Mark CrockerUniversity of Kentucky
Center for Applied Energy Research (CAER)
CO2 Capture and Utilization using Microalgae
Energy in Kentucky
• 92% of KY electricity from coal• KY is 1.4% of US population• KY produces:
– 2.3% of US electricity– 3.7% of carbon dioxide
• KY electricity use:– 2.7% of US industrial
• 35% of US stainlesssteel production
• 40% of US aluminumproduction
– 1.7% of US residential
CO2 Capture and Utilization Using Microalgae
• Selection of sulfur-tolerant algae strains, identification of optimum conditions for cultivation/CO2 capture
• Development of low cost cultivation medium
• Photobioreactor design
• Optimization of algae processing: algae recovery, dewatering
• Algae oil extraction and upgrading to fuel
• Utilization of algae cake
Project goals:
Media
Drying
Dewatering
Coal Power Plant
Biomass Fractionation
ProteinsCarbohydrates
Lipids
CO2 Lean Gas
Recovered Nutrients (N,P,K)
Recovered Media
Recovered Water
Algae Cultivation
Overall Process
Liquid fuels,Biogas, etc.
Screening for Optimal Algae Strain • 150 candidate strains identified from literature
• Screening for specific growthrate at pH 5.5 and 35 ᵒC
• Four different growth mediaused
• Promising strain of Scenedesmus identified –native to KY; currently ourstrain of choice
Scenedesmus
Scenedesmus acutus
• Lower capital cost than PBR• Easier to operate• Contamination by otherstrains/organisms problematic
• Water loss by evaporation
• Better CO2 capture efficiency• Up to 3 times more photosyntheticallyactive volume per unit area of land
• Efficient water utilization through lowevaporative losses
• Biofilm formation problematic
Ponds vs. Photobioreactors (PBRs)
Evolution of CAER PhotobioreactorDesign (2008 ‐ present)
UK CAER Photobioreactor
Design Criteria:
• Inexpensive to build: cheap components, simple construction
• Inexpensive to operate: low liquid pumping and gas compression costs
• Easy to operate: maintain optimal conditions for algae growth (pH, adequate dissolved CO2 concentration, etc.)
UK CAER Photobioreactor
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Key Design Features of UK Photobioreactor: PET packaging tubes: 3.5” diameter, 8’ in length;
significantly cheaper than PVC or glass Flue gas introduced at return (3” pipe) – sufficient
suction generated to enable flue gas entrainment; hence no compression costs
Pressure driven; uses variable speed pump PBR cost estimated at < $1/L of photoactive volume
at scale Modular design for easy scale up
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Dissolved
Oxygen (m
g/L)
PAR (m
icromol*m
^‐2*s^‐1)
Actual Process Date and Time
UK CAER Reactor Process Data (Week of 10/10/2011)
Internal PAR
Dissolved Oxygen (mg/L)
• Dissolved oxygen reading is excellent indicator of algal growth/health • Strong correlation between dissolved oxygen and PAR
Medium‐scale (650 L) Experimental Growth Studies
y = 3.5182E‐03x2 ‐ 2.8371E+02x + 5.7194E+06R² = 9.6292E‐01
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Den
sity (g(drymass)/L)
Varicon PBR ‐ Algal Growth Curve
Varicon Growth Campaign (May 20th ‐ June 7th 2010)
Harvest
Inoculation
Carbon Balance (by Mass)
• Total V of tank: 552 L• Density of algae: 1.5 g/L• g of C input (as CO2): 667 g
• Our Scenedesmus is 42% carbon via elemental analysis
• 348 g C in our Scenedesmus
• 52% CO2 used by our algae
Input Output
400X magnification
1. Flocculation and sedimentation
• Leverages experience in coal preparation and waste products utilization
• Low molecular weight cationic flocculant (3 ppm)
2. Decanting tank increases density of biomass (2‐10% solids)
3. Further dewatering via filtration (up to 28% solids)
Algae Harvesting
Algae Harvesting
Flocculant-Assisted Sedimentation
• 828 g of algae in system (based on dry mass samples)
• Recovered 751 g of dried algae 90% of algae in systemwas recovered
• 99% of H2O recovered• All water, nutrients and
unrecovered algae recycledback to system
55 g/L
1.56 g/LPre‐flocculation
Left over after flock
Flocked biomass
East Bend Station Demonstration Facility
Capacity: 650 megawattsLocation: Boone County, KYCommercial Date: 1981 • Define kinetics of process
– Monitor dissolved CO2 and O2 to determine photosynthetic rate
– Help size large system and next generation design
• Gain understanding of real capital and operating costs– Minimize energy consumption
• Measure biomass composition to track heavy metals and other flue gas constituents
East Bend Photobioreactor (18,000 L)
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End view
Side view
M.H. Wilson, J. Groppo, A. Placido, S. Graham, S.A. Morton III, E. Santillan‐Jimenez, A. Shea, M. Crocker, C. Crofcheck, R. Andrews, Appl. Petrochem. Res., 2014, 4: 41‐53.
East Bend Growth Study: Winter 2012Productivity & Photosynthetically Active Radiation (PAR)
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Average growth rate = 10 g/(m2.day)
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East Bend Growth Study: Summer 2013
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1‐Jun 11‐Jun 21‐Jun 1‐Jul 11‐Jul 21‐Jul
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uctiv
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Harvest
Outage
Average growth rate = 39.4 g/(m2.day)
Techno‐economic Analysis Effect of payback period (10 vs. 30 years), capital cost
reduction and algae growth rate
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Baseline
30 yr base CAP
30 Yr Low Cap
(10 years)
Baseline (30 years)
Low capex (30 years)
FuelsFertilizers
Energy (Combustion)
Animal Feed SupplementsAnimal Feed
Aquaculture Feed
NutraceuticalsPersonal Hygiene
CosmeticsFood Products
FDARegulatedApplications
Value Market Size
Algal Biomass Utilization
Conclusions
• CO2 recycling using microalgae is feasible from a technical point of view:
‐ a low cost PBR has been designed, built and operated ‐ a low cost methodology for algae harvesting and dewatering has beendevised‐ areal productivity of routinely ≥ 30 g/m2/day (summer) and ≥ 10 g/m2/day(winter) has been demonstrated at significant scale (18,000 L)‐ lipid extraction and conversion to biodiesel and diesel range hydrocarbonshas been demonstrated
• At present, the economics remain uncertain. Current calculations suggest that the cost of capturing and recycling CO2 using microalgae will fall close to $1600/ton CO2
• The largest sources of cost reside in the algae culturing stage of the process, corresponding mainly to the capital cost of the photobioreactor system
• The overall economics will be driven by the value of the biomass ‐ hence, the production of high value products is a pre‐requisite
Summary: From Flue Gas to Liquid Fuels
M.H. Wilson, J. Groppo, E. Santillan-Jimenez, M. Crocker et al., Appl. Petrochem. Res. 4 (2014) 41
CO2 in flue gasAlgae cultivation
Flocculation, sedimentation
& gravity filtration
Lipid extractionColumn purificationCatalytic upgradingDiesel-range hydrocarbons
Acknowledgements
• KY Department of Energy Development and Independence
• Duke Energy
• Department of Energy: CERC‐ACTC
• The UK algae team:Michael WilsonDr. Jack Groppo Tonya MorganDr. Eduardo Santillan‐Jimenez Robby PaceDr. Czarena Crofcheck Sarah MarquesAubrey Shea Renan SalesXinyi (Abby) E Stephanie Kesner
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Questions?
http://greenchicgeek.blogspot.com/2009_08_01_archive.html
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