GREENHOUSE GAS EMISSIONS FROM LIQUID SWINE
MANURE STORAGE FACILITIES IN SASKATCHEWAN
C. Laguë, É. Gaudet, J. Agnew, T. A. Fonstad
ABSTRACT. Greenhouse gas (GHG) emissions from manure storage facilities at four different commercial farrow-to-finish
swine operations under liquid manure management located in Saskatchewan, Canada, were experimentally determined
during the spring-to-fall period between 2001 and 2003. These operations featured three types of manure storage facilities:
uncovered concrete tank, uncovered earthen manure basin (EMB), and covered (blown chopped straw) EMB. GHG emission
rates were expressed in terms of unit mass of animal producing the stored manure. On average, methane and carbon dioxide
emission rates were respectively 3.75 g CO2 equivalent day−1 kg−1 and 1.73 g CO2 equivalent day−1 kg−1, while nitrous oxide
emission rates were negligible. The total average GHG emission rate measured in this study was 5.48 g CO2 equivalent day−1
kg −1. On average, GHG emissions from the uncovered EMB were the largest, while those from the covered EMB were the
lowest. Emissions were maximum during the summer and at their lowest during the spring, and night emissions were larger
than those that occurred during the daytime. Estimations based on the results of this study indicate that the addition of a blown
chopped straw cover on an EMB can yield reductions in CO2 and CH4 emissions of 56 and 786 tonnes of CO2 equivalent per
year, respectively, for each 1,000-sow increment.
Keywords. Concrete tank, Cover, Earthen manure basin, Emission, Greenhouse gas, Manure storage, Swine.
T
he Kyoto Protocol to the United Nations Framework Convention on Climate Change was adopted
in 1997 (Grubb et al., 1999). The protocol targets
six different greenhouse gases that are determinant
in the global warming phenomenon: carbon dioxide (CO2),
methane (CH4), nitrous oxide (N2O), HFCs (hydrofluorocarbons), PFCs (perfluorocarbons), and SF6 (sulfur hexafluoride). In 1990, mass emissions for the first three of these gases
accounted for almost 99% of the total GHG emissions (Grubb
et al., 1999). On a molecular basis, the global warming potential (GWP) of CH4 is 21 times that of CO2, and N2O has a
GWP 310 times greater than that of CO2 (Grubb et al., 1999).
Once emitted into the atmosphere, the lifetimes of these three
gases are approximately 100, 12, and 120 years for CO2, CH4,
and N2O, respectively (Grubb et al., 1999). According to
Subak et al. (1993), Canada’s annual emissions amounted to
32,250 kT of CO2, 3,218 kT of CH4, and 37 kT of N2O, which
represent respectively 0.5%, 0.9%, and 1% of the total anthropogenic world emissions. As part of the Kyoto Protocol
Article was submitted for review in August 2004; approved for
publication by the Structures & Environment Division of ASABE in
October 2005. Presented at the 2004 ASAE Annual Meeting as Paper No.
044157.
The authors are Claude Laguë, ASABE and CSAE/SCGR Member
Engineer, Professor and Dean, College of Engineering, University of
Saskatchewan, Saskatoon, Canada; Éric Gaudet, ASABE Student
Member, Graduate Student, Département des sols et de génie
agroalimentaire, FSAA, Université Laval, Québec, Canada; Joy Agnew,
ASABE Member Engineer, Research Engineer, and Terrance A.
Fonstad, ASABE Member Engineer, Assistant Professor, Department of
Agricultural and Bioresource Engineering, College of Engineering,
University of Saskatchewan, Saskatoon, Canada. Corresponding author:
Claude Laguë, College of Engineering, University of Saskatchewan, 57
Campus Dr., Saskatoon, SK, Canada S7N 5A9; phone: 306-966-5273; fax:
306-966-5205; e-mail: [email protected].
agreement, Canada committed itself to reduce its GHG emissions during the 2008-2012 period to a level corresponding
to 94% of its 1990 emissions (AAFC, 2000).
