizer
in the Netherlands, was 2.5%.
2.4. Total ammonia emission
The total NH3 emission from agriculture was calculated as the
sum of the NH3 emissions of housing, manure storage outside
housing, manure application to soil, grazing, and mineral N fertilizer. In this paper the results for 2009 are presented, i.e. the year
with most up-to-date inventory data.
2.5. Scenario analyses
The effect of changes of several input parameters of the NEMA
model on the total NH3 emission were calculated:
The assumption of mineralization in stored slurry (10% of
excreted organic N) is uncertain. The effect of a nett mineralization of 0 and 20% of the organic N in slurry on the total NH3
emission was quantified.
The effect of changes in TAN excretion was assessed by
assuming that the TAN fraction in the N excretion of all livestock categories was 10% smaller and larger, relative to the
default value for 2009.
There are indications that the NH3-emission factor for cubicle
housing systems for dairy cattle is underestimated, because of
larger air inlets (Smits and Huis in ’t Veld, 2007). The effect of
a higher emission factor of relative 20% higher than the default
emission factor for dairy housing systems on NH3 emission was
quantified.
Management and housing systems of pigs, poultry, and cattle
evolve during the years, which can change emissions. In this
calculation, the effect of a 20% smaller and larger emission
factor on NH3 emission relative to the default emission factor
was assessed for pig, poultry, and beef cattle systems.
The emission factors for N2, N2O and NO are poorly quantified
because measurements are lacking. The effect on NH3 emission
of a 50% smaller and larger emission factor relative to the
default emission factors was quantified.
Huijsmans et al. (submitted for publication) show that the
NH3-emission factor for shallow injected slurry on grassland
has increased since the nineties. It has been suggested that this
increase was (partly) due to less careful slurry application. The
G.L. Velthof et al. / Atmospheric Environment 46 (2012) 248e255
251
Table 1
Number of animals and excretion of total N and TAN in 2009.
Animal
category
Cattle
Pigs
Poultry
Other
Dairy cattle
Young cattle
Veal calves
Beef cattle
Fattening pigs
Sows
Other pigs
Layers (>18 weeks)
Broilers
Other poultry
Sheep and goats
Horses
Fur animals
Number of
animals
Total N
excretion
106 kg N
TAN-excretion þ N
mineralization in
stored manure
106 kg N
TAN excreted
and mineralized,
% of total
excreted N
1489071
1237222
894248
347058
5872351
985244
260361
35293716
43285129
20497031
769369
144924
910701
189
68
14
22
75
30
4
27
23
13
11
7
2
484
120
47
9
14
53
20
3
21
17
9
7
5
1
327
63
69
64
64
71
67
75
78
74
69
64
71
50
68
Total
effect on NH3 emission of 20% smaller and larger emission
factors for all slurry application techniques relative to the
default emission factors was assessed.
The emission factors for application of poultry manure are
equal to those of slurry. However, it is known that part of the
excreted uric acid by poultry is not hydrolyzed during storage,
especially when the manure is dried (Nicholson et al., 1996).
The fate of uric acid of poultry manure after application to the
soil and its effect on NH3 emission are not well quantified. If
soil-applied uric acid does not contribute to NH3 emission, the
use of a NHþ
4 based emission factor in an approach with
calculated TAN excretion (i.e. the sum of NHþ
4 and uric acid)
may lead to an overestimation of the NH3 emission. The effect
of an emission factors for poultry manure which were 50%
smaller than the default emission factors on NH3 emission was
quantified.
The implementation of the manure application techniques are
derived from statistics, but in practice an application technique
may be applied in a different way. In this calculation it is
assumed that the share of cattle slurry application to grassland
with narrow band application increases from 23 to 50% and
that the share of shallow injection of cattle slurry grassland
decreases from 56 to 29%.
Differences in the distribution of manure over grassland and
arable land may affect NH3 emission, because the emission
factors differ between slurry application methods on grassland
and arable land. It was assumed that the distribution of manure
N of grazing livestock (cattle, sheep, goat, horses) between
grassland and arable land differs 20% relative to that for
2009.
