anaerobic digestion larson bayfield 2015...• 17% anaerobic digestion • 50% anaerobic digestion...

FROM WASTE TO WORTHANAEROBIC DIGESTION

Becky LarsonAssistant Professor and Extension SpecialistBiological Systems Engineering

November 24, 2015

What is Anaerobic Digestion?• Biological process• Breakdown of organic materials (called feedstocks) • Absence of oxygen (anaerobic conditions)• Produced biogas - methane (CH4) and carbon dioxide (CO2)

Why install a digester?• Energy independence• Reductions in green house gases• Flexibility in manure management • Reduced odors & pathogens• Reduction in other environmental impacts• Potential for additional asset streams (?)

• Bedding• Tipping fees• Environmental credits

• Profits?• What can’t digesters do?

Anaerobic Digestion in the U.S.

USEPA AgSTAR, 2011

Anaerobic Digestion Livestock & Swine Operations

Animals No. of Digesters Operational or in Construction

Methane Emissions

Reductions (metric tons CO2-eq/year)

Shutdown Projects

All Livestock 261 3,480,955 52Swine 39 1,491,718 10

• North Carolina has 10 swine digesters, others are scattered around country

• Operational from as far back as 1985• From 1,200 to 1,200,000 million animals• Completely mixed, covered lagoons, mixed plug flow

designs• Gas use in boilers, electricity, cogeneration, flares

USEPA AgSTAR, 2015

Biogas Opportunities RoadmapVoluntary Actions to Reduce Methane Emissions and Increase Energy Independence

U.S. Department of Agriculture, U.S. Environmental Protection Agency, U.S. Department of Energy

August 2014

Traditional Anaerobic Digestion Process Flow

Slurry

Biogas

SeparatorDigestate

Filtrate (liquid)

Fiber (solid)

Feedstock's

Anaerobic Digestion Feedstocks

Cheese Whey

Swine Manure

Dairy Manure

Cattle Manure

Cucumber Waste

Yard ClippingsMunicipal Organics

Human Waste

Food Processing Waste

Vegetables

Grasses

Characterized by rapid bacterial growth

“Weak link” in the process of producing biogas

Goal?...Avoid inhibition, maintainstabilization!

Stage Three: Acetogenesis

Stage One: Hydrolysis

Stage Two: Acidogenesis

Stage Four: Methanogenesis CO2 reducing

methanogensaceticiastic

methanogens

acetogens(H2

producing)

fermentative bacteria

fermentative bacteria

PROPIONATE, BUTYRATE, etc.

(Short-chain volatile organic acids)

fermentative bacteria

fermentative bacteria

COMPLEX POLYMERS(Proteins, polysaccharides, etc.)

MONOMERS AND OLIGOMERS(Sugars, amino acids, peptides)

acetogens(H2 consuming)

H2 + CO2 ACETATE

CH4, CO2

Source: Syed Hashsham, PhD, lecture notes, Michigan State University

The Biological Process of Producing Biogas

Biogas Yield

Kestutis Navickas. 2007. Bioplin Tehnologija in Okolje,

Anaerobic Digester Completely Mixed and Plug Flow

AD System Types

Covered storage

Covered Lagoon Digester and FlareBaldwin Dairy, Baldwin, WI Covered Lagoon at a Swine Farm

Olivia, MN

Advantages included odor control, low cost, integrated manure storage and minimal operational costsDisadvantage include seasonal biogas production in cold climates and difficulties with sludge removal

Plug flow & mixed plug flow

Plug flow digester and flare Emerald Dairy, Baldwin, WI

Inside a plug flow digester under construction Baldwin Dairy, Baldwin, WI

Advantages include low cost of construction and ease of daily operationDisadvantage include the limited range of feedstock TS concentration

Completely mixed

Complete mix digester Green Valley Dairy, Krakow, WI

Complete mix digester Five Star Dairy, Elk Mound, WI

Inside a completely mixed AD

Slow speed agitator fixed to the digester floor

Inside a complete mix digester under construction Westfalia, Germany

Submersible mix mounted to a mast

Fixed film

Fixed film digester mediaJ.J. Farber Farm, East Jewett, NY

Fixed film digesterROPA, Regensburg, DE

Advantages include low cost of construction and ease of daily operationDisadvantage include the limited range of feedstock TS concentration

Dry Digestion

OshKosh Dry Digester, BIOFerm

Small Scale Digesters

Small Scale Digestion

Ecofys bag digester, ecofys.com

Community DigestersDane County Digester, 2011

Biogas • Biogas Components

• CH4 (50 – 65%)• CO2 (40 – 50%)• H2S (<1%)• Other Trace Elements (?)

