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Atmospheric Environment 38 (2004) 3017–3024
Measuring ammonia emission rates from livestock buildings
and manure stores—part 2: Comparative demonstrations of
three methods on the farm
C.J. Dorea,*, B.M.R. Jonesa, R. Scholtensb, J.W.H. Huis in’t Veldb,
L.R. Burgessc, V.R. Phillipsc
a
b
AEA Technology plc, Culham, Oxon OX14 3ED, UK
Institute of Agricultural and Environmental Technology, Postbox 43, Wageningen 6700 AA, Netherlands
c
Silsoe Research Institute, Wrest Park, Silsoe, Bedford MK45 4HS, UK
Received 24 September 2001; received in revised form 29 January 2004; accepted 11 February 2004
Abstract
Comparative demonstrations of three methods (flux sampling, external tracer ratio, and internal tracer ratio), were
mounted in four real farm situations. A flux sampling method was demonstrated at a commercial dairy cow house
(slurry-based), at a commercial piggery (straw-based), at a full-scale above-ground cylindrical slurry store (dairy cow
slurry) and a full-scale earth-bank lagoon (pig slurry). An external tracer ratio method was demonstrated, in parallel
with the flux sampling method, at the dairy cow house and at the above-ground slurry store. An internal tracer ratio
method was demonstrated at the dairy cow house only. At the dairy cow house, the corrected emission rates from the
flux sampling method and from the external tracer ratio method agreed to within the estimated experimental range,
while the emission rate from the internal tracer ratio method was significantly lower.
The overall conclusion of the study is that all three methods can have a useful role, the choice of which to deploy
depending on the particular measurements needed in each case. The paper includes a table (No. 7) which indicates
which is the recommended method when each of various considerations has top priority.
r 2004 Elsevier Ltd. All rights reserved.
Keywords: Ammonia; Emission rate; Method; Livestock building; Manure store
1. Introduction
This paper reports work carried out jointly for the
UK Department of the Environment, Food and Rural
Affairs by Silsoe Research Institute (SRI), AEA
Technology plc (AEAT) and the Institute of Agricultural and Environmental Technology (IMAG), Netherlands. The overall scientific objective of the work was to
devise, test and demonstrate one or more cost-effective
robust techniques for measuring the emission of
ammonia from naturally ventilated animal houses and
wastes stores.
*Corresponding author.
E-mail address: [email protected] (C.J. Dore).
The development and validation of external and
internal versions of the tracer ratio method; and of a
flux sampling method, are reported in the earlier paper
(Scholtens et al., 2004). This second paper reports work
to demonstrate all three methods, following their
validation, on commercial UK farms.
2. Experimental procedures
2.1. Demonstrations at a slurry-based dairy cow house
All three techniques were demonstrated at a slurrybased dairy unit (175 cows) near Ludlow, UK, during
the 1998–99 winter housing period. The Ludlow unit
1352-2310/$ - see front matter r 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.atmosenv.2004.02.031
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was typical of many UK dairy units. It consisted of a
closely spaced group of buildings (+above ground
slurry store). The overall dimensions were 102 m 56 m,
on an otherwise exposed site. The main cubicle house
always held the majority of the cows in the herd, with
smaller numbers in both a dry cow house (straw-bedded)
and a straw-bedded yard for (lactating) cows with health
queries. The distribution of cow numbers was typically
125 in the cubicle house, 25 in the dry cow house and 25
in the straw-bedded yard.
The cubicle house had space-boarded side walls, end
walls with conventional steel doors with large openings
above them, and an open roof ridge. It was thus of a
very commonly-encountered type. Slurry was scraped
from the building at around 5 a.m. and 2 p.m. each day,
to a reception pit from where it was pumped up to a
gantry-mounted separating machine. The separated
liquid drained into the slurry store while the separated
solids fell to form a heap next to it.