However, the total Canadian GHG emissions from
anthropogenic sources have increased from 608,000 to
720,000 kt of CO2 equivalent per year between 1990 and
2001 (Environment Canada, 2003). During that same period
of time, agricultural emissions have increased by 800 kt of
CO2 equivalent (from 59,200 in 1990 to 60,000 in 2001), with
the result that the relative contribution of the Canadian
agricultural sector to the total anthropogenic GHG emissions
has decreased from 9.7% in 1990 to 8.3% in 2001. Most
agricultural GHG emissions are in the form of methane
(38%) and nitrous oxide (61%) (AAFC, 2000). According to
Environment Canada (2003), the total GHG emissions from
the Canadian livestock sector have increased from 24,270 kt
of CO2 equivalent in 1990 (41% of the total agricultural
emissions) to 28,900 kt of CO2 equivalent in 2001 (48% of
the total agricultural emissions). There exists a need to better
determine the relative contributions of the different stages of
livestock production and manure management to the GHG
emissions caused by this agricultural sector. Benchmarking
of current GHG emissions on the basis of livestock management systems and region has therefore been identified as an
important short-term need for the Canadian livestock
industry (AAFC, 2000).
The objective of the research reported herein was to
contribute to this benchmarking effort by evaluating methane, carbon dioxide, and nitrous oxide emissions from liquid
swine manure storage facilities in Saskatchewan. Greenhouse gas emission data have been expressed in terms of mass
of GHG per unit time per unit animal mass in order to allow
for direct comparisons between emissions from the different
components of pork production systems to identify the
Transactions of the ASAE
Vol. 48(6): 2289−2296
E 2005 American Society of Agricultural Engineers ISSN 0001−2351
2289
components of the system toward which mitigation and
reduction efforts should be targeted.
during the spring) and between 17.9 and 92.0 g day−1 m−3 for
solid manure storages (over a 31-day period during the
summer). Table 1 summarizes GHG emission data from
manure storage facilities obtained from the literature.
REVIEW OF LITERATURE
Phillips et al. (1997) measured CH4 emission rates ranging
from 0.014 to 0.39 g day−1 m−3 of stored manure over
different types of manure storage facilities; N2O emissions
were found to be insignificant. However, it is believed that
there is a large potential for N2O emissions during storage of
manure, particularly for solid manure (Brown et al., 2000).
Methane emissions from stored manure have been found to
be inversely proportional to the solids content of the manure,
while N2O emissions reached a maximum (1.5% of manure
total-N) at a total solids content of 15% (Hüther et al., 1997).
These authors also determined that either straw or swelledclay covers on manure storages can increase N2O emissions
and, in the case of straw, CH4 emissions also. On the other
hand, the use of covers can be an effective way of reducing
odor emissions from manure storage facilities (Bundy et al.,
1997, Miner and Suh, 1997). Husted (1994) reported CH4
emissions from manure storage facilities of 5.9 (solid cattle
manure), 8.2 (cattle slurry), 11.6 (pig slurry), and 28.3 (solid
pig manure) g day−1 m−3. Hao et al. (2000) evaluated CO2,
N2O, and CH4 emissions during the composting of cattle
feedlot manure piles. Direct emissions ranged from 73.8 to
168 kg CO2, from 6.3 to 17.5 kg CH4, and from 0.044 to
0.19 kg N2O per tonne of manure depending upon the types
of aeration (passive vs. active) and bedding material (straw
or wood chips) used in the composting process. Peu et al.
(1999) developed a floating open-chamber system to measure N2O emissions from the surface of liquid manure storage
or treatment facilities. During a two-month period, they
measured N2O emissions ranging from 79 to 91 mg h−1 m−2
at the surface of an aerated liquid pig manure storage facility.
They estimated that these emission rates corresponded to less
than 1% of the total input rates of nitrogen in the manure
storage facility. Husted (1993) evaluated the feasibility of
using an open-chamber technique for measuring CH4
emissions from either liquid or solid pig manure storage
facilities. Daily emission rates varied between 0.5 and 49.8 g
day−1 m−3 for liquid manure storages (over a 19-day period
MATERIALS AND METHODS
An open-chamber technique was used for the collection of
air samples at the surface of manure storage facilities.
Cylindrical chambers having an internal diameter of 600 mm
(cross-sectional area, Achamber, equal to 0.280 m2) and a
height of 1,000 mm were made of PVC tubing. The top end
of the chamber was closed by means of a circular 6.35 mm
PVC sheet and sealed. An inflated tire inner tube placed
around the bottom end of the chamber ensured the floatation
of the chamber on the manure surface. The inner tube was
positioned such that the bottom end of the chamber
penetrated into the manure down to a depth of about 150 mm.
