Published November 24, 2014
Ammonia and hydrogen sulfide emissions
from swine production facilities in North America: A meta-analysis1
Z. Liu,*2 W. Powers,† J. Murphy,* and R. Maghirang*
*Department of Biological and Agricultural Engineering, Kansas State University, Manhattan 55506; and †Department
of Animal Science and Biosystems and Department of Agricultural Engineering, Michigan State University, East Lansing 48824
Abstract: Literature on NH3 and H2S emissions
from swine production facilities in North America was
reviewed, and a meta-analysis was conducted on measured emissions data from swine houses and manure storage facilities as well as concentration data in the vicinity
of swine production facilities. Results from more than
80 studies were compiled with results from the 11 swine
sites in the National Air Emissions Monitoring Study
(NAEMS). Data across studies were analyzed statistically using the MIXED procedures of SAS. The median
emission rates from swine houses across various production stages and manure handling systems were 2.78 and
0.09 kg/yr per pig for NH3 and H2S, respectively. The
median emission rates from swine storage facilities were
2.08 and 0.20 kg/yr per pig for NH3 and H2S, respectively. The size of swine farm that may trigger the need to
report NH3 emissions under the Emergency Planning and
Community Right-to-Know Act (EPCRA) is 3,410 pigs
on the basis of the median NH3 emission rate (4.86 kg/yr
per pig), but the threshold can be as low as 992 pigs on the
basis of the 90th-percentile emission rates (16.71 kg/yr
per pig). Swine hoop houses had significantly higher NH3
emission rate (14.80 kg/yr per pig) than other manurehandling systems (P < 0.01), whereas deep-pit houses had
the highest H2S emission rate (16.03 kg/yr per pig, P =
0.03). Farrowing houses had the highest H2S emission
rate (2.50 kg/yr per pig), followed by gestation houses,
and finishing houses had the lowest H2S emission rate
(P < 0.01). Regression models for NH3 and H2S emission
rates were developed for finishing houses with deep pits,
recharge pits, and lagoons. The NH3 emission rates increased with increasing air temperature, but effects of air
temperature on H2S emission rates were not significant.
The recharge interval of manure pits significantly affected
H2S but not NH3 emission rates. The H2S emission rates
were also influenced by the size of the operation. Although
NH3 and H2S concentrations at the edge of swine houses
or lagoons were often higher than corresponding acute or
intermediate minimum risk levels (MRL), they decreased
quickly to less than corresponding chronic or intermediate MRL as distances from emission sources increased.
At the distances 30 to 1,185 m from emission sources, the
average ambient concentrations for NH3 and H2S were
46 ± 46 µg/m3 and 4.3 ± 8.6 µg/m3 respectively.
Key words: ammonia, emission, hydrogen sulfide, manure, meta-analysis, swine
© 2014 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2014.92:1656–1665
doi:10.2527/jas2013-7160
Introduction
Air emissions from swine production facilities
have received considerable attention because of human health and environmental implications. The major
farm emissions of interest include ammonia (NH3) and
hydrogen sulfide (H2S). Hydrogen sulfide is of inter1Funding for this work was provided by the National Pork Board
(NPB) Project 12-002. This is contribution 14-083-J from the Kansas
Agricultural Experiment Station.
2Corresponding author: [email protected]
Received September 17, 2013.
Accepted January 8, 2014.
est mainly at the local level because of health concerns,
whereas NH3 has regional-scale impacts on ecosystems (NRC, 2003). Air emissions from industries are
subject to permitting requirements under the Clean Air
Act (CAA) as well as reporting requirements under the
Emergency Planning and Community Right-to-Know
Act (EPCRA) and the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA)
if emissions reach specified thresholds; for example, operations that exceed 45.4 kg/d (100 lb/d) NH3 or H2S
emissions are required to report under EPCRA. Accurate
quantification of farm emissions is essential to ensure
compliance with the regulatory requirements, but direct
1656
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Ammonia and hydrogen sulfide emissions from swine facilities
measurements of farm emissions are expensive and difficult. Fortunately, a large volume of published studies on
NH3 and H2S emissions from swine production facilities
are available for a meta-analysis. Meta-analysis is a quantitative statistical analysis of a collection of results from
individual previous studies for the purpose of integrating
the findings. Results from meta-analyses are usually more
robust and have less bias than individual studies because
of improved statistical power (Cohn and Becker, 2003;
Garg et al., 2008).