The emission factor for grazing is 2.7% of the TAN excreted
during grazing in 2009 (Huijsmans et al., submitted for
publication). The effects on total NH3 emission of an emission
factor of 10% (the default emission factor in the guidebook of
EMEP/EEA, 2009) and 4.5% of the TAN excreted (the emission
factor for grazing derived by Bussink (1994) at a N application
of 250 kg N per ha) was assessed.
or immobilization, was 63e69% for cattle, 67e75% for pigs, 69e78% for
poultry, and 50e71% for other livestock categories (Table 1).
The distribution of the housing systems and manure systems for
major livestock categories is presented in Table 2. Slurry-based
systems are the most common systems in the Netherlands. The
majority of dairy cows (95% in 2009) were held in common cubicle
housing systems and only 5% of the dairy cows are kept in housing
systems with low NH3 emission, like tied stalls. During summer,
most of the dairy cattle grazed during the day and were kept in
housing at night (about 54%); 24% of the dairy cattle were kept in
zero grazing systems and 22% in day and night grazing systems (not
shown). About 40% of the pigs were kept in housing systems with
low NH3 emission in 2009 (Table 2). There is a large diversity in
type housing systems for poultry: battery, floor housing and aviary
(Table 2). Almost 27% of cattle slurry, 15% of pig slurry, and 88% of
poultry slurry is stored outside the housing. Shallow injection is by
far the most common slurry application technique for grasslands
(Table 3), followed by narrow band application. On arable land,
most of the slurry is injected or surface spread followed by direct
incorporation into the soil (Table 3). Nearly all solid manure is
surface spread to arable land, after which it is incorporated in the
soil in a second track.
The total N excretion by livestock in housing was 269 Gg TAN
and during grazing 51 Gg TAN from which 8 Gg TAN was deposited
on natural grasslands and 43 Gg TAN on managed grasslands
(Fig. 1). The NH3 emissions from natural grassland are recorded for
the national emission inventory, but these emissions are not reported as agricultural emissions. About 48 Gg TAN of the produced
Table 2
Share of housing systems and manure storage systems for major animal categories in
2009.
Animal category
Housing system
Share, %
Dairy cows
Cubicle house
Low emission
Tie stall
Common
Low emission
Common
Low emission
Battery cages
Floor housing; common
Floor housing; low emission
Aviary house; common
Aviary house; low emission
Other
Common
Low emission
95
1
4
61
39
57
43
43
17
7
8
20
5
82
18
Fattening pigs
Sows including piglets
3. Results
Layers >18 weeks
3.1. N excretion and activity data
The total N excretion by livestock in the Netherlands in 2009 was
484 Gg N, from which 61% excreted by cattle, 22% by pigs, 13% by
poultry, and 4% by other livestock categories (Table 1). The fraction of
TAN in percentage of the total N excreted, including net mineralization
Broilers
252
G.L. Velthof et al. / Atmospheric Environment 46 (2012) 248e255
changed the total NH3 emission with 6.6 Gg NH3eN. Other factors
that had a relatively large effect were changes in the emission
factors of housing systems, mineralization of organic N in slurry,
and the emission factor for grazing (Fig. 2).
Table 3
Implementation rates of manure application techniques in the Netherlands in 2009.
Land use
Application method
Grassland
Shallow injection
Partly shallow injected and partly band applied
Narrow band application
Surface application
Injection
Shallow injection
Narrow band application
Partly shallow injected and partly band applied
Surface spreading and incorporation in two tracks
Surface spreading and incorporation in one track
Broadcast surface spreading
Arable land
56%
12%
23%
9%
61%
8%
6%
7%
3%
11%
4%
4. Discussion
A method was developed to calculate both the total N excretion
and the percentage of TAN in the N excretion, using information of
the feed composition and crude protein digestibility. Decreasing
the protein content in animal feed may both decrease the N
excretion and the percentage of TAN in the N excretion. Van
Bruggen et al. (2011) calculated the TAN excretion of livestock in
the Netherlands from 1990. The total N excretion of dairy cows in
1991 was 155 kg N per cow per year, with an average TAN fraction
of 0.75. The total N excretion in 2009 was 127 kg N per cow per year,
with an average TAN fraction of 0.60. Both the N excretion and TAN
fraction decreased, which is mainly due to a decrease in N application rates to grassland resulting in lower N content in roughage.
