Post on 05-Apr-2018
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Advantages and Limitations with usingVarious Substrates in Manure Biogas Plants
Anna Crolla1, Chris Duke2, Chris Kinsley1 and Terrence Sauv2
1 Ontario Rural Wastewater Center at University of Guelph Campus dAlfred2 Ontario Ministry of Agriculture, Food and Rural Affairs
4th Annual Canadian Farm & Food Biogas Conference and ExhibitionLondon Convention Center, London, ON
March 5 7, 2012
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Co-digestion of Manure
Addition of co-substrates to manure improves nutrient balanceof carbon, nitrogen and phosphorus
Manure dilutes high strength wastes
Dairy manure has good buffering capacity with alkalinity ashigh as 9000 mg CaCO3/L
Organic rich substrates improve methane yields
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385
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546
675
638
514
375
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575
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600
550
450
775
1000
0 200 400 600 800 1000 1200
Cow manure (9%TS)
Pig manure (7%TS)
Chicken manure (15%TS)
Corn (whole Crop)*
Wheat (grain)*
Grass*
Sugar beets*
Harvest re sidues (straw, stems)
Sewage sludge
Expired animal feed
Food Industry Waste
Stillage from breweries
Green wastes (markets)
Biowastes (source separated)
Flotation sludge/animal fat
Waste fat
Mean Biogas Yields of Substrates (m3gas/t VSsubstrate)
[Compilation of data from Braun et al. (2009), Braun and Wellinger (2003) and Weiland (2000)]
Europe: A lot of interest inenergy crops (e.g. grass,clover, cereals, corn)
Ontario: Focus in using
wastes (e.g. waste grease,stillage, food leftovers)
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Sources of Possible Substrates
Compounds Sources Possible Inhibition
Carbohydrates:
Sugars
Starch
Cellulose
beets, corn, fruit
potatoes, corn
straw, grass, wood
pH drop
Proteins animals & animalproducts
pH drop
ammonia increase
Fats animals & animal
products
VFA increase
pH drop
Volatile FattyAcids (VFA)
fats, oils, grease (FOG) pH drop
inhibition of some bacteria
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Parameters for Stable DigestionSubstrates will affect these values
pH 6.8 to 7.2
Alkalinity 1500 to 4000 mg CaCO3/L
IA/TA 0.1 to 0.2 (
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Testing of Substrates
Substrate Characterization Digester Stability
pH
AlkalinitytCOD, sCOD
VS, TS (VS/TS)
VFAs (acetic, propionic, butyric)
Ammonium Nitrogen (NH4+-N)
C:N
pH*
IA/TA (at start of changing OLRs)* VFAs (at start of changing OLRs)
Biogas production andcomposition
VFA Analysis at ORWC Laboratory
Important parameters to monitor
pH monitoring alone may prove tobe unreliable
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BMP & ATA Batch Tests
MesophilicIncubator
ThermophilicIncubator
Manometer 500 mL Wheaton bottles
Incubators for temperature
control and agitation (120 rpm) Manometer for gas volume
Acclimatized inoculum fromon-farm manure digester
Incubated for >30 days
Biochemical Methane Potential(BMP)
Indication of biodegradabilityof substrate to produce CH4
Anaerobic Toxicity Assay (ATA) Determines substrate
inhibition on CH4 production
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Semi-Continuous Bench-scale Digesters
30 L bench-scale digesters(20 L operating volume)
Intermittent mixing
Housed in heat room (35 2oC)
Biogas volume measured usingwet tip meters
CH4 and CO2 composition
determined using gaschromatograph
Typically run for several months
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Characteristics of Cellulosic Substrates
ParameterLiquid Dairy
ManureCorn Silage Switchgrass Woodchips
pH 7.35 (0.17) 7.22 6.99 7.73
Alkalinity, mg CaCO3/kg 7564 (223) 111 130 120
TS, g/kg 78 (20) 900 922 470
VS, g/kg 57 (19) 851 869 450
VS/TS, % 73 95 94 96
tCOD, g/kg 74.6 (14.1) --- --- ---
sCOD, g/kg 8.9 (3.5) --- --- ---
C:N 22:1 (3) 27:1 24:1 500:1
TN, g/kg 4.1 (0.7) 11.9 9.8 2.1
TP, g/kg 0.6 (0.1) 1.7 1.2 0.4
Corn Silage Switchgrass Woodchips
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Co-digestion of Dairy Manure with
Switchgrass or Corn SilageManure Co-digestion with Switchgrass and Corn Silage
(Co-substrates contribute 20% (w/w) of feed VS)
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0.10