The objective of this study was to review published literature on NH3 and H2S emissions from swine production
facilities in North America and to conduct a meta-analysis
that integrates results of independent studies. Measured
emissions data from both swine houses and manure storage facilities as well as concentration data in the vicinity of
swine production facilities were included in the study.
Materials and Methods
Literature Search and Data Extraction
Multiple strategies were undertaken to identify potentially eligible studies to be included in the meta-analysis.
The inclusion criteria were that studies must have been conducted in North America and must have reported measured
NH3 or H2S emission data from swine production facilities,
including manure storage systems, or concentration data in
the vicinity of swine facilities. Data from reports of the 11
swine sites in the National Air Emissions Monitoring Study
(NAEMS) were included in the database. Two individuals
independently conducted the search processes and screened
the studies by reading the title and abstract to select studies
for full review according to the inclusion criteria.
The included studies were distributed to a group of
7 trained analysts for data extraction. Standard data extraction sheets were developed for consistency. Emission
data were extracted following the protocol presented in
Table 1. Some studies provided emission data from different sites or under different settings; in these cases, more
than 1 data point was extracted from 1 study. Each study
was reviewed in duplicate by 2 individual analysts for
quality control. The author met with all analysts regularly
to address issues during the data extraction process. Data
quality was checked and disagreements were resolved by
consensus between the analysts or by the author. After the
data extraction spreadsheets were completed by the group
of analysts, 1 of the analysts synthesized the completed
data extraction spreadsheets from different analysts, and
the process was reviewed by the authors. As a result of the
data review and extraction processes, a meta-analysis database was created. Emission data for NH3 and H2S were
compiled into the 2 emission sources (swine houses and
manure storage facilities). Air concentration data were
Table 1. Emission data extraction protocol
Categories of data
Information on the paper
Name of authors
Year of publication
Title of the study
Information on emission sources
Emission source type
Stage of production
Ventilation type
Size of operation
Average pig weight
Area of manure storage facilities
Temperature
Extracted values
Input the text
Input numeric values
Input the text
Type of swine house manure systems:
select from deep pit, dry,1 hoop, drain
pit, or recharge pit with frequency recorded; type of manure storage facilities:
select from lagoon or slurry storage
Select from gestation, farrowing, nursery, and finishing
Select from mechanical and natural
Input number of animals
Input numeric values (kg)
Input numeric values (m2)
Input indoor temperatures for swine
house, ambient temperatures for manure
storage facilities, in °C
Treatment
Record any strategies applied that may
affect emissions
Information on the measurement
Select from traditional methods,2
OP-FTIR method,3 micrometeorologimethods
cal method, inverse dispersion modeling method, SF6 (sulfur hexafluoride)
tracer method,4 RPM method,5 and bLS
method6
Average emission rates and standard Input numeric values and units
deviation for NH3 and H2S
1In a dry manure handling system, manure is handled as a solid, collected
and stored temporarily on solid floors and removed regularly.
2Emission rate was calculated as the product of concentration and ventilation rate, with or without a chamber.
3The plane-integrated concentration data from open-path Fourier transform infrared spectrometry (OP-FTIR), along with wind speed and direction,
were analyzed using an emission flux computational method.
4CH and SF concentration were measured at downwind sites, and CH
4
6
4
emission rates were determined using the ratio of measured concentration and
known source strength of SF6.
5Radial plume mapping method that was used for determining lagoon
emission rates in National Air Emissions Monitoring Study (NAEMS) sites.
6Backward Lagrangian stochastic method that was used for determining
lagoon emission rates in NAEMS sites.
compiled separately and included sampling locations and
distances from emission sources.
Data Analysis
Various units of emission data were used in the literature.