The TAN fraction in N excretion of fattening pigs decreased from
72% in 1991 to 68% in 2009, which was due to changes in N contents
of the feed. The changes in TAN fraction for poultry are much
smaller. For example, the TAN fraction in the N excretion of layers
remained stable; 77% in 1991 to 78% in 2009. Approaches based on
calculated TAN excretion using feed composition have more
potential to quantify the effects of feeding strategies on ammonia
emission than approaches using a fixed TAN fraction or total N.
However, the calculation of TAN requires detailed information
about the composition of the feed, which is often not available. The
calculations show that a relative change in the fraction of TAN in
the excreted N by 10% (for all livestock categories) changed the total
calculated NH3 emission from agriculture in the Netherlands by
about 8%. Thus, the sensitivity of the NEMA model for the TAN
fraction is high, which is due to the fact that the TAN fraction affects
NH3 emission in all parts of the manure management systems, i.e.
housing, manure storage outside, grazing, and manure application.
The TAN content of manure is also affected by mineralization
and immobilization during storage. The results of the calculations
show that the total NH3 emission in the Netherlands changes with
3.2 Gg N (or 3.5%; Fig. 2) if the net N mineralization of the organic N
in slurry during storage changes with 10%. There is little information about mineralization and immobilization of NHþ
4 in manure
during storage. This is mainly because such measurements are
manure is not applied to agricultural soils, but removed by manure
processing, and exported to other countries. The amount of manure
applied to grassland (89 Gg TAN) is somewhat higher than that
applied to arable land (82 Gg TAN; Fig. 1). The total amount of
mineral N fertilizer applied was 238 Gg N in 2009. Calcium
ammonium nitrate was by far the most common mineral N fertilizer in the Netherlands, i.e. 65% of the total mineral N use in 2009.
3.2. Ammonia emission in 2009
The total NH3 emission from agriculture in the Netherlands in
2009 was 88.8 Gg NH3eN, from which 50% from housing, 37% from
manure application, 9% from mineral N fertilizer, 3% from outside
manure storage, and 1% from grazing (Table 4). Cattle farming was the
dominant source of NH3 emission in the Netherlands (about 50% of
the total NH3 emission). The NH3 emission expressed as percentage of
the total excreted N decreased in the order poultry (22% of the
excreted N), pig (20%), cattle (15%), and other livestock (12%). The NH3
emission expressed as percentage of the excreted and mineralized
TAN was 34% for poultry, 32% for pigs, 23% for cattle, and 23% for other
livestock. On average, 18% of N excreted by livestock (or 26% of the
TAN excreted and mineralized in manure storage) in the Netherlands
in 2009 volatilized as NH3 to the atmosphere.
3.3. Scenario analyses
Changing the TAN fraction in N excretion with 10% had a large
effect on the total NH3 emission: 7.5 Gg NH3eN (Fig. 2). Changes
in the NH3-emission factor for manure application with 20%
Table 4
Ammonia emission from agriculture in the Netherlands in 2009.
