Concentrations and Emissions of Ammonia in Livestock Buildings in Northern Europe

J. agric. Engng Res. (1998) 70, 79—95

Concentrations and Emissions of Ammonia in Livestock Buildings in Northern Europe P. W. G. Groot Koerkamp1; J. H. M. Metz1; G. H. Uenk1; V. R. Phillips2; M. R. Holden2; R. W. Sneath2; J. L. Short2; R. P. White2; J. Hartung3; J. Seedorf3; M. Schro¨der3; K. H. Linkert3; S. Pedersen4; H. Takai4; J. O. Johnsen4; C. M. Wathes2 1 Instituut voor Milieu- en Agritechniek, Postbus 43, 6700 AA Wageningen, The Netherlands; 2 Silsoe Research Institute, Wrest Park, Silsoe, Bedford MK45 4HS, UK; 3 Tiera¨rztliche Hochschule Hannover, Institut fu¨r Tierhygiene und Tierschutz, Bu¨nteweg 17 p, 30559 Hannover, Germany; 4 Danish Institute of Animal Science, Research Centre Bygholm, Dept. of Agricultural Engineering, PO Box 536, DK-8700 Horsens, Denmark (Received 27 August 1996; accepted in revised form 5 January 1998)

Emissions of ammonia from livestock farming are responsible for the acidification and eutrophication of deposited ammonia in the environment. Research into the ammonia emission from livestock houses was carried out in 14 housing types for cattle, pigs and poultry in England, The Netherlands, Denmark and Germany. Concentrations of ammonia and carbon dioxide (the latter for estimating ventilation rates) were measured at seven locations inside and one location outside in four replicates of each housing type over 24 h under summer and winter conditions. Mean concentrations and emissions per housing type per country were estimated together with some variance components. Mean ammonia concentrations were lower than 8 p.p.m. in cattle houses, between 5 and 18 p.p.m. in pig houses and between 5 and 30 p.p.m. in poultry houses. The concentrations of ammonia in a number of pig and poultry houses exceeded the threshold value of 25 p.p.m. and may affect adversely the health of both stockmen and animals. Ammonia emissions from cattle houses (dairy cows, beef and calves) varied between 80 and 2001 mg/h per animal or 315 and 1798 mg/h (500 kg) live weight. Ammonia emissions from pig houses (sows, weaners and finishers) varied between 22 and 1298 mg/h per animal or 649 and 3751 mg/h (500 kg) live weight. Ammonia emissions from poultry houses (laying hens and broilers) varied between 2)1 and 39)4 mg/h per bird or 602 and 10 892 mg/h (500 kg) live weight. The emission rates should be used carefully, because of large variations between countries, between commercial houses and between seasons. Not all variations could be explained in terms of physical and chemical processes involved in the emission of ammonia. A comparison with other Dutch results revealed that the method used in this research for measuring ammonia emission rates produced accurate mean emission rates. ( 1998 Silsoe Research Institute 0021-8634/98/050079#17 $25.00/0/ag980275

Notation E

NH3 E

a

E

b

a b N !/*.!-4 f (t)

n

yearly mean emission of ammonia (g NH /animal—place yr) 3 mean emission of ammonia during production periods (g NH /h) 3 mean emission of ammonia during the periods between production (g NH /h) 3 length of production period (d) length of period between production periods (d) number of animals at a predefined moment (e.g. start) or a time-average course of the daily mean ammonia emission as a function of time (d) in g NH /h 3 number of production periods within a year

1. Introduction The effects of ammonia on the environment due to acidification and eutrophication can be severe. 1,2 Ammonia and its chemical combinations (NH ) are important x components of acidification in addition to sulphur compounds (SO ), nitrogen oxides (NO ) and volatile orx y ganic compounds (VOC). 3 The contribution of ammonia to the total acid deposition can be substantial; for example, 45% of total acid deposition in The Netherlands was caused by ammonia in 1989. Emission, transport and deposition of ammonia extends beyond regional boundaries and the deposition of NH exceeds acceptx able levels for large areas of Western Europe. 79

( 1998 Silsoe Research Institute

80

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

Table 1 Annual emission of ammonia in kt NH3-N in 1990 from animal husbandry sources in the United Kingdom (UK), The Netherlands (NL), Denmark (DK) and Germany (G) and the relative contribution to the total NH3 emission per country 4

Houses#storage, kt/yr Pastures (grazing), kt/yr Manure application, kt/yr Total livestock, kt/yr Contribution to total emission (%)

UK

NL

DK

G

136 69 161 366

60 16 124 200

31 5 62 97

245 46 212 504

75

85

82

76

Agricultural sources, and livestock farming in particular, are the largest contributors to ammonia emissions. For example, about 85% (over 220 000 t/yr) of the total ammonia emission in The Netherlands originates from livestock farming. Ammonia from livestock husbandry is emitted from buildings, slurry and manure stores, pastures (grazing) and during manure application, e.g. slurry spreading. The relative contribution of these sources to the total ammonia emission for four countries is given in Table 1. Livestock housing and storage tanks contributed 40—60% of the total emission from livestock farming in these North European countries and Table 2 shows that cattle and pig housing are mainly responsible. The lack of accurate emission rates for various livestock housing systems in different countries is a major problem in estimating emissions.4 This causes substantial uncertainties with the current estimates in Tables 1 and 2. Ammonia emissions from livestock housing must be reduced to abate environmental damage.9,10 National 11,12 and international13–16 conferences have been held in the last decade to accumulate the results of research into levels of emissions and to exchange knowledge and experiences about possible ways to reduce emissions. Generally, the results available so far have been obtained in

Table 2 Relative contribution (% %) of animal species to the total emission of ammonia from animal husbandry sources in the United Kingdom5 (UK), The Netherlands6 (NL), Denmark 7 (DK) and Germany8 (G) UK 1990 Cattle Pig Poultry Horses Sheep Other

65 11 11 2 11 (1

NL 1990

DK 1987

G 1989

55 37 8 (1 (1 (1

45 37 16 1 (1 1

77 17 3 1 2 (1

one or a restricted number of experimental houses, consisting of a limited number of time-point measurements only and were conducted with a range of different measuring equipment and measuring techniques or calculation methods for concentrations and ventilation rates. Concern about the effects of ammonia on man and livestock, and thus ammonia concentration as one of the parameters within livestock buildings, preceded the attention now given to ammonia emission and its effect on the environment. Acceptable levels of ammonia concentrations for the working environment of the stockman and/or the living environment of livestock lie below nationally defined and established maximum acceptable concentrations (MAC values). These levels vary from 10 to 50 p.p.m. depending on animal type, working time (exposure) and country. Several authors have shown that these levels are often exceeded in poultry and pig houses and concluded that efforts must be made to improve the living and working environment.17–20 The object of the work described in this paper was to accumulate knowledge about ammonia concentrations in buildings and ammonia emissions from livestock farming in North European countries. We describe the results of an extensive research project that was carried out in England, The Netherlands, Germany and Denmark.21 The use of a uniform measuring technique for concentrations and emissions rates in commercial houses over several years guaranteed the construction of a solid database. Ammonia concentrations in and emissions from various types of housing for dairy, pigs and poultry are presented and compared with available data from literature. Together with some basic theoretical background, this work will contribute to an understanding of how and why differences in concentrations and emissions occur.

