2005 Poultry Science Association, Inc.
Management Strategies to Reduce
Air Emissions: Emphasis—Dust
and Ammonia
P. H. Patterson*,1 and Adrizal†
*Department of Poultry Science, The Pennsylvania State University, University Park,
Pennsylvania 16802; and †Department of Feed and Animal Nutrition,
Faculty of Animal Husbandry, University of Jambi, Jambi, Indonesia
Primary Audience: Production Managers, Nutrient Management Specialists, and
Environmental Engineers
SUMMARY
Air emissions generated by poultry production are numerous and can include dust, odors,
endotoxins, microorganisms, and numerous gases. Ammonia (NH3) emissions have the potential
to contaminate surface waters and are an environmental concern on both a local and global scale.
These emissions in and around poultry production facilities can be a health and performance issue
for birds and their caretakers. Dietary strategies can aid in the reduction of many airborne
emissions, including dust and ammonia. Management techniques to quell, capture, or eliminate these
air contaminants are numerous but vary in their cost, effectiveness, and practicality. Endotoxins,
microorganisms, and nitrogenous compounds also can adhere to dust particles. Techniques for
dust control include simple house cleaning, oil and water fogging, windbreaks, different filters,
precipitation, certain housing systems and equipment, and vegetative shelterbelts. Many of the
same strategies to reduce dust will also reduce ammonia losses as well. Simple procedures, including
good manure management, reducing stress and maintaining bird health, reduce nitrogenous losses.
Litter and manure amendments aid in reducing ammonia volatilization, and like those techniques
for dust control, poultry housing systems, biofilters, water filters, composting, and vegetative
shelterbelts also have potential for ammonia mitigation.
Key words: air emission, dust, particulate matter, ammonia, management strategy
2005 J. Appl. Poult. Res. 14:638–650
DESCRIPTION OF PROBLEM
Air emissions from poultry and livestock
production are numerous and may include dust
or particulate matter, odors, endotoxins, methane, H2S, CO2, H2O, and nitrogenous compounds, including ammonia [1, 2, 3]. Ammonia
emissions can be significant. Our own data gathered using mass balance techniques with commercial laying hens, pullets, broilers, and tur1
keys (Table 1) indicates that between 18 to 40%
of feed N is lost to the atmosphere mostly as
ammonia N [4, 5, 6, 7]. Ammonia emissions
have the potential for wet and dry deposition
and contamination of surface and ground waters
[8, 9, 10]. The US Environmental Protection
Agency estimates that 64 to 71% of ammonia
emissions are from livestock and poultry production [11]. In the Chesapeake Bay airshed, current
estimates indicate that poultry and livestock con-
To whom correspondence should be addressed: [email protected].
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639
TABLE 1. Partitioning (%) of feed nitrogen in commercial poultry1
Poultry
Laying hens
Pullets
Turkeys
Broilers
Feed N
Manure
or litter N
Carcass N
Egg N
Atmospheric N
100
100
100
100
25.01
43.20
28.00
30.56
0.84
25.30
46.00
51.08
34.07
—
—
—
40.01
31.50
26.00
18.36
1
Source: [4, 5, 6, 7].
tribute as much as 81% of the annual NHx atmospheric burden [12]. Nitrogen and sulfur oxide
compounds (NOx SOx) can be converted to nitric
and sulfuric acid and are factors in acid rain
formation [12]. Ammonia is, however, practically the only base in the gas phase of the atmosphere and reacts rapidly with available acids
mainly sulfuric, nitric, and sometimes hydrochloric, forming their corresponding salts [13].
If ammonia molecular concentration is less than
twice the sulfuric acid level, all available ammonia is transferred to the particulate phase to neutralize sulfuric acid clouds and droplets forming
ammonium bisulfate. If ammonia concentration
is greater than twice the sulfuric acid level, the
excess is available to react with other acid vapors
[13]. Nitrate and sulfate compete for available
ammonia-forming particulate aerosols that, depending on their concentration, can influence
inorganic particulate matter levels in the atmosphere [14].