To perform statistical analysis and to compare the emission
data between different studies, the units of measured emission data were converted to kilograms per year per pig and
kilograms per year per AU (AU is an animal unit corresponding to 500 kg body mass) for emissions from swine
houses and to kilograms per year per pig and kilograms per
year per square meter for emissions from manure storage fa-
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Liu et al.
Table 2. Emission rates of NH3 and H2S from swine houses and manure storage facilities
Item
NH3
Swine houses
Manure storage
facilities
H2S
Swine houses
Manure storage
facilities
Unit1
All studies (including NAEMS)
Range2
Mean
Median
Range2
NAEMS
Mean
Median
kg/yr per pig
kg/yr per AU
kg/yr per pig
kg/yr per m2
0.33 to 31.6 (97)
0.79 to 124.2 (101)
0.00 to 23.23 (74)
0.00 to 7.28 (72)
3.95 ± 4.51
20.64 ± 18.09
3.83 ± 4.43
1.68 ± 1.66
2.78
16.43
2.08
1.08
0.70 to 10.73 (16)
1.75 to 24.33 (16)
2.66 to 23.23 (6)
0.89 to 7.28 (6)
3.53 ± 2.21
15.09 ± 7.97
11.82 ± 7.50
2.90 ± 2.35
2.97
16.54
12.06
2.39
kg/yr per pig
kg/yr per AU
kg/yr per pig
kg/yr per m2
0.00 to 3.12 (65)
0.00 to 11.09 (70)
0.00 to 1.33 (27)
0.00 to 0.70 (30)
0.26 ± 0.56
1.08 ± 1.07
0.33 ± 0.37
0.18 ± 0.21
0.09
0.55
0.20
0.07
0.09 to 3.12 (16)
0.28 to 6.26 (16)
0.05 to 1.10 (6)
0.00 to 0.34 (6)
0.78 ± 1.02
2.24 ± 2.18
0.39 ± 0.44
0.12 ± 0.13
0.26
1.39
0.16
0.09
1AU = animal unit corresponding to 500 kg body mass.
2Values in parentheses represent numbers of data points in each category.
cilities. When unit conversion was not possible because of a
lack of key information, the original emission data were excluded from statistical analysis. A full list of included studies and completed data extraction spreadsheets are available
to allow for independent scrutiny of the process.
Data from the NAEMS sites were results of 2-yr
continuous monitoring using consistent methods, and
statistics from these studies were compiled separately
to be compared with the statistics of all studies (including NAEMS). Data across studies were analyzed statistically using the MIXED procedures of SAS (SAS for
Windows, version 9.3, SAS Inst. Inc., Cary, NC). Study
(or publication) was treated as a random variable. The ratios of emission rate over standard deviation were used
as a weighting variable. Data points with relatively small
standard deviations were given more weight in the analysis. Effects of production stage and manure handling/
storage system on emission rates were examined using
Tukey’s test. Significant effects were declared at P < 0.05.
Multilinear regression models were developed for certain
emission sources to reflect the effects of indoor or ambient air temperature, average pig weight, size of operation
(number of pigs), area of manure storage, recharge interval of manure pits (number of days before manure pits are
drained and recharged with water or lagoon effluent), etc.
A backward-elimination process was used to remove the
confounded terms and to reduce nonsignificant terms one
by one. When a regression model failed to pass normality tests, a natural log transformation was applied to the
response variable (emission rate).
Results and Discussion
Statistics of NH3 and H2S Emissions from
Swine Houses and Manure Storage Facilities
The ranges, means, and medians of NH3 and H2S
emission rates for swine houses and manure storage
facilities are presented in Table 2. Large variations in
emission rates were observed. Histograms of NH3 and
H2S emission rates for swine houses and manure storage facilities all showed a positively skewed distribution (Fig. 1 to 4). The median emission rates were more
robust, and the means were all larger than the medians
because of a few large values.
The median NH3 emission rate for swine houses was
2.78 kg/yr per pig, but the highest emission rate was 11
times higher. The median NH3 emission rate for swine
manure storage facilities was 2.08 kg/yr per pig, and the
highest emission rate was 11 times higher. The median
NH3 emission rate of the NAEMS swine houses was comparable with the median of all studies; however, the median NH3 emission rate of the NAEMS manure storage facilities was 5.8 times higher than the median of all studies.