2. Background: sources and processes related to nitrogen turnover 2.1. Production and composition of faeces Ammonia originates from faeces and urine. Both the quantity and the composition of the faeces and urine are of interest when studying ammonia emission. Faeces are defined here as the fresh excreta from animals, while manure (solid) and slurry (liquid) are the mixture of faeces and urine as they are encountered in the animal house. Cows and pigs excrete their superfluous nitrogen as urea in the urine and undigested proteins in the faeces, while poultry excrete uric acid and undigested proteins in their faeces. Uric acid and undigested proteins are the main nitrogen components in the faeces of poultry,

E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

representing about 70 and 30% of the total nitrogen, respectively.22,23 Urea in urine and undigested proteins in faeces contribute also 70 and 30% to the total nitrogen excretion of cows and pigs, respectively, but this can vary considerably. The nitrogen components of uric acid, urea, ammonia/ammonium and undigested proteins are potential sources for ammonia volatilization.

2.2. Release of ammonia Ammonia is mainly a product of the degradation of nitrogenous compounds. The biochemical degradation processes of uric acid (1), urea (2) and undigested proteins (3) are complex, but can be simplified as follows: C H O N #1)5O #4H OP5CO #4NH (1) 5 4 3 4 2 2 2 3 CO(NH )#H OPCO #2NH (2) 2 2 2 3 Undigested proteinsPNH (3) 3 All three processes are affected by microbial action. Various authors have described the aerobic decomposition of uric acid to ammonia24,25 [Eqn (1)]. According to these descriptions, water and oxygen must be available, and ammonia and carbon dioxide arise as products of this degradation process. The enzyme uricase, commonly present in microorganisms, is specific to this reaction with uric acid. The degradation of uric acid and proteins is positively influenced by temperature, pH and moisture content.26,27 The degradation process of urea [Eqn (2)] follows the law of Michaelis—Menten and is positively influenced by the urease activity, pH and temperature.28 The enzyme urease is produced by microorganisms that are commonly present in manure. Elzing et al. 29 described the breakdown of urea in cattle urine on a dirty slatted floor. They measured a total breakdown of urea within several hours under normal housing conditions. This is relatively fast compared with the degradation of uric acid to ammonia in poultry manure which lies between 8 and 40% of the amount of uric acid per day.30 Above temperatures of about 30°C the degradation process is known as composting, and requires aerobic conditions.31,32 Composting will take place as long as sufficient water, carbon and oxygen are available in manure. The nitrogen in the organic material can be released as ammonia. 33,34 If oxygen is absent the degradation is called fermentation. Under anaerobic circumstances, e.g. in slurry, many gaseous components can be produced, e.g. ammonia (NH ), methane (CH ), carbon 3 4 dioxide (CO ), hydrogen sulphide (H S) and fatty acids. 2 2 Taiganides35 gives a scheme for the anaerobic degradation of organic material into N, C and S compounds. A review of microbial transformation of inorganic nitrogen is given by Painter.36 Three main processes can be

81

distinguished. First, the fixation of dinitrogen (N ) lead2 ing to ammonia production (aerobic or anaerobic). Second, due to nitrification (autotrophic or heterotrophic), ammonium can be converted to nitrite (NO~ ) and hence 2 nitrate (NO~ ). Autotrophic nitrification is considered to 3 be most important, in which case sufficient oxygen must be available. Third, nitrate can be utilized by microorganisms either for its nitrogen (assimilation—synthesis of N), or for its oxygen (dissimilation). For assimilation, ammonia is generally preferred to nitrate, since nitrate first has to be reduced to ammonia. The end product of the dissimilation can be nitrite (NO~ ), nitric oxide (NO), 2 nitrous oxide (N O) or dinitrogen (N ). If any of the 2 2 last three are formed, the process is called denitrification. For dissimilation the conditions must be anaerobic or nearly so.

2.3. »olatilization of ammonia The ammonia in manure or litter is liable to volatilization to the surrounding air. Before being liberated into the air, ammonia is involved in equilibria in the liquid (l) and gas (g) phase, as in the Eqns (4)—(7): (4) NH` (l) b NH (l)#H` 4 3 The ammonium—ammonia equilibrium is influenced37 by temperature (denoted as ¹ ) and pH. Below a pH of 7 nearly all ammonia is bound as ammonium and not liable to volatilization. Higher temperatures favour ammonia concentrations, because of the positive influence of temperature on the dissociation constant K , which is a defined as (5) K "[NH ] [H O`]/[NH` ] 4 a 3 3 The volatilization equilibrium of ammonia to the gas phase, follows Henry’s law for dilute systems, 38 NH (l) b NH (g) (6) 3 3 NH (g, manure) b NH (g, air) (7) 3 3 The partial pressure of gaseous ammonia, NH (g), is 3 proportional to the NH (l) concentration. The volatiliz3 ation of ammonia from manure to air, is defined as the mass flux. This flux is generally defined as the product of difference in partial pressure between the two media and a mass transfer coefficient. Higher partial pressure difference increases the flux. Mass transfer coefficients increase with increasing air velocity.39 Ventilation brings fresh air into the animal house while ammonia, water vapour, other gases and air contaminants are removed with the exhaust air. The ventilation rate and pattern affect not only the global internal climate, but also the local climate above the manure and litter.

