Comparative Evaluation of CO2 Fixation of Microalgae Strains at