0.20
0.30
0.40
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0.60
0 200 400 600 800 1000 1200 1400
Duration of Digestion (hours)
C
umulativeBiogasYield(Lbioga
s/gVS
Dairy Manure + Switchgrass Dairy Manure + Corn Silage Dairy Manure
30 days of Digestion
SubstratesBiogas Production(L biogas/g feed)
Biogas Yield(L biogas/g VS)
Manure + Switchgrass 0.06 0.49
Manure + Corn Silage 0.05 0.45
Dairy Manure 0.04 0.38
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Co-digestion of Dairy Manure with
Switchgrass or Corn SilageManure Co-digestion with Switchgrass and Corn Silage
(Co-substrates contribute 40% (w/w) of feed VS)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0 200 400 600 800 1000 1200 1400
Duration of Digestion (hours)
Cumu
lative
Biogas
Yield(Lbioga
s/gVS)
Dairy Manure + Switchgrass Dairy Manure + Corn Silage Dairy Manure (12% TS)
30 days of Digestion
SubstratesBiogas Production(L biogas/g feed)
Biogas Yield(L biogas/g VS)
Manure + Switchgrass 0.07 0.52
Manure + Corn Silage 0.06 0.51
Dairy Manure 0.04 0.38
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Co-digestion of Horse Manure with Woodchips
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0 500 1000 1500 2000 2500 3000
Duration of Digestion (hours)
Cumu
lative
Biogas
Yield(L
biogas
/gVS
Woodchips - 25% of Feed VS Woodchips - 50% of Feed VS
Woodchips - 75% of Feed VS Horse Manure - 100% of Feed VS
30 days of Digestion
Co-digestion of Horse Manure
with Woodchips
Substrates Biogas Production(L biogas/g feed) Biogas Yield(L biogas/g VS)
Woodchips 25% of Feed VS 0.14 0.51
Woodchips 50% of Feed VS 0.13 0.39
Woodchips 75% of Feed VS 0.10 0.23
Horse Manure 0.15 0.64
Study in Collaboration with H. H. Angus & Associates Ltd.
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Characteristics of Fat Based Substrates
ParameterLiquid Dairy
ManureHorse & Giraffe
ManureDAF Grease Waste
pH 7.35 (0.17) 8.33 5.87 3.99
Alkalinity, mg CaCO3/kg 7564 (223) 5489 7073 0
TS, g/kg 78 (20) 408 172 468
VS, g/kg 57 (19) 263 147 461
VS/TS, % 73 65 85 99
tCOD, g/kg 74.6 (14.1) --- 102.1 207
sCOD, g/kg 8.9 (3.5) --- 38.3 74.5
C:N 22:1 (3) 32:1 37:1 34:1
TKN, g/kg 3.9 (0.9) 3.3 2.7 6.1
Ammonium (NH4+-N), g/kg 1.9 (0.7) --- 0.8 0.9
TP, g/kg 0.6 (0.1) 0.6 0.3 0.4
Horse & Giraffe Manure DAF Grease Waste
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Co-digestion of Dairy and Poultry Manure Mix (14%TS) with DAF
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 200 400 600 800 1000 1200 1400 1600
Duration of Digestion (hours)
CumulativeBiogasYield(Lbio
gas/gVS)
DAF - 20% of Feed VS DAF - 30% of Feed VS
DAF - 48% of Feed VS Manure (Dairy + Poultry)
30 days of Digestion
Co-digestion of Dairy and Poultry Manure
Mix with DAF
SubstratesBiogas Production(L biogas/g feed)
Biogas Yield(L biogas/g VS)
DAF 20% of Feed VS 0.08 0.74
DAF 30% of Feed VS 0.10 0.83
DAF 48% of Feed VS 0.10 0.98
Dairy & Poultry Manure Mix 0.09 0.62
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Co-digestion of Horse & Giraffe Manure Mixture with Waste Grease
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 200 400 600 800 1000 1200 1400 1600 1800
Duration of Digestion (hours)
BiogasYield(Lbiog
as/gVS)
Grease - 30% of Feed VS Grease - 58% of Feed VS
Grease - 80% of Feed VS Manure - 100% of Feed VS
30 days of Digestion
Co-digestion of Horse and Giraffe Manure
Mix with Waste Grease
Study in Collaboration with H. H. Angus & Associates Ltd.
SubstratesBiogas Production
(L biogas/g feed)
Biogas Yield
(L biogas/g VS)
Grease 30% of Feed VS 0.28 0.92
Grease 58% of Feed VS 0.37 1.07
Grease 80% of Feed VS 0.41 1.03
Horse & Giraffe Manure Mix 0.16 0.61
Waste grease
as 70% of feedVS may bemore realistic
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Characteristics of Food Wastes
ParameterLiquid Dairy
ManureHorse &GiraffeManure
Food Waste(ORRS)
Fish Offal
pH 7.35 (0.17) 8.33 5.69 6.86
Alkalinity, mg CaCO3/kg 7564 (223) 5489 5942 7620
TS, g/kg 78 (20) 408 196 349VS, g/kg 57 (19) 263 191 300
VS/TS, % 73 65 97 86
tCOD, g/kg 74.6 (14.1) --- 95.3 218
sCOD, g/kg 8.9 (3.5) --- 27.1 46
C:N 22:1 (3) 32:1 36:1 19:1
TKN, g/kg 3.9 (0.9) 3.3 2.6 12.1
Ammonium (NH4+-N), g/kg 1.9 (0.7) --- 1.2 5.9
TP, g/kg 0.6 (0.1) 0.6 0.4 1.0
Horse & Giraffe ManureORRS Organic Resources Recovery System (form Organic Resource Management Inc.)