82

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

3. Techniques for measuring ammonia concentrations and ventilation rates The amount of ammonia emitted from a livestock building is the sum of the net ammonia mass flows through all outlets. Each mass flow is the product of the ventilation rate and the ammonia concentration.40 Both parameters must be measured at the same time to determine the ammonia emission at a certain moment. Techniques are available to measure both ammonia concentrations41 and ventilation rates in mechanically42 and naturally43 ventilated houses, even on a continuous basis, which lead to highly accurate calculations for emission rates. Efforts have been made to calculate ammonia losses from houses on the basis of nitrogen input—output balances.44 A special note should be made about the accuracy of this method. In many cases the ammonia losses measured represent only a relatively small part of the total amount of nitrogen in the manure, 45 up to about 20% but often less, depending on the livestock type and housing system. In addition, errors due to sampling of manure or litter, and errors when determining their N content lead to errors in estimates of ammonia losses that are often as large as the losses themselves. The technique used for measuring ammonia concentrations and ventilation rates in this research is extensively described by Phillips et al. 46 and therefore described here only briefly. The ammonia analyser used was a combination of a chemiluminescence NO analyser and a thermal NH converter.47 Gaseous compounds such as 3 NH are converted into NO and are measured as ammo3 nia. A data-logging system controlled the valves of the gas handling unit in order to measure the concentration of ammonia and carbon dioxide at seven sampling points in the house and one point outside. Ventilation rates and emissions were calculated by means of a computer program called ‘‘STALKL’’. It used the heat and respiratory carbon dioxide balance according to the equations of van Ouwerkerk and Pedersen.48 For broilers the CIGR equations of total heat production were used. For cattle, pigs and laying hens more sophisticated algorithms involving feed intake and ambient temperature were developed. The ‘‘STALKL’’ program calculated the hourly heat production, ventilation rate and emissions of the ammonia. Production and emission rates were expressed as ‘‘per house’’, ‘‘per animal’’, ‘‘per 500 kg live weight’’ and ‘‘per heat producing unit’’ (1 hpu equals 1 kW). In each country about ten typical housing types for cattle, pigs and poultry were selected. Four replicates of each housing type were surveyed under winter and summer conditions during 24 h. Concentrations of ammonia and carbon dioxide were measured at seven sampling points inside the house, and one outside the house. The

seven sampling points were in a cross-section in the middle of a house: three at about 1)5 m height, three at 2)5 m height and one close to the exhaust. A table of the housing types surveyed in each country is given in Phillips et al. 46 A complete description of the housing types, including plan views and cross-sections, together with manure handling methods, has been lodged in the library of each participating institute.

4. Statistical model Measurements of NH and CO concentrations were 3 2 made in four countries (i) (England, The Netherlands, Denmark and Germany), for 14 housing types ( j ), four replicates (k), in summer and winter (l), every hour (m) and at seven sampling points (n"1—7) inside the house and one outside (n"0). The mean CO concentrations 2 of the seven internal sampling points were used to calculate ventilation rates (see Section 3) at every hour. Daily mean ventilation rates were calculated on the basis of 24 hourly values. A loglinear model was used for the ammonia emission rate where the effects of country, housing type, replicate and season were assumed to be multiplicative and the variance was assumed to be proportional with the level (gamma distribution): ln (h)"g"Xb#Zc

(8)

where b is the vector of parameters for the fixed effects, c the vector of parameters for the random effects, h the expected value for the ammonia emission rate, mg/h per animal, per 500 kg live weight or per hpu, g the linear predictor and X and Z the design matrices. Statistical analyses were carried out with the Iteratively Reweighed Residual Maximum Likelihood procedure (IRREML), available as a Genstat Procedure.49 This procedure estimated the effect of housing type and outside temperature and the variance components at different error strata. The following relationship between ammonia concentration k, ventilation rate ' and emission rate h was used: k"h/'

(9)

where ' is the ventilation rate, m3/h per animal, per 500 kg live weight or per hpu and k the ammonia concentration, mg/m3. The full model for the measured ammonia concentration y was ijklmn y "(1/') exp [(housing type #b ¹ ) ijklmn ij 1 0654*$%,ijkl #(replicate #season #hour )] (10) ijk ijkl ijklm In this model housing type and outside temperature (¹ ) were considered as fixed effects, whereas 0654*

%$ E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

replicate, season and hour were random effects. The outside temperature was averaged over 24 h for the outdoor sampling point. The model was applied to each country separately. The ventilation rate was put in the model as an offset variable o"!ln('). The model produced estimates of NH emission h"exp(g) when only 3 sampling point 7 (close to the exhaust) was used and produced estimates for the internal NH concentrations 3 k"exp (g#o) when all seven sampling points were used. Emission rates were corrected for the outside NH 3 concentration.

5. Results 5.1. Concentrations of ammonia Table 3 gives the mean ammonia concentrations in parts per million (p.p.m.) for different housing types in England (UK), The Netherlands (NL), Denmark (DK) and Germany (G), together with the maximum concentration, the coefficients of variation and the effect of the outside temperature. The mean ammonia concentrations in houses for dairy cows, beef cattle and calves varied between 0 and 8 p.p.m., but were under 1)5 p.p.m. in England. The ammonia concentrations in houses for sows, weaners and finishers were between 5 and 18 p.p.m., of which the highest values were generally found in houses for finishers with slats. In houses for laying hens and broilers, concentrations of ammonia between 5 and 30 p.p.m. were found, but battery houses in Germany were below this level (1)6 p.p.m.). The coefficients of variation of the mean ammonia concentrations were, in general, between 25 and 35% and were formed from the variances given in the lower part of the table. The standard errors of the variance components were in general half or less of the level of the variance, meaning that variance components were estimated accurately. The relative contribution of the four variance components to the c.v. was more or less the same in the four countries. The variance between replicates was very low in Germany, while the remaining seasonal variation in The Netherlands and Denmark was lower than in England and Germany. The variance between seasons is the variance between summer and winter concentration which is not covered by the modelled effect of the outside temperature. The daily mean outside temperature was used in the model in order to account for the effect of temperature changes between seasons, instead of the temperature changes between hours within one day. The variance between the seven sampling points was low ((0)01) in all countries except England where the absolute level was high (0)06). The residual variance was assumed to have

83

a Poisson distribution and consisted of the variance between hours within one day and the unexplained variance in the model. Graphs (not shown) of the residual variance and the sum of all variance components were plotted and confirmed this assumption. The (decreasing) effect of the daily mean outside temperature on the concentrations in the animal houses varied in general between !8 and 0% per degree K. No temperature effect was estimated in cases where no summer measurements were carried out. Some cattle houses had (significant) positive temperature effects, while some houses showed extreme temperature effects, e.g. finishers on slats in England (!25%), broilers in Denmark (#6)7%) and laying hens in battery cages in Germany (!20%). Poultry houses especially often showed a significant decrease of ammonia concentrations with increasing outside temperatures.

