potential air quality impacts of anaerobic digestion of dairy manure
DESCRIPTION
Proceedings available at: http://www.extension.org/67666 Anaerobic digestion (AD) of livestock manure is better known for the economic return derived from biogas for energy rather than for its, inherent, environmental benefits. The effect of AD of dairy manure on the emissions of odor, ammonia (NH3), and greenhouse gases (GHG) including: carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), during manure storage and also in subsequent land applications will be presented. Air samples were collected in 10-L Tedlar bags, at pertinent locations within the AD system, and shipped immediately to the lab for odor analyses by a trained odor panel using the “Dynamic Dilution Forced-choice Olfactometer.” Measurements of GHG emissions from both AD and non-AD manure storages were made using a floating chamber and a photoacoustic gas analyzer (INNOVA model 1412). Emissions of GHG were determined using the standard closed chamber method from field plots applied with AD and non-AD manure. Although odor analyses of collected air samples indicated increased detection threshold (D/T), odor strength (intensity) and unpleasantness (hedonic tone) decreased after AD of manure. Data indicated significantly higher fluxes of GHG from land applied with non-AD manure than from land applied with AD manure. Injection of non-AD manure further increased CH4 flux from applied manure. More than 50% emissions of CO2 and CH4 were observed during the first 3 days after manure was land applied. Emissions of GHG from the anaerobic lagoon holding AD manure, during all four seasons, were significantly lower than from the anaerobic lagoon with non-AD manure. In contrast, the reverse was observed with NH3 emissions suggesting potential increased emissions of NH3 during storage of post AD manure.TRANSCRIPT
Potential Air Quality Impacts of Anaerobic Digestion of Dairy Manure
Washington State University:H.S. Joo, P.M. Ndegwa, J.H. Harrison, E. Whitefield, S.
Fei, X. Wang, G. Neerackal
Purdue University:
A.J. Heber, J.Q. Ni
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Outline
• Background
• Objectives of the study
• Materials and Methods
• Results
• Summary & Conclusions
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Background
• This study is funded under NRCS-CIG program to demonstrate the impact of anaerobic digestion (AD) of dairy manure on air quality during effluent storage and/or subsequent manure application on land.
• Motivation: The environmental benefits of AD has been shown in research but adoption of the technology is still low.
• Interests: • Odor and VOCs emissions,• Greenhouse gases (GHGs) emissions,• NH3 and H2S emissions.
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Methods and Materials: AD site plan
AD Mixing tank
Lagoons
Composting vessel
Manure from Dairy
Liquid effluent
Solids separation
Solids/compost
GeneratorRoom
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Methods and Materials: AD site
AD
Receiving/mixing tank
Primary lagoon
Composting drums
Liquid effluent tank
Solids/liquid separator
Electricity generator
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Methods and Materials: Manure application
28 ft
125
ft
Broadcasted Non-AD
Injected non-AD
Injected AD
Broadcasted Non-AD
Broadcasted Non-AD
Injected AD
Injected AD
Injected non-AD
Injected non-AD
Broadcasted AD
Broadcasted AD
Broadcasted AD
Drag hose applicator
Chamber in place
Evacuated vials
Manure application plan/strategy in the plots
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Methods and Materials: Lagoon measurements
Floating chamber
Chambers’ access
Photoacoustic gas analyzer (INNOVA model 1412)
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Methods and Materials: Lagoon and Land Application Simulations in the lab.
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Methods and Materials: Odor samples
AD
Receiving/mixing tank
Influent
Liquid effluent tank
Separator
Effluent
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
• Air samples were collected in 10-L Tedlar bags.
• At: Raw manure, influent, effluent, and separated liquid.
• Samples shipped immediately to the lab for odor analyses by a trained odor panel (Overnight).
• Dynamic Dilution Forced-choice Olfactometer.