Food Waste Fish Offal
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Co-digestion of Dairy Manure with Food Waste (ORRS)
0.00
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0.20
0.30
0.40
0.50
0.60
0 100 200 300 400 500 600 700 800 900
Duration of Digestion (hours)
CumulativeBiogas
(Lbiogas/gVS)
Food Waste - 35% of Feed VS Food Waste - 45% of Feed VS
Food Waste - 55% of Feed VS Dairy Manure - 100% of Feed VS
Study in Collaboration with Organic Resources Management Inc.
Co-digestion of Dairy Manure and Food Waste
SubstratesBiogas Production
(L biogas/g feed)
Biogas Yield
(L biogas/g VS)
Food Waste 35% of Feed VS 0.02 0.41
Food Waste 45% of Feed VS 0.03 0.45
Food Waste 55% of Feed VS 0.03 0.49
Dairy Manure 0.01 0.26
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Co-digestion of Horse & Giraffe Manure Mixture with Food Waste
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0 200 400 600 800 1000 1200 1400 1600 1800
Duration of Digestion
CumulativeBiogasYield(Lbiogas/gVS)
Food Waste - 35% of Feed VS Food Waste - 62% of Feed VS
Food Waste - 82% of Feed VS Manure - 100% of Feed VS
30 days of Digestion
Study in Collaboration with H. H. Angus & Associates Ltd.
Co-digestion of Horse and Giraffe Manure
Mix with Food Waste
SubstratesBiogas Production
(L biogas/g feed)
Biogas Yield
(L biogas/g VS)Food Waste 35% of Feed VS 0.18 0.77
Food Waste 62% of Feed VS 0.19 0.90
Food Waste 82% of Feed VS 0.18 0.91
Horse & Giraffe Manure 0.16 0.61
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Co-digestion of Fish Offal with Sawdust
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0 200 400 600 800 1000 1200 1400 1600 1800
Duration of Digestion (hours)
Cumu
lative
Biog
as
Yield(Lbiogas
/gVS)
Fish Offal - 25% of Feed VS Fish Offal - 50% of Feed VS Fish Offal - 75% of Feed VS
Fish Offal - 88% of Feed VS Fish Offal - 100% of Feed VS
30 days of Digestion
Co-digestion of Fish Offal with Sawdust
SubstratesBiogas Production(L biogas/g feed)
Biogas Yield(L biogas/g VS)
Fish Offal 25% of Feed VS 0.10 0.36Fish Offal 50% of Feed VS 0.20 0.57
Fish Offal 75% of Feed VS 0.30 0.71
Fish Offal 88% of Feed VS 0.29 0.76
Fish Offal 0.35 0.89
Study in Collaboration with Meeker Aquaculture Inc.
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Industrial Wastes
Characteristics of Thin StillageParameter Liquid Dairy Manure
ThinStillage
pH 7.35 (0.17) 3.64
Alkalinity, mg CaCO3/kg 7564 (223) 0
TS, g/kg 78 (20) 85
VS, g/kg 57 (19) 67
VS/TS, % 73 79
tCOD, g/kg 74.6 (14.1) 141.4
sCOD, g/kg 8.9 (3.5) 63.6C:N 22:1 (3) 39:1
TKN, g/kg 3.9 (0.9) 2.1
Ammonium (NH4+-N), g/kg 1.9 (0.7) 0.8
Total Phosphorus, g/kg 0.6 (0.1) 1.1
Liquid Dairy Manure Corn Thin Stillage
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Co-digestion of Dairy Manure with Thin Stillage
0
0.1
0.2
0.3
0.4
0.5
0.6
0 100 200 300 400 500 600 700 800 900 1000
Duration of Digestion (hours)
CumulativeBiogasYield(Lbiogas/gVS)
Stillage - 20% of Feed VS Stillage - 40% of Feed VS
Stillage - 60% of Feed VS Dairy Manure - 100% of Feed VS
Co-digestion of Dairy Manure withCorn Thin Stillage
Substrates
Biogas Production
(L biogas/g feed)
Biogas Yield
(L biogas/g VS)
Thin Stillage 20% of Feed VS 0.02 0.43
Thin Stillage 40% of Feed VS 0.03 0.56
Thin Stillage 60% of Feed VS Complete Inhibition
Dairy Manure 0.02 0.32
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0.0
0.5
1.0
1.5
2.0
2.5
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Duration of Digestion, hours
Bioga
sProduction,m
3/m3/day
Two Phase Digestion (Dairy Manure & Stillage)Single Phase Digestion (Dairy Manure & Stillage)
Single Stage Two-Stage
Acid Production
Methane Production
Biogas
Biogas
Co-digestion of Dairy Manure withCorn Thin Stillage
(Two-Stage Digestion System)
Thin stillage is 50% of feed VS
Two stage system will be used to push
digestion to 70% stillage as feed VS
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Impact of Rumensinon Biogas Production
SubstratesBiogas Production(L biogas/g feed)
