The Effect of Litter Management on Ammonia Emissions
from U.S. Broiler Chicken Houses
Paper #615
Kenneth D. Casey, Richard S. Gates, Anshu Singh, Anthony J. Pescatore
University of Kentucky, 128 CE Barnhart Bldg. Lexington, KY 40546
Eileen F. Wheeler
The Pennsylvania State University, Agricultural Engineering Bldg. University Park, PA 16801
Hongwei Xin, Yi. Liang
Iowa State University, 100 Davidson Hall, Ames, IA 50011
ABSTRACT
Recently acquired ammonia emissions baseline data for U.S. broiler housing indicates that the
emission rate may exceed previous expectations, potentially triggering regulatory reporting
requirements. Broiler chickens are raised on litter which is the mixture of decomposing feces and
bedding. This litter is the major source of volatilizing ammonia. The management of the litter is
a key factor affecting emission rate.
Litter in US broiler houses is typically replaced once and then reused for at least one year with
caked litter being removed after each flock and optional addition of a small layer of new bedding.
This practice is often referred to as ‘built-up’ litter in the industry and is a combination of the
original litter material and accumulated manure. Thus on broiler farms where built-up litter is
used, the primary storage of manure is within the houses.
The development of a comprehensive database of ammonia emission rates from U.S. poultry
facilities has been the objective of a multi-state, multi-disciplinary project over the past three
years. The influence of common management strategies and practical means of reducing
ammonia emissions including several litter management strategies have been included as part of
the study.
Ammonia emission data have been collected from 8 houses in Kentucky and 4 houses in
Pennsylvania over a twelve month period. Litter management practices including built-up litter,
removal each flock and the use of ammonia suppressing amendments were compared during the
study. Results from these broiler houses will be presented and compared.
INTRODUCTION
Broiler chickens are raised on litter which is the mixture of decomposing feces and bedding.
Litter in US broiler houses is typically replaced once and then reused for at least one year with
caked litter being removed after each flock and optional addition of a small layer of new bedding.
This practice is often referred to as ‘built-up’ litter in the industry and is a combination of the
original litter material and accumulated manure. Thus on broiler farms where built-up litter is
1
used, the primary storage of manure is within the houses. This litter is the major source of
volatilizing ammonia and its management is a key factor affecting emission rate.
The litter is usually managed to minimize the ammonia level to which young birds are exposed.
Controlling the litter moisture content and pH are the major avenues for reducing ammonia
volatilization.1 Litter moisture is managed by minimizing water leaks and ingress while
maintaining adequate ventilation to remove moisture from the building. Control of litter pH over
the life of the flock has proven to be a difficult task. Maintaining the litter pH below 7 has been
shown to minimize ammonia volatilization. Ammonia release is maximized when the litter pH is
8 or above.
In poultry litter, the decomposition of uric acid has been shown to be brought about almost
exclusively by aerobic bacteria.2, 3 The author observed that the uric acid was converted to
ammonia by some of the organisms but to urea by the majority. The use of urease inhibitors
(PPDA, CHPT, NBPT) to disrupt the transformation of urea to ammonia has been
demonstrated.4, 5 It has been shown that the uricase enzyme can be inhibited by the addition of
certain minerals to poultry manure.6 The use of the urease inhibitor is likely to substantially
reduce the amount of ammonia released from the litter however it’s effect last only 7 – 14 days
requiring reapplication for continued effect. The use of this strategy may reduce ammonia
emissions whilst improving the plant nutrient status of the poultry litter through increased
nitrogen content.
As the emission of ammonia is inhibited by low pH levels when the equilibrium between NH4+
and NH3 is affected, emissions can be minimized by reducing the pH of the litter. One method of
doing this is to apply phosphoric acid (H3PO4) to the litter.7, 8 The quality of the litter as a plant
nutrient source would be improved by the increased nitrogen level however this treatment greatly
increased the water soluble P levels increasing the potential for environmental damage through
the offsite movement of phosphorus.
One very widely used method of suppressing ammonia emissions from poultry litter is the
application of alum [Al2(SO4)3.18H2O]. Researchers have demonstrated that this treatment
significantly reduces ammonia loss from the litter resulting in higher nitrogen concentration in
the litter when applied to land as a source of plant nutrients.7, 8 It has also been shown that this
treatment reduces water soluble P levels in the final litter, reducing the potential for offsite export
of this nutrient.8
Another widely used method of suppressing ammonia emissions from poultry litter is the
application of sodium bisulphate [NaHSO4]. However some research has failed to demonstrate a
difference in ammonia emissions from litter treated with NaHSO4 and untreated litter.8 This litter
amendment is commonly used in Kentucky and Pennsylvania and was used as part of the
standard operating procedures on the farms included in this study.