The NRC National Academy of Science ad
hoc committee on air emissions from animal
feeding operations [15] recently summarized
their concerns listing key air pollutants and their
relative importance with respect to air quality
in different geospatial scales (Table 2). The primary air pollutant of concern on a global, national, and regional scale is ammonia because
of atmospheric deposition and haze. On a local
scale, ammonia generated by animal feeding operations is a minor concern because it is rarely
perceived at the low concentrations encountered
outside confinement poultry housing as a result
of dilution and dispersion after exhausting from
the building. However, a major concern at the
local level is odor because of its implications
for quality of life for people in the immediate
area. A significant concern is also placed on H2S
at the local level for health and haze considerations as it is often a component of odor and
particulate matter. Particulate matter (PM) 2.5
and PM10 are airborne particulate matter or dust
less than 2.5 and 10 µm in size. They can result
from combustion processes, but secondarily
when ammonia, SOx and NOx react in the atmosphere to form ammonium sulfate and nitrate,
they can contribute as much as half of the PM2.5.
Although odor and H2S can be significant concerns at the local level, they may not be a dominant concern with poultry compared with other
livestock species, as they do not have the impact
on human health and haze as do dust and PM.
In June 2004, the US Environmental Protection
Agency sent letters to state authorities with additional counties showing nonattainment of the
PM2.5 air quality standard (Figure 1). These
were the basis of their final designations in November 2004 [16].
The negative impacts of air contaminants on
poultry health and performance have been well
documented. Dust with airborne microorganisms, including bacteria, viruses, fungi, and
molds are concerns for respiratory disease. Endotoxins in litter are from the lipopolysaccharide
membrane fragments of gram-negative bacteria.
These inflammatory substances are capable of
soliciting neutrophil recruitment, macrophage
and complement activation, and histamine release [17]. Ammonia at various concentrations
has been reported to result in keratoconjunctivitis [18], greater circulating white blood cells,
and lymphocytic infiltration of the eye [19], increased susceptibility to airsacculitis [20] and
Newcastle disease [21], poor growth and feed
conversion [22, 23], and reduced egg production
[24]. A recent report by Wathes et al. [25] suggests ammonia can have implications for animal
welfare with potential damage to olfactory cells,
affecting the birds’ sensation of taste, their feeding behavior, and performance. However, other
researchers have noted little or no impact of
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640
TABLE 2. Potential importance of air emissions from animal feeding operations1
Area and scale of concern
Emission type
Global, national
and regional
Local property line
or nearest dwelling
NH3
N2O
NOx
CH4
VOC2
H2S
Particulate matter (PM), PM10
PM2.5
Odor
Major
Significant
Significant
Significant
Insignificant
Insignificant
Insignificant
Insignificant
Insignificant
Minor
Insignificant
Minor
Insignificant
Minor
Significant
Significant
Significant
Major
Primary effects
Atmospheric deposition, haze
Global climate change
Haze, atmospheric deposition, smog
Global climate change
Quality of human life
Quality of human life
Haze
Health, haze
Quality of human life
1
Source: [15].
Volatile organic compounds.
2
environmental ammonia at 30 and 90 ppm on
hen performance and egg quality [19] or on
broiler production [26], with the exception of
an increased feed:gain ratio at 60 vs. 0 ppm.
The health impacts of this same group of
airborne contaminants on people working in
poultry and livestock confinement settings have
also been well documented [18, 27, 28, 29, 30].
Symptoms include coughing, phlegm, eye irritation, dyspnea, congestion and discharge, chest
tightness, wheezing, sneezing, and headache resulting in fatigue, behavior changes, lost days at
work, and increased health and insurance costs.
Reduced pulmonary function in poultry workers,
including forced vital capacity, forced expiratory
volume, and forced expiratory flow, are primarily from obstructive disorders [29, 30]. Chronic
exposure to poultry and livestock airborne contaminants can result in hypersensitive lung disease, bronchial constriction, bronchitis, asthma,
and other immunological changes, resulting in
damage to epithelial and endothelial cells [30].
Donham et al. [29] concluded that the combined
negative health effects of dust and ammonia in
poultry housing are greater than their independent additive effects. They also concluded that
the Occupational Safety and Health Administration exposure limits for dust (15 mg/m3) and
ammonia (50 ppm) are too high, recommending
lower exposure limits for these combined substances at levels of 2.5 mg/m3 and 7 ppm, respectively [29].
