waste to watts: anaerobic digestion of livestock manure (sood)

04/08/23

Waste to Watts: Anaerobic Digestion (AD) of Livestock

Manure

By:

Dave SoodConsultant

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-FormingBacteria

Methane-Forming Bacteria

Methane, C02, & Trace Gases

Acetate

Organic Residue

Acid-FormingBacteria

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.