2
DISCUSSION
Overview
Environmental conditions in twelve commercial broiler houses in the United States were
monitored during thirteen, 48-hour periods over the course of one year. The monitoring periods
obtained data to determine ammonia emission from the broiler houses during different seasons
with various age birds during at least five flock grow-out cycles. In order to economically obtain
data from as many houses as possible over the year, the instrumentation was taken to one set of
houses the first week and another set of houses the second week. The interval between 48-hour
collection periods was typically three weeks in PA and two weeks in KY, with the third week
being spent in data organization, instrumentation checks, and time to thoroughly disinfect for
biosecurity. A “day” of data collection started when all the instrumentation was installed in the
house and ended 24-hours from that point. Four of the study houses were in Pennsylvania (PA)
representing a “cold” climate and eight were in Kentucky (KY) representing a “mixed humid”
climate. Farms were selected to represent the variety in modern broiler production practices,
including those that practiced methods that were presumed to reduce ammonia emissions.
Pennsylvania houses
The four PA houses were paired, for repetition of conditions, on two farm sites (Farm B and H),
with different managers, under contract to different companies. These houses were each 14.6 m
wide x 152.4 m long (48 ft x 500 ft) and housed a nominal 32,500 or 32,700 birds during cold
weather, Farm B and Farm H, respectively. Placement density was 14.6 or 14.7 birds m-2 (1.35
or 1.36 birds ft-2), Farm B and Farm H, respectively. All four were recently built (2000-2001)
by the same construction company and were identical for purposes of this study.
The primary difference between the two PA study locations was that Farm H houses had concrete
floors and new litter each flock while Farm B had built-up litter on dirt (crushed shale) floors.
Farm B’s second study flock was on new litter after the annual litter cleanout. New litter for both
PA farms was 1 cm deep kiln-dried wood shavings. By the end of five flocks use at Farm B, litter
was about 8 cm deep. For flocks with cold-weather start dates, Farm B incorporated a 0.243 kg
m-2 litter treatment of NaHSO4 to litter lower pH in the brood section on both houses on the day
before chick placement. Additional litter treatment is applied in the non-brood section of the
house, at the same application rate, the day birds are moved into that section.
Kentucky houses
Two KY sites were monitored, each with four houses, for replications of conditions. Each site
was under contract to a different integrator company. Each broiler house was 12.2 m x 152.5 m
(40 x 500 ft; except House 4 at Site 1, which was 12.2 x 157.4 m (40 x 516 ft)) and with a
nominal 20,000 or 25,000 birds, dependent upon finished bird requirements. This produced a
placement density of 13.44 birds m-2 at 25,000 birds placed and 10.75 birds m-2 at 20,000 birds
placed. The houses at Site 1 were built in 2000 (except House 4, which was built in 1995) while
those at Site 2 were constructed in 1997. Greater detail on each site is provided elsewhere.9
All KY houses employed built-up litter; some used a litter amendment to reduce ammonia
volatilization. At Site 1, NaHSO4 was applied to the litter of the brooding section prior to chick
3
placement in the period November through March. The product was applied at the rate
recommended by the manufacturer. At Site 2, NaHSO4 was applied in the brooding area prior to
placement only in houses 1 and 2 at rate of 0.226 kg m-2.
The annual cleanout of all houses at Site 2 took place in September at the end of flock 5.
Whereas the annual cleanout at Site 1 was spread over two flocks with house 1 being cleaned out
at the end of flock 5 (March) while houses 2, 3 and 4 were cleaned out at the end of flock 6
(May). During this cleanout all built-up litter is removed from the houses and replaced with
fresh sawdust
Instrumentation
For the data collected and reported here, ammonia ER was obtained from Portable Measuring
Units (PMU) developed for this project. Complete details of the PMU are given in other
references and not repeated here.10, 11, 12 One PMU was installed in each broiler house. The PMU
was located near and monitored the primary minimum ventilation timer fan used for cold weather
ventilation. A second PMU is located on the first of the tunnel ventilation fans at this site during
warmer conditions when the house is likely to transition into tunnel ventilation mode. PMUs
typically collected data at each house for about 48 hours however, for one monitoring period,
data collection exceeded 72 hours. The interval between collection periods at a site was typically
two or three weeks. A ‘day’ of data collection was nominally from noon of one day to noon of
the following day.