There are numerous dietary strategies for
poultry aimed at reducing the generation and
emission of ammonia in the production setting
[31, 32, 33, 34, 35, 36]. For dust and particulates,
experience has indicated that adding dietary fat
can reduce feed dust for the animals and their
caretakers [37, 38, 39, 40]. Although dietary
strategies are important first lines of action that
can significantly reduce air emissions, they are
not the focus of this review. Management techniques aimed at reducing or capturing air contaminants generated in poultry production are
numerous but vary in cost, effectiveness, and
practicality. For the reasons stated above, we
will be addressing management strategies aimed
at reducing air emissions with an emphasis on
dust and ammonia in this article.
MANAGEMENT STRATEGIES
FOR REDUCING DUST
Reducing airborne contaminants and their
release requires several approaches to reduce
generation and emission and, finally, to enhance
their dispersion. Effective control usually relies
on more than 1 strategy beginning in the poultry
house, then manure storage, and on to land application. Best management practices begin with
reducing generation and emission. However, on
a local scale enhancing dispersion can be an
effective means of reducing the impact of
PM2.5, PM10, H2S, and other odors upon neighbors and others negatively affected by their close
proximity. Utilizing site planning, weather dispersion, and setback distances are effective
means of allowing natural dilution of odor, dust,
and gases. These same principles can be applied
to ammonia and other airborne contaminants,
although their negative impacts are primarily on
PATTERSON AND ADRIZAL: AIR EMISSIONS AND POULTRY PRODUCTION
641
FIGURE 1. The US Environmental Protection Agency nonattainment counties for PM2.5 air quality standards (June
2004) [16].
a regional, national, or global scale, requiring
preemptive strategies focusing on reducing their
generation and emission.
House Cleaning
A simple technique to reduce dust emissions
from poultry buildings is regular house cleaning,
including vacuuming and power washing between flocks, thereby reducing the volume and
potential for contamination of the air in the house
as well as air exhausted from the building [28,
37, 38]. Other potential benefits include reducing
the potential of disease transmission, improved
weight gain, feed conversion, and a reduction
of the number of birds condemned at slaughter
[41]. The main steps for house cleaning are remove equipment, remove litter or manure, dry
clean, wet wash, disinfect, and thoroughly clean
and disinfect the feeding and drinker systems
and then allow enough downtime for the building to dry and to make house and equipment
repairs and bait for rodents and other pests [42].
With dust and other airborne contaminants a
greater issue than ever before, perhaps a new
paradigm in house cleaning will be necessary
with greater frequency for all bird types and
cycles of production. Regular sweeping and vacuuming of poultry houses in locations where
dust, feathers, and dander collect would likely
improve air quality for birds and farm workers
as well.
Oil and Water Application
Sprinkling oil in swine barns has been successfully used to reduce dust (23 to 80%) and
other gases, including ammonia by 30% [43,
44]. Oil can be applied both manually with a
handheld sprayer or automatically using a per-
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642
manently installed sprinkler system [45]. It is
important that droplet size is not too large, resulting in poor oil distribution, or too small,
which may be a health hazard. According to
Takai and Pederson [46], droplet size should be
greater than 150 µm to obtain effective liquid
application. In housing for laying hens, an ultrasonic sprayer generating 7- to 150-µm diameter
particles with a 2% solution of emulsified canola
oil significantly reduced dust with a diameter of
0.5 to 2 µm and 10 to 30 µm by 42 and 49%,
respectively [47]. The authors went on to measure the dust that settled in petri dishes and found
significantly greater amounts in the sprayed
house compared with the control. Very high levels of dust at diameters of 0.3 to 5.0 µm were
also measured in control and ultrasonic-sprayed
housing for floor-reared broilers (1.29 × 109 and
6.81 × 108 particles/m3, respectively). Although
the ultrasonic-sprayed house levels represent a
significant 47% reduction in dust concentration,
the authors cautioned they were still 100 times
that measured in the layer house [47]. Wachenfelt [48] compared dust levels in aviary systems
for hens in reference periods before and during
treatment spraying periods with pure water or
oil and water mixtures with 10% oil. The oil
and water mixtures reduced dust concentrations
approximately 50%, whereas the pure water applications reduced dust to about one-third that
of the reference periods. Ellen et al. [49] measured the impact of modifying relative humidity
on dust levels in broiler houses. In houses fitted
with fogging equipment, inhalable dust levels
were reduced 13 and 22.5% during fall and
spring flocks, when the buildings were maintained at 75% RH, compared with control buildings [49]. However, no differences were observed for respirable dust between the buildings.