Results showed NH3 emission rates for manure storage
facilities from the NAEMS sites were significantly higher
than those from other studies when emission rates were
expressed in kilograms per year per pig (P < 0.01), but the
difference was not significant when emission rates were
expressed in kilograms per year per square meter (P =
0.10). The discrepancy between data from the NAEMS
sites and those from other studies may be related to the
different methods of measurement. The NH3 emission
rates of the NAEMS manure storage facilities were determined using the radial plume mapping (RPM) method,
whereas other studies used the traditional method (emission rate was calculated as the product of concentration
and ventilation rate), micrometeorological method, openpath Fourier transform infrared spectrometry (OP-FTIR),
or inverse dispersion modeling. Further investigation is
needed to explain the discrepancy.
The median H2S emission rate for swine houses was
0.09 kg/yr per pig, but the highest emission rate was 35
times higher. The median H2S emission rate for swine
manure storage facilities was 0.20 kg/yr per pig, and the
highest emission rate was 7 times higher. The H2S emis-
Ammonia and hydrogen sulfide emissions from swine facilities
1659
Figure 1. Histogram of measured emission rates of NH3 from swine houses.
sion rates from the NAEMS sites were not significantly
different from those in other studies.
Emission Rates from Swine Houses: Effects of
Production Stage and Manure Handling System
Means and least squares means of NH3 and H2S emission rates from swine houses for various production stages
and manure handling systems are presented in Table 3.
Swine hoop houses had significantly higher NH3 emission
rates than other manure handling systems (P < 0.01 for
NH3 emission rates in both kg/yr per pig and kg/yr per AU).
Effects of production stages (gestation, farrowing, nursery,
or finishing) were not significant for NH3 emission rates
from swine houses (P = 0.23 and 0.15 for NH3 emission
rates in kg/yr per pig and kg/yr per AU, respectively).
Deep-pit houses had higher H2S emission rates than
other manure handling systems (P = 0.03 and <0.01 for
H2S emission rates in kg/yr per pig and kg/yr per AU,
respectively). Farrowing houses had the highest H2S
emission rates, followed by gestation houses, and finishing houses had lowest H2S emission rates, regardless of
whether emission rates were expressed in kilograms per
year per pig or kilograms per year per AU (P < 0.01 in
both cases). The effect of production stage on H2S emission rates observed in the meta-analysis contradicted the
findings of Rahman and Newman (2012), who reported
that both NH3 and H2S emission rates were higher in the
Figure 2. Histogram of measured emission rates of NH3 from swine manure storage facilities.
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Liu et al.
Figure 3. Histogram of measured emission rates of H2S from swine houses.
gestation barns than in the farrowing barns. In their study,
the gestation barns had deep-pit systems, and the farrowing barns had shallow pull-plug-type pits that drained
manure into the corresponding gestation barn pits every
3 wk; therefore, the variation observed in H2S emission
rates from barns were likely the result of different manurehandling systems as well as different production stages.
and 0.30, respectively) or H2S emission rates (in kg/yr
per pig, P = 0.47 and 0.13, respectively; or kg/yr per m2,
P = 0.06 and 0.60, respectively). Harper et al. (2006)
reported that NH3 emission rates on an animal basis increased as pigs aged, with nursery animals having the
lowest rates and sows having the highest, agreeing with
the results of this meta-analysis.
Emission Rates from Manure Storage Facilities:
Effects of Production Stage and Storage Type
Regression Models for NH3 and H2S Emission Rates
Means and least squares means of NH3 and H2S
emission rates from manure storage facilities for various production stages and storage types are presented
in Table 4. No storage type or production stage effects
were observed for NH3 emission rates (in kg/yr per pig,
P = 0.45 and 0.24, respectively; or kg/yr per m2, P = 0.75
Regression models for NH3 and H2S emission rates
were developed for finishing houses with deep pits, recharge
pits, and lagoons (Table 5) to reflect the effects of indoor or
ambient air temperature, average pig weight, size of operation (number of pigs), area of manure storage, recharging
interval of manure pits, etc. The indoor air temperatures
ranged from 8°C to 28°C, average pig weights ranged from
Figure 4. Histogram of measured emission rates of H2S from swine manure storage facilities.
