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  • FROM WASTE TO WORTH ANAEROBIC DIGESTION

    Becky Larson Assistant Professor and Extension Specialist Biological 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 52 Swine 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 Roadmap Voluntary 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 Clippings Municipal Organics

    Human Waste

    Food Processing Waste

    Vegetables

    Grasses

  • Characterized by rapid bacterial growth

    “Weak link” in the process of producing biogas

    Goal?...Avoid inhibition, maintain stabilization!

    Stage Three: Acetogenesis

    Stage One: Hydrolysis

    Stage Two: Acidogenesis

    Stage Four: Methanogenesis CO2 reducing methanogens

    aceticiastic 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 Flare Baldwin Dairy, Baldwin, WI Covered Lagoon at a Swine Farm

    Olivia, MN

    Advantages included odor control, low cost, integrated manure storage and minimal operational costs Disadvantage 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 operation Disadvantage 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 media J.J. Farber Farm, East Jewett, NY

    Fixed film digester ROPA, Regensburg, DE

    Advantages include low cost of construction and ease of daily operation Disadvantage 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 Digesters Dane County Digester, 2011

  • Biogas • Biogas Components

    • CH4 (50 – 65%) • CO2 (40 – 50%) • H2S (

  • 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

    TK N  C on

    ce nt ra tio

    n  (m

    g/ kg )

    Facility

    TKN

    Input

    Output

  • Nutrients & Anaerobic Digestion

    0

    500

    1000

    1500

    2000

    2500

    3000

    AA DDI FA ML* NHAm m on

    ia  C on

    ce nt ra tio

    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

    A m

    m on

    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

    0 100 200 300 400 500 600 700 800 900

    AA DDI FA ML* NHT ot al  P ho

    sp ho

    ru s  Co

    nc en

    tr at io n 

    (m g/ kg )

    Facility

    Total Phosphorus

    Input

    Output

  • Phosphorus

    0 20 40 60 80

    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 2 Liquid 4 1 3

    Solid 2 2 1

  • Odor Swine Manure Hansen 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, 2009 Spring, 2010

    Autumn, 2010 Spring, 2011

  • 1

    10

    100

    1000

    10000

    100000

    1000000

    10000000

    100000000

    1E+09

    M ea n  Pa th og en

     C on

    ce nt ra tio

    n  (g c/ 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

  • -60.00

    -50.00

    -40.00

    -30.00

    -20.00

    -10.00

    0.00

    10.00

    -60

    -50

    -40

    -30

    -20

    -10

    0

    10

    SLS AD AD+SLS

    kg C

    O 2-

    eq to

    n- 1

    ex cr

    et ed

    m an

    ur 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-e

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