The exhaust fan ventilation capacity was determined with a Fan Assessment Numeration System
(FANS) unit. Details of this unit’s design and performance specifications are provided
elsewhere.13, 14 The FANS unit has recently been used to evaluate each fan in all four of the
broiler houses on this site. It takes about 1 hour to fully evaluate each fan over a range of typical
operating static pressure differences, so several trips to each farm were necessary to fully
characterize each houses’ ventilation system. Under minimum ventilation during cold weather,
the fan on-off times were known so that ventilation rate is a constant over the evaluation time
period. Fan on-off time was monitored using fan motor loggers. Average static pressure
difference over the fan on-time interval was used to determine fan ventilation rate, using fan
curves developed for each fan as determined from the FANS testing.
The litter in the brooding and non-brooding sections of the houses was separately sampled at the
conclusion of each flock using the random walk method.15 A single composite sample was
analyzed from each house section. Analyses included moisture content, pH, total ammoniacal
nitrogen (TAN), total nitrogen (TN) and total phosphorus (TP).
Litter management strategies
One of the objectives of the ammonia emission monitoring project was to investigate the
influence of litter management strategies on overall ammonia emissions. The PA sites formed a
contrast of new litter each flock versus built-up litter, while the KY sites allowed investigation of
the efficacy of a litter amendment (NaHSO4) at Site 2 and the effect of different timing of the
annual cleanout between Site 1 and Site 2.
4
1000
5000
Farm B
100
4000
m hr
-1
A.
3
3000
80
2000
ppm NH3
Figures
601 through 4 show ammonia emission results versus bird age as a composite of all study
1000
dates at each of the four farms.
0
40
2.5
-1
-1 -1
1000 birds g NH
3 bird d
20
2.0
0
1.5
8000
1.0
6000
0.5
4000
0.0
3
m hr
-1
Feb
C.
Flock 2 ER = 0.028*Age – 0.164
Flock 3 ER = 0.025*Age – 0.123
Flock 4 ER = 0.021*Age – 0.077
Flock 5 ER = 0.026*Age – 0.183
Flock 6 ER = 0.018*Age – 0.152
r2 = 0.855
r2 = 0.928
r2 = 0.909
r2 = 0.952
r2 = 0.832
B.
Flock 1
Flock 2
Flock 3
Flock 4
Flock 5
Flock 6
Linear Regression
Mar
Apr Interval
May
95% Confidence
95% Prediction Interval
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2003
2000
Figure 1. Farm H Average daily emission rate per bird is shown with individual flock regression
equations:
g NH3 bird
-1
d
-1
0
2.5
Flock 1 ER = 0.026*Age – 0.030
Flock 2 ER = 0.042*Age – 0.236
2.0 Flock 3 ER = 0.021*Age + 0.138
Flock 4 ER = 0.069*Age – 0.663
Flock 5 ER = 0.035*Age + 0.128
1.5 Flock 6 ER = 0.049*Age – 0.301
r2 = 0.888
r2 = 0.987
r2 = 0.939
r2 = 0.988
r2 = 0.966
r2 = 0.962
C.