5.2. Emissions of ammonia Table 4 gives the mean emission of ammonia, the coefficient of variation and the effect of the outside temperature on the emission for various housing systems for cattle, pigs and poultry in England, The Netherlands, Denmark and Germany. Table 4 shows the emission in mg/h per animal, while Tables 5 and 6 show the emission of ammonia in mg/h per 500 kg live weight and per heat producing unit (1 hpu equals 1 kW), respectively. The lower parts of Tables 4—6 show the variances between replicates, between seasons and the residual variance. The variance between seasons is the variance between summer and winter emissions which is not covered by the modelled effect of the outside temperature. In some cattle houses, measurements during the winter period only were made. The mean value represents the winter emission and no effect of temperature was estimated in these cases. The mean emission of ammonia over 24 h was assumed to have a Poisson distribution, such that the variance was proportional to the level of ammonia emission. Graphs (not shown) of the residual variance and the sum of all variance components were plotted and confirmed this assumption. The emission from litter houses for cows (with straw as bedding material), including tie houses (cows fixed at a place), amounted in all four countries to about half or less of the emission from cubicle houses (with a walking area). The emission from both litter (314—974 mg/h per animal, 260—890 mg/h (500 kg) live weight or 319— 790 mg/h per hpu) and cubicle houses (987—2001 mg/h per animal, 843—1769 mg/h (500 kg) live weight or 848—1649 mg/h per hpu) varied considerably between the four countries. The emission per animal from beef cattle houses with litter in England was almost twice as high as

84 Table 3 Concentrations of ammonia (p.p.m.) for the mean outside temperature, maximum concentration, coefficient of variation (% %) and the effect of the outside temperature (T effect) on the concentrations (% % / K, & p)0)1,* p)0)05,** p)0)01,*** p)0)001) for various housing systems for cattle, pigs and poultry in England (10)1°C), The Netherlands (9)8°C), Denmark (8)4°C) and Germany (10)5°C). The variance components and their SE on the link scale and the c.v. on the linear scale are given in the lower part of the table England Animal type and housing system

Variance between replicates Variance between seasons Variance between sampling points Variance between hours/ residual

Denmark

Germany

Mean Maxi- c.v., % ¹ effect Mean Maxi- c.v., % ¹ effect Mean Maxi- c.v., % ¹ effect Mean Maxi- c.v., % ¹ effect mum mum mum mum 0)9 1)3 0)3 — 0)4 — 5)1 11)0 7)8 4)3 12)1

3)6 5)7 1)7 — 3)2 — 14)3 41)1 36)7 58)3 58)6

35 35 36 — 30 — 29 29 29 31 31

s 5)7 s 3)8 s — — 2)9 !5)4 — — 7)7 — !7)0& 0)0 17)8 !7)2 4)6 !3)0 — !25*** 18)2

13)7 13)3 — 10)7 — 13)7 — 43)4 22)4 — 59)8

27 26 — 26 — 27 — 27 31 — 26

3)8 0)6 — 0 — !1)7 — !4)2 3)7 — !5)4**

2)7 3)3 — 6)4 1)9 — — 8)7 5)3 9)1 14)9

18)6 20)1 — 17)7 5)7 — — 22)1 17)9 21)7 43)4

25 26 — 24 25 — — 24 25 26 24

!13** 4)9 7)6* 7)1 — 3)2 !4)7 5)2 4)3 1)9 — 5)1 — 12)5 ! 5)0* 10)2 !4)9 4)5 !0)4 — ! 5)1* 14)3

22)7 14)4 29)3 11)9 8)3 8)5 27)3 43)7 35)5 — 35)2

29 29 26 29 23 23 34 24 25 — 21

s s 1)2 s 2)1 !1)7 !0)8 !4)2* !6)5* — !2)9

8)3 11)9 27)1

63)9 67)1 56)3

30 29 32

0)3 !1)5 !6)2

29)6 5)9 11)2

72)9 16)5 50)3

26 30 27

!7)7** !12* !2)0

25)2 6)1 8)0

72)3 14)5 40)3

28 39 48

!4)8& — !5)4 1)6 6)7*** 20)8

— 21)4 43)3

— 27 24

— !20& !2)8

p2

SE

c.v., %

p2

SE

c.v., %

p2

SE

c.v., %

p2

SE

c.v., %

0)18 0)31

0)10 0)08

42 55

0)21 0)09

0)07 0)02

46 30

0)17 0)12

0)07 0)03

41 35

0)08 0)26

0)07 0)07

29 51

0)06

0)01

25

0)01

0)001

11

0)01

0)001

9

0)02

0)001

14

0)56

0)01

75

0)67

0)01

82

0)87

0)01

93

0)39

0)005

63

s No temperature effect was estimated because measurements were carried out during the winter only.

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

Dairy cows, litter Dairy cows, cubicles Beef cattle, litter Beef cattle, slats Calves, litter Calves, slats/group Sows, litter Sows, slats Weaners, slats Finishers, litter Finishers, slats Laying hens, deep litter/ perchery Laying hens, battery cages Broilers, litter

¹he Netherlands

England

¹he Netherlands

Animal type and housing system

Mean

c.v., %

¹ effect

Dairy cows, litter Dairy cows, cubicles Beef cattle, litter Beef cattle, slats Calves, litter Calves, slats/group Sows, litter Sows, slats Weaners, slats Finishers, litter Finishers, slats Laying hens, deep litter/ perchery Laying hens, battery cages Broilers, litter

314s 1245s 482s — 80s — 303 503 26)0 108 185

45 52 48 — 41 40 40 40 42 42

t 974 t 2001 t — — 686 !7)2 — — 522 4)0 — 6)1 535 !8)0& 26)6 11& — !16* 385

30)9 39)4 19)8

41 40 44

Variance between replicates Variance between seasons Variance between hours/ residual

—

Mean

Denmark

c.v., %

¹ effect

24 24 — 24 — 24 — 24 28 — 23

4)6 5)8& — 1)9 — !0)7 — 6)6& 13** — 0.0

56>0 987s — 580 332 — — 730 45)8 394 319

24 25 — 22 23 — — 23 23 26 23

1)0 !4)3 3)4

38)3 7)7 8)9

26 40 44

p2

3)3 2)6 3)2

36)0 6)4 11)2

24 27 24

p2

SE

c.v., %

Mean

c.v., %

Germany ¹ effect

Mean

c.v., %

!5)0 6)5 — 5)6 1)2 — — 1)9 3)9 3)6 4)4

538s 1320 262 346s 193 323 1298 325 22)0 — 308

31 31 27 31 24 24 35 25 26 — 22

4)5 3)9 4)3***

— 2)1s 18)5

— 29 25

SE

c.v., %

p2

SE

c.v., % 22 58

p2

SE

c.v., %

0)48 0)30

0)17 0)09

69 55

0)18 0)07

0)06 0)02

43 26

0)08 0)23

0)07 0)06

28 48

0)05 0)34

0)08 0)09

0)47

0)02

—

0)46

0)02

—

0)49

0)02

—

0)25

0)01

¹ effect t t !5)7 t !2)5 2)8 2)9 0)6 !0)5 — 7)1& — !22& 2)8

—

s The outside NH concentration amounted to 20% or more of the inside NH concentration t No temperature effect was estimated because measurements were 3 3 carried out during the winter only.