To demonstrate the external tracer ratio method,
sulphur hexafluoride was continuously released at a
controlled rate at near floor level (ca. 1 m), at six
positions within the main cubicle house of the unit,
using a simple cow-proof tubing manifold. Two mobile
monitoring units were installed, 50 m west and 150 m
north-east (i.e. downwind, according to the prevailing
wind direction) of the unit. The mobile monitoring units
housed the instrumentation for monitoring sulphur
hexafluoride and gas phase ammonia.
To demonstrate the internal tracer ratio method, an
instrumentation container was set up immediately outside the southeast corner of the cubicle house. A tubing
manifold led into the cubicle house, and was equipped
with 44 branches, each with a mesh filter and a critical
orifice (198:m) for controlling the air flow. An SF6/air
mixture (50–50 by volume, 20 ml/min, closely monitored
using mass flow controllers) was continuously released
inside the building, evenly across the 44 low-level release
points. A second tubing manifold sniffed air samples
from different positions. This manifold was trace-heated
to prevent condensation and hence loss of ammonia.
Five sampling positions along the axis of the building,
1 m below the open roof ridge, were used to provide one
integrated sample of the exit air. Four other individual
sampling positions sniffed air from just outside the
centre of each of the four walls of the cubicle house.
Whichever of these four was lowest in ammonia on each
occasion was taken as the background level (i.e. upwind)
on that occasion.
To demonstrate the flux sampling method, a set of recurved flux samplers (Scholtens et al., 2004) was
installed on the cubicle house for a period of 24 h
(nominal) on each of six different occasions when dry
weather had been forecast, with one and two of
these being during the periods of the external and
internal ratio demonstrations, respectively. Samplers
were distributed as follows: one per space-boarded
bay along each side wall, 20, equally spaced, and
vertically mounted, in the open roof ridge, and the
remaining 37 in the space-boarded sections of each
end wall and in the large openings above each steel
end door, with the one following exception: the
farmer kept one of the north end doors permanently
open, to allow access by the forage wagon. The farmer
was not willing to shut this door at other times of day.
Therefore only those areas of that opening which were
outside the profile of the forage wagon could be
sampled.
2.2. Demonstrations at an above-ground cylindrical store
of dairy cow slurry
The external tracer ratio method and the flux sampler
method were demonstrated at a slurry store, near
Leighton Buzzard, during June 1999.
The store was constructed of bolted steel panels and
had an open top. It was situated in a field remote from
buildings, being fed by an underground pipe. It was
23.7 m in diameter and 3.5 m high, giving a nominal
capacity of 1500 m3 and a cross-sectional area of 440 m2.
The tank contained an estimated 400 m3, on top of
which was a significant crust. Small additions of slurry
were pumped in each morning (arising from collecting
yards only, as the cows were out grazing most of the
day). The slurry was believed to be mainly old slurry
from the previous winter housing period, but with some
silage effluent and some ‘‘dirty water’’.
To demonstrate the external tracer ratio method,
ammonia and SF6 were monitored continuously at two
locations: one 110 m north east and one 50 m south–
southeast of the slurry store. A simple tubing manifold
released pure SF6 at six symmetrical positions at the
surface of the slurry in the store. The release rate was
controlled by a mass flow controller and checked daily
using a bubble flowmeter: The release rate varied by less
than 2%.
The selected store was considered to be too large to
deploy flux samplers on all four sides allowing
measurements independent of wind direction. A large
(planar) flux frame was therefore constructed immediately northeast of the store (down-wind of the prevailing
wind), based on nine street lighting columns spaced
6.9 m apart. The sampling area was 55 m across (more
than double the store’s diameter, to accommodate some
variation in wind direction) and 12 m high (more than
three times the store’s wall height, to minimize the risk
of not sampling the top of the plume leaving the store).
At the top of the middle column was a wind vane. Pulley
systems allowed light-weight sub-frames, each carrying
an array of 18 re-curved flux samplers, to be raised
and lowered between each adjacent pair of lighting
columns. Three re-curved flux samplers were also
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mounted up-wind of the store, to give an estimate of the
(background) flux of ammonia coming onto the tank,
e.g. from any grazing cattle upwind.
