Techno‐economic Assessment of Mi l Bi P d i SMicroalgae Biomass Production Systems: 

Current Status & Future Opportunities

Sudhagar ManiAssistant Professor Faculty of EngineeringAssistant Professor, Faculty of Engineering

University of Georgia, Athens Email: smani@engr.uga.edu

Bioenergy Engineering 2009 Conference October 11‐14 Bellevue WA

g g

October 11 14, Bellevue, WA

Outline

Introduction – Microalgae

Microalgae Cultivation Practices

Techno economic modelTechno‐economic model

(1) Photo‐bioreactor system

(2) Raceway pond system

l & di iResults & Future directions

ConclusionConclusion

What are Microalgae?

• Groups of simple living aquatic organisms

• Converts inorganic substances into organic materials 

through photo‐syntheses in the presence of CO2 & sun 

light energy

• Single cell to multi‐cellular & even complex (seaweeds)g p ( )

• Responsible for 70‐80% production of global O2  

• High Areal Productivity (10 – 60 g/m /day )• High Areal Productivity (10 – 60 g/m2/day )

Chemical Composition of Algae Expressed on Dry Matter Basis (%) 

Strain Protein Carbohydrates Lipids Nucleic acid

Scenedesmus obliquus 50-56 10-17 12-14 3-6Scenedesmus obliquus 50 56 10 17 12 14 3 6

Scenedesmus quadricauda 47 - 1.9 -

Scenedesmus dimorphus 8-18 21-52 16-40 -

Chl d h i h dii 48 17 21Chlamydomonas rheinhardii 48 17 21 -

Chlorella vulgaris 51-58 12-17 14-22 4-5

Chlorella pyrenoidosa 57 26 2 -

Spirogyra sp. 6-20 33-64 11-21 -

Dunaliella bioculata 49 4 8 -

Dunaliella salina 57 32 6 -

Euglena gracilis 39-61 14-18 14-20 -

Prymnesium parvum 28-45 25-33 22-38 1-2

Tetraselmis maculata 52 15 3 -

Porphyridium cruentum 28-39 40-57 9-14 -

Spirulina platensis 46-63 8-14 4--9 2-5

Spirulina maxima 60-71 13-16 6-7 3-4.5

Synechoccus sp. 63 15 11 5

Anabaena cylindrica 43-56 25-30 4-7 -

Annual Oil Yield/Acre

Algae 5000 ‐ 15000 gallons/acreOil P l 635 ll /Oil Palm  635 gallons/acreCoconut  287 gallons/acreJatropha 207 gallons/acreRapeseed/Canola 127 gallons /acreRapeseed/Canola         127 gallons./acrePeanut  113 gallons/acreSunflower  102 gallons/acreSafflower 83 gallons/acreSafflower  83 gallons/acreSoybean  48 gallons/acreHemp  39 gallons/acreCorn  18 gallons/acreg

*Sources: http://www.unh.edu/p2/biodiesel/article_alge.html, http://oakhavenpc.org/cultivating_algae.htm

If we can produce it “Economically”

Application and Potential

BIODIESEL/EtOHBIOFERTILIZER

MICRO‐ALGAE

CHEMICALS PHARMACEUTICALS WASTEWATER 

TREATMENT

ELECTRICITY FEED ADDITIVES & Protein Supplements

CO2 ABATEMENT

Microalgae Cultivation

Raceway PondsRaceway Ponds (Open system)

Photo bioreactorsPhoto‐bioreactors(Closed system)

Closed Type Photo‐bioreactor Configurations

H – Tubular systemHelical Tubular systemHelical Tubular system

V – Column system

Alpha shaped system Flat plate system

Open Pond SystemOpen Pond System

Race way Pond – Earthrise Farms Race way Tanks

Open vs. Closed Photo‐bioreactors

Features Open System (Raceway pond)

Closed system (PBR)( y p )

Area‐to‐volume ratio Large (4‐10 times) Small

Growth efficiency Low (0 01‐0 2 g L‐1d‐1) High(0 1‐7 g L‐1 d‐1)Growth efficiency Low (0.01 0.2 g L d ) High(0.1 7 g L d )