Windbreaks
One simple strategy of enhancing the dispersion of dust and odor on a local scale are the
use of natural and artificial windbreaks [37, 50,
51]. They reduce dust and odor downwind by
both dropping particulates and lifting emissions
into the upper air stream for greater dispersion
and dilution. Natural windbreaks comprised of
trees and shrubs take 3 to 10 yr to grow, offer
visual protection for the farm, and also trap particulates and odor [50]. Artificial windbreak
walls are erected downwind from exhaust fans to
reduce dust and odor emissions onto neighboring
property [37]. Windbreak walls may not be
suited for poultry buildings equipped with multiple fans at nonuniform locations around the
building and are better suited for houses with
concentrated fans, such as tunnel-ventilated
houses. They can be built with various materials
covering a wood or steel frame, such as plywood,
tarps, or straw framed with wood and held in
place with chicken wire. When walls are placed
3.0 to 6.1 m downwind of the fans, they work
by reducing the forward momentum of the exhausted air allowing dust and odor to settle out
at low air speeds near the building. At higher
air speeds, the wall provides a sudden vertical
lift for dispersion of exhausted air to mix with
fresh outside air [50].
Biomass Filters
Biomass filters are a cross between a windbreak wall and biofilter that will be addressed
later in the section on Management Strategies for
Reducing Ammonia. They are simply vertical
barriers in close proximity to building exhaust
fans made from inexpensive materials, such as
chopped cornstalks, corncobs, loose straw, or
other materials. Biomass filters use the principle
that if dust is removed from the ventilation exhaust, a large amount of odor will be trapped
with the dust. Researchers have tested the filters
in swine buildings under cold weather ventilation conditions with significantly reduced dust
(52 to 83%) and odor levels (43 to 90%) [37].
However, the performance of the biomass filters
under high ventilation rates or with poultry species is not known. Nevertheless, their successful
application in reducing dust and odor in swine
barns [52] may also be applicable in poultry
houses.
Water Filters
Particulate emissions from poultry houses
can be trapped in filters utilizing water as a
scrubbing media. These systems have been used
in industrial air pollution control and have the
potential to scrub dust, ammonia, sulfur compounds, and nitrous oxides from poultry houses.
In a tunnel-ventilated swine building, fitted with
evaporative cooling pads across the entire end
PATTERSON AND ADRIZAL: AIR EMISSIONS AND POULTRY PRODUCTION
of the building 1.2 m upwind from the exhaust
fans, researchers measured a 20 and 60% reduction in total dust and a 33 and 50% reduction
in ammonia levels at high and low ventilation
rates, respectively [53]. Other systems have used
2 filter banks made from cellulose elements with
water flowing from top to bottom through the
first element and acidified water through the second [54]. Preliminary observations reduced dust
(PM10) ammonia and odor from 70 to 80% in
the exhaust air from a piggery. Reports on these
systems in poultry houses are lacking, but their
application and impact in poultry houses could
be considerable, since the water filters aid in
minimizing not only dust and odor but also ammonia, the gas of most concern in poultry operations.
Electrostatic Precipitation
Electrostatic charging of air in confined
spaces has been used to reduce dust levels in
both swine and poultry facilities [38, 55, 56].
These devices impart a negative charge to airborne particles, resulting in their precipitation
on grounded surfaces. Application of an electrostatic space charge system in a broiler breeder
house resulted in a 60% reduction in airborne
dust; total bacteria were reduced 76% and ammonia by 56% [57]. Egg samples collected from
this study showed less Salmonella contamination as well [57]. Other research with hatching
cabinets and caged layers utilizing electrostatic
charging have reduced dust from 82.8 to 98.7%
and 36.6 to 65.6%, respectively, with particle
sizes ranging from 0.3 to 25 µm [38, 58]. These
authors have also demonstrated reduced airborne
levels of Salmonella enteritidis in rooms with
experimentally infected hens [59]. Although
technically feasible, the authors cautioned that
the economic merits of electrostatic charging in
commercial poultry houses still needs to be determined.