E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

Table 4 Emission of ammonia (mg/h per animal) for the mean outside temperature, coefficient of variation (% %) and the effect of the outside temperature (T effect) on the emissions (% % / K, &p) )0·1,* p) )0·05,** p) )0·01,*** p) )0·001) for various housing systems for cattle, pigs and poultry in England (10·1°C), The Netherlands (9·8°C), Denmark (8·4°C) and Germany (10·5°C). The variance components and their SE on the link scale and the c.v. on the linear scale are given in the lower part of the table

85

86 Table 5 Emission of ammonia (mg/h per 500 kg live weight) for the mean outside temperature, coefficient of variation (% %) and the effect of the outside temperature (T effect) on the emissions (% % /K, &p) )0·1,* p) )0·05,** p) )0·01,*** p) )0·001) for various housing systems for cattle, pigs and poultry in England (10·1°C), The Netherlands (9·8°C), Denmark (8·4°C) and Germany (10·5°C). The variance components and their SE on the link scale and the c.v. on the linear scale are given in the lower part of the table England

¹he Netherlands

Denmark

Germany

Mean

c.v., %

¹ effect

Mean

c.v., %

Dairy cows, litter Dairy cows, cubicles Beef cattle, litter Beef cattle, slats Calves, litter Calves, slats/group Sows, litter Sows, slats Weaners, slats Finishers, litter Finishers, slats Laying hens, deep litter/ perchery Laying hens, battery cages Broilers, litter

260s 1048s 478s — 315s — 744 1049 1047 1429 2592

42 49 44 — 39 — 38 38 38 39 39

t t t — !5)8 — 5)6 3)8 !8)1* 1)4 !17**

890 1769 — 853 — 1148 — 1282 786 — 2076

24 23 — 23 — 23 — 24 27 — 23

7392 9316 8294

38 38 41

4)1 2)8 1)2

9455 1624 4179

23 26 24

0)8 !4)0 3)2

p2

SE

c.v., %

p2

SE

c.v., %

p2

SE

c.v., %

p2

SE

c.v., %

0)46 0)21

0)15 0)06

68 46

0)18 0)06

0)06 0)02

42 24

0)01 0)21

0)05 0)06

8 46

0)04 0)32

0)08 0)09

21 57

0)47

0)02

—

0)46

0)02

—

0)81

0)03

—

0)25

0)01

—

Variance between replicates Variance between seasons Variance between hours/ residual

¹ effect 4)8& 4)2 — 3)4* — 2)0 — 5)9& 11** — 1)0

c.v., %

¹ effect

Mean

c.v., %

¹ effect

491 843s — 900 1037 — — 1701 1562 3751 2568

19 20 — 17 18 — — 17 18 20 18

!5)7 7)3& — 9)2& !0)9 — — 2)0 9)2 4)0 4)3&

467s 1168 431 371s 886 1797 3248 1212 649 — 2398

30 30 26 30 23 23 34 24 25 — 21

t t !3)0 t !19 2)8 2)9 3)2 0)0 — 7)1*

10 892 2160 2208

20 34 33

3)6 4)1 25***

— 602s 7499

— 28 24

— !22* 5)2&

Mean

s The outside NH concentration amounted to 20% or more of the inside NH concentration t No temperature effect was estimated because measurements were 3 3 carried out during the winter only.

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

Animal type and housing system

England

¹he Netherlands

Animal type and housing system

Mean

c.v., %

¹ effect

Mean

c.v., %

Dairy cows, litter Dairy cows, cubicles Beef cattle, litter Beef cattle, slats Calves, litter Calves, slats/group Sows, litter Sows, slats Weaners, slats Finishers, litter Finishers, slats Laying hens, deep litter/ perchery Laying hens, battery cages Broilers, litter

319s 1222s 690s — 252s — 848 1240 508 1200 1366

40 47 43 — 35 — 34 34 34 37 37

t t t — !4)4 — 3)9 4)4 !5)5 !0)5 !15*

790 1649 — 1197 — 1023 — 1747 364 — 1627

24 23 — 23 — 24 — 24 27 — 23

2753 3120 1676

35 34 39

3179 550 900

23 26 24

Variance between replicates Variance between seasons Variance between hours/ residual

2)6 3)3 2)3

Denmark

Germany

¹ effect

Mean

c.v., %

¹ effect

Mean

c.v., %

4)5 6)6* — 3)8* — 1)7 — 6)3& 13** — 0)8

485 848s — 1166 1024 — — 1234 750 2241 1635

20 22 — 18 20 — — 19 19 22 20

!5)6 7)1& — 5)8 2)4 — — 3)3 5)2 3)9 4)3&

497 1113 571 575s 519 1410 2226 1401 339 — 1588

31 30 25 30 22 22 34 23 24 — 20

t t !3)4 t 1)4 3)0 !0)7 1)7 !2)8 — 5)8

0)9 !4)1 2)9

3643 711 343

21 36 36

3)7 4)0 31***

— 199s 1476

— 28 23

— !22& 5)3&

¹ effect

p2

SE

c.v., %

p2

SE

c.v., %

p2

SE

c.v., %

p2

SE

c.v., %

0)30 0)31

0)13 0)09

54 56

0)18 0)07

0)06 0)02

42 26

0)02 0)23

0)06 0)07

12 48

0)00 0)37

0)08 0)10

0 61

0)47

0)02

—

0)46

0)02

—

1)04

0)03

—

0)25

0)01

—

s The outside NH concentration amounted to 20% or more of the inside NH concentration t No temperature effect was estimated because measurements were 3 3 carried out during the winter only.

