Captura co2

Carbon Dioxide Capture with Algae
Mark Rasmussen Ph.D.

8/20/2008

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Global Carbon Cycle
Respiration + Combustion + Decay (releases CO2) Versus Photosynthesis (captures CO2)

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Global Carbon Cycle

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Algae: Basis of Food Chain

Algae bloom off of Newfoundland, NASA “Visible Earth”
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Algae Blooms

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Algae: Nature’s CO2 Scrubber
• Earth’s photosynthetic capacity is large. • It is estimated that algae fix >65 Gt of carbon per year. • Algae in nature fix carbon equal to the output of about 65,000, 500-MW generating plants

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The Potential of Algae Cultivation:Wastes to Resources
• Waste heat • Waste carbon dioxide • Plus Water & Sunlight • • • • Watershed nutrients Animal waste Sewage waste Marginal lands
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Commercial Food Supplements
• Algae: Dunaliella salina • Halophilic algae • 20 tons/acre • Nutra-Kol Pty Ltd Australia • High value beta carotene
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Algae Cultivation Methods
• Open Pond or Tank Methods • Closed Bioreactor Systems

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Open Culture Systems
Open systems
– Less expensive – Temperature fluctuation – Open to contamination – Excess evaporation – Types: open pond, center pivot, raceway
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Closed Culture Systems
Closed bioreactors
– Controlled environment – Less evaporation – Capital costs – Light issues – Productivity – Types: air lift, tubular, flat plate
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Coal Plant Study: A Summary
• • • • • • • DOE study in 2002 Calculations based upon a pond yield of 4g/l/day Assumption of 25% CO2 capture from flue gas 2136 t/d algae biomass @ 26% lipid content Breakeven = $97/ton of algae produced Or $0.18/lb algae oil Current soybean oil prices >$0.70/lb Productive algae: a competitive feedstock
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Criteria for a Midwest Algae/CO2 System
Open pond system • Larger area requirements • Native midwest algae • Midwestern winters • Less expensive Closed