• Generator (CHP) – electricity production• Most common (ease of use)• High cost• Requires pretreatment or specially

designed equipment• Compressed Biogas

• High cost of clean-up• Requires design• High revenue

• Biogas Treatment• High cost systems• Multi-phase approach

Digestate

• Must be disposed• Liquid and solid commonly used for fertilizer

• Solids potential for higher value products

• AD results in:• nutrient mineralization• odor reduction• pathogen reduction• antibiotic degradation

Nutrients & Anaerobic Digestion

Wright, et al. 2004. Preliminary Comparison of Five Anaerobic Digestion Systems on Dairy Farms in New York State

0

1000

2000

3000

4000

5000

6000

AA DDI FA ML* NH

TKN Con

centratio

n (m

g/kg)

Facility

TKN

Input

Output

Nutrients & Anaerobic Digestion

0

500

1000

1500

2000

2500

3000

AA DDI FA ML* NHAmmon

ia Con

centratio

n (m

g/kg)

Facility

Ammonia

Input

Output

Wright, et al. 2004. Preliminary Comparison of Five Anaerobic Digestion Systems on Dairy Farms in New York State

Increase of 24%

Ammonia

0

5000

10000

15000

20000

25000

30000

35000

40000

Pre Digestion Post Digestion

Am

mon

ia (m

g/L)

Nutrients & Anaerobic Digestion

Wright, et al. 2004. Preliminary Comparison of Five Anaerobic Digestion Systems on Dairy Farms in New York State

0100200300400500600700800900

AA DDI FA ML* NHTotal Pho

spho

rus Co

ncen

tration 

(mg/kg)

Facility

Total Phosphorus

Input

Output

Phosphorus

020406080

100

Liquid %Solid %

N-P-K

Concentration N (g/kg) P2O5 (g/kg) K2O (g/kg)

Manure 50 18 41

Liquid 101 27 75

Solid 15 14 8

Ratio N P2O5 K2O

Manure 3 1 2Liquid 4 1 3

Solid 2 2 1

OdorSwine ManureHansen et al. 2006, Applied Engineering in Agriculture• Slurry concentrations of

malodorous VFA were reduced 79-97% from AD

• Odor concentration above undisturbed slurry store reduced (higher odors after mixing)

• Land application odor reductions:• 17% anaerobic digestion• 50% anaerobic digestion

and solid liquid separation

Orzi et al., 2015, Science of the Total Environment• Odors reduced 98%• P2-P6 are pig slurries• VFA destruction related to measured odor

reductions

Pathogens in manure from a single farm by year and season

Autumn, 2009Spring, 2010

Autumn, 2010Spring, 2011

1

10

100

1000

10000

100000

1000000

10000000

100000000

1E+09

Mean Pathogen

 Con

centratio

n (gc/gm

)Bovine Polyomavirus

Farm #1

Farm #3

Farm #4

Farm #5

Farm #6

Farm #7

Farm #8

Antibiotic Degradation

Alvarez et al., 2010, Bioresource Technology• Fate of antibiotics in pig manure in AD• oxytetracycline (OTC) and chlortetracycline (CTC)• Reduction in antibiotics over time, as well as

methane production• Antibiotics adsorbed to solids increasing duration

for destruction

• Many antibiotics to be tested

• Not many studies to date

• May increase intermediates

• Beef manure studies by Arikan(2006, 2007, 2008) found some degradation in initial component, increases in some intermediaries

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0.00

10.00

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-50

-40

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-20

-10

0

10

SLS AD AD+SLS

kg C

O2-

eq to

n-1ex

cret

ed m

anur

e

CO2(f) CO2(b) N2O(f) N2O(b) CH4(f) CH4(b) NET

Global Warming Potential

Ammonia Emissions

0.0

0.3

0.6

0.9

1.2

1.5

1.8

Collection Storage Application

NH3 emissions (AD)kg NH3-eq ton-1 excreted manure

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

Collection Storage Application

NH3 emissions (BC)kg NH3-eq ton-1 excreted manure

Limitations to Adoption• Lack of Awareness of Biogas Benefits.• Unpredictable Biogas Market

Conditions• Lack of Market Maturity. • Lack of Full Valuation• Inconsistencies across Federal, State,

and Local Governments.• Lack of Technical and Applied

Research & DevelopmentBiogas Opportunities RoadmapVoluntary Actions to Reduce Methane Emissions and Increase Energy Independence U.S. Department of Agriculture, U.S. Environmental Protection Agency, U.S. Department of EnergyAugust 2014

• Capital cost• Operating cost• Energy use• Energy value• By-product

Revenue

Thank You!

Becky Larsonralarson2@wisc.edu(608) 890-3171