Poultry Housing Systems and Equipment
Takai et al. [2] measured airborne dust concentrations and emission rates in poultry and
livestock buildings and in England, Denmark,
Germany, and The Netherlands and determined
that cage systems for layers had significantly
less inhalable and respirable dust than did perch-
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TABLE 3. Inhalable and respirable dust emission rates
(mg/h 500 kg) from poultry buildings1
Bird and
housing type
Layer, cage
Layer, perch
Broilers, floor litter
Inhalable
dust
Respirable
dust
398–872
1,771–4,340
1,856–6,218
24–161
467–862
245–725
1
Range of values from England, Denmark, Germany, and
The Netherlands [2].
style systems. Also, floor-reared broiler houses
had more inhalable dust than either layer system
(Table 3). Respirable dust is composed of small
particles (<10 µm) that may be pulled deep into
the alveoli, whereas nonrespirable or inhalable
dust particles (>10 to 50 µm), which enter the
nose and throat during normal breathing, may
be found in upper airways [27, 60]. The authors
went on to report that both inhalable and respirable dust concentrations were higher in winter
than summer because of greater seasonal ventilation rates in summer. Inhalable and respirable
dust concentrations were greater in poultry housing compared with either pig or cattle buildings [2].
Wathes et al. [1] reported similar differences
between poultry housing systems, documenting
greater dust levels among floor-reared broilers
compared with perch or cage layer systems. In
addition, endotoxin levels in both the inhalable
and respirable fractions were greater in perch
systems for layers compared with either layers
in cages or floor-reared broilers [1]. These observations indicate there remain beneficial properties of cage layer systems in terms of air quality
for both poultry welfare and farmer health compared with popular perch-type systems or traditional floor-reared broilers. Other nontraditional
cage systems for broilers with manure belts that
run intermittently (8 cm/s per 3 h) removing
manure from the house demonstrated potential
benefits, including better air conditions, low levels of breast blisters, and bacterial contamination
of skin and feathers [61].
Vegetative Shelter Belts
Strategically planting trees, shrubs, and other
vegetation around poultry houses offers several
potential benefits according to Malone and VanWicklen [50]. Trees can foster better neighbor
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644
FIGURE 2. Merits of using vegetative shelter belts around poultry houses [50].
relations by filtering dust, feathers, odor, and
noises from the operation, providing a visual
screen from routine activities, and enhancing the
publics’ perception of the industry. Furthermore,
there are possible production benefits as a windbreak and a source of shade to reduce seasonal
temperature extremes and as a filter for airborne
pathogens for improved biosecurity (Figure 2).
Malone [62] reported a 3-row planting of bald
cypress (4.9 m high), Leyland cypress (4.3 m),
and red cedar (2.4 m) 9 m wide and 9 m from
2 tunnel fans on a commercial broiler farm reduced air speed from 127.4 to 1.5 m/min from
the front to the back of the trees. Total dust
levels were reduced 53% (0.659 to 0.333 mg/
m3) and 50% (1.039 to 0.527 mg/m3) in years
2002 and 2003, respectively.
MANAGEMENT STRATEGIES
FOR REDUCING AMMONIA
The metabolic end product of protein and
nitrogen metabolism in the domestic fowl is uric
acid. Typical excreta contains 13 to 17 g/kg total
N on a DM basis, with 60 to 75% as uric acid
N, 0 to 3% urea N, 0 to 3% ammonium N, and
25 to 34% as undigested protein N [63]. The
breakdown of uric acid (C5H4O3N4 + 1.5O2 +
4H2O → 5CO2 + 4NH3) and protein is mediated
by microorganisms. The enzyme uricase is com-
monly present in microorganisms and specific
to this reaction. The first step in the breakdown
of uric acid is hydrolysis to allantoin (Figure 3).
Most uric acid breakdown is aerobic, although
a small fraction is anaerobic as well. Conditions
that favor uric acid decomposition by bacteria
include temperatures greater than 20°C, pH in
the range of 5.5 to 9.0, and litter moisture and
water activity of 40 to 60% and <0.625, respectively [63]. Although water activity (Aw), which
is the amount of water available for microbes to
start decomposition, is considerably important,
water potential is more readily measured and
indicative of the water interaction within the
manure or litter [63]. These same conditions that
favor the decomposition of uric acid favor the
growth and proliferation of pathogenic microorganisms, such as Salmonella and Escherichia
coli [64]. Therefore, a thorough understanding
of these principles is paramount to implementing
litter and other management strategies for reducing ammonia losses.
