Utilization of flue gas for cultivation of microalgae <Emphasis Type="Italic">Chlorella</Emphasis> sp.) in an outdoor open thin-layer photobioreactor |
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Authors: | Email author" target="_blank">Ji?í?DouchaEmail author Franti?ek?Straka Karel?Lívansky |
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Institution: | (1) Laboratory of Cell Cycles and Microalgal Biotechnology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 379 81 Třeboň, Czech Republic;(2) Fuel Research Institute, Praha 9, Běchovice, 190 11, Czech Republic |
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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. NOX and CO gases (up to 45 mg m−3 NOX 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 (η) 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. |
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Keywords: | carbon dioxide flue gas microalgae outdoor open photobioreactor process analysis |
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