NH3 emission in 106 g N
Source of NH3
Cattle
Pigs
Poultry
Other
Dairy cattle
Young cattle
Veal calves
Beef cattle
Total
Fattening pigs
Sows and other pigs
Total
Layers
Poultry for meat production
Total
Sheep and goats
Horses and ponies
Fur animals
Total
Total manure
Mineral N fertilizers
Total agriculture
NH3 emission in
Housing
Manure
storage
Grazing
Manure
application
Total
% of excreted N
% of
excreted TAN
11.0
3.6
1.7
1.2
17.4
10.9
4.6
15.5
6.2
4.0
10.2
0.4
0.4
0.2
1.0
44.1
0.4
0.2
0.0
0.1
0.7
0.2
0.1
0.3
1.0
0.2
1.2
0.1
0.1
0.0
0.1
2.3
0.5
0.4
0.0
0.1
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
16.9
5.0
0.7
1.5
24.2
3.8
2.0
5.8
0.3
1.5
1.9
0.6
0.4
0.1
1.1
33.0
28.7
9.2
2.5
2.9
43.3
14.9
6.7
21.6
7.6
5.7
13.2
1.2
1.0
0.3
2.4
80.5
8.3
88.8
15
14
18
14
15
20
20
20
28
16
21
10
13
15
12
17
24
19
27
21
23
28
29
28
36
22
28
17
20
22
19
25
0.2
1.2
G.L. Velthof et al. / Atmospheric Environment 46 (2012) 248e255
253
EF grazing 10%
3.1
EF grazing 4.5%
0.8
Manure to grassland: +20%
2.0
Manure to grassland: -20%
-2.0
Increase narrow band manure application
on grassland
1.7
EF application poultry manure -50%
-1.2
EF manure application +20%
6.6
EF manure application -20%
-6.6
EF N2, N2O, NOX +50%
-0.3
EF N2, N2O, NOX -50%
0.3
EF housing pigs and poultry +20%
4.6
EF housing pigs and poultry -20%
-4.6
EF housing dairy cows +20%
1.7
TAN fraction all manures +10% (relative)
TAN fraction all manures -10% (relative)
7.5
-7.5
3.2
Mineralisation 20% of excreted organic N in slurry
Mineralisation 0% of excreted organic N in slurry
-3.2
-10
-5
0
5
10
Fig. 2. Effects of changing parameters on total calculated NH3eN emission in the Netherlands in 2009 using NEMA model see Materials and methods for description of the
scenarios. EF is emission factor. The total calculated NH3 emission was 88.8 Gg N (see Table 4).
difficult, as the NHþ
4 contents in the manure are not only affected by
NH3 emission, but also by emissions of NO, N2O and N2 of which the
latter is very difficult to measure. The few studies in literature show
a large variation in N mineralization ranging from less than 10% to
more than 50%, depending on factors such as temperature and type
of manure (e.g. Sommer et al., 2007; Sørensen et al., 2003; and
Beline et al., 1998). In the approach of Dämmgen and Hutchings
(2008), it is assumed that 10% of organic N in cattle slurry and
solid cattle manure is mineralized during storage. For solid cattle
manures, it is assumed that 40% of the excreted TAN is immobilized
during storage. The model of Webb and Misselbrook (2004) also
assumes 10% mineralization of organic N in slurry storage. Moreover, it was assumed that 1 kg TAN is immobilized per 150 kg added
straw in solid manures, which was about 47% of TAN remaining in
the manure after NH3 emission in a scenario equated in Reidy et al.
(2009). In the NEMA model it is assumed that 10% of the organic N
of animal slurry mineralizes during storage in housing. Because of
the large uncertainties, no mineralization in the manure storage
outside is calculated, assuming that most of the easily mineralizable organic N is already mineralized in the housing. For solid
manure, it is assumed that 25% of the TAN is immobilized during
storage. Clearly, the mineralization (and immobilization) of manure
during storage is poorly quantified.
For manure from mammals, urea and easy degradable urine-N will
þ
be rapidly converted into NHþ
4 , thus TAN equals NH4 . However, the
calculated TAN fraction of poultry after storage, before application
includes both NHþ
4 and uric acid, especially when the manure is dried.
Indeed, Van Faassen and Van Dijk (1987) measured NH4 and uric acid
contents for layers of 15% and 57% of total N respectively, summing up
to a total TAN fraction of 72%. NEMA calculated an average TAN
fraction for layer manure of 71% for slurry and 74% for solid manure
(not shown), which is close to these findings. Also for broilers, the
254
G.L. Velthof et al. / Atmospheric Environment 46 (2012) 248e255
total TAN fraction was 72% in the study of Van Faassen and Van Dijk
(1987), of which 12% was NHþ
4 eN and 60% uric acid N. The calculated average TAN fraction in broiler manure was 66% according to
NEMA. After application to the soil, the uric acid is degraded within
about 10 days (Kirchmann, 1991). The NH3-emission factor for
manure applied to the soil is based on the measured NHþ
4 content of
the manure (Huijsmans et al., submitted for publication) The fate of
uric acid of poultry manure after application to the soil and its effect
on NH3 emission are not well quantified. If soil-applied uric acid does
not contribute to NH3 emission, the use of a NHþ
4 based emission
factor in an approach with calculated TAN excretion (i.e. the sum of
NHþ
4 and uric acid) may lead to an overestimation of the NH3 emission. The calculations showed that decreasing the emission factor of
application of poultry manure by 50% relative to the default emission
factor, decreased the total NH3 emission in the Netherlands by
1.2 Gg N (about 1%). There is a need of quantification of the effect of
uric acid in poultry manure on NH3 emission, because the TAN-based
models relate NH3 emission to the TAN content, while measured NH3
emissions are generally related to measured NHþ
4 contents in the
manure.