Reduce Stress and Maintain Bird Health
Bird health and status of the gastrointestinal
tract are critical for proper nutrient retention.
Temperature and humidity stressors are real
challenges and can occur with improper brooding conditions or equipment and poor ventilation
PATTERSON AND ADRIZAL: AIR EMISSIONS AND POULTRY PRODUCTION
645
ter must be controlled from rain, surface, and
ground water sources. In the case of turkeys that
may be on litter for 20 or more weeks, good
litter management includes frequent rototilling
to reduce litter moisture levels to 30% or less.
Lastly, proper ventilation in all seasons will exhaust bird moisture on a daily basis, minimizing
moisture accumulation in the litter. This principle of balancing ventilation rate with house temperature within the thermal neutral zone for
poultry or pigs was demonstrated by Vranken
et al. [65] to reduce potential yearly ammonia
emissions 8 to 13%. In their study, higher ventilation rates induced a greater discharge of inside
air and caused lower inside temperatures. However, for Belgian weather conditions, the effect
of the lower temperature was greater than the
effect of the higher ventilation rate and resulted
in lower ammonia emissions.
Manure and Litter Amendments
FIGURE 3. Aerobic breakdown of uric acid [63].
design, equipment, or practices. Exposure to viral, bacterial, and other agents can stress birds,
resulting in watery droppings, diarrhea, and poor
feed conversion. Healthy birds maintained in a
thermoneutral environment are better able to use
dietary nutrients to their fullest potential and
minimize flushing of dietary and endogenous
nitrogen and moisture. Lastly, bird density and
crowding can magnify other stressors, leading
to poorer nutrient use.
Manure and Litter Management
Simple management procedures can greatly
impact manure moisture and the loss of ammonia. Moisture contamination of litter can come
from excessively wet feces, and dietary factors
that control wet droppings are important factors.
Drinker management, including maintenance for
leaks and height adjustment, impacts litter moisture. Research has shown that litter dry matter
content is higher and nitrogen losses are reduced
with nipple drinkers compared with bell drinkers
[31, 32]. Exogenous water contamination of lit-
An important tool in modern broiler management is the use of litter amendments that can
trap and hold litter nitrogen using one of several
techniques, including adsorption, acidification,
or salts to manipulate microbial populations and
enzyme activities. Reece et al. [66], Terzich [67],
and Moore et al. [68] demonstrated the ability of
several compounds, including sodium bisulfate,
ferric chloride, ferrous sulfate, phosphoric acid,
superphosphate, and aluminum sulfate to reduce
ammonia volatilization from the litter of floorreared broilers. Work by Kim and Patterson [69]
demonstrated that ZnSO4, CuSO4, MgSO4, and
MnCl2 can all reduce microbial uricase activity.
Zinc sulfate was the most effective in reducing
manure pH and the growth of uric acid utilizing
bacteria. When added to fresh broiler manure,
ZnSO4 reduced ammonia volatilization and increased manure uric acid N and total N retention
in the samples by almost 2-fold. Dietary supplementation of Zn can also reduce ammonia losses
[70] and increase manure uric acid N and total
N retention [71]. However, these and other litter
amendments with trace elements, such as Cu
and Zn, may have issues for plant toxicity and
environmental contamination.
Wilson [72] reported on the application of
liquid alum in the pit of a commercial high-rise
hen house, utilizing RainBird irrigation nozzles
to spray 10 s every h. Ammonia levels at bird
646
height were reduced from 70 to 40 ppm within
20 min of the first application, and with additional time ammonia levels continued to fall in
a stairstep fashion to approximately 20 ppm by
3 h. Organic acids are another choice to acidify
litter and reduce ammonia volatilization. Ivanov
[73] treated broiler litter with 5% citric acid, 4%
tartaric acid, or 1.5% salicylic acid and reduced
litter pH below 5, reduced both litter and air
ammonia concentrations, and inhibited the
growth of E. coli, Salmonella enteritidis, Proteus, and Pseudomonas spp. (2.2 × 103 cfu g−1
of litter). The cost of the organic acid treatments
ranged from $0.08 to $0.10 per bird with 15
birds/m2 and a 2.5 feed conversion. Amendments with nitrifying bacteria have the potential
to reduce manure NH3 and NH4+ levels as bacteria oxidize them to nitrite and nitrate, NO2− and
NO3−, respectively [37, 74].
