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    Microalgae Route to Biodiesel:Microalgae Route to Biodiesel:

    Prospects, Potential and ProcessProspects, Potential and ProcessDesignDesign

    Dr. V. S. MoholkarDepartment of Chemical Engineering

    Indian Institute of Technology Guwahati

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    In the beginning, there were algae, but there wasno oil

    Then, from algae came oil.

    Now, the algae are still there, but oil is fastdepleting

    In future, there will be no oil, but there will still bealgae

    So, doesnt it make sense to explore if we canagain get oil from algae?

    This is what we try to do explore the potentialof getting oil from algae

    Biodiesel From Algae

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    Biodiesel Feedstock Tree

    Source: African Biofuels 200

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    Lipid Content of Algal species Some algae naturally manufacture hydrocarbonsthat are suitable as high energy fuels.

    Botrycoccus braunii, a common species, cancontain more than 50% oil, mostly in form ofhydrocarbons.

    Genetically engineering species of Botrycoccusbraunii can be made to grow faster.

    1 1Sy nechoccus sp.

    9 - 1 4Porphy r id ium sp .

    2 2 - 3 8Pry m nesium sp .

    1 4 - 2 0Eug lena sp.

    6 - 8Dun al ie l la sp.

    1 1 - 2 1Sp i rogy ra sp .

    1 4 - 2 2Clor el la sp.

    2 1Chlam yd om onas sp.

    1 2 - 4 0Scenedesm us sp.

    % Lip id

    ( b y m ass o n d r y b asi s)

    St r a in or Spec ies

    1 1Sy nechoccus sp.

    9 - 1 4Porphy r id ium sp .

    2 2 - 3 8Pry m nesium sp .

    1 4 - 2 0Eug lena sp.

    6 - 8Dun al ie l la sp.

    1 1 - 2 1Sp i rogy ra sp .

    1 4 - 2 2Clor el la sp.

    2 1Chlam yd om onas sp.

    1 2 - 4 0Scenedesm us sp.

    % Lip id

    ( b y m ass o n d r y b asi s)

    St r a in or Spec ies

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    Microalgal Oil

    Composition of microalgae (dry basis): protein(1235%); lipid (7.223%); carbohydrate (4.623%).

    Algal-oil is very high in unsaturated fatty acids,like the canola oil. Some UFA's found in differentalgal-species include:

    Arachidonic acid(AA)

    Eicospentaenoic acid(EPA)

    Docasahexaenoic acid(DHA)

    Gamma-linolenic acid(GLA)

    Linoleic acid(LA)

    Catalytic hydrogenation of oil prior totranesterification is a possible solution.

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    Microalgal Biodiesel

    Not significantly different than the biodiesel

    produced from vegetable oil. Microalgal oil contains high levels ofpolyunsaturates which can pose stabilityproblem due to possibility of oxidation.

    Due to lower melting point of polyunsaturates(than mono-unsaturates or saturates), algalbiodiesel possesses better cold weather

    properties. Growing algae using exhausts of power plants

    for CO2 source can help reduce carbon and NOxemissions.

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    What Effects Algal Growth?

    Selected Algal strain Light conditions

    Temperature Water flow rate Supply of carbon dioxide (use exhaust of power

    plants) Macronutrients: C, N, P, Mg, Ca, K, Na, Cl Micronutrients (Trace elements): Fe, B, Zn, Mn, Mo,

    Cu, SO4, Co, Cd, Va, Al, Br, Etc..

    Vitamins Marine microalgae: Seawater supplemented with

    commercial fertilizers

    Biodiesel is carbon neutral no net accumulation ofCO2 in atmosphere.

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    Bag culture

    Tubular ReactorAirlift Bioreactor

    Stirred Tank Reactor Bag Culture

    PHOTOBIOREACTORS

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    Features of Raceway Ponds

    Closed loop recirculation channel; mixing achievedwith paddle wheel.

    MOC: concrete, compacted earth or lining with

    white plastic to reduce seepage losses. Typical dimensions: Depth 20-30 cm; Area

    100-250 hectare, production 0.1 to 0.5 g dryweight per liter.

    Limitations: Significant evaporation losses.

    Poor thermal or temperature control.

    Poor utilization of CO2 due to evaporation orstripping.

    Contamination from unwanted algae and micro-organisms.

    Low biomass concentration due to poor mixing andoptically dark zones.

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    Features of Photobioreactors

    Known as closed systems and permit cultivation ofsingle species for longer duration.

