HousekeepingHousekeepingQuiz answersQuiz answers

Add technical details to answersAdd technical details to answersBe sure you can answer last year’s questionsBe sure you can answer last year’s questionsWhy agriculture isn’t regulatedWhy agriculture isn’t regulatedHow it might be pushed to eco-awarenessHow it might be pushed to eco-awareness

Change of Plans….Change of Plans….How was the Municipal P2 viewing?How was the Municipal P2 viewing?State of the Art topicsState of the Art topics

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  Average Scores Max

  All Grads Under Pts

1/11/2012Intro to P2 9.0417 8.9667 9.1667 10

1/18/2012Ind. Activity and Env. 10.239 10.036 10.556 10

1/25/2012Municipal P2 10

1/31/2012Field Trip - Cargill  

2/1/2012Fuel Cells, Biogas, SOA, Pumps 10

2/8/2012Life Cycle Assessment 10

2/15/2012Design for Env. -- Spiller 10

2/22/2012MSW Field Trip 10

2/29/2012P2 Economics 10

3/7/2012P2 Planning / Town Hall -- Legare 10

3/21/2012Energy Conservation - Walton 10

Field Trip - Zimmerman  

3/28/2012Fugitive Emissions -- Legare 10

Field Trip - Recycled Materials  

4/4/2012P2 and BMPs in Industry 10

4/11/2012Brewery and P2 -- Smith 10

Field Trip - Coors  

4/18/2012Metals Removal 10

4/25/2012Water Resources, DNAPLs, and Fracking 10

Personal Quiz Average 10

Total Quiz and Homework Points 150

Sidney Innerebner, PhD, PESidney Innerebner, PhD, PE

Indigo Water GroupIndigo Water Group

What is Biogas and Where Does What is Biogas and Where Does it Come From?it Come From?A methane rich byproduct produced when A methane rich byproduct produced when

organic matter breaks down anaerobicallyorganic matter breaks down anaerobicallySources of biogas:Sources of biogas:

Decomposing vegetationDecomposing vegetationFarm and ranch animalsFarm and ranch animalsManure from farm and ranch animalsManure from farm and ranch animalsWastewater plantsWastewater plantsLandfillsLandfills

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Typical Biogas UtilizationTypical Biogas UtilizationAs fuel for boilers (heat production)As fuel for boilers (heat production)As fuel for combustion engines (electric As fuel for combustion engines (electric

energy production and heat recovery)energy production and heat recovery)After CO2 separation, gas can be pressed After CO2 separation, gas can be pressed

into a gas grid (use like natural gas)into a gas grid (use like natural gas)

Heating and cooking “off the grid”Heating and cooking “off the grid”

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6Source: http://www.inverter-china.com/blog/articles/green-energy/Definition-of-biogas.html

Combined Heat and Power Applications

Advantages of BiogasAdvantages of BiogasRenewable resourceRenewable resourceCheaper and simpler than other biofuelsCheaper and simpler than other biofuelsWell suited for small scale applicationWell suited for small scale applicationDecentralized productionDecentralized productionMethane recovery is spontaneousMethane recovery is spontaneousDilute waste materials can be used as substrate (2 – Dilute waste materials can be used as substrate (2 –

10%)10%)Any biodegradable material can be usedAny biodegradable material can be usedReducedReduced explosion risk compared to pure methane explosion risk compared to pure methaneAnaerobic digestion inactivates pathogens and Anaerobic digestion inactivates pathogens and

parasitesparasitesConverts methane to CO2 and waterConverts methane to CO2 and water

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Tonight’s AgendaTonight’s AgendaA close look at anaerobic digestionA close look at anaerobic digestionOpportunities for biogas useOpportunities for biogas use

Combined Heat and PowerCombined Heat and PowerBiofuel?Biofuel?