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Ammonia and hydrogen sulfide emissions from swine facilities
Table 3. Means and least squares means of NH3 and H2S emission rates from swine houses by various production
stages and manure handling systems1
Swine house type
Gestation
Hoop
Dry
Deep pit
Recharge pit
Drain pit
Least squares mean
(0)
(0)
5.85 ± 5.13 (3)
14.61 ± 14.39 (4)
3.44 ± 0.09 (2)
6.69 ± 1.06 (9)
Hoop
Dry
Deep pit
Recharge pit
Drain pit
Least squares mean
(0)
8.67 ± 1.94 (2)
10.59 ± 6.54 (7)
7.39 ± 1.23 (2)
8.61 ± 0.23 (2)
20.53 ± 6.88 (13)
Hoop
Dry
Deep pit
Recharge pit
Drain pit
Least squares mean
(0)
(0)
1.709 ± 1.503 (3)
0.110 ± 0.014 (2)
0.275 ± 0.007 (2)
1.098 ± 0.245b (7)
Hoop
Dry
Deep pit
Recharge pit
Drain pit
Least squares mean
(0)
0.730 (1)
2.309 ± 2.063 (7)
0.304 ± 0.039 (2)
0.688 ± 0.675 (2)
1.791 ± 0.822a (12)
Farrowing
Finishing
NH3 emission rates, kg/yr per pig
(0)
12.93 ± 0.89 (2)
(0)
4.19 ± 4.77 (7)
7.030 (1)
3.57 ± 2.00 (36)
7.80 ± 10.97 (3)
2.38 ± 1.48 (32)
2.18 ± 2.09 (2)
1.32 ± 0.40 (3)
5.46 ± 1.74 (6)
4.89 ± 0.49 (80)
NH3 emission rates, kg/yr per AU
(0)
69.18 ± 8.22 (2)
(0)
32.38 ± 40.70 (7)
17.18 (1)
24.67 ± 13.52 (34)
4.08 ± 4.66 (2)
17.95 ± 13.26 (32)
2.51 ± 2.63 (6)
7.81 ± 2.02 (3)
16.90 ± 9.13 (9)
32.95 ± 3.83 (78)
H2S emission rates, kg/yr per pig
(0)
0.015 ± 0.004 (2)
(0)
0.017 ± 0.007 (6)
1.065 (1)
0.136 ± 0.127 (25)
2.790 (1)
0.071 ± 0.057 (17)
1.375 ± 0.007 (2)
0.023 ± 0.006 (3)
2.499 ± 0.309c (4)
-0.012 ± 0.121a (53)
H2S emission rates, kg/yr per AU
(0)
0.078 ± 0.004 (2)
(0)
0.121 ± 0.048(6)
2.604 (1)
1.019 ± 0.912 (24)
7.707 (1)
0.525 ± 0.391 (17)
1.703 ± 1.737 (4)
0.137 ± 0.038 (3)
5.056 ± 0.960b (6)
0.410 ± 0.460a (52)
Nursery
Least squares mean
(0)
(0)
0.66 (1)
0.860 (1)
(0)
(2)
14.80 ± 1.97b (2)
3.26 ± 1.22a (7)
4.30 ± 0.90a (41)
2.90 ± 0.80a (40)
3.13 ± 0.84a (7)
(0)
(0)
16.04 (1)
(0)
(0)
(1)
73.62 ± 13.69b (2)
8.05 ± 9.13a (9)
16.03 ± 5.60a (43)
8.77 ± 4.99a (36)
10.83 ± 4.96a (11)
(0)
(0)
0.455(1)
(0)
(0)
(1)
1.457 ± 0.378a,b (2)
1.224 ± 0.309a,b (6)
1.545 ± 0.205b (30)
0.970 ± 0.183a,b (20)
0.778 ± 0.190a (7)
(0)
(0)
11.089 (1)
(0)
(0)
(1)
3.690 ± 1.173a,b (2)
2.132 ± 1.186a,b (6)
4.068 ± 0.686b (33)
1.450 ± 0.620a (20)
0.754 ± 0.601a (9)
a–cValues
1Values
within the same effect section without a common letter differ significantly (P < 0.05).
in parentheses represent the number of data points in each category. AU = animal unit corresponding to 500 kg body mass.