3. Results
2.3. Demonstration at an automatically controlled
naturally-ventilated piggery
The emission rate results (averaged over an exposure
period of 24 h nominal) from the six flux sampler runs
are shown in Table 1. Over the period 16–17 November
1998, the external tracer ratio method gave a range of
emission rates (before correction for non-ideal recovery)
of 12–73 g NH3 min 1. According to the validation tests
on the building section at SRI (Scholtens et al., 2004),
the derived emission rate from the external tracer ratio
method is 1.43 times the value from measured release
rates. Correcting accordingly, we obtain an emission
rate range of 8 to 51 g NH3 min 1, over that period.
Assuming the sampled plume was well-mixed, the
derived values would represent the ammonia emission
rate from the whole dairy unit. It is possible, however,
that from time to time the sampled air was more
representative of the slurry store, depending on meteorological conditions.
In order to compare this range with the value
obtained using flux samplers over a similar time period
(see Table 1), we need to try and estimate how much of
the above total emission rate range can be attributed to
the cubicle house alone. (In principle, flux samplers
could have been used to obtain independent measures of
the ammonia emission rates from the unit’s slurry store
and from its slurry-wetted outdoor concrete areas,
but unfortunately resources had not allowed this.) An
estimate can be made via animal numbers, as follows.
On 17 November 1998, the total number of cows at the
unit was 174, of which 119 were in the cubicle house.
Scaling accordingly, we arrive at an estimated range of
emission rates, by the external tracer ratio method, from
the cubicle house alone, of 5–35 g NH3 min 1 (mean
value 20 g NH3 min 1).
A separate estimate, of the emission rate from the
cubicle house alone, was made by taking the value for
the whole dairy unit and subtracting estimates of the
emission rates from all the other components of the
dairy unit (straw-bedded buildings, slurry store, slurrywetted outdoor concrete areas). This second estimate
tended to confirm the first one. Converted to the same
units, the emission rate measured by flux samplers on
17–18 November 1998 for the cubicle house alone was
9 g NH3 min 1, which is within the above estimated
short-term experimental range for the external ratio
method.
The internal tracer ratio method ran smoothly
throughout the period 20 February 1999–24 March
1999, except for a failure in data logging between 12
and 14 March. The range of daily average emission
rates measured for the cubicle house was from 650 to
4700 g NH3 d 1 (giving a long-term average of 2160 g
NH3 d 1 or 1.5 g NH3 min 1). The instantaneous
At this building, near Bedford, which held 240
pregnant sows, only the flux sampler method was
demonstrated. Four 24-h measurement periods were
completed in September 1998, at times when dry
weather had been forecast. The dry sow house, in which
the sows had generous straw bedding, had 48 ventilation
openings, each equipped with a temperature-controlled
flap, along each side wall. The weather was warm, so it
was possible to maintain all these flaps fully open
throughout. Each of the 96 openings was fitted with recurved flux sampler, mounted on a simple bracket, while
another 16 re-curved flux samplers (now vertically
mounted) were installed, equally spaced, along the
building’s full length open roof ridge. All access doors
to the building were kept closed throughout each 24 h
experiment, except for a few periods each of a few
minutes e.g. for bringing in and taking out feed barrows.
Sampling of the air flows in and out of the building was
thus very complete.
A few uncoated flux samplers were also exposed
(mounted normally, in re-curved holders), to see if dust
from inside the piggery, depositing in the tubes, would
lead to a significant value of ammonia. Dust deposition
was never more than very slight, and in no case was a
significant value of ammonia obtained from any such
uncoated tube.
2.4. Demonstration at an earth-bank lagoon storing
pig slurry
At this store, only the flux sampler method was
demonstrated. A suitable pig slurry lagoon was
identified near Bedford. The lagoon was remote from
the main unit, being fed by an underground pipe. The
‘‘high tide’’ dimensions of the lagoon were 52 m 15 m.
At the time of mounting the demonstration experiments,
the lagoon was full. The same planar flux frame
as described above was set up along the 52 m (North
West) side of the lagoon, 10 m back from the high
tide line.