Each chamber was provided with two cylindrical air
manifolds made of PVC tubing (150 mm O.D. × 38 mm
height). A first distribution manifold provided with eight
11.1 mm diameter openings was placed close to the surface
of the manure to diffuse the incoming clean airflow
horizontally across the surface of the manure. At the top of
the chamber, a second collection manifold collected the
contaminated air and evacuated it out of the chamber. Four
chambers were used simultaneously for air sampling.
Figure 1 illustrates the main features of those open chambers.
A portable air compressor supplied fresh air to the
chambers through a charcoal filter and a distribution
manifold that divided the total air output of the compressor
into four equal airflows by means of four VF VISI-Float
VFB-90-BV Rotameters (unit airflow in each chamber, Qair,
equal to 0.00094 m3 s−1) (Gaudet et al., 2003). Teflon tubing
(9.5 mm I.D.) carried the air to each chamber, where it was
fed into the distribution manifold and diffused horizontally
near the surface of the manure. The resulting velocity of the
airflow at the outlet of the distribution manifold was 1.22 m
s−1. Teflon tubing was also used to carry the contaminated air
captured by the collection manifold at the top of each
chamber to a mixing chamber, where the air coming from the
four chambers was thoroughly mixed. An air pump was
Table 1. Greenhouse gas emissions from swine manure storage facilities.
Greenhouse Gas
Source
Husted (1994)
Units
g day−1 m−3
CH4
CO2
N2O
0.4 to 34.8
−−
−−
Comments
Liquid pig manure
17.9 to 92.0
−−
−−
Solid pig manure
11.6
−−
−−
Liquid pig manure
28.3
−−
−−
Solid pig manure
mg h−1 m−2
−−
−−
25
Liquid pig manure
ppm
1,430
−−
1,400
2.6
49 to 92
−−
Liquid pig manure in concrete tank
0.049
68
−−
Composting swine manure
Swine waste water
Kuroda et al. (1996)
Leonard et al. (2004)
g day−1 m−2
Osada et al. (1995)
kg day−1 m−3
−−
−−
0.5
Peu et al. (1999)
mg h−1 m−2
−−
−−
79 to 91
Phillips et al. (1997)
g day−1 m−3
0.014 to 0.39
−−
−−
Sommer and Moller (2000)
2290
tonne−1
191
−−
58
kg tonne−1
−−
0.09 to 7.37
−−
g
Swine feces compost
Aerated liquid pig manure
Range over different types of manure storage facilities
Deep litter manure system
TRANSACTIONS OF THE ASAE
(a)
(b)
(c)
(d)
Figure 1. (a) Overall view of one sampling chamber being put in place, (b) air inlet (near wall) and outlet (center), (c) air distribution (foreground) and
collection (background) manifolds, and (d) complete air sampling system.
connected to the mixing chamber to evacuate the contaminated air from the open chambers into the mixing chamber.
Composite air samples were withdrawn from the mixing chamber into Tedlar bags by means of a pulmonary pumping system
at regular intervals during each sampling period. Subsamples
were collected from the Tedlar bags using syringes and stored
in evacuated glass containers. The design and operation of the
system allowed for the collection of air samples from any location at the surface of the manure storage while research personnel remained safely on firm ground (Gaudet et al., 2003).
Emissions from manure storage facilities were monitored
throughout the day. For daytime sampling, composite
samples were withdrawn from the mixing chamber during the
morning (between 6:00 and 10:00), at mid-day (between
10:00 and 14:00), and during the afternoon (between 14:00
and 18:00). At night, composite samples were collected
Vol. 48(6): 2289−2296
during the evening (between 18:00 and 22:00), at the middle
of the night (between 22:00 and 02:00), and in early morning
(between 02:00 and 06:00). Fresh air samples were also
collected upwind from the manure storage facility during
those periods of time to obtain background GHG concentrations. The subsamples (in glass containers) were refrigerated
and stored for gas chromatography analyses at the University
of Saskatchewan. N2O and CH4 were analyzed with a Varian
CP-3800 gas chromatograph equipped with a flame ionization detector (FID) for CH4 analysis and an electron capture
detector (ECD) for N2O analysis. The column used for CH4
was a CP-sil 5 CB coated WCOT fused silica 15 m in length,
while the column used for N2O was a Poraplot Q coated plot
fused silica 10 m in length. The CO2 detector was a Varian
Micro-GC CP-2003 equipped with a thermal conductivity
detector (TCD) and a Poraplot U column 10 m in length. All
2291
Table 2. Characteristics of the sampled manure storage facilities and ranges of prevailing meteorological conditions.