Harvesting efficiency Low High

Light util. efficiency Poor‐fair Fair‐excellent

Gas (mass) transfer Poor High( ) g

Water loss Possible Restricted

Capital Investment Small (10‐20 times) High 

Sources: Eriksen, 2008; Carvalho et al., 2006; Ugwu et al., 2008

Micro‐algae Production Cost32000

30000

35000

)

Raceway Pond

1700020000

25000

Cost ($

/t)

7320

17000

800010000

15000

oduction

 

470266011601000 921 600 430 398 272

0

5000

Alga Pr

ObjectivesSystematic techno‐economic evaluation of algae 

cultivation & harvesting systemsC d t iti it l i th i d l tConduct sensitivity analysis on the economic model to 

improve and progress towards advanced systems 

So, what's New?

Annual target based dedicated microalgae productionAnnual‐target based dedicated microalgae production   facility – Capital cost vs Operating cost 

Individual cost estimation each unit operations

Production cost vs Influencing factorsProduction cost vs Influencing factors

System Boundary – Economic Analysis

GROWTH Primary Harvest

Secondary harvest

Algae 20% solid 

RacewayMicro‐strainer

V B l FilCentrifugeRaceway 

PondsVacuum Belt Filter

DAFBelt Press Algae 

with 20%

Photo‐BioReactors(PBR)

Centrifuge

Belt Press

20% solid content ( )

Basis of Comparison: 1000 dry tons/year for 300 daysBasis of Comparison: 1000 dry tons/year for 300 days operational plant

Methodology

Spreadsheet based model analyzing different options for each stage

Order of magnitude estimation ( 20 to +30 accuracy) fromOrder of magnitude estimation (‐20 to +30 accuracy) ‐ from already published data (Peters, Timmerhaus, West 2003)

Cost of A’s capacity  =  Cost of B’s capacity * (A’s capacity/B’s   capacity)^scale factor

Cost updated to the present value using Chemical Engineering Cost IndexCost Index 

Capital cost – Equipment  cost, installation, piping, electric lines, land cost, taxes, interests & insurances 

Power, Labor, Equipment maintenance & Material requirements accounted for operating cost

d i ( ) d i $Production cost (Cap. + Op. costs) are reported in 2009 US $

Photo‐BioReactor (PBR)

GROWTH No First Harvest Second Harvest

Capital cost comparison for•Controlled & high Growth  

•Maximizing photosynthetic 

Capital cost comparison forflat plate, bag and tubularsystemefficiency

•Contamination controlOperating cost for tubularsystem only Tubular PB

•Scalability Issues

y y

Productivity assumed to be3 g/L/d (very optimistic)•Higher Maintenance3 g/L/d (very optimistic)

Harvest by centrifuge

Plastic BagFlat panel PB

Photo‐BioReactor (PBR) 

Item Value UnitPer PB harvest (Tubular system) 343 cu.mTotal Harvest Flow 1029 cu.m/hrHarvesting Operational Hr 20 hrHarvesting Operational Hr 20 hrMedium Refill Pump 17.15 cu.m/hrPrimary Storage tank depth 3 2 mPrimary Storage tank depth 3.2 mMaximum Volume 1029 cu.mArea of the primary storage tank 321.56 sq.mCentrifuge capacity 45 cu

Assumption: Continuous Steady State harvesting StrategyPBR System: Algae link system

Photo‐BioReactor (PBR) – Algae cost 

Annual Capital cost ($/dry t) = 580

Operating cost ($/dry t) = 650

Total algae production cost ($/dry t) = 1,230

16%

46%Materials 

18%46% Maintenance 

Energy cost

21%Labor

Percent operating cost split

PBR Algae Production cost vs. Productivity

$3 000

$3,500

/t

Total cost ($/t)If nutrients are available freely

$2,500

$3,000

cost, $ capital cost ($/t)

Op. cost ($/t)

$1 500

$2,000

uction

  p ($/ )

New total cost ($/t)

$1,000

$1,500

ae Prod

$0

$500Alga

$0

0 2 4 6Algae Productivity, g/l

Raceway Pond

Raceway Ponds

Growth First Harvest Second Harvest

Pond Volume 565 cu. mPond area 1 acrePond area 1 acreHeight of the Pond 0.15 mP d i i 25 / /dProductivity 25 g/sq.m/dayRetention time 4 days

Carbonation system1 carbonation pit for 1 ha (3.6 m or 12 ft deep)

Harvest flow 25% pond volumePaddle wheel speed 30 cm/sec

Harvesting System

GROWTH First harvest

Second harvest

Raceway pond Operation : Steady‐state continuous mode, 25% volRaceway pond Operation : Steady state continuous mode, 25% volDaily Harvest Flow:  4658 cu. m @ 194 cu.m/hEach harvest unit operates 24 X 7 for 300 days/year. 