Case studiesCase studies

Discussion of SOA ProjectDiscussion of SOA Project

Fuel cell intro (time permitting)Fuel cell intro (time permitting)

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Cooking with BiogasCooking with BiogasIngredients for a single family anaerobic Ingredients for a single family anaerobic

digesterdigesterClosed 800 gallon tankClosed 800 gallon tank165 pounds per day of waste material165 pounds per day of waste material5 to 8 cattle plus kitchen and bathroom waste5 to 8 cattle plus kitchen and bathroom waste

Produces 106 cf of biogas per dayProduces 106 cf of biogas per day

23 cf of biogas = 1 kw of electricity23 cf of biogas = 1 kw of electricityResults in about 5 to 6 kw per dayResults in about 5 to 6 kw per day

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How much is 5 kw?How much is 5 kw?5,000 watts5,000 wattsEnough to runEnough to run

One 60 watt bulb for 83 One 60 watt bulb for 83 hourshours

Charging a cell phone at 3.7 Charging a cell phone at 3.7 watts for 6 hours uses 22 watts for 6 hours uses 22 watts of electricitywatts of electricity

19-inch CRT television for 55 19-inch CRT television for 55 hourshours

A 1,000 watt microwave for A 1,000 watt microwave for 5 minutes5 minutes

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Single Family Biogas UnitSingle Family Biogas UnitGas may be burned Gas may be burned

directly for heatingdirectly for heatingSend to 100% biogas Send to 100% biogas

generator followed by generator followed by alternator ($800 - alternator ($800 - $1000)$1000)

Payback on Payback on construction is 4 to 8 construction is 4 to 8 yearsyears

Can sell excess Can sell excess biogas and electricitybiogas and electricity 11

Source: http://tianwai.wordpress.com/2009/10/29/hooray-poop/

http://khaoyai.wordpress.com/2007/11/20/sustainable-energy-project-reduces-logging/

Number of People Relying on Number of People Relying on Biomass for Cooking and Heating Biomass for Cooking and Heating

(Millions)(Millions)2000 2030

China 706 645

India 585 632

Other Asia 420 456

Sub-Sahara Africa

583 996

Latin America 96 72

Mostly the rural poor.

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Digestion ProcessesDigestion ProcessesAnaerobic DigestionAnaerobic Digestion

PondsPondsSeptic TanksSeptic TanksEngineered SystemsEngineered Systems

Bacteria break down in Bacteria break down in Endogenous Endogenous RespirationRespiration

End products of digestion are carbon dioxide, End products of digestion are carbon dioxide, waterwater, and bits that don’t degrade easily, and bits that don’t degrade easily

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C4H7O2N CO2 + H2O

Anaerobic DigestionAnaerobic DigestionAbsence of Oxygen and Absence of Oxygen and

NitrateNitrateFermentation processFermentation processDepends on two groups Depends on two groups

of bacteriaof bacteriaAcid Formers or Acid Formers or

Saprophytic OrganismsSaprophytic OrganismsMethane FormersMethane Formers

Generally not cost Generally not cost effective below 5 mgd - effective below 5 mgd - changingchanging

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Anaerobic DigestionAnaerobic Digestion

Raw Sludge

Acid Formers

Organic Acids

CO2, H2O

Methane Formers

MethaneCO2, H2O

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Volatile Solids ReductionVolatile Solids Reduction% VSS Reduction = ( In – Out) In – (In*Out)

* 100

100 lb Total Solids80% Volatile

20 lbs inert solids40 lbs volatile solids67% Volatile

% VSS reduction = 50%% TS reduction = 40%

% VSS Reduction = ( In – Out) In – (In*Out)

* 100

% VSS Reduction = ( 0.82 – 0.67) 0.82 –

(0.82*0.67)

* 100

% VSS Reduction = 55.4%18

Types of Anaerobic DigestersTypes of Anaerobic DigestersType Temperatu

re Range, oF

Solid Retention Time, days

Psychrophilic Unheated 60+

Mesophilic 68 – 113 (95oF)

25 - 30

Thermophilic 120 - 135 5 – 12

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Anaerobic Digester Anaerobic Digester ComponentsComponentsCylindrical, cubical, or egg-shaped tankCylindrical, cubical, or egg-shaped tankSloped floor (1:4 to 1:6 side slope)Sloped floor (1:4 to 1:6 side slope)Fixed or Floating CoverFixed or Floating CoverMixing EquipmentMixing EquipmentSupernatant TubesSupernatant TubesSludge Draw Off TubesSludge Draw Off TubesGas SystemGas System

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Fixed Cover TankFixed Cover TankDesigned to maintain 8-inch water column of Designed to maintain 8-inch water column of

gas pressure on tank roofgas pressure on tank roofOccasionally designed for higher pressureOccasionally designed for higher pressureFlat versus Domed CoverFlat versus Domed Cover