AMS [a] MassLW [a] Air Temp. Air RH Wind Speed
(°C)
(%)
(m s−1)
(m2)
(kg)
Characteristics
Dimensions
Site
2-cell EMB. Bottom filling of primary cell; overflow of primary cell directed to top of secondary cell.
Length × width × depth at top of berm
Primary cell: 60 × 63 × 5 m
Secondary cell: 118 × 63 × 5 m
Floral
Circular concrete storage tank.
Top filling.
Diameter: 22 m; depth: 3.5 m
Rosthern
3-cell EMB. Bottom filling of primary cell; overflow of primary cell directed to top of secondary cell; overflow of secondary cell directed to top
of tertiary cell.
Length × width × depth at top of berm
Primary cell: 56 × 55 × 3.7 m
Secondary cell: 56 × 55 × 3.7 m
Tertiary cell: 56 × 55 × 3.7 m
2-cell EMB. Bottom filling of primary cell; overflow of primary cell directed to top of secondary cell.
Length × width × depth at top of berm
Primary cell: 56 × 55 × 3.7 m
Secondary cell: 56 × 55 × 3.7 m
Elstow
St. Denis
[a]
1,934
390,000
0 to 31
28 to 100
0 to 12
378
63,180
−2 to 28
30 to 83
0 to 10
1,900
979,600
11 to 33
31 to 94
2 to 5
1,900
489,800
11 to 30
26 to 87
3 to 9
AMS = average surface area of manure storage facility; MassLW = live weight mass of animals inside barn during sampling periods.
Table 3. Summary of sample sites, locations, seasons, times
of day, and cover types. Each sampling day yielded
three samples, unless otherwise indicated.
Time of
Cover
No. of
Day
Type
Sampling Days
Location
Season
Elstow
Primary
Primary
Primary
Primary
Secondary
Secondary
Secondary
Summer
Fall
Summer
Summer
Summer
Summer
Fall
Day
Day
Night
Day
Day
Night
Day
None
Straw
Straw
Straw
Straw
Straw
Straw
1
2
1
2
3
1
1
Greenhouse gas emissions, expressed in terms of mass of
gas per unit time per unit animal mass, were determined by
multiplying gas concentration and ventilation rate in the
sampling chamber, dividing it by the cross-sectional area of
the sampling chamber, and using conversion factors relating
the surface area of the manure storage facilities and the mass
of the animals that produced the manure stored in those
facilities (eq. 1):
Qmass =
*
Floral
Tank
Tank
Tank
Tank
Fall
Spring
Spring
Summer
Day
Day
Night
Day
None
None
None
None
2
1
1
2
Rosthern
Primary
Secondary
Summer
Summer
Day
Day
None
Straw
1
2
St. Denis
Primary
Summer
Day
None
Summer
Summer
Day
Night
None
None
2 full days,
1 morning
1
1
Secondary
Secondary
columns were maintained at 100°C, and the carrier gas for all
detectors was helium.
Table 2 lists the characteristics of the different commercial manure storage facilities that were monitored at different
periods during the spring (2002 and 2003), summer (2001,
2002, and 2003), and fall (2001 and 2002) seasons as well as
the range of prevailing meteorological conditions during the
sampling events. Table 3 lists the number of sampling days
at each site during each season. One sampling day represents
three samples (morning / noon / afternoon, or evening /
middle of the night / morning). All four facilities were used
to store untreated manure from farrow-to-finish operations
under liquid manure management (partially or totally slatted
floors over shallow pull-plug type gutters). Some of the earthen manure storage basin (EMB) facilities were covered with
a layer of chopped barley straw during all or part of the
spring-to-fall periods as part of the farms’ odor management
programs. Only the concrete tank storage facility at Floral
and the EMB at St. Denis remained uncovered at all times
during the 3-year period of the study.