Results: Land application (field studies)
R² = 0.97
R² = 0.94
R² = 0.92
R² = 0.95
0
2
4
6
8
10
0 15 30 45 60
CH
4C
once
ntra
ion
(ppm
)
Time (minutes)
AD-Broadcast:
NonAD-Injection:
AD-Injection:
NonAD-Broadcast:
R² = 0.99
R² = 0.97
R² = 0.97
R² = 0.99
0
200
400
600
800
0 15 30 45 60
CO
2C
once
ntra
tion
(ppm
)
Time (minutes)
AD-Broadcast:
NonAD-Injection:
AD-Injection:
NonAD-Broadcast:
R² = 1.00
R² = 0.99
R² = 0.93
R² = 1.00
0
0.5
1
1.5
2
2.5
0 15 30 45 60
N2O
Con
cent
rati
on (p
pm)
Time (minutes)
AD-Broadcast:
NonAD-Injection:
AD-Injection:
NonAD-Broadcast:
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Results: Land application – emissions (field studies)
0 2 4 6 8 10 12 140
1000
2000
3000
4000
5000
6000
AD-Broadcast
NonAD-Injection
AD-Injection
NonAD-Broadcast
Time (day)
CH
4 E
mis
sion
s (µ
g/kg
-VS
)
0 2 4 6 8 10 12 140
500
1000
1500
2000AD-BroadcastNonAD-InjectionAD-InjectionNonAD-Broadcast
Time (day)
CO
2 E
mis
sion
(m
g/kg
-VS
)
0 2 4 6 8 10 12 140
2000
4000
6000
8000AD-BroadcastNonAD-InjectionAD-InjectionNonAD-Broadcast
Time (day)
N2O
Em
issi
on (
µg/
kg-T
AN
)
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Results: Land application – Ammonia emissions (field vs. studies)
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0
20
40
60
80
0 100 200 300 400 500
NonAD-B NonAD-I
AD-B AD-I
Cum
mul
ativ
eN
H3
emis
sion
(m
g)Time (h)
0
300
600
900
1200
1500
0 1 2 3 4 5 6 7
AD-I NonAD-I
AD-B NonAD-B
Time (day)
Cu
mm
ula
tive
NH
3em
issi
on
(p
pm
)
Field studies
Note the higher ammonia loss from non-AD surface applied manure – contrary to what one would anticipate or expect!
Lab simulation studies
Results: Lagoon GHG Emissions
0
10
20
30
April-May July September November
AD nonAD
CH
4(m
g/m
2 /m
in)
0
30
60
90
April-May July September November
AD
nonAD
CO
2(m
g/m
2 /m
in)
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
0
5
10
15
20
April-May July September November
AD nonAD
N2O
(µg/
m2 /
min
)
Results: Lagoon NH3 Emissions
0
0.3
0.6
0.9
1.2
April-May July September November
AD nonAD
NH
3(m
g/m
2 /m
in)
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
0
400
800
1200
1600
2000
0 5 10 15 20 25
Cu
mm
ula
tive
NH
3 em
issi
on (m
g)
Time (Day)
RM
AD Influent
AD Effluent
AD Liquid Effluent
Field studies
Lab simulated studies
AD effluent liquid after separation – probably huge volatilization or loss occurs during solids-liquid separation process.
Results: Odor Analyses
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Intensity 6-point scale: • 1—very weak• 2—weak”• 3—distinct• 4—strong• 5—very strong• 6—extremely
strong
Hedonic tone a nine-point scale:“-4:extremely unpleasant to “0 or neutral”) to “+4:extremely pleasant”
0
1500
3000
4500
6000
Water (Control) Raw Manure AD Influent AD Effluent AD Liquid Effluent
OU
E/m
3
0.0
1.0
2.0
3.0
4.0
Water (Control) Raw Manure AD Influent AD Effluent AD Liquid Effluent
Inte
nsi
ty
-5.0
-4.0
-3.0
-2.0
-1.0
0.0Water
(Control)Raw Manure AD Influent AD Effluent AD Liquid
Effluent
He
do
nic
To
ne
Summary & Conclusions
• Emission of CO2 was much higher from non-AD manure compared with AD manure. Injection of manure did not seem to play a major part on CO2 emissions.
• CH4 emission was also much higher from non-AD manure compared with AD manure. Injection of non-AD manure increased emissions of CH4.
• N2O emissions were slightly higher from non-AD manure compared with AD manure. Injection of either AD or non-AD manure did not seem to affect emissions of N2O.
• Although AD manure had more TAN, NH3 emissions were highest in surface applied non-AD manure!
Waste-2-Worth ConferenceDenver, Co, April 3, 2013
Summary & Conclusions
• GHG emissions from the anaerobic lagoon holding AD manure, during all four seasons, were significantly lower than from the anaerobic lagoon with non-AD manure.
• In contrast, the reverse was observed with NH3 emissions. This was also confirmed via lab simulation studies.
• While odor concentration (DT) increased some going through the digester, the intensity and hedonic tone improved.
• AD of dairy manure prior to its storage and land application demonstrate significant environmental benefits (GHGs, odor, NH3).
• Potential liability - increased NH3 emissions during storage.Waste-2-Worth ConferenceDenver, Co, April 3, 2013
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