E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

Table 6 Emission of ammonia (mg/h per heat producing unit) for the mean outside temperature, coefficient of variation (% %) and the effect of the outside temperature (T effect) on the emissions (% % /K, &p) )0·1,* p) )0·05,** p) )0·01,*** p) )0·001) for various housing systems for cattle, pigs and poultry in England (10·1°C), The Netherlands (9·8°C), Denmark (8·4°C) and Germany (10·5°C). The variance components and their SE on the link scale and the c.v. on the linear scale are given in the lower part of the table

87

88

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

in Germany, while this difference was negligible for the emission rates per 500 kg live weight and hpu. The emission from beef cattle houses with slats seemed to be slightly higher than the houses with litter. The emission from houses for calves varied between 80 (UK, litter) and 522 (NL, slats) mg/h per animal, or 315 (UK, litter) and 1798 (G, slats) mg/h (500 kg) live weight or 252 (UK, litter) and 1410 (G, slats) mg/h per hpu. The emission rate for calf houses with litter in England was extremely low as compared with the emission rates in the other countries. The figures in Germany showed higher emissions from houses with slats than from litter. The emission from houses for sows varied between 303 and 1298 mg/h per animal, or between 744 and 3248 mg/h (500 kg) live weight or between 848 and 2226 mg/h per hpu. Sow houses with slats in England emitted considerably more ammonia than houses with litter, while the opposite was the case in Germany. Emission of ammonia from weaner houses with slats were about 25 mg/h per animal, except for Denmark, where the emission rates per animal, per 500 kg live weight and per hpu from weaner houses were higher. The emissions from finishing houses were between 108 and 394 mg/h per animal. The emissions per animal from finishing houses in England (108—185 mg/h) were much lower than in the other three countries (308—394 mg/h). However, this difference was not so clear in Tables 5 and 6 where emission rates were expressed per 500 kg live weight and hpu. The difference between finishing houses with slats and with litter was opposite for England (slats higher) and Denmark (litter higher). The emission from houses for laying hens varied strongly, i.e. a factor 18 between the lowest (G, cages) and the highest emissions rates (UK, cages or DK, litter). Except for England, where emissions from battery cages were more or less equal to litter houses, emissions from battery houses were much lower than from litter houses. Emissions from broiler houses with litter were between 8)9 (DK) and 19)8 (UK) mg/h per bird, or between 2208 and 8294 mg/h (500 kg) live weight or between 343 and 1676 mg/h per hpu. The emission from broiler houses in England and Germany were almost equal, while houses in The Netherlands had lower emissions and houses in Denmark showed very low emission rates. The estimates of the variance components were rather consistent between the three types of emission rates (Tables 4—6). Hardly any differences were found for The Netherlands and Germany. The variance between replicates in Germany in case of emission rates per hpu was extremely low (zero). Some differences were found for England, while in Denmark both the variance between replicates and the residual variance were different for the emission rates per animal, per 500 kg live weight and per hpu. The coefficients of variation between replicates in

England and The Netherlands were above 42%, while in Denmark and Germany they were below 28 and 22%, respectively. The coefficients of variation between seasons amounted to above 46% in England, Denmark and Germany, and were about 25% in The Netherlands. The residual variance amounted to about 0)46 in England and The Netherlands, varied strongly in Denmark and was 0)25 in Germany. The coefficients of variation in Tables 4—6 for the estimates of the emission rates in England (34—52%) were much higher than the coefficient of variation in The Netherlands, Denmark and Germany (17—36%, layers and broilers in Denmark Table 4 excluded). The effect of seasonal variations of the outside temperature were in general between !5 and #5% per K. However, these effects were only significant in a few cases, as indicated in Tables 4—6. In some cases larger positive or negative temperature effects were found (UK weaners and finishers, NL weaners, DK broilers and G laying hens in cages). It should be noted that the given temperature effects were used in the statistical model for the ammonia emissions to estimate the mean emission for the mean outside temperature. The estimated emissions of ammonia are thus corrected for the mean outside temperature per country as given in the heading of Tables 4—6.

6. Discussion 6.1. Concentrations of ammonia Ammonia is an irritant gas and causes inflammation of the mucous membrane in the eye and the respiratory tract. Very high levels of ammonia concentrations, such as 2500 p.p.m., may even be (rapidly) fatal. 50 In several countries the labour inspectorate has established standards for ammonia concentrations, the so-called threshold values that should not be exceeded.51–53 In many countries, the threshold limit is 25 p.p.m. (time weighted) for an 8 h working day for staff and for the living environment for livestock, while a higher limit is often applied for short term exposures, e.g. 35 p.p.m. over 15 min in England. However, sometimes the limit is stricter, e.g. 10 p.p.m. for stockmen in Sweden. Shorter working days may allow higher threshold values, but little is known about the long term effects of gaseous ammonia in the working environment. However, lower concentrations are always preferable to higher concentrations, both for men and livestock. Comparison of the results in Table 3 with the threshold values revealed that the mean concentrations in cattle houses (below 8 p.p.m.) probably do not cause health risks for staff. Several pig houses showed mean concentrations above 10 p.p.m., but were still lower than

E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

the typical limit of 25 p.p.m. Several poultry houses, both for laying hens and broilers, contained ammonia concentrations between 20 and 30 p.p.m. The variation around these means thus caused instantaneous levels far above the limit of 25 p.p.m. A spatial distribution of ammonia concentrations inside the animal houses was present, as shown by the variation between the seven sampling points which were placed at three heights in a crosssection. However, this variation was negligible compared with the variation between replicates and seasons. The variance between replicates showed that a considerable variation was present between similar types of houses. The residual variance was large in all four countries, but this was the sum of the unexplained variation and the variation between hours within a day. The decreasing effect of rising outside temperatures on the internal ammonia concentrations in pig and poultry houses could be explained by the higher ventilation rates and was also found in other research. 54 Cattle houses differed in this study from pig and poultry houses. Cattle houses were naturally ventilated and in general not temperature controlled by means of the ventilation rate. Therefore, the ventilation rate was not strongly related to the outside temperature. Also some other processes may have played a role, because the net effect only of the outside temperature is given in Table 3. Higher outside temperature may also have cause higher inside temperatures, thus stimulating microbial and physical processes involved in the emission of ammonia. Higher ventilation rates also caused higher air velocities above manure and slurry surfaces, thus enhancing evaporation of ammonia.55 Very strong or unexpected effects of the outside temperature may further be introduced by a correlation between outside temperature and manure handling activities.