Cattle farming, both dairy and beef, is the dominant source of NH3
emission in the Netherlands. However, when the NH3 emission for
each livestock categories is expressed as percentage of excreted N, the
NH3 emission decreases in the order poultry (22% of the excreted N),
pig (20%), cattle (15%), and other livestock (12%). This effect is mainly
due to the differences in housing systems and application techniques.
The emission factors for housing systems are generally highest for
poultry housing, and especially the solid manures. Furthermore, the
solid poultry manure cannot be (shallow) injected or directly incorporated, resulting in higher emissions after application. The higher
emission per kg excreted N for pigs than for cattle is due to a combination of higher emission factors for pig housing systems and the fact
that part of the manure of dairy cattle is excreted during grazing
(resulting in low NH3 emission).
The results of the calculations suggest that the total NH3 emission from agriculture in the Netherlands can vary by several
millions kg NH3eN (Fig. 2). The parameters that have largest effect
on the total emission are the TAN excretion and the emission
factors for manure application. Housing systems are the largest
source of ammonia in the Netherlands (Table 4). Manure application is also major source of NH3 emission in the Netherlands
(Table 4), even though all manures have to be applied with techniques with a low NH3 emission. Other factors that may significantly contribute to the variation of the calculated NH3 emission
include the estimate of N mineralization during slurry storage, and
the emission factors for housing systems and grazing.
NEMA includes the major NH3 sources in agriculture, which are
related to manure management and fertilizer use. Other potential
sources of NH3 are not yet included, such as emissions during
ripening of crops or from crop residues (e.g. De Ruijter et al., 2010;
Holtan-Hartwig and Bøckmann, 1994; Sommer et al., 2004).
Moreover NH3 emission during manure transport or temporal
storage of manure during transport of manure from livestock farm
to an arable farm are not included. The NEMA model is developed
for the national scale, but the NEMA methodology has also been
implemented in a tool which is be used to calculate farm specific N
excretion of dairy cows and NH3 emission for dairy farming (Sebek,
personal communication). From 2011, NEMA will be used as official
methodology to calculate the national NH3 emission from agriculture in the Netherlands (Van der Maas et al., 2011).
Acknowledgements
The NEMA model was developed in a project of the Scientific
Committee of the Manure Act (CDM), financed by the Ministry of
Economic Affairs, Agriculture and Innovation in the Netherlands
(projects BO-05-007 and WOT-04-003-008). The following persons
are acknowledged for their contributions: Frans Aarts (WUR-PRI),
André Bannink (WUR-Livestock Research), Wim Bussink (NMI),
Mark de Bode (Ministry of Economic Affairs, Agriculture and
Innovation), Age Jongbloed (WUR-Livestock Research), Leon Sebek
(WUR-Livestock Research), Harry Luesink (WUR-LEI), Kaj Sanders
(Ministry of Infrastructure and the Environment), Michel Smits
(WUR-Livestock Research), Henk Strietman (Ministry of Infrastructure and the Environment), Bert Vermeulen (WUR-PRI), and
Folkert de Vries (WUR-Alterra). Klaas van der Hoek (RIVM), Peter
Groot Koerkamp (WUR-Livestock Research), Oene Oenema (WURAlterra) and members of the Dutch Pollutant Release and Transfer
Register are acknowledge for their review of the report which was
the basis of the current paper.
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