Table 4. Means and least squares means of NH3 and H2S emission rates from swine manure storage facilities by various production stages and storage systems1
Storage system
NH3 emission rates, kg/yr per pig
Lagoon
Slurry tank
Least squares mean
NH3 emission rates, kg/yr per m2
Lagoon
Slurry tank
Least squares mean
H2S emission rates, kg/yr per pig
Lagoon
Slurry tank
Least squares mean
H2S emission rates, kg/yr per m2
Lagoon
Slurry tank
Least squares mean
1Values
Gestation
Farrowing
(0)
(0)
(0)
8.92 ± 6.68 (10)
(0)
6.00 ± 3.79 (10)
(0)
(0)
(0)
Nursery
Least squares mean
3.70 ± 3.74 (47)
1.85 ± 2.28 (12)
4.36 ± 1.51 (59)
0.020 (1)
0.45 ± 0.38 (4)
2.19 ± 1.89 (5)
5.35 ± 1.53 (58)
3.01 ± 2.96 (16)
2.26 ± 1.69 (11)
(0)
4.27 ± 1.71 (11)
1.59 ± 1.81 (45)
1.67 ± 1.15 (11)
2.47 ± 0.76 (56)
0.030 (1)
1.35 ± 1.30 (4)
3.04 ± 0.88 (5)
3.02 ± 0.68 (57)
3.50 ± 1.49 (15)
(0)
(0)
(0)
0.387 ± 0.321 (8)
(0)
0.516 ± 0.278 (8)
0.256 ± 0.344 (13)
0.438 ± 0.554 (5)
0.774 ± 0.109 (18)
(0)
0.204 (1)
0.121 ± 0.271 (1)
0.388 ± 0.155 (21)
0.554 ± 0.181 (6)
(0)
(0)
(0)
0.128 ± 0.117 (10)
(0)
0.374 ± 0.115 (10)
0.121 ± 0.160 (14)
0.378 ± 0.300 (5)
0.450 ± 0.042 (19)
(0)
0.656 (1)
0.556 ± 0.114 (1)
0.360 ± 0.063 (24)
0.660 ± 0.071 (6)
in parentheses represent numbers of data points in each category.
Finishing
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Liu et al.
Table 5. Regression models for NH3 and H2S emission rates from various emission sources
Emission sources
Finishing houses with deep pits
Finishing houses with recharge pits
Lagoons for finishing operations
Regression model1
NH3 emission rates in kg/yr per pig = EXP (-0.63 + 0.019W + 0.025Ti)
NH3 emission rates in kg/yr per AU = EXP (2.69 + 0.026Ti)
H2S emission rates in kg/yr per pig = EXP (-3.45 + 0.0024W + 0.00038N)
H2S emission rates in kg/yr per AU = EXP (-1.10 + 0.000061N)
NH3 emission rates in kg/yr per pig = EXP (-1.42 + 0.013W + 0.056Ti)
NH3 emission rates in kg/yr per AU = EXP (1.55 + 0.055Ti)
H2S emission rates in kg/yr per pig = EXP (–5.93 + 0.038W + 0.047R)
H2S emission rates in kg/yr per AU = EXP (-2.83 + 0.022W + 0.049R)
NH3 emission rates in kg/yr per pig = EXP (-0.38 + 0.070Ta)
NH3 emission rates in kg/yr per m2 = EXP (-1.38 + 0.074Ta)
1AU = animal unit corresponding to 500 kg body mass; T = indoor air temperature in swine houses, °C; T = ambient air temperature, °C; W = average weight
i
a
of pigs, kg; N = number of pigs in the farm; R = recharge interval of manure pits, d.
21 to 249 kg, the number of pigs ranged from 6 to 13,680,
the recharge interval of manure pits ranged from 1 to 42
d, ambient air temperatures ranged from 2°C to 32°C, and
areas of lagoons ranged from 1,131 to 97,600 m2.