Other novel strategies we may see in the
future include immunizing birds against the enzymes responsible for ammonia formation. Pimentel and Cook [75] immunized broiler breeder
and Leghorn hens with jackbean urease enzyme.
The hens developed antibodies to the enzyme
and passed them on as maternal antibodies to
their chicks. The harmful effects of ammonia in
the intestinal tract were reduced by preventing
urea hydrolysis to ammonia by intestinal bacteria. Kim and Patterson [76] showed that it was
possible to immunize hens with microbial uricase and produce high levels of uricase-specific
antibodies in the egg yolk. This is the first enzymatic step in the natural hydrolysis of uric acid.
These antibodies (IgY) have the potential as manure amendments or as a dietary supplements
to reduce the breakdown of uric acid to urea.
Composting
Ammonia emissions during litter composting can be significant, increasing environmental
pollution and reducing fertilizer value. However,
composting at the right moisture, carbon:nitrogen ratio, and temperature with proper aeration
can reduce ammonia losses and retain fertilizer
value [77, 78, 79]. Among 4 types of carbon-rich
amendments for aerobic composting of poultry
manure, Mahimaraja et al. [79] found that wheat
straw and peat reduced ammonia losses by 33.5
and 25.8%, respectively, compared with untreated control manure and were superior to
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wood chips or paper waste as carbon amendments. The authors also compared adsorbent
amendments and determined that zeolite was a
more effective NH3 (or NH4) adsorbent than soil
and reduced NH3 losses by 60%. Extractable
NH4+−N was almost 1,000 times higher than
NO3−−N in all compost mixtures, suggesting little oxidation of NH4+ to NO3− (nitrification).
Total N levels in the compost at the end of the
experiment showed a loss of about 50% during
aerobic incubation but only 17% from NH3 volatilization, indicating N loss through denitrification could be considerably higher than through
NH3 volatilization. Other investigators have
shown that composting amendments, including
zeolites, calcium and aluminum salts, and acidifiers have improved nitrogen retention and reduced ammonia volatilization compared with
nonamended hen manure [80]. Properly done,
composting can bring litter to a stable end point
for overwinter storage and effectively reduce
ammonia losses to the atmosphere.
Poultry Housing Systems
Wathes et al. [1] reported differences in environmental ammonia levels between poultry
housing systems in the UK with greater average
concentrations in floor-reared broiler houses
compared with cage or perch systems for layers
at 24.2, 13.5, and 12.3 ppm, respectively. Similarly ammonia emissions from housing systems
for laying hens with litter were about 4 times
higher than with battery cages [63]. Focusing
on ammonia emissions related to building design
in his review of literature, Groot Koerkamp [63]
found that battery systems with manure belts
underneath the cages would reduce the emission
rate of ammonia to 34 g/hen per year compared
with deep pit housing systems at 386 g/hen per
year. The belted system was even more efficient
at reducing ammonia losses if the manure was
removed at least twice daily instead of twice
weekly [63]. Novel housing systems for broilers
in The Netherlands that used a trampoline floor
with air circulation through the floor for rapid
drying of droppings increased litter DM to almost 80% compared with 56% in conventional
housing and reduced ammonia levels in half
[81]. The efficiency of managing manure and
emissions using a net-belted floor for broilers to
eliminate the manure from the house was also
PATTERSON AND ADRIZAL: AIR EMISSIONS AND POULTRY PRODUCTION
demonstrated by Okumura and Hosoya [61].
These observations indicate there remain beneficial properties of belted-cage or perch systems
for layers and novel nonlitter systems for broilers
in terms of air quality for both poultry welfare
and farmer health compared with traditional
floor-rearing facilities.
Biofilters
Biofilters are a proven technology to filter
dust, ammonia, hydrogen sulfide, and odors [37].
They rely on a biological filter material usually
organic in nature with a resident microbial film
that aids in the degradation of gases and odors
in addition to its trapping function. The contaminants are then oxidized to produce biomass, CO2,
H2O, and inorganic salts. Straw, compost, and
woodchips are good filter materials as long as
particle size and porosity is maintained for good
airflow without significant pressure drop and
added amperage draw on the fans. Passing the
exhaust air from a pig-finishing unit through a
humidifier and biofilter consisting of a wood
chip media (>20 mm) with a moisture content
of >63% helped reduce odor and ammonia by
77 to 95% and 54 to 93%, respectively [82].