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GHGMS − GHGamb
* ρGHG
1,000,000
Q Air
AMS
*
* 86,400 * GWPGHG
Achamber Mass LW
(1)
where
Qmass
= unit mass GHG emissions, kg CO2 equivalent day−1 kg−1 (±10% for CO2 and N2O;
±16% for CH4)
GHGMS = GHG concentration in air above manure
surface, ppmv or m3 (106 m3)−1 (±0.005 for
N2O; ±2 for CH4; ±10 for CO2)
GHGamb = GHG concentration in ambient air, ppmv or
m3 (106 m3)−1 (±0.005 for N2O; ±2 for CH4;
±10 for CO2)
ρGHG
= GHG density, kg m−3 (±0.1)
Qair
= flow rate of air through sampling chamber,
m3 s−1 (±0.000047)
Achamber = cross-sectional area of sampling chamber,
m2 (±0.012)
AMS
= average surface area of manure storage
facility, m2 (±100)
MassLW = live weight mass of animals inside barn
during sampling periods, kg (±10,000)
86,400
= conversion factor, s day−1
GWPGHG = relative global warming potential of each
GHG, kg CO2 equivalent kg−1 (= 1 for CO2;
= 21 for CH4; = 310 for N2O).
The mass of the animals was an estimate of the average
mass of animals in the buildings during the 3-year sampling
period. Error analyses were completed for equation 1 to
estimate the relative experimental error on GHG emission
measurements by calculating the effect of each measurement
error on the overall emission calculation (Taylor, 1982).
The value of AMS was constant for the concrete tank
storage facility, which had vertical walls. However, this was
not the case for an EMB that had inclined walls and for which
TRANSACTIONS OF THE ASAE
the value of AMS increased proportionally with the depth of
manure inside the storage facility. For this reason, an average
value for AMS was used for the EMB facilities. This average
value corresponded to the surface area of the manure storage
facility when the facility was filled at 50% of its total capacity
(table 2).
Greenhouse gas emission experimental data were analyzed in terms of: (1) type of GHG (methane, carbon dioxide,
and nitrous oxide), (2) type of storage facility (concrete tank,
and covered vs. uncovered EMB), (3) seasonal (spring,
summer, fall) effects, and (4) time of day effects (daytime vs.
nighttime emissions) and are discussed in the next section. A
full statistical analysis could not be performed because of the
variation in sample sites and the lack of repetitions (table 3).
RESULTS AND DISCUSSION
TYPE OF GREENHOUSE GAS
The overall GHG emission rate data on a mass basis over
the 73 different monitoring events were calculated for each
gas. Average methane emission rates per unit animal mass
(3.75 g CO2 equivalent day−1 kg−1) were 2.2 times larger than
those for carbon dioxide (1.73 g CO2 equivalent day−1 kg−1),
while nitrous oxide emission rates (<0.01 g CO2 equivalent
day−1 kg−1) were negligible. Overall methane emission rates
ranged from 0 to 28 g CO2 equivalent day−1 kg−1, while the
variability of carbon dioxide emission rates was much
smaller (0 to 12 g CO2 equivalent day−1 kg−1). The total unit
mass GHG emission rate, averaged over the three types of
manure storage facility monitored and the 73 monitoring
events, was 5.48 g CO2 equivalent day−1 kg−1, and this value
will be referred to as the overall average emission rate in
further analyses. The relevant experimental error analysis
showed that the sum of measurement errors resulted in a 10%
error for the CO2 and N2O emissions and a 16% error for the
CH4 emissions.
The lack of uniformity of units and sampling methods, as
well as the varying manure sources and types, makes it very
difficult to compare these values with those found in the
literature. While Phillips et al. (1997) found N2O emissions
to be negligible, Husted (1994) and Peu et al. (1999) found
N2O emissions from liquid manure to be significant. The CH4
and CO2 emissions measured from stored liquid swine
manure in Leonard et al. (2004) were 88% and 42% lower,
respectively, than those found in this study. This variation
could be attributed to the use of a wind tunnel in Leonard et
al. (2004) versus the open-chamber method used in this study.
TYPE OF STORAGE FACILITY
Table 4 presents the minimum, maximum, and average
unit GHG emission rate data for the three different types of
liquid manure storage facilities monitored during this study.