For finishing houses with deep pits or recharge pits,
NH3 emission rates were positively related to indoor air
temperature. Finishing operation lagoons had NH3 emission rates that were positively related to ambient air temperature (P < 0.01). Effects of temperature on H2S emission rates were not significant. Many individual studies
observed the effects of temperature on NH3 emission
rates (Harper et al., 2000, 2004; Heber et al., 2000; Aneja
et al., 2000, 2008; Pelletier et al., 2006; Blunden and
Aneja, 2008), and so did the results of the meta-analysis.
Aneja et al. (2000, 2008) and Pelletier et al. (2006) both
reported NH3 emission rates increased exponentially with
increasing lagoon or manure temperature.
The recharge interval of manure pits in finishing houses significantly affected H2S but not NH3 emission rates.
Swine houses with pits that had longer recharge intervals
emitted more H2S (P < 0.01), a finding that is in agreement with the findings of Predicala et al. (2007) and Lim
et al. (2004). Predicala et al. (2007) reported that daily removal of manure resulted in significantly lower H2S emissions but found no difference for NH3 emissions. Lim et al.
(2004) observed that H2S emissions significantly increased
as recharge intervals increased from 7 to14 d and to 42 d,
but the effect on NH3 emissions was not significant.
The NH3 and H2S emission rates from swine houses in kilograms per year per pig increased with increasing pig weights. When expressed in kilograms per year
per AU, NH3 emission rates were no longer influenced
by pig weight, but for finishing houses with recharge
pits, H2S emission rates in kilograms per year per AU
remained positively related to pig weight (P = 0.01).
The H2S emission rates were also influenced by size
of operation. Deep-pit finishing houses with larger pig
numbers tend to have higher H2S emission rates in kilograms per year per AU (P = 0.02).
Sizes of Swine Farm That May Trigger
the Need to Report NH3 or H2S Emissions
The EPCRA and CERCLA require reporting of NH3
and H2S emissions that exceed 45.4 kg/d. Swine farm
sizes that may approach the limit to report NH3 and H2S
emissions under EPCRA and CERCLA were calculated
and are presented in Table 6. The median emission rate of
NH3 from swine facilities was 17 times higher than that
of H2S; therefore, swine farm sizes that may reach the
45.4 kg/d threshold were much smaller for NH3 than for
H2S. The farm size that may approach the limit to report
NH3 emissions is 3,410 pigs on the basis of the median
NH3 emission rate (4.86 kg/yr per pig), but it can be as
low as 992 pigs on the basis of the 90th percentile emission rate (16.71 kg·yr-1·hd-1).
NH3 Concentrations in the Vicinity of Swine Facilities
The Agency for Toxic Substances and Disease
Registry (ATSDR) has suggested minimum risk levels
(MRL) for NH3 and H2S to protect sensitive populations
(ATSDR, 2008). The MRL for NH3 are 1,700 and 1200
and 70 µg/m3 (1,700 and 100 ppb) for an acute (1 to 14 d
Table 6. Size of swine farm that may trigger the need to
report NH3 or H2S emissions
Emission rate (kg/yr per pig)
Swine
Manure
Basis
house
storage
Total
Median emission rates
NH3
2.78
2.08
4.86
H 2S
0.09
0.20
0.29
75th percentile emission rates
NH3
4.49
6.27
10.76
H 2S
0.20
0.63
0.83
90th percentile emission rates
NH3
7.17
9.54
16.71
H 2S
0.47
0.83
1.30
Size that may reach
the 45.4 kg/d NH3 or H2S
per day threshold
3,410 pigs
57,141 pigs
1,540 pigs
19,965 pigs
992 pigs
12,747 pigs
Ammonia and hydrogen sulfide emissions from swine facilities
1663
Figure 5. Measured NH3 concentrations at various distances from swine facilities.