2.5. Meteorological data
Appropriate data (wind speed, wind direction and
temperature) were obtained from the Meteorological
Office. The data were taken from whichever of the
Office’s sites recording the necessary data were nearest
to the farm site in question (see Tables 1–4).
3.1. Demonstrations at a slurry-based dairy cow house
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Table 1
Emission rate measurements from demonstration experiments using re-curved flux samplers at a slurry-based (tractor-scraped) dairy
cow house (approximately 130 cows, each of estimated live weight 525 kg)
Dates of expt
Average outside air temp at
1.25 m height, over the 24 h
( C)
Average wind speed at 10 m
height, over the 24 h (m s 1)
Emission factor averaged
over 24 h (already corrected
for non-ideal capture by flux
samplers) (g NH3 lu 1 d 1)
10–11 Nov ‘98a
17–18 Nov ‘98a
26–27 Nov ‘98b
1–2 Dec ‘98b
11–12 March ‘99a
15–16 March ‘99a
4.8
2.4
8.3
3.1
5.4
8.6
1.9
0.6
3.2
2.8
0.5
1.4
50
98
101
90
83
106
Average 88
a
b
Meteorological data were from Shobdon site, 20 km SSW of the farm.
Meteorological data were not available from Shobdon site, so data from Shawbury site, 42 km N of the farm, were used.
Table 2
Emission rate measurements from demonstration experiments using (a) the external tracer ratio method, and (b) re-curved flux
samplers, at an above-ground cylindrical slurry store (nominal capacity 1500 m3: contained an estimated 400 m3 during the
experiments)
Selected periods over which
results were obtained
(a) External tracer ratio method
0200 on 19 June 99 to 0800 on
20 June 99
0800 on 20 June 99 to 2200 on
21 June 99
2200 on 24 June 99 to 1100 on
25 June 99
Corrected emission rate from whole store, in g NH3 min
1
Average converted
to g NH3 d 1
min
max
average
0.09
0.85
0.34
490
0.03
1.15
0.16
230
0.01
0.22
0.04
60
Average 260
Dates of expt
(b) Re-curved flux samplers
16–17 June ‘99
22–23 June ‘99
30 June–1 July ‘99
Average outside
air temperature at
1.25 m height, over
the 24 h ( C)
Average wind
speed at 10 m
height, over the
24 h (m s 1)
Emission rate g NH3 d 1 from whole store
(already corrected for non-ideal capture by
flux samplers)
19.6
15.4
16.7
2.3
Not available
4.3
190
290
420
Average 300
Meteorological data were from Northolt site, 38 km SSE of the dairy farm.
ammonia emission rate showed distinct and repeatable
maxima (20% above the daily average) at both morning
and afternoon milking/slurry scraping times. On 15–16
March 1999, the average emission rate from the cubicle
house by the internal tracer ratio method was 30 g NH3
lu 1 d 1, with estimated 95% confidence limits of 73 g
NH3 lu 1 d 1. (lu=livestock unit=500 kg of live
weight.) The value from flux samplers over the same
period, for comparison, was 106 g NH3 lu 1 d 1
(see Table 1), so this was statistically significantly
higher. Also from Table 1, the flux sampler value on
11–12 March 1999 was 83 g NH3 lu 1 d 1. There was no
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Table 3
Emission rate measurements from demonstration experiments using re-curved flux samplers at an automatically controlled naturally
ventilated dry sow house (around 250 sows of live weight approx. 230 kg each, on generous straw bedding (14 kg new straw sow 1
week 1))
Dates of expt
Average outside air temp at
1.25 m height, over the 24 h
( C)
Average wind speed at 10 m
height, over the 24 h (m s 1)
Emission factor (already
corrected for non-ideal
capture by flux samplers)
(g NH3 lu 1 d 1)
27–28 Aug ‘98
2–3 Sept ‘98
10–11 Sept ‘98
16–17 Sept ‘98
13.2
16.4
13.9
12.5
3.6
4.8
7.6
9.0
22.2
28.9
47.6
28.4
Average 31.8
Meteorological data were from RAE Bedford site, 6 km N of the pig farm.