6.2. Emissions of ammonia 6.2.1. Methods for expressing ammonia emission rates The ammonia emissions in Table 4—6 are given in mg/h per animal, per 500 kg live weight and per heat producing unit (1 hpu equal 1 kW), respectively. The relation between an animal and 500 kg live weight is simple. In this way the emission rate is corrected for the weights of the animals in the building and assumes a linear and constant relation between weight and emission. An increase of the emission rate during the production period is often found,56,57 and is mainly caused by an increase of body weight within the building and consequently the amount of manure that is produced. However, the relation between body weight and emission rate has not been proved for all species and housing types. The relation between 500 kg live weight and a hpu mainly depends on the weight of the animal, and in some cases also on the

89

level of production or metabolic feed intake. The use of the emission rate per hpu thus also assumes a linear and constant relation between heat production and ammonia emission. Further, calculation of emission rates per 500 kg live weight and hpu introduces faults due to errors in the estimated weight per animal and assumed heat production. Use of the emission rate per 500 kg live weight and hpu are thus restricted to cases where the necessary additional information is available to justify the assumed relations. The most basic way of presenting ammonia emissions is per animal. The number of animals used in calculations should be clearly defined. This can be (1) the instantaneous or average number of animals during the measurements, or (2) the maximum number of animals that can be kept in the house. The first figure is probably most useful for housing systems with a more or less continuous turnover of animals, while the second figure is more useful in case of all in/all out systems, e.g. growing or finishing periods. The use of the maximum number of animals, together with a correction for a nonproduction period, has led to the definition of ‘‘animal places’’ in The Netherlands (see Appendix 1). An elaborate description of the housing system, manure handling and the production figures must go together with the emission rate per animal (place), to prevent misinterpretation of the results. 6.2.2. Comparison of ammonia emission rates The effect of the manure handling (especially daily, weekly or monthly removal from the building) and the growth of the animals during the production period (e.g. beef cattle, calves, weaner and finishing pigs, and broilers) on ammonia concentrations and emissions were not taken into account in the statistical analyses. The values presented must be considered as the mean emission rates for mean conditions of manure handling and growing stage of the animals. Measurements in The Netherlands were taken at three quarters of the time through the production period. Table 7 summarizes ammonia emission rates reported in the literature for some countries. The first column gives general emission rates for cattle, pigs and poultry together with results from research carried out in Germany (Oldenburg56 ). The second and third columns show the standardized (normative) Dutch emission rates that are used for legislative purposes in The Netherlands, in g NH /yr per animal place and in mg/h per animal 3 during the production period. These figures are, in general, based on long-term measurements of experimental units or commercial houses. The emission of ammonia per year animal place is generally defined as the emission of an animal house with the maximum number of animals and includes a period between production cycles during which a zero emission is assumed. The actual

90

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

Table 7 Yearly mean emissions of ammonia (mean and /or range) from various housing systems for cattle, pigs and poultry. All data from literature General emission rates

Standardized rates (N¸ legislation)

Recent research (N¸)

mg NH /h (500 kg) 3 live weight Germany 56 and other countries.58,59 German results marked with*

g NH /yr per 3 animal place60,61

mg NH /h 3 per animal

mg NH /h 3 per animal

Cattle Dairy cows, litter Dairy cows, cubicles Beef cattle, slats ('6 months) Calves, boxes

2500 (2100—3000), 240* — — —

— 3000 8800 8100

— 657 1930 925

— 438 — 933

—

2500

184

400

64

Pigs Sows, slats Dry sows, slats Nursing sows, slats Weaners, partially slatted floor Weaners, fully slatted floor Finishers, litter Finishers, partially slatted floor Finishers, fully slated floor

2200 (2000—4500) 930* — —

— — 4200 8300

— — 505 1053

— — — —

— — — —

—

600

76

36

57

1300* 2150*

600 —

76 —

— 146 & 291s

65

1350*

2500

317

242

57

2380*

3000

381

—

—

Poultry Laying hens, litter Laying hens, aviary Laying hens, cages, manure belts (with or without drying) Laying hens, cages, slurry storage/ composting Broilers, litter (traditional) Broilers, litter drying (about 80% d.m.)

2900 (1500—9100) 7800* —

— 178 —

— 21 —

— 37)5 12)5

66

2000*

35

4)2

—

—

2000*

83—386

10—46

—

—

10 000—15 000*

50

7)6

—

—

—

5—14

0)8—2)1

—

—

Animal type and housing system

Ref. number — 62

— 63

—

— 67

s Substantial emissions of N O and NO were measured. 2

number of animals in a house may therefore often be less than the number of animal places due to mortality, e.g. in the case of broilers. The relative length of the periods with zero emission varies in general between 0 and 10% per year, with 25% for broilers as an exception. The fourth column gives results of recent research carried out in The Netherlands and gives additional information to the second and third columns. The emission rates in the first column of Table 7 can be compared with those in Table 5 (per 500 kg live weight) and those in the third and fourth columns of Table 7 can be compared with those in Table 4 (per animal). Although emission rates per 500 kg live weight allow for the live weight of the animals, Table 7 shows that the mean emission rates of 2500 mg/h for cattle buildings,

2200 mg/h for pig buildings and 2900 mg/h 500 kg live weight for poultry buildings are only rough estimates and neglect the difference in emission rates between animal and housing types within a livestock category and between countries. The emission rates per (500 kg) live weight (Table 7) per animal and housing type as reported by Oldenburg56 (German situation) lie in the range as given for pigs (2000—4500) and poultry (1500—9100), but differed considerably for cattle (240 versus 2100—3000). The measured emission rates in this research (Table 5) from cattle houses were below 2100 mg/h (500 kg) live weight, but not as low as reported by Oldenburg (240 mg/h (500 kg) live weight for a mixture of cattle houses). Measured emission rates from pig houses were

91

E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

Table 8 Schematic overview of processes and factors involved in ammonia release from livestock houses Processes