Can develop explosive gas mixtureCan develop explosive gas mixture5 – 15% gas/air mixtures5 – 15% gas/air mixturesAdd new sludgeAdd new sludgeWithdraw an equal amount of supernatant or Withdraw an equal amount of supernatant or

sludgesludgeMaintain constant levelMaintain constant level

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Floating Cover TankFloating Cover TankCover moves up and down with tank levelCover moves up and down with tank levelVertical travel of 8 feet typicalVertical travel of 8 feet typicalTotal depth of 20 feet or moreTotal depth of 20 feet or moreStops or Stops or CorbelsCorbels spaced every 10-16 feet spaced every 10-16 feet

aroundaroundRoller Guides ensure even travelRoller Guides ensure even travelMaximum water level controlled by overflow Maximum water level controlled by overflow

pipepipe

Water seal Water seal prevents air from entering tankprevents air from entering tank25

Source: http://i178.photobucket.com/albums/w263/queenjen136/Otsego.jpg

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MixingMixingUtilizes entire digester volumeUtilizes entire digester volumeDistributes raw sludge throughout tankDistributes raw sludge throughout tankContacts microorganisms with foodContacts microorganisms with foodDistributes inhibitory byproductsDistributes inhibitory byproductsAssists with pH and alkalinity controlAssists with pH and alkalinity controlDistributes heatDistributes heatMinimizes separation of grit and scumMinimizes separation of grit and scum

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Gas or Lance MixingGas or Lance Mixing

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Other Types of Other Types of MixingMixingImpeller MixingImpeller MixingBubble Gun SystemBubble Gun SystemDraft TubeDraft Tube

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Supernatant and Sludge Supernatant and Sludge Withdrawal TubesWithdrawal TubesThree to five tubes set at different Three to five tubes set at different

depthsdepthsMultiple lengthsMultiple lengthsAllow operator to draw supernatant Allow operator to draw supernatant

and sludge from different depthsand sludge from different depthsSome digesters use a single, Some digesters use a single,

adjustable tube for supernatantadjustable tube for supernatant

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Gas SystemGas SystemDigestion Process ProducesDigestion Process Produces

8 to 12 cubic feet of gas for every lb VSS 8 to 12 cubic feet of gas for every lb VSS ADDEDADDED

12 to 18 cubic feet of gas for every lb VSS 12 to 18 cubic feet of gas for every lb VSS DESTROYEDDESTROYED

Gas Mixture should beGas Mixture should be65 – 75 percent methane by volume 65 – 75 percent methane by volume 30 – 35 percent carbon dioxide by volume30 – 35 percent carbon dioxide by volume

Trace gases also presentTrace gases also presentHydrogen, nitrogen, hydrogen sulfide, etcHydrogen, nitrogen, hydrogen sulfide, etc

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Heating Value for Digester GasHeating Value for Digester Gas500 to 600 BTU per cubic foot500 to 600 BTU per cubic foot

BTU = British Thermal Unit = BTU = British Thermal Unit = Energy to raise 1 lb of water by Energy to raise 1 lb of water by one one ooFF

Natural gas has a heating value Natural gas has a heating value of 900 to 1,200 BTU per cubic of 900 to 1,200 BTU per cubic footfoot

Reuse to heat digester and/or Reuse to heat digester and/or buildings or “flare” for safetybuildings or “flare” for safety

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Digester HeatingDigester HeatingHeat required to raise temperature of Heat required to raise temperature of

incoming sludgeincoming sludgeHeat required to make up transmission lossesHeat required to make up transmission losses

Sludge Heating FormulaSludge Heating FormulaQ = (S)(CQ = (S)(Css)(T)(Too-T-Tii))

Q = Heat requirement in BTU/hrQ = Heat requirement in BTU/hrS = Solids flow rate in lb/hrS = Solids flow rate in lb/hrCs = Specific Heat of Solids (1 BTU / lb * Cs = Specific Heat of Solids (1 BTU / lb * ooF)F)T = Temperature of operation and initial, T = Temperature of operation and initial, ooFF