Table 4
Emission rate measurements from demonstration experiments using re-curved flux samplers with a flux frame at an earth-bank lagoon
of pig slurry
Dates of expt
29–30 July’ 99
23–24 Aug’ 99
2–3 Sept’ 99
Status of lagoon
full
1/4 full
1/2 full
Estimated
surface area of
slurry m2
680
530
610
Average outside
air temperature
at 1.25 m
height, over the
24 h ( C)
18.4
14.8
19.7
Average wind
speed at 10 m
height, over the
24 h (m s 1)
4.6
4.6
2.6
Emission rate g NH3 d
1
From whole
lagoon
Per m2 of slurry
surface
706
278
2730
1.0
0.5
4.5
Meteorological data were from RAE Bedford site, 6 km N of the pig farm.
Table 5
Estimates of numbers of man-days needed on site when using each of the methods on the farm
Method
External tracer ratio
Internal tracer ratio
Flux samplers
Naturally ventilated livestock building
Waste store
Set-up
Take-down
Set-up
Take-down
3
6
2
2
3
2
3
Not tested
6
2
Not tested
2
result from the internal tracer method for 12 March,
because of data-logging problems, but for 11 March it
was 19 g NH3 lu 1 d 1, so it appears that on this
occasion also, the flux sampler tube result was significantly higher.
To summarize the findings of the three methods when
applied simultaneously, or almost so, the result from the
flux sampler method was within the estimated experimental range from the external tracer ratio method
(after scaling down from the whole dairy unit to the
cubicle house alone). However, results from both these
methods were significantly higher than the result from
the internal tracer ratio method. One possible explanation for this is the incomplete mixing of SF6 and NH3 at
sampling points for the internal tracer ratio method
within the cow house. This may be due to the fact that
the SF6 release points did not match the distribution of
the NH3 emissions adequately. However, the agreement
between the flux sampler and external tracer ratio
methods suggests that the SF6 and NH3 were well
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mixed at the sampling locations of the external tracer
ratio (downwind of the cow house).
3.2. Demonstrations at an above-ground cylindrical store
of dairy cow slurry
Results from the external tracer ratio method are
shown in Table 2(a): several long periods of wind
direction suitable for the method were achieved. The
calculated NH3 emission rate displayed diurnal variations, with low values at night (often less than
0.05 g min 1), and peak values towards mid-day (typically less than 1.0 g min 1). The average emission rate
for each period varied between 0.04 and 0.34 g min 1.
Short-lived periods with high NH3 emission rate were
also observed, and it is believed that these corresponded
to periods of pumping slurry in. The emission rate over
these short periods were noted to be an order of
magnitude greater than over other periods.
The results of the three flux sampler demonstration
experiments are shown in Table 2(b). Once again, no
correlation with air temperature or wind speed is
apparent. No significant flux of ammonia was ever
detected by the top row of samplers, confirming that the
lighting columns were tall enough always to sample the
whole height of the plume.
When seeking to compare the results from the two
methods used at the slurry store, there is the problem
that each method has given rise to results for somewhat
different dates: this prevents an exact comparison. The
problem arises because the external tracer ratio method
gives results only when one of the two measuring points
is in the plume downwind of the store, which of course
depends on the positions which have been chosen for
those measuring points. Meanwhile, with the flux
sampler/planar flux frame method, it is necessary to
commit oneself in advance to a particular 24 h period
when a suitable range of wind direction has been
predicted. There is never a guarantee that both sets of
conditions will be met on the same days! Nevertheless,
the results from the two methods (Tables 2(a) and (b))
are certainly of the same order (low hundreds of
grammes of ammonia per day from the whole store),
indicating that when the external tracer ratio method is
applied to a single source, rather than to a group of
sources, better agreement with the flux sampler method
can be achieved.
