By: Dave Sood, Consultant, The presentation will cover key aspects of anaerobic digestion: -Methane Production from Manure -AD and Its Benefits -AD Process -Operating Conditions for AD -Manure Characteristics and Digester Types -AD and Water Quality -Manure Characteristics and Digester Types -Economic Analysis -AD in Europe -Why Digesters Fail? -Cold Climate Digesters -Key to Successful Digesters in Cold Climates -A success story & Carbon Credits: Haubenschild Dairy, Minnesota, USA

1. 08/17/14
Waste to Watts:
Anaerobic Digestion (AD) of Livestock
Manure
By:
Dave Sood
Consultant
Email: davesood@aol.com

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Overview
The presentation will cover key aspects of anaerobic digestion:
• Methane Production from Manure
• AD and Its Benefits
• AD Process
• Operating Conditions for AD
• Manure Characteristics and Digester Types
• AD and Water Quality
• Manure Characteristics and Digester Types
• Economic Analysis
• AD in Europe
• Why Digesters Fail?
• Cold Climate Digesters
• Key to Successful Digesters in Cold Climates
• A success story & Carbon Credits: Haubenschild Dairy, Minnesota, USA

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AD and its Benefits
• Odor and fly control
• Electricity, fuel for heating and Residual
by-product
• Reduced pathogens; weed seed destruction
• Greenhouse Gas Reduction
• Others

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Turkey Livestock
Manure storage
Gå till första sidan

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The AD Process
Acetate
Hydrolytic &
Fermentative Bacteria
Soluble Acids,
Alcohols, &
Neutral Compounds
Acid-Forming
Bacteria
Methane-Forming
Bacteria
Methane, C02, &
Trace Gases
Acetate
Organic Residue
Acid-Forming
Bacteria
Acetate
H2
H2, C02
Source:
USEPA/AgStar

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Methane Production from Manure

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AD and Water Quality
• Existing Sources:
– Open Feedlots, Pasture, Stock piles, storage etc.
• N most monitored: CWA, EU’s Nitrate
Directives
• AD Converts Organic N to Ammonia better
predictable
• Reduces runoff: By-product Residue more
stable

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Manure Characteristics &
Digester Types

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Operating Conditions for AD
Operating Parameter Typical Value
Temperature
Mesophilic 950
F
Thermophilic 1300
F
pH 7-8
Alkalinity 2,500 mg/liter (minimum)
Retention time 10 – 30 days
Loading Rate 0.15 – 0.35 lb VS/ft3
/day
Biogas yield 3 – 8 ft3
/lb VS
Methane content 60 – 70%
Calorific Value 17 – 25 MJ/m3

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Manure Digestion Issues
• High Capital Costs
• System Sizing: Technology Type, Permitting
• By-product Use (Electricity and Residues)
• Feedstock Supplements
• Type of Engine/Generator
• Cold Weather
• Comfort Level of Lenders
• Operator Knowledge and Training

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Types of Digesters
• Plug-Flow
• Complete Mix
• Covered Lagoons
• Others

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Family-size Biodigesters
• Most Popular are Chinese (Fixed dome) and Indian
(Floating Dome) and their Modifications; (4 m3
and
larger)
•● Provide Energy for Lighting and Cooking to Over 23
Million, Mostly Rural Households Worldwide; Most
Installations are in China, India and Nepal
• National Program’s Sustainability have Often Required
Subsidies, Easy Access to Credit, Market Development
and Owner/operator Training.