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Digester HeatingDigester HeatingDigester gas scrubbedDigester gas scrubbedSent to BoilerSent to BoilerRecirculate digesting Recirculate digesting

sludge through heat sludge through heat exchangerexchanger

Internal or external to tankInternal or external to tank

Recirculation pump keeps Recirculation pump keeps velocity at 4 fps to velocity at 4 fps to minimize foulingminimize fouling

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Anaerobic Digester OperationAnaerobic Digester OperationPump as thick as sludge to digester as possiblePump as thick as sludge to digester as possibleThin sludge is < 3.5% solidsThin sludge is < 3.5% solidsExcess water causesExcess water causes

Additional heating capacity to maintain temperatureAdditional heating capacity to maintain temperatureReduction in retention timesReduction in retention timesReduces buffering capacity by forcing out Reduces buffering capacity by forcing out

supernatantsupernatantIncreased decant frequencyIncreased decant frequency

Sludge concentrations greater than 10% don’t Sludge concentrations greater than 10% don’t digest welldigest well

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Anaerobic Digester OperationAnaerobic Digester OperationAir entering tank creates explosive gas Air entering tank creates explosive gas

mixturemixtureAdjust sludge withdrawal rate toAdjust sludge withdrawal rate to

Maintain positive pressure in digesterMaintain positive pressure in digesterPrevent vacuum formationPrevent vacuum formation

Monitor Volatile Acid to Alkalinity RatioMonitor Volatile Acid to Alkalinity RatioGenerally less than 0.1Generally less than 0.1Volatile acids less than 500 mg/LVolatile acids less than 500 mg/LProblem when ratio gets to 0.5Problem when ratio gets to 0.5

pH should be near 7.0 or a little higherpH should be near 7.0 or a little higher43

Anaerobic Digester OperationAnaerobic Digester OperationLoading rate of 0.15 – 0.35 lb VSS per cubic foot Loading rate of 0.15 – 0.35 lb VSS per cubic foot

OROR150 – 300 lbs of VSS per day per 1,000 cubic feet150 – 300 lbs of VSS per day per 1,000 cubic feet

Primary and secondary digesters often usedPrimary and secondary digesters often usedPrimary digester receives raw sludgePrimary digester receives raw sludgeSecondary digesterSecondary digester

Digests at a slower rateDigests at a slower rateSettles digested sludgeSettles digested sludgeProvides seed sludge for Primary when neededProvides seed sludge for Primary when needed

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Operating Parameter Cheat SheetOperating Parameter Cheat SheetParameter Units Target

Temperature Degrees F 90 – 100

Volatile Acids mg/L 50 – 330

Alkalinity Mg/L as CaCO3

1500 – 5000

VA/Alk Ratio none 0.1 – 0.2

pH S.U. 6.8 – 7.2

Gas Production

cfd 12 – 16 cf/lb VS destroyed

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Common Operational ProblemsCommon Operational ProblemsSouring of DigesterSouring of Digester

Acid formers out-pace methane formersAcid formers out-pace methane formersNeutralize with 1 lb lime per 1,000 gallons Neutralize with 1 lb lime per 1,000 gallons

sludgesludgeJar test for accurate dosingJar test for accurate dosing

FoamingFoamingOften caused by over feedingOften caused by over feedingMethane formers grow rapidlyMethane formers grow rapidlyReduce feeding and mix gently to Reduce feeding and mix gently to

release gas release gas46

Control StrategyControl StrategyStop or reduce solids feedStop or reduce solids feedDetermine the cause of the imbalanceDetermine the cause of the imbalanceCorrect the causeCorrect the causeProvide pH control until balance returnsProvide pH control until balance returns

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Advantages of Advantages of Anaerobic DigestionAnaerobic Digestion

Methane Gas UtilizationMethane Gas UtilizationBetter VS Reduction than Aerobic Better VS Reduction than Aerobic

DigestionDigestionReduces Total Solids MassReduces Total Solids MassGood Pathogen DeactivationGood Pathogen DeactivationLow Net Energy RequirementsLow Net Energy RequirementsDecreases Sludge VolumeDecreases Sludge VolumeLess Sludge Storage RequiredLess Sludge Storage RequiredLower Annual Operating CostsLower Annual Operating Costs

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Anaerobic Digestion Anaerobic Digestion DisadvantagesDisadvantages