3.3. Demonstration at an automatically controlled
natural-ventilated piggery
The emission rate results measured using the flux
sampling method are shown in Table 3. Average air
temperature and wind speed was different over each of
the four demonstration experiments. Since ammonia
loss is believed to be essentially a physical volatilization
process, both these parameters are expected to influence
emission rate, but in the event no clear trend of emission
rate against either parameter could be seen.
3.4. Demonstration at an earth-bank lagoon storing
pig slurry
Full results of the three demonstrations achieved are
shown in Table 4.
As outlined in Section 3.2., the logistics of operating
the planar flux frame require a commitment in advance
to a particular 24 h period when a suitable range of wind
direction has been predicted. The risk of problems from
the actual range of wind direction differing from that
predicted is minimised by making the flux frame as large
as possible and by positioning it the minimum feasible
distance downwind. Despite these precautions, wind
directions on both 29–30 July 1999 and 23–24 August
1999, resulted in only partial sampling of the plume at
times. In contrast, the range of wind direction on 2–3
September 1999 was very favourable, the wind remaining square on to the flux frame throughout. Therefore,
the results from the last set of measurements are
considered more reliable.
4. General discussion
4.1. Assessment of the practicability of the three methods
in the light of the experience gained during the
demonstration experiments
No great practical difficulties were found in mounting
the on-farm demonstrations of any of the three methods
(external tracer ratio; internal tracer ratio; flux sampler).
The numbers of man-days needed on site varied across
both the methods and the scenarios: estimates of the
numbers needed are presented in Table 5.
4.2. Assessment of robustness of methods in the light of
hands-on experience
Table 6 outlines the advantages and disadvantages
with the external and internal tracer ratio methods and
with passive flux samplers, as a result of our experiences.
The internal version of the tracer ratio method, which is
particularly applicable to buildings, eliminates the
dependence on wind direction which is a drawback of
the external version, but does require the SF6 to be
released in a way which mimics the ammonia release
much more closely than is necessary with the external
version. This requires more care in designing and
installing an SF6 release system (cf. Table 5), and means
that the internal version may be more appropriate for
longer-term measurements, and the external version for
shorter-term ones.
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Table 6
Advantages and disadvantages of using the three different methods to measure ammonia emission rates from livestock buildings and
manure stores
Advantages
External tracer ratio method
Continuous (a complete new reading of emission rate is
generated every 6 min).
No inherent need to measure wind speed.
Works in heavy rain and with dew.
Needs only simple installation inside the source structure.
Internal tracer ratio method (not tested for waste stores)
Continuous (a complete new reading of emission rate is
generated every 6 min).
No inherent need to measure wind speed.
Works in heavy rain and with dew.
Disadvantages
Power supply needed.
Dependent on wind direction.
The AMANDA ammonia analysers can be prone to
breakdown.
In validation tests, gave considerable bias (recovered 143%
of released ammonia in the building test and 75% in the store
test). The standard deviations on these two recovery rates
were 13% and 76%, respectively.
Power supply needed.
Needs considerable installation inside the source structure.
The NOx analyser + catalytic NH3 converter used to follow
ammonia concentration needs an experienced operator.
Independent of wind direction.
In its building validation test, gave 90% recovery of released
ammonia—the closest to ideal of all three methods.
Re-curved passive flux samplers
Simple to deploy in the field (no power supply, cables,
tubing, etc.).
No questions over adsorption of ammonia on tubing wall.
No need to measure wind speed: they give flux directly.
Independent of wind direction.
Bi-directional, so suitable for complex air flows (eddies, etc.),
and no need to measure background concentrations of
ammonia.
The methods pursued in this study also differ in their
ability to deal with the common on-farm scenario of
several ammonia-emitting buildings and/or stores in
close proximity. The external tracer ratio method can
only give a gross emission rate for the whole group of
sources. The position at which concentrations are
measured needs to be sufficiently downwind that plume
mixing will allow a release of SF6 in only one source of
the group to represent ammonia emissions from the
whole group. In practice, this means measuring concentrations at a distance downwind which is at least ten
times the overall ‘‘width’’ of the group of sources.