Biogas Yield(L biogas/g VS)
Dairy Manure (No Rumensin) 0.02 0.30
Beef Manure (With Rumensin) 0.02 0.38
Dairy Manure (No Rumensin) + Beef Manure(with Rumensin)
0.02 0.28
Toxicity assays (ATA) are currently being conducted
Impact of Rumensin in Biogas Production
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0 500 1000 1500 2000
Duration of Digestion, hoursCumulativeBiogasY
ield(Lbiogas/g
VS)
Dairy Manure (No Rumensin)Beef Manure (With Rumensin)
Dairy Manure (No Rumensin) + Beef Manure (With Rumensin) [50% w/w]
Rumensin
fed at 29 ppm
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Summary
Good co-substrates available
Need to characterize co-substrates toevaluate potential in digester performance
Batch lab studies are useful to determine
optimum addition of co-substrates todigestion
Need to monitor digester performance to
detect for possible digester upset
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Managing and Diagnosing Digester
Start Up Digester start-up phase is critical and can take 2 to 10 months
Increasing temperature takes external heat Incoming substrates are cold
Biology ecology not developed Gas quality is normally better than quantity Very unstable, low gas production means limited heat, slow digestion
Substrate feeding rate optimises: Biological consumption Heat requirements
Gas yield Substrate feeding recipe evolves, requires management
Parameters : temperature, gas quality, gas quantity, pH, FOS/TAC, C:N, TS, VS, VFA, eyes Variables : heat demand, mixing schedule, feeding schedule, substrates
Engine commissioning requires substantial biogas production to enable extendedrun-time
Delayed start up delays revenue 500 kW ~ $1800/day 100 kW ~ $400/day
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FOS/TAC Acid concentration and the buffer capacity in the digester
substrate:
pH - measure of a liquid's acidity - neutral is 7, FOS stands for Flchtige Organische Suren (volatile organic
acids) TAC stands for Totales Anorganisches Carbonat (total inorganic
carbonate (alkaline buffer capacity)
The FOS/TAC ratio is a guidevalue for assessing digestionprocesses.
It enables detecting imminentdigester biology disruptions atan early stage so that correctiveactions can be taken
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40
50
60
70
80
04-Oct 24-Oct 13-Nov 03-Dec 23-Dec 12-Jan 01-Feb 21-Feb 12-Mar
Date
CH4Conc
entration
%
20
25
30
35
40
Tem
pC
CH4% Digester T
Example start-up Liquid dairy, off-farm substrates are grease trap liquids
1500 m3, continuous stirred, mesophilic, heating startedin September
No gas flow meter
Farmer working with digester firm, seeking assistance,conducting daily measurements
Gas analyser not calibrated
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0
24
6
8
10
12
14
04-Oct 24-Oct 13-Nov 03-Dec 23-Dec 12-Jan 01-Feb 21-Feb 12-Mar
Date
pH
0
0.2
0.4
0.6
0.8
1
FOS,TAC,FOS/TA
Digester pH FOS TAC FOS/TAC
0
20
40
60
80
100
120
04-Oct 24-Oct 13-Nov 03-Dec 23-Dec 12-Jan 01-Feb 21-Feb 12-Mar
Date
Substratesm3
20
25
30
35
40
TempC
Manure Input [m3] Of f-farm Input [m3] Digester T
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Important Lessons Digester acidification was narrowly avoided but start-up is still slow
and ongoing
Daily+ measurement Digestate and gas measurement equipment on-site is very useful Recipe development for start-up phase and normal Consult with biogas system firm, consultants Substrates having different digestion rates and gas yields manage
accordingly Fats, high sugar substrates cause rapid responses and increase in
acid levels Substrates may have inhibition effects (i.e. Rumensin) Heat demand is critical Delayed start-up means thousands
of dollars delayed revenue
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Acknowledgments
Funding for these projects was provided by:
OMAFRA Organic Resources Management Inc. (ORMI)
H. H. Angus & Associates Ltd.
Meeker Aquaculture Inc. Fisheries and Oceans Canada
Iogen Corporation