IngentaConnect Utilization of flue gas for cultivation of microalgae Chlorella s...

Abstract:

Flue gas generated by combustion of natural gas in a boiler was used for outdoor cultivation of Chlorella sp. in a 55 m² culture area photobioreactor. A 6 mm thick layer of algal suspension continuously running down the inclined lanes of the bioreactor at 50 cm s^-1 was exposed to sunlight. Flue gas containing 6–8% by volume of CO₂ substituted for more costly pure CO₂ as a source of carbon for autotrophic growth of algae. The degree of CO₂ mitigation (flue gas decarbonization) in the algal suspension was 10–50% and decreased with increasing flue gas injection rate into the culture. A dissolved CO₂ partial pressure (pCO₂) higher than 0.1 kPa was maintained in the suspension at the end of the 50 m long culture area in order to prevent limitation of algal growth by CO₂. NO_X and CO gases (up to 45 mg m^-3 NO_X and 3 mg m^-3 CO in flue gas) had no negative influence on the growth of the alga. On summer days the following daily net productivities of algae [g (dry weight) m^-2] were attained in comparative parallel cultures: flue gas = 19.4–22.8; pure CO₂ = 19.1–22.6. Net utilization ( eta

) of the photosynthetically active radiant (PAR) energy was: flue gas = 5.58–6.94%; pure CO₂ = 5.49–6.88%. The mass balance of CO₂ obtained for the flue gas stream and for the algal suspension was included in a mathematical model, which permitted the calculation of optimum flue gas injection rate into the photobioreactor, dependent on the time course of irradiance and culture temperature. It was estimated that about 50% of flue gas decarbonization can be attained in the photobioreactor and 4.4 kg of CO₂ is needed for production of 1 kg (dry weight) algal biomass. A scheme of a combined process of farm unit size is proposed; this includes anaerobic digestion of organic agricultural wastes, production and combustion of biogas, and utilization of flue gas for production of microalgal biomass, which could be used in animal feeds. A preliminary quantitative assessment of the microalgae production is presented.

Keywords: carbon dioxide; flue gas; microalgae; outdoor open photobioreactor; process analysis

Document Type: Research article

DOI: 10.1007/s10811-005-8701-7

Affiliations: 1: Laboratory of Cell Cycles and Microalgal Biotechnology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 379 81, T rcaron ebo ncaron , Czech Republic, Email: doucha@alga.cz ebo ncaron , Czech Republic, Email: doucha@alga.cz "> 2: Fuel Research Institute, Praha 9, B ecaron chovice, 190 11, Czech Republic, chovice, 190 11, Czech Republic, "> 3: Laboratory of Cell Cycles and Microalgal Biotechnology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 379 81, T rcaron ebo ncaron , Czech Republic,ebo ncaron , Czech Republic,">

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Utilization of flue gas for cultivation of microalgae Chlorella sp.) in an outdoor open thin-layer photobioreactor