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Plug-Flow Digester
AA Dairy in upstate New York, USA – processes manure from around
600 cows and powers the farm with biogas product

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Complete Mix Digester
RCM Digesters - Colorado, US

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Covered Lagoon
8,600 Hog Finishing Farm

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Economic Analysis
500-Cow Dairy Farm (2004)
• System Components: Manure Digester, Settling tank,
Solids Separator, Engine/Gen.
• Capital Costs (2001): 475,000 (includes 150 W Generator)
• O & M Costs: $19,500/Yr.
• Miscellaneous: $18,000/year
• Revenues: Highly dependent on electricity
rates, extent of avoided fertilizer
purchases, extent of (free) labor by
owner/operator etc.
• Payback Period: 4-6 years at 7.5 cents/kWh,
Operator Labor, Some grants

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AD in Europe
• Leading Countries: Denmark, Sweden,
Germany, Others
• Current EU Deployment: 307 MW; potential 12,296
MW
• Types: Community Digesters,
Heating/Mixing.
Feedstock: Manure/dairy,
fish, catering wastes etc.
• Supporting Policies: grants/premium elect. Price
(15c kWh/Germany/v. high)
• Evolving/Improving 14 Euros/credit; U.S.
Carbon Market: $4.10/credit (Values Change)

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Why Digesters Failed?
• Poor Digester Design
– Incompatibility
– Each farm unique
• Poor Equipment
– Digester
– Engine Generator
• Toxic Substances
– Excessive NH3 (such as from urine)
– Harmful feed additives
• Poor Management
– Biological System
– Lack of knowledge/training/interest
• Poor Rate of Return
– Low price (3 cents/kWh) vs 7 cents/kWh
– Weak regulatory support

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Few General Rule-of-Thumb Figures
• AD costs lower with greater animal nos.
• 13-14 pigs = One lactating cow
• 500-Cow Dairy Digester = 30-50k ft3
/day
• 1kW = 5-8 Cows = 40- 65 hogs/finishers =
1,000 birds/Layers
• Cow/methane/yr. = 200 liters of gasoline
• 1 cow/day = 1 ½ - 2 ½ kWh/day = 100 W
for 22 hrs.

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Key to Successful Cold Climate
Digesters
• Manure collection, non-frozen
• Thermal system design (efficient/effective)
• Digester design (adequate size, insulation)
• Insulate exposed pipes
• Others, as needed

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Cold Climate Operating Digesters
• Haubenschild Dairy, IL, 1999, 950 cows
• New Horizon, IL, 2002, 2,400 cows
• Stencil Farms,WI, 2001, 1,200 cows
• AA Dairy, NY, 1997, 1,000 cows
• Dairy Dev. Intl., NY, 1997, 1,000 cows.
• Matlink Farm, NY, 2001, 700 cows

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Costs/Benefits
Dairy Farm Start Date Capital Cost Electric Savings / Sales
($ / year)
Hot Water Savings
($/year)
Fiber Value
($/year)
Haubenschild 1999 $335,000 $80,000 $20,000 No recovery
Stencil 2001 $450,000 $40,000 $15,000 $40,000
New Horizons 2002 $875,000 $100,000 $19,000 $60,000
AA Dairy 1997 $311,500 $40,000 -- $10,000
DDI 2001 $325,000 None $30,000 $15,000
Matlink 2001 $625,000 $80,000 $15,000 $30,000
Source: USEPA/RCM Digesters
Six Cold Climate Region Digesters in the U.S.

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A Success Story: Haubenschild Dairy

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Haubenschild Dairy, Princeton, MN
• 900 dairy cows, 1,000 acres, 4-generation family
farm
• Plug-flow digester; gravity flow
• Total Cost (2005): $775,000; Generator:
$375,000; O & M/Year: By owner; 1 ½ cents/kW
• Revenues:Variable, Electricity use on-farm and
some area houses, Carbon credit/year (since
2003), credit for solids
• Funding Sources: 1/3rd owner; Rest: USEPA, MN
State Agencies (0 % loan)

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Engine-generator at Haubenschild, MN

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Electricity Metering, Haubenschild
Dairy, Connection to the Power Co.

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By-product Storage Tank, Haubenschild,

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Fuel Cell at Haubenschild Farm, MN

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Digester Systems
Biogas Flare
Digester Building

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Future Needs Include:
• Documenting System’s Performance/Costs
• Optimize Designs and Operations
• New Business Models/Electricity Pricing
• Farmer Training/Information Dissemination
• Country-specific needs including
supporting policies.