On average, total unit mass emission rates from the
uncovered EMB facilities (8.65 g CO2 equivalent day−1 kg−1)
were 30% larger than those from the uncovered concrete tank
facility (6.65 g CO2 equivalent day−1 kg−1). The presence of
blown chopped straw covers on EMB facilities resulted in an
average reduction of total GHG emissions by a factor of 3 on
average (2.98 vs. 8.65 g CO2 equivalent day−1 kg−1). The bulk
of those reductions were attributed to methane, while average
carbon dioxide emissions were comparable across the three
types of storage facility. The average unit mass emission rates
from the three types of storage facilities corresponded to
158% (uncovered EMB), 121% (uncovered concrete tank),
and 54% (covered EMB) of the overall average emission rate.
The ratios of average CH4 to average CO2 emissions were
6.82 (tank), 3.29 (uncovered EMB), and 0.72 (covered
EMB). Average nitrous oxide emissions were negligible for
all three types of manure storage.
SEASONAL EFFECTS
Table 5 presents the minimum, maximum, and average
unit mass GHG emission data by season. On average, total
emissions during the summer (6.59 g CO2 equivalent day−1
kg−1) were 27% larger than during the fall (5.17 g CO2
equivalent day−1 kg−1) and more than eight times larger than
during the spring (0.70 g CO2 equivalent day−1 kg−1). The
average unit mass emission rates during the three seasons
corresponded to 13% (spring), 120% (summer), and 94%
(fall) of the overall average emission rate.
TIME OF DAY EFFECTS
Table 6 presents the minimum, maximum, and average
unit mass GHG emission rate data by time of day. On average,
total emission rates were at their maximum during the early
evening hours (14.97 g CO2 equivalent day−1 kg−1) and were
lowest in late afternoon (2.41 g CO2 equivalent day−1 kg−1).
On average, total daytime emission rates (i.e., between the
hours of 06:00 and 18:00) were 5.00 g CO2 equivalent day−1
kg−1, while nighttime (between 18:00 and 06:00) emissions
Table 4. Average unit GHG emission rates by type of manure storage facility.
Average Unit GHG Emission Rate (g CO2 equivalent day−1 kg−1)
CO2
CH4
N2O
Type of Manure Storage Facility
Min.
Max.
Avg.
Min.
Max.
Avg.
Min.
Max.
Avg.
Total
Uncovered concrete tank (18 samples)
Uncovered EMB (19 samples)
Covered EMB (36 samples)
0.00
0.00
0.00
2.02
7.14
12.13
0.85
2.01
1.73
0.10
0.00
0.00
24.66
27.50
14.21
5.80
6.62
1.25
0.00
0.00
0.00
0.07
0.33
0.21
0.00
0.02
0.00
6.35
8.65
2.98
Table 5. Average unit GHG emission rates by season.
Average Unit GHG Emission Rate (g CO2 equivalent day−1 kg−1)
CO2
CH4
N2O
Season
Min.
Max.
Avg.
Min.
Max.
Avg.
Min.
Max.
Avg.
Total
Spring (6 samples)
Summer (52 samples)
Fall (15 samples)
0.00
0.00
0.00
0.61
12.13
5.32
0.22
2.09
1.32
0.10
0.00
0.00
1.06
27.50
14.22
0.48
4.50
3.85
0.00
0.00
0.00
0.00
0.33
0.21
0.00
0.01
0.00
0.70
6.60
5.17
Vol. 48(6): 2289−2296
2293
Table 6. Average unit GHG emission rates by time of day.
Average Unit GHG Emission Rate (g CO2 equivalent day−1 kg−1)
CO2
CH4
N2O
Time of Day
Min.
Max.
Avg.
Min.
Max.
Avg.
Min.
Max.
Avg.
Total
02:00 - 06:00 (4 samples)
06:00 - 10:00 (21 samples)
10:00 - 14:00 (20 samples)
14:00 - 18:00 (20 samples)
18:00 - 22:00 (4 samples)
22:00 - 02:00 (4 samples)
0.39
0.00
0.00
0.00
0.31
0.00
4.40
12.13
3.14
6.94
8.63
3.31
2.12
2.42
0.93
1.18
5.41
1.05
0.33
0.00
0.00
0.00
1.06
0.01
14.76
24.66
19.51
5.10
27.50
18.95
4.04
6.23
2.97
1.23
9.53
4.96
0.00
0.00
0.00
0.00
0.00
0.00
0.05
0.33
0.12
0.14
0.04
0.01
0.02
0.01
0.02
0.00
0.03
0.00
6.18
8.66
3.92
2.41
14.97
6.01
were 80% greater at 9.05 g CO2 equivalent day−1 kg−1. The
average unit mass emission rates during daytime and nighttime periods corresponded to 91% and 165%, respectively, of
the overall average emission rate.