High Initial Capital CostsHigh Initial Capital CostsHigh Operator AttentionHigh Operator AttentionMayMay Experience Foaming Experience FoamingGrit Removal Grit Removal Supernatant Can Have SignificantSupernatant Can Have Significant

Ammonia Recycle LoadAmmonia Recycle LoadHigh Cleaning CostHigh Cleaning CostStruvite PotentialStruvite Potential

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Class “A” With Respect to Class “A” With Respect to PathogensPathogensFecal < 1000 MPN/g or Salmonella s.p. < 3 Fecal < 1000 MPN/g or Salmonella s.p. < 3

MPN/4g (based on seven samples per event) MPN/4g (based on seven samples per event) ANDANDUse one of 5 approved methods to Use one of 5 approved methods to Further Further

Reduce PathogensReduce Pathogens:: Time/temp depending on solids contentTime/temp depending on solids content pH/time then dry to at least 50% solidspH/time then dry to at least 50% solids Testing for enteric viruses/viable helminth ovaTesting for enteric viruses/viable helminth ova Testing Testing PFRP: composting, heat drying, heat treatment, TAD, PFRP: composting, heat drying, heat treatment, TAD,

beta ray irradiation, gamma ray irradiation, beta ray irradiation, gamma ray irradiation, pasteurization, other as approved by EPA Region 8pasteurization, other as approved by EPA Region 8

Class “B” With Respect to Class “B” With Respect to PathogensPathogens7 samples - Geometric Mean <2,000,000 MPN/g or 7 samples - Geometric Mean <2,000,000 MPN/g or

CFU* (based on seven samples per event) CFU* (based on seven samples per event) ORORUse 1 of 5 Approved Use 1 of 5 Approved Process to Significantly Reduce Process to Significantly Reduce

PathogensPathogens (PSRP) methods: (PSRP) methods: Aerobic Digestion: 40 days @ 20 Aerobic Digestion: 40 days @ 20 °°C no less than 60 days C no less than 60 days

@15 @15 °°C C Air Drying: 3 months with two months above 0 Air Drying: 3 months with two months above 0 °°C C Anaerobic Digestion: 15 days @ 35-55 Anaerobic Digestion: 15 days @ 35-55 °°C no less than 60 C no less than 60

days at 20 days at 20 °°C C Composting: Minimum 40 Composting: Minimum 40 °°C for 5 days with min 4 hours C for 5 days with min 4 hours

at 55 at 55 °°C C Lime Stabilization: Add lime to raise pH to 12 after two Lime Stabilization: Add lime to raise pH to 12 after two

hours of contacthours of contact Other as approved by EPA Region 8Other as approved by EPA Region 8

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MWRD - MWRD - Metro Wastewater Reclamation DistrictMetro Wastewater Reclamation District

MetroGroMetroGroAbout 52,000 dryland farm

and pasture acres where they apply biosolids.

Crop variety includes winter wheat, sorghum/sudan grass, and corn.

Pasture areas are often used for sheep and cattle grazing.

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(US Department of Energy, 2010) - http://www.eia.doe.gov/

Putting it into perspectivePutting it into perspective2010 Energy Consumption was 98 2010 Energy Consumption was 98

Quadrillion BTUsQuadrillion BTUs98,000,000,000,000,000 BTUs (15 zeros!)98,000,000,000,000,000 BTUs (15 zeros!)

1 MW = 3414425 BTUs per hour1 MW = 3414425 BTUs per hour98 Quad BTU’s is then about 3,276,456 MW98 Quad BTU’s is then about 3,276,456 MW

Totals from previous slides is 17,835 MWTotals from previous slides is 17,835 MWAbout 0.5% of our total energy use each yearAbout 0.5% of our total energy use each year

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Europe Takes the LeadEurope Takes the LeadEurope has about 200 biogas plants in the Europe has about 200 biogas plants in the

early 1990’searly 1990’sToday they have more than 16,000Today they have more than 16,00060% are located in Germany60% are located in GermanyEstimated to have 30,000+ by year 2015Estimated to have 30,000+ by year 2015

Older models only about 28% efficient or lessOlder models only about 28% efficient or less

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Other Applications for BiogasOther Applications for BiogasSyngasSyngasHydrogen Production from MethaneHydrogen Production from MethaneFuel CellsFuel Cells

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