The pressure drop across the biofilter ranged
from 14 to 64 Pa. The authors observed greater
odor and ammonia concentrations when the
moisture level in the filter medium dropped below 50%. Others have suggested best management practices for the systems include maintaining media moisture levels at approximately
50% [83] and implementing rodent control programs to prevent infestation. In swine facilities
fitted with biofilters, Nicolai and Jani [84] measured a 53, 80, and 83% reduction in ammonia,
hydrogen sulfide, and odor, respectively. Performance results under cold and mild weather ventilation have been acceptable; however, there were
challenges under high airflow situations, resulting in elevated static pressure, as airflow is
restricted through the media.
Water Filters
Emissions can be trapped in filters utilizing
water as a scrubbing media. These systems have
been used for control of industrial air pollution
and have the potential to scrub dust, ammonia,
sulfur compounds, and nitrous oxides from poul-
647
try houses. In a tunnel-ventilated swine building,
fitted with evaporative cooling pads across the
entire end of the building 1.2 m upwind from
the exhaust fans, researchers measured a 33 and
50% reduction in ammonia levels and a 20 and
60% reduction in total dust at high and low
ventilation rates, respectively [53]. Another system reported in the literature used 2 filter banks
made from cellulose elements with water flowing from top to bottom through the first element
and acidified water through the second [54]. Results indicated ammonia, odor, and dust (PM10)
were reduced from 70 to 80% in exhaust air of
a swine building. While we are not aware of any
poultry examples using water filters, they may
have application once their economic and technical practicality is demonstrated.
Ozonation
Ozone (O3) is a powerful oxidizing agent
and a natural germicide. Ozone in the upper
atmosphere protects the earth from harmful solar
radiation; however, it is also a toxic gas at high
levels here on the surface. Researchers have
demonstrated its ability to react with other gases
reducing odor intensity, ammonia (15 to 58%),
and dust (58%) in swine facilities [37]. Although
not used in commercial practice, future ozone
evaluations and applications with poultry would
be useful.
Vegetative Shelter Belts
As previously stated, trees, shrubs, and other
vegetative materials strategically planted around
poultry houses have the potential to foster better
neighbor relations by filtering dust, feathers,
odor, and noises [50]. Potential environmental
benefits include reduced atmospheric ammonia
losses and surface and groundwater contamination. A demonstration site on the Delmarva Peninsula has shown a 67% reduction in ammonia
levels downwind of the vegetative filter belt
planted on commercial broiler farms [62]. The
ability of plant materials to filter, adsorb, or
incorporate airborne ammonia remains to be
documented on commercial poultry farms, although there are other data sets of literature that
suggest plants differ in their sensitivity and ability to use atmospheric ammonia [85, 86, 87, 88,
89, 90]. Work with vegetative filter belts for
JAPR: Symposium
648
poultry farms is ongoing in Delaware, Iowa,
and Pennsylvania with a USDA research and
outreach project. Furthermore, there are other
possible production benefits for commercial
poultry as a windbreak and a source of shade to
reduce seasonal temperature extremes and as a
filter for airborne pathogens for improved biosecurity.
CONCLUSIONS AND APPLICATIONS
1. The goals of all strategies aimed at reducing air emissions are ultimately the welfare and
performance of the birds, the comfort and health of caretakers and neighbors, and the preservation
of air and water quality on a local, regional, and global scale.
2. Reducing airborne contaminants requires several approaches to first reduce their generation,
emission, and, in some instances, enhance their dispersion to reduce concentrations at bird and
worker level.
3. Dust management begins with simple house cleaning, oil, water, and electrostatic precipitation,
and various filter techniques, including vegetative shelter belts as a last measure to trap dust
and particulates leaving the farm.
4. Management strategies for ammonia are equally numerous and include good bird and manure
management, the use of litter amendments, poultry housing systems that impact manure moisture and ammonia emissions, biofilters, water filters, and vegetative shelter belts for adsorption
and incorporation of nitrogenous compounds.
5. Although regulations concerning particulates, ammonia, and other gases are already in place,
their application and interpretation for animal agriculture remains to be defined. Furthermore,
only regulatory pressure will drive the application of dust and ammonia mitigation strategies
and only then will the cost-to-benefit ratio of these techniques be realized.
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