    Basic designs: Flat plate reactors and tubular reactors.

    Principle is to reduce path length of light. Tubular array with each tube of 3-4 in. dia.

    Microalgal broth is circulated through a degassing tankwith either mechanical pump or airlift pump.

    Either horizontal or vertical array is possible.Illumination could be natural or artificial.

    Temperature control of broth by placing a coil indegassing tank or circulation of water through a jacket

    around tube. Operational difficulties:

    Growth of algae in tube walls blocking light.

    High oxygen concentration that can inhibit

    photosynthesis. Limit on the length of the tube in single run.

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    Raceway Ponds vs.

    Photobioreactors 13-fold high biomass

    productivity and higher oil yieldper hectare in photobioreactors.

    Recovery of biomass is also animportant issue.

    Recovery cost in

    photobioreactor is a minorfraction of total processing costdue to high biomassconcentration.

    Total area need forphotobioreactor is smaller.

    Effective utilization of area canbe achieved with BIOCOIL.

    Typical volume of BIOCOIL:1000 Liter

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    Comparison of Large Scale Systems

    EasyAchievableEasyLow-highLow-high

    ExcellentExcellentUniformTubularreactor(Biocoil)

    ReasonableAchievableEasyLow-highLow-high

    ExcellentExcellentUniformTubularreactor(serpentine)

    DifficultAchievableEasyLow-highHighExcellentExcellentUniformFlat platereactor

    DifficultEasilyachievable

    EasyLowLow-high

    Good(indoors)

    Fair-GoodVariableBag culture

    DifficultEasilyachievable

    EasyLowHighExcellentGoodGenerallyuniform

    Airliftreactor

    DifficultEasilyachievable

    EasyHighLow-high

    ExcellentFair-GoodLargelyuniform

    Stirred tankreactor

    Very difficultNoneDifficultLowPoorNoneFair-GoodFair-goodPaddlewheel

    Raceway

    V.difficultNoneDifficultLowPoorNoneFair-GoodFairCircularstirred pond

    V.difficultNoneDifficultV. PoorPoorNoneV. poorPoorTanks

    V.difficultNoneDifficultV. lowPoorNonePoorV.poorUnstirredshallow

    ponds

    Scale upSterilitySpeciescontrol

    Hydrodynamicstress on algae

    Gastransfer

    Temperaturecontrol

    LightutilizationEfficiency

    MixingReactorType

    EasyAchievableEasyLow-highLow-high

    ExcellentExcellentUniformTubularreactor(Biocoil)

    ReasonableAchievableEasyLow-highLow-high

    ExcellentExcellentUniformTubularreactor(serpentine)

    DifficultAchievableEasyLow-highHighExcellentExcellentUniformFlat platereactor

    DifficultEasilyachievable

    EasyLowLow-high

    Good(indoors)

    Fair-GoodVariableBag culture

    DifficultEasilyachievable

    EasyLowHighExcellentGoodGenerallyuniform

    Airliftreactor

    DifficultEasilyachievable

    EasyHighLow-high

    ExcellentFair-GoodLargelyuniform

    Stirred tankreactor

    Very difficultNoneDifficultLowPoorNoneFair-GoodFair-goodPaddlewheel

    Raceway

    V.difficultNoneDifficultLowPoorNoneFair-GoodFairCircularstirred pond

    V.difficultNoneDifficultV. PoorPoorNoneV. poorPoorTanks

    V.difficultNoneDifficultV. lowPoorNonePoorV.poorUnstirredshallow

    ponds

    Scale upSterilitySpeciescontrol

    Hydrodynamicstress on algae

    Gastransfer

    Temperaturecontrol

    LightutilizationEfficiency

    MixingReactorType

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    Algal Production andEconomics Model

    WaterA. Net make up

    B. Supply system cost

    Media Recycle

    Algal ProductionA. Yield (gross)

    B. Efficiency on ParC. Facility designD. Facility costE. Flow/mass balanceF. Power requirementG. Module hydraulics

    H. Energy requirementI. Salinity tolerance

    HarvesterA. Capital costB. Energy cost

    EconomicsA. Annual operating cost

    B. Capital investmentC. Lifecycle revenue required

    D. Product pricing

    Processing and Storage

    Product State

    A. Net biomassB. Lipid quantityC. Carbohydrate quantity

    D. Protein quantity

    Nutrient Recycle

    Nutrients for N,K,PA. QuantityB. CostC. System cost

    CarbonA. QuantityB. CostC. System cost

    WaterA. Net make up

    B. Supply system cost

    Media Recycle

    Algal ProductionA. Yield (gross)