The results from this study indicate that the main
contributor to unit mass GHG emission rates from the three
types of manure storage facility that were monitored was
methane. Measured emission rates varied according to the
type of manure storage facility, the season, and the time of
day. These results suggest that the use of constant emission
rates may not be appropriate for assessing GHG emissions
from liquid swine manure storage facilities in Saskatchewan.
ESTIMATION OF GHG EMISSIONS
The experimental results obtained in this study have been
used to estimate GHG emissions from manure storage
facilities for farrow-to-finish swine operations under liquid
manure management in Saskatchewan. For such operations,
the total animal mass in the production building(s) at any
given time for each 1,000-sow increment (including gestating and farrowing sows, gilts and boars, weaner and
grower-finisher pigs) is approximately 650,000 kg.
The unit mass GHG emission rates for both carbon dioxide
and methane were weighted to take into account the type of
manure storage facility, the season, and the period of the day
(i.e., day or night) using the average values of the experimental results as presented in tables 4 through 6. Weighted unit
GHG emission rates were determined using equation 2:
qGHG = (qGHG ) overall *
*
where
qGHG
(qGHG )overall
(qstorage )GHG
(qstorage )avg
(qseason )GHG
2294
(qstorage )GHG
(qstorage ) avg
(qseason )GHG (q periodofday )GHG
*
(qseason ) avg
(q periodofday ) avg
house gas GHG for a specific season
(table 5), g CO2 equivalent day−1 kg−1
(qseason )avg
= average unit emission rate for green
house gas GHG for the three seasons
(table 5), g CO2 equivalent day−1 kg−1
(qperiodofday )GHG = average unit emission rate for green
house gas GHG for a specific period of
the day (table 6), g CO2 equivalent
day−1 kg−1
(qperiodofday )avg = average unit emission rate for green
house gas GHG for the entire day
(table 6), g CO2 equivalent day−1 kg−1.
Table 7 presents the estimates of GHG emissions for a
1,000-sow farrow-to-finish operation under liquid manure
management in Saskatchewan during the spring-to-fall
period based on the results obtained in this study. Assuming
the estimated mass of the animals (650,000 kg) has an error
of 15% and using the relative experimental errors for the
emissions of CO2 and CH4 (10% and 16%, respectively), the
relative error in the GHG emission estimations presented in
table 7 is approximately 30%.
Two-cell and three-cell EMBs constitute very popular
storage systems for liquid swine manure in Western Canada
because of their relatively low unit cost and their adaptability
to the use of blown chopped straw covers to control odor
emissions. The emission estimates presented in table 7
indicate that these covers can also yield important reductions
in GHG emissions. For each 1,000-sow equivalent, it can be
estimated that the addition of a blown chopped straw cover
on an EMB would yield reductions in CO2 and CH4 emissions
of 56 and 786 tonnes of CO2 equivalent, respectively, during
the spring-to-fall period.
(2)
= unit weighted emission rate for green
house gas GHG, g CO2 equivalent
day−1 kg−1
= average overall unit emission rate for
greenhouse gas GHG, g CO2 equivalent day−1 kg−1
= average unit emission rate for green
house gas GHG for a specific type of
storage facility (table 4), g CO2
equivalent day−1 kg−1
= average unit emission rate for green
house gas GHG for the three types of
storage facilities (table 4), g CO2
equivalent day−1 kg−1
= average unit emission rate for green
CONCLUSION
Greenhouse gas (GHG) emissions from manure storage
facilities at four different commercial farrow-to-finish swine
operations under liquid manure management located in
Saskatchewan, Canada, were experimentally determined
during the spring-to-fall period between 2001 and 2003.
These operations featured three types of manure storage
facilities: uncovered concrete tank, uncovered earthen
manure basin (EMB), and covered (blown chopped straw)
EMB. GHG emission rates were expressed in terms of unit
mass of animal producing the stored manure.