Ideally SF6 should be released at each individual source,
at a rate proportional to the ammonia release rate from
each individual source, but as the relative magnitudes of
the individual sources are generally not known, multiple
SF6 release points will not give any additional useful
For manure stores, masts need erecting around the source
(or, at least, downwind of it).
Need considerable lab time before and after exposure, at
least in present form.
Each set needs at least a few hours’ exposure—and maybe 24
h for lower concentrations. So, obviously, far from a
continuous measurement.
Do not work with heavy rain or dew, because their acid
coating then gets dissolved and drains away.
In the building validation tests, they could only account for
66% of released ammonia, albeit with a standard deviation
of only 2.9%.
information. The passive flux sampler method can give
the individual source strengths, provided that each
source in the group has been equipped with its own set
of samplers. The internal tracer ratio method lies
between the other two methods, in the sense that it
can readily be applied to one source within a group of
sources, but would far less readily be applied to more
than one in a group.
The methods also differ in the levels of both
equipment sophistication and (therefore) operator skill
needed: in both cases the tracer ratio methods have the
higher requirements. Nevertheless the overall conclusion
of the study is that all the methods can have a useful
role, the choice of which to deploy depending on the
particular measurements needed in each case. Table 7
presents the recommended method when each of various
considerations has top priority.
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Table 7
Indications of which is the recommended method when each of various considerations has top priority
Consideration having top priority
Recommended method
Best performance in validation tests (i.e. needing least correction factor)
Least level of skill and experience in the operators
Least total labour requirement to complete and analyse measurements at
one site
Least capital investment to set up a measuring system from scratch
Least reliance on needing a particular wind direction
Internal tracer ratioa
Flux samplers
External tracer ratio
Least reliance on dry weather
Need to know the strengths of individual sources within a group of sources
(buildings and/or stores and/or outdoor concrete areas)
Need to know only the overall source strength of a group of buildings and/
or stores and/or outdoor concrete areas
Flux samplers
Internal tracer ratioa (also, for buildings
only, flux samplersb)
External tracer ratio (also, for buildings,
internal tracer ratioa)
Flux samplers
External tracer ratio
a
The internal tracer ratio method was not tested for waste stores.
The use of flux samplers at full-sized waste stores could be made independent of wind direction if considerable extra money and
time were spent on installing additional sampler arrays, based on street lighting columns, on the other three ‘‘sides’’ of the store (the
ones other than that which is downwind of the prevailing wind direction).
b
5. Conclusions
Acknowledgements
5.1. Three methods have been developed and validated to the point where a number of detailed
demonstrations of them on the farm could be mounted.
5.2. All three methods were practicable on the farm.
In the light of experience, each was judged to be more,
or less, appropriate for different farm scenarios: details
are given in Table 7.
5.3. When the three methods were demonstrated side
by side, at a dairy cow cubicle house, results from the
flux sampler method were within the estimated experimental range of those from the external tracer ratio
method, but results from the internal tracer method
were significantly lower. This difference may be due to
incomplete mixing of SF6 and NH3 within the cow
house.
5.4. Further work is recommended to identify the
causes of the biases in the external tracer ratio and flux
sampler methods, and hence to eliminate them; and then
to mount full on-farm validations.
We thank the UK Department for the Environment,
Food and Rural Affairs for funding the project (OC
9523). We thank Mike Sargeant, Stephen Medlicott
and Graham Tucker for offering much help, advice and
access to their animal houses and/or manure stores. We
thank the Meteorological Office for the provision of
data, and, last but not least, all the colleagues from SRI,
AEAT and IMAG without whose help the study could
not have been completed.
References
Scholtens, R., Dore, C.J., Jones, B.M.R., Lee, D.S., Phillips,
V.R., 2004. Measuring ammonia emission rates from
livestock buildings and manure stores. Part 1 Development
and validation of external tracer ratio, internal tracer ratio
and passive flux sampling methods. Atmospheric Environment, this issue, doi:10.1016/j.atmosenv.2004.02.030.