Nitrogen compounds and appearance

1. Faeces production B 2. Degradation B 3. Volatilization B 4. Ventilation B 5. Emission

Uric acid, urea, undigested proteins

Animal

Ammonia/ammonium in manure

Process conditions (manure): T, pH, A

Ammonia in air

Process conditions &

Ammonia in animal house

Local climate (air): ¹, r.h., air velocity

Ammonia in environment

Air cleaning

T temperature; pH: acidity; A : water activity; r.h.: relative humidity; w

between 744 and 3751 mg/h (500 kg) live weight (Table 5) and these levels were comparable with the range measured by Oldenburg (930—2380 mg/h (500 kg) live weight). The emission rates from poultry houses varied between 1624 and 10 892 mg/h (500 kg) live weight (cages in Germany excluded). These levels and this wide range were similar to those reported by Oldenburg (2000—10 000 mg/h (500 kg) live weight). Comparison of the measured emission rates in The Netherlands from the commercial houses in this research (Table 4) with the standard normative values (second and third columns of Table 7) showed good agreement in general. The mean values were close (dairy cows cubicles and sows slats) to the present normative value, or were close to results of other research that have not yet been used to update the normative value (calfs boxes and laying hens litter). Some higher measured values were caused by the time of measurement in relation to the manure handling (manure removal for laying hens cages) or increased ammonia emission during the production period (veal calves, fattening pigs and broilers litter). Lower emissions from houses for weaners and beef cattle than the normative value were confirmed (in the first case) or contradicted (in the latter case) by other research. The higher emission from tie houses for dairy cows could be attributed to the higher emission during the Summer, which is not included in the normative value. 6.2.3. Causes of variations in ammonia emissions Table 8 gives a global overview of the processes and factors involved in the emission of ammonia. Knowledge of nitrogen sources and degradation and volatilization processes leads to the following classification of influencing factors:59,23 Housing system: The housing system can be defined as a combination of the typical housing system for an animal type, and the waste treatment and/or removal system and storage system.

Contributory factors

w

local climate

interaction between process conditions and local climate.

Animal: Feed intake, feed composition and nitrogen retention determine the nitrogen excreted; consequently, the age, weight and animal production methods are relevant. Inside climate: The outside climate, especially temperature, has a major influence on temperature, relative humidity and air exchange rate within a building. The ventilation rate and the ventilation system (natural or mechanical), together with the positioning of inlet and outlet openings determine the airflow pattern and hence the temperature and air velocity above the ammoniaemitting surfaces. Management: Examples of management factors include waste handling, ventilation and looking after the animals. The concentrations of ammonia and the ventilation rate, and hence the emission of ammonia are subject to these influencing factors. The following variations in time and place were found in this study: (1) Variation between countries within a certain housing type; the results in Tables 4—6 clearly showed that differences in ammonia emissions and concentrations between countries were present if animal species in the same housing type were compared. (2) Variation between replicates of a certain housing type in a country; the coefficients of variation ranged up to 70% and thus showed that considerable variation existed between commercial housing types of the same kind. (3) Yearly or seasonal variation not modelled with the outside temperature; only in a restricted number of combinations of animal species and housing types was a clear relationship found between ammonia concentration/emission and the outside temperature. (4) Spatial variation between the seven sampling points at the same moment; the airflow patterns caused a relatively small variation between the sampling points, compared with the other sources of variation.

92

P . W . G . G RO O T K O ER KA M P E ¹ A ¸.

(5) Daily or diurnal variation due to, e.g. activity of the animals; the variation of emissions/concentrations within one day could certainly not be neglected.

7. Conclusions Mean ammonia concentrations in cattle houses were below 8 p.p.m. and did not give reason for concern. Mean ammonia concentration in pig houses were between 5 and 18 p.p.m. and between 5 and 30 p.p.m. in poultry houses, while momentary peak levels over 50 p.p.m. were recorded in several housing types. It could be concluded that health risks due to high concentrations of ammonia were present in various types of pig and poultry houses. Mean emission rates per animal and housing type were determined. Ammonia emissions from cattle houses (dairy cows, beef calves) varied between 80 and 2001 mg/h per animal or 315 and 1798 mg/h (500 kg) live weight. Ammonia emission from pig houses (sows, weaners and finishers) varied between 22 and 1298 mg/h per animal or 649 and 3751 mg/h (500 kg) live weight. Ammonia emissions from poultry houses (laying hens and broilers) varied between 2)1 and 39)4 mg/h per bird or 602 and 10 892 mg/h (500 kg) live weight. These emission rates should be used carefully even though they are based upon a very large survey because of large variation between countries, between commercial houses and between seasons. The cause of this variation could not be explained completely in terms of the underlying physical and chemical processes. In a number of cases an effect of the outside temperature on concentrations and emissions was found, but effects of manure handling and the increase of the emission rate during growing or production periods were not quantified. The possible disadvantage of the short measuring period in each house was probably well overcome by the number of repetitions of measurements in four replicates of each housing type under summer and winter conditions. A comparison with Dutch data showed that the measurement method for ammonia emissions used in this research could produce accurate mean emission rates per animal and housing type in the four countries. Clear and uniform methods for reporting results of measurements on ammonia emissions and the use of these figures for calculations on national or European scale are necessary. An emission rate per animal seems most appropriate, but the number of animals should be defined while mortality and the effect of the non-production period should be taken into account.

Acknowledgements The work was funded mainly by the Commission of the European Union as Project No. PL900703. Supplementary funding was also received in England from the Ministry of Agriculture, Fisheries and Food via Commission CC 0204; in Germany from the Hannover School of Veterinary Medicine and the Institut fu¨r Biosystemtechnik of the Bundesforschungsanstalt fu¨r Landwirtschaft; in The Netherlands from the Ministry of Agriculture, Nature Management and Fisheries and in Denmark from the Ministry of Agriculture and Fisheries. We thank the many technicians in all the partner countries, without whose help the project could not have been completed, and also Professor Th. Blaha, Head of the Unit of Epidemiology of the Hannover School of Veterinary Medicine, at Bakum, Germany, for his organisational and logistic support. We thank Chris Michael and his staff at Meaco Sales and Marketing for their enthusiasm and dedication in developing with us the novel wire-less data logging system. Finally, we thank the many farmers in England, The Netherlands, Germany and Denmark who not only allowed access to their buildings for the measurements to be made, but also helped in many other ways.

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E M IS S I O N S OF A M M O N I A IN L I V ES TO C K B UI LD I N GS IN N OR TH E RN E U R O PE

Appendix 1. Calculation of emission rates per animal place per year If a production period of length a is assumed, followed by a non-production period b, the yearly average emission of ammonia per animal can be calculated as follows: E

NH3

365 1 "(24E a#24E b) a b (a#b) N !/*.!-4

95

The mean emission rate during the production period of length a (days) can be calculated as follows: n : ai 24 f (t) dt i E "+ 0 a 24a i i/1 The course of the ammonia emission during a production period can be influenced by seasonal effects of the outside temperature, effects of the growing animals and effects of the manure handling (removal and treatment).