On average (73 monitoring events), methane and carbon
dioxide emission rates were respectively 3.75 g CO2
equivalent day−1 kg−1 and 1.73 g CO2 equivalent day−1 kg−1,
while nitrous oxide emission rates were negligible. The total
average GHG emission rate measured in this study was 5.48 g
TRANSACTIONS OF THE ASAE
Table 7. Estimated spring-to-fall GHG emissions from manure storage for a 1,000-sow farrow-to-finish swine operation
under liquid manure management in Saskatchewan for three different types of manure storage facilities.
Unit GHG Emission Rate
GHG Emissions
(g CO2 equivalent day−1 kg−1)
(t CO2 equivalent)
Type of Manure
Period
CO2
CH4
CO2
CH4
Total
Storage Facility
of Day
Season
Days
Uncovered tank
Uncovered EMB
Covered EMB
Spring
Daytime
Nighttime
0.12
0.23
0.56
1.00
45.63
45.63
3.58
6.78
16.63
29.54
20.21
36.33
Summer
Daytime
Nighttime
1.15
2.17
5.26
9.34
45.63
45.63
34.02
64.44
155.89
276.95
189.91
341.40
Fall
Daytime
Nighttime
0.72
1.37
4.50
7.99
45.63
45.63
21.49
40.70
133.37
236.95
154.86
277.65
Total annual emissions:
273.75
171
849
1,020
Spring
Daytime
Nighttime
0.29
0.54
0.64
1.14
45.63
45.63
8.47
16.04
18.98
33.72
27.45
49.76
Summer
Daytime
Nighttime
2.71
5.14
6.00
10.66
45.63
45.63
80.46
152.39
177.93
316.11
258.38
468.50
Fall
Daytime
Nighttime
1.71
3.25
5.13
9.12
45.63
45.63
50.81
96.24
152.23
270.45
203.04
366.69
Total annual emissions:
273.75
404
969
1,374
Spring
Daytime
Nighttime
0.25
0.47
0.12
0.21
45.63
45.63
7.29
13.81
3.58
6.37
10.87
20.17
Summer
Daytime
Nighttime
2.34
4.42
1.13
2.01
45.63
45.63
69.25
131.16
33.60
59.69
102.84
190.85
Fall
Daytime
Nighttime
1.47
0.97
2.79
1.72
Total annual emissions:
45.63
45.63
43.74
82.84
28.74
51.07
72.48
133.90
273.75
348
183
531
CO2 equivalent day−1 kg−1. On average, total unit emission
rates from the uncovered concrete tank facility amounted to
6.65 g CO2 equivalent day−1 kg−1, compared to 8.65 g CO2
equivalent day−1 kg−1 for the uncovered EMB facilities and
2.98 g CO2 equivalent day−1 kg−1 for the covered EMB facilities. The bulk of those reductions were because of methane.
On average, total unit emission rates during the spring, summer, and fall seasons amounted to 0.70, 6.59, and 5.17 g CO2
equivalent day−1 kg−1, respectively. On average, total daytime emission rates (i.e., between the hours of 06:00 and
18:00) were 5.00 g CO2 equivalent day−1 kg−1, while nighttime (between 18:00 and 06:00) emissions were 9.05 g CO2
equivalent day−1 kg−1.
The experimental results obtained in this study have been
used to estimate annual GHG emissions from farrow-to-finish swine operations under liquid manure management in
Saskatchewan for which the total animal mass in the
production building(s) at any given time for each 1,000-sow
increment (including gestating and farrowing sows, gilts and
boars, weaner and grower-finisher pigs) can be estimated at
approximately 650,000 kg. Those estimations indicate that
the addition of a blown chopped straw cover on an EMB
could yield reductions in CO2 and CH4 emissions of 56 and
786 tonnes of CO2 equivalent, respectively, for each
1,000-sow increment during the spring-to-fall period.
ACKNOWLEDGEMENTS
Agriculture and Agri-Food Canada (Climate Change
Funding Initiative in Agriculture (CCFIA) program), the
Fédération des producteurs de porcs du Québec (FPPQ), and
Sask Pork provided funding to support this research project.
Vol. 48(6): 2289−2296
The authors acknowledge the financial support provided to
the Sask Pork Chair in Environmental Engineering for the
Pork Industry by the Agri-Food Innovation Fund of Saskatchewan, Prairie Swine Centre Inc., and Sask Pork. Scientific
and technical assistance provided by Dr. M. T. Alam is also
gratefully acknowledged.
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TRANSACTIONS OF THE ASAE