continuous) and chronic (>365 d continuous) exposure,
respectively. In the following analysis, we compared
the average values of observed concentrations with the
MRL, although the concentrations were not necessarily continuous measurements for the MRL period. The
average NH3 concentration at the edge of the emission
sources (swine houses or lagoons) was 3.8 ± 3.6 mg/m3
(ranging from 0.2 to 11 mg/m3), which is higher than
the acute MRL for NH3 (1200 µg/m3). The ambient
NH3 concentrations in the vicinity of swine facilities decreased quickly to less than the chronic MRL (70 µg/m3)
as distances from emission source increased (Fig. 5). At
distances of 30 to 1,185 m from emission sources, the
average ambient NH3 concentration was 46 ± 46 µg/m3
(ranging from 7 to 190 µg/m3). In comparison, the average background ambient NH3 concentration outside
swine production areas was 5.4 ± 2.4 µg/m3, whereas
Godbout et al. (2009) and Donham et al. (2006) reported the average ambient NH3 concentration within swine
production areas was 8.2 ± 3.8 µg/m3. The average ambient NH3 concentration in the vicinity of swine facilities (46 ± 46 µg/m3 at distances from 30 to 1,185 m)
was about 8 times higher than the average background
ambient NH3 concentration in areas not influenced by
swine production facilities (5.4 ± 2.4 µg/m3).
H2S Concentrations in the Vicinity of Swine Facilities
The MRL for H2S are 97 and 28 µg/m3 (70 and 20 ppb)
for acute and intermediate (15 to 365 d continuous) exposures, respectively. The average H2S concentration at the
edge of the emission sources (swine houses or lagoons)
was 56 ± 66 µg/m3 (ranging from 3 to 203 µg/m3), which
is less than the acute MRL (97 µg/m3) but higher than the
intermediate MRL (28 µg/m3) for H2S. The ambient H2S
concentrations in the vicinity of swine facilities decreased
quickly to less than 20 ppb as distances from emission
source increased (Fig. 6). The average ambient H2S concentration was 4.3 ± 8.6 µg/m3 at distances of 30 to 1,185
m from emission sources. In comparison, Godbout et al.
(2009) and Donham et al. (2006) reported average ambient
H2S concentrations of 2.6 ± 1.5 µg/m3 in areas not influenced by swine production facilities.
Conclusions
On the basis of meta-analysis of published emission
data, the following conclusions can be made.
1) Many factors can affect NH3 and H2S emission
rates from swine, and large variations were observed in the literature. The emission rates of NH3
were much higher than those of H2S. The farm size
that may trigger the need to report NH3 emissions
under EPCRA is 3,410 pigs on the basis of the median NH3 emission rates, but it can be as low as
992 pigs on the basis of 90th percentile emission
rates.
2)The NH3 emission rates for manure storage facilities from NAEMS sites were significantly higher
than those from other studies when emission rates
were expressed in kilograms per year per pig. The
discrepancy may be related to the different sampling and computing methods, and further investigation is needed.
1664
Liu et al.
Figure 6. Measured H2S concentrations at various distances from swine facilities.
3)Swine hoop houses had significantly higher NH3
emission rates than other manure-handling systems,
whereas deep-pit houses had the highest H2S emission rates.
4)Farrowing houses had the highest H2S emission
rates, followed by gestation houses, and finishing
houses had the lowest H2S emission rates. The effects of production stages were not significant for
NH3 emission rates from swine houses.
5)No significant effects of production stage or storage type were observed for NH3 and H2S emission
rates from manure storage facilities.
6)The NH3 emission rates increased with increasing
air temperature, whereas the effects of air temperature on H2S emission rates were not significant.
7) The recharge interval of manure pits significantly
affected H2S but not NH3 emission rates. The H2S
emission rates were also influenced by the size of
the operation. Farms with longer recharge intervals
or larger pig numbers tended to have higher H2S
emission rates.
8)Although NH3 and H2S concentrations at the edge
of swine houses or lagoons were often higher than
corresponding acute or intermediate MRL, they
decreased quickly to be than corresponding chronic or intermediate MRL as distances from emission
source increased. At distances 30 to 1,185 m from
emission sources, the average ambient concentrations for NH3 and H2S were 46 ± 46 µg/m3 and
4.3±8.6 µg/m3, respectively.
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