DISSOLVED AIR FLOATATION CENTRIFUGE

45 cu.m/h

6% SFLOATATION

MICRO

CENTRIFUGE194 cu.m/h

194 cu.m/h 20% S

6% S

RACEWAY POND

STORAGE POND

MICROSTRAINER

VACUUM BELTBELT PRESS0.4% 

solids

4% S

VACUUM BELT FILTER

solids

6% S 20% S

Dissolved Air Floatation (DAF) System

Micro‐Strainer

Belt Press/Filter System

Open Pond Algae Cost Comparisons

operating cost/tonne Annual Capital cost/tonne Total Cost/tonne

1,120 1,221 

1,067  1,054 1,210 

1,058 1230

$/tonn

e

Pond + microstrainer 

Pond + belt filter + Cfg 

Pond + DAF + Cfg (3)

Pond + microstrainer 

Pond + belt filter + belt 

Pond + DAF + belt press(6)

Photo bioreactor + 

+ Cfg (1) (2) +belt press (4)

press (5) Centrifuge

Scenarios

Algae Drying Energy

Source: NREL

HDD System 

Future Challenges & Opportunities

• Genetic Engineering approach on algae species to improve algaeproductivity and species that can withstand stress conditions• Better understanding on Lipid and carbohydrate biosynthesispathways•Identification and isolation of new algae species that can capable ofIdentification and isolation of new algae species that can capable ofgrow faster and accumulate lipids• Improved photo‐bioreactor designs for large scale applicationsD l f h i id h i• Development of new harvesting systems or even avoid harvesting

• Attached algae growth system show some promises as they cancompletely avoid both primary and secondary harvesting options• Use of low cost nutrient and CO2 sources can reduce algaeproduction cost, but will not solve the entire problem• Combination of PBR & Raceway pond systems are becomingCombination of PBR & Raceway pond systems are becomingattractive for large scale algal production system

Conclusions1. Microalgae biomass can play a significant role in the Renewableg p y g

Energy Portfolio2. Photo‐bioreactors are also attractive to grow algae ($1230/t) under

stress conditions for lipid accumulation and at higher productivitystress conditions for lipid accumulation and at higher productivity(3g/l). However more research is required on designing low cost andefficient photo‐bioreactor systems.

d i f i l i d ($ / ) l k3. Production of microalgae using raceway ponds ($1050/t) looksattractive. However, significant research progress has to be made toadvance this technology to become commercially and economicallygy y yviable

4. Currently, DAF+Belt press or DAF+Centrifuge systems are attractiveeconomically for open pond systemseconomically for open pond systems

5. Newer harvesting technologies are evolving, however they need tosatisfy current economic constraints.

6 I i l d i i h h G i E i i6. Increasing algae productivity through Genetic Engineeringapproaches and improving lipid biosynthesis would further reducethe cost of algae significantly.

Acknowledgement

Research TeamMr. Thiru Viswanathan – Graduate StudentDr S Chinnasamy Research ScientistDr. S. Chinnasamy, Research ScientistDr. KC Das, Associate Professor

Financial Support:Financial Support:Department of Energy (DOE)TIP3 Program – State of Georgia

References

Max S. Peters, Klaus D. Timmerhaus, Ronald. E. West, Plant Design Economics forCh i l E i Fifth Editi M G Hill NY 2003Chemical Engineers‐ Fifth Edition, McGraw‐Hill , NY, 2003.

Perry et al., Chemical Engineering Handbook Fifth Edition, McGraw‐Hill, NY, 2007.

Benneman and Oswald, System and Economic analysis of Microalgae ponds forconversion of carbon dioxide to biomass 1996; PETC Final Report.

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