    B. Efficiency on ParC. Facility designD. Facility costE. Flow/mass balanceF. Power requirementG. Module hydraulics

    H. Energy requirementI. Salinity tolerance

    HarvesterA. Capital costB. Energy cost

    EconomicsA. Annual operating cost

    B. Capital investmentC. Lifecycle revenue required

    D. Product pricing

    Processing and Storage

    Product State

    A. Net biomassB. Lipid quantityC. Carbohydrate quantity

    D. Protein quantity

    Nutrient Recycle

    Nutrients for N,K,PA. QuantityB. CostC. System cost

    CarbonA. QuantityB. CostC. System cost

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    Parameters Affecting Microalgal

    Production Economy

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    Economic Analysis of

    Microalgae Production

    Product Cost Contributions by

    General Category

    Total capital,23.30%

    Maintenance

    costs, 8.80%

    Operating

    costs, 67.90%

    Economic potential can bejudged by assessingindividual cost centers.

    General cost distribution

    for total product cost: Operating costs: 68%

    Capital costs (depreciable

    and non-depreciable): 23% Maintenance costs: 9%

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    Capital Costs(Depreciable and Nondepreciable)

    Fixed costs: 23.3% withdepreciable equipment

    costs: 51% of presentvalue of capital. Culture system (37.7%)

    includes moduleconstruction, internaldistribution systems,pond lining, mixingsystem etc.

    Other major factors

    include site preparationand surveying (26.2%),harvester system (13%)and contingency (12%).

    Contributions to Capital Cost

    Categories

    Harvest

    system, 13%

    Site

    preparation,

    26.20%

    Culture

    system,

    37.70%

    Contingency

    allowance,

    11.70%

    Engineering

    fees, 7.60% Land, 3.80%

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    Depreciable Investment

    Specific life time foreach equipment

    differs but average lifeis ~ 15 years.

    Highest contribution

    by the harvestingsystem.

    Lining of pondbottoms, construction

    of piping system,mixing system areother components

    contributing todepreciation.

    Contributions to DepreciableCapital Investment

    Harvesters,

    25.70%

    Lining,

    26.20%

    Buildings,

    1.70% Carbondioxide

    transfer

    system,

    4.20%

    Electric

    services,

    9.10%

    Mixing

    system,

    13.10%

    Culture

    system, 14%

    Water

    system, 6%

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    Summarization

    Hills analysis gives an idea of economic potentialof microalgal biodiesel:

    Production of 33,171 tpa of microalgae incurs totalannualized production cost of $13 million.

    This gives cost of algal biomass as $393 per ton or$0.35 per kg with approx lipid content of 30%.

    Thus, annual lipid yield is 71072 bbl with production costof $1.2 per liter.

    Compare to this, the cheapest vegetable oil costs $465per ton or $0.52 per liter.

    Petrodiesel costs approx $0.75/liter (inclusive of taxes at20%, crude oil cost 52%, refinery expenses 19% anddistribution and marketing 9%).

    Target price for microalgal oil should be $0.5 per literassuming it is tax free!

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    Improvement of MicroalgalBiodiesel Economics

    Biorefinery based strategy to utilize everycomponent of biomass raw material. Residual biomass can be animal feed. Anaerobic digestion of biomass for methane production

    which can be used for producing electricity.

    Revenue earned out of side products can improveeconomics of production.

    Other strategies would be genetic and metabolicengineering. Possible methodologies are: Increase photosynthetic efficiency. Enhance biomass growth rate. Increase lipid or oil content of biomass. Elimination of light saturation phenomena, photo-

    inhibition effect, susceptibility to bio-oxidation.

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    Conclusion

    Microalgal route to biodiesel is a potentialalternative to vegetable oil.

    Overall economics of the process needs

    improvement to be competitive substitute topetrodiesel.

    Roots of improvement in economy lie in bothscience and technology of microalgae.

    Enhancement in lipid content through geneticmodification is one route.

    Much simpler and effective way to achieve the

    same goal would through photobioreactorengineering. Extensive research on diverse aspectsof photobioreactor is needed.

    Biorefinery approach can also improve the

    economics significantly.

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    ACKNOWLEDGMENTS

    The microalgal biodiesel project atI.I.T. Guwahati has been sponsored

    by Defense Research Laboratory(DRDO) at Tezpur, Assam.

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