1.0
0.5
0.0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2003
Figure 2. Farm B Average daily emission rate per bird is shown with individual flock regression
equations:
5
3.00
2.75
2.50
Emission Rate, g NH3 bird d
-1 -1
2.25
Flock 4 :
ER  0.349  0.032 Age, r 2  90%
Flock 5 :
ER  0.127  0.034 Age, r 2  96%
Flock 6 :
ER  2.777  0.033 Age, r 2  87%
Flock 7 :
ER  0.062  0.037 Age, r 2  91%
Flock 8 :
ER  0.054  0.045 Age, r 2  70%
Flock 9 :
ER  0.048  0.034 Age, r 2  89%
Flock 4
Flock 9
Flock 6
Flock 7
Flock 8
Flock 5
Linear Regression
95% Confidence Interval
95% Prediction Interval
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
01-Dec-02
01-Feb-03
01-Apr-03
01-Jun-03
01-Aug-03
01-Oct-03
Figure 3. Site 1 Average daily emission rate per bird is shown with individual flock regression
equations:
3.00
Flock 2
Flock 3
Flock 4
Flock 5
Flock 6
Linear Regression
95% Confidence Interval
95% Prediction Interval
2.75
2.50
Emission Rate, g NH3 bird d
-1 -1
2.25
2.00
1.75
Flock 2 :
ER  0.334  0.026 Age, r 2  89%
Flock 3 :
ER  0.340  0.032 Age, r 2  85%
Flock 4 :
ER  0.202  0.041 Age, r 2  82%
Flock 5 :
ER  0.158  0.033 Age, r 2  74%
Flock 6 :
ER  0.416  0.035 Age, r 2  89%
1.50
1.25
1.00
0.75
0.50
0.25
0.00
01-Dec-02
01-Feb-03
01-Apr-03
01-Jun-03
01-Aug-03
01-Oct-03
Figure 4. Site 2 Average daily emission rate per bird is shown with individual flock regression
equations:
6
New versus Built-up Litter
Daily emissions are expressed as g NH3 bird-1 d-1 versus bird age (days) in figures 1 to 4. Slope of
regressions of all collected daily ER versus age agreed well among the three built-up litter, study
sites, with values of 0.040, 0.033 and 0.036 g NH3 bird-1 d-1 per day of age. Farm H with new
litter had a slope of 0.024 g NH3 bird-1 d-1. For sites with used litter, the intercept was near 0,
(Site 1), equivalent of one-day ER (Site 2) and 2.7 days for Farm B. In contrast, the new litter
farm has an intercept equivalent to six-day ER.
Use of NaHSO4 Litter Amendment
3.00
ER  0.158  0.033 Age ,
r 2  74 %
2.75
Houses with NaHSO4 Litter Amendment
Linear Regression
95% Confidence Interval
95% Prediction Interval
Houses with No Litter Amendment
Emission Rate, g NH3 bird d
-1 -1
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
0
10
20
30
40
50
60
Flock Age, days
Figure 5. Site 2, Flock 5 Average daily emission rate per bird is shown for houses with and
without litter amendment:
The evaluation of the efficacy of the NaHSO4 litter amendment was confounded by management
decisions regarding ventilation and limited measurements during the early part of the flocks
when it would be expect to see a difference. The houses in which the litter amendment was
applied as per standard operating practice ran two fans at 3 minutes ON in a ten minutes cycle
whereas the houses in which no litter amendment was applied ran two fans at five minutes ON in
a ten minutes cycle. This difference in ventilation rate potentially impacted the moisture content
of the litter and thus ammonia volatilization.
A clear conclusion cannot be drawn from the data, however it can be seen from figure 5 showing
data from flock 5, that NH3 emissions were lower in the amended houses during the first 10 days
of brooding. Following this period, emissions were higher in the amended houses, when it would
be expected that the amendment would loose its effectiveness and stored NH3 would be released.
During the flock grow-out period, emissions were similar for both amended and unamended
7
houses. In no flock, did it appear that the application of the NaHSO4 litter amendment reduced
total emissions.
Scheduling of Total House Cleanout
At Site 2, all houses were cleaned out in September in contrast to Site 1 where the houses were
cleaned out over two flocks in spring. While definite conclusions can be drawn from the data, it
appears that reduced ventilation rates during cold weather may result in an accumulation of
nitrogen and moisture in the litter during these flocks. This nitrogen and moisture is stripped out
during summer flocks with much higher ventilation rates. At Site 1, despite lower ventilation
rates during winter, emissions were higher than those at Site 2. However cleaning out during
spring reduced emissions at Site 1 to less than those from Site 2 even with similar ventilation
rates. This can be seen by comparing figures 3 and 4.
CONCLUSION
While only broad guidance can be drawn for the data collected during this study due to
confounding of the effects and the discontinuous nature of the data record, it is clear that
commonly used management strategies will not substantially reduce ammonia emissions from
broiler houses. General conclusions that can be drawn include:

The use of new litter each flock resulted in almost no emissions in the first 6 days of each
flock and a reduced rate of increase in the emission rate thereafter.

The application of the NaHSO4 litter amendment did not appear to reduce the total
emissions during any flock.

Where there did appear to be a reduction of ammonia emissions due to the application of
the NaHSO4 litter amendment during the first ten days of the flock, there were greater
emissions in the following period, were it appeared that stored ammonia volatilized as the
effect of the litter amendment was exhausted.

Scheduling the annual house clean-out during early spring may reduce annual emissions
as stored nitrogen may be removed in the litter rather that volatilized and exhausted with
the higher ventilation rates required during summer. The availability of suitable land
application opportunities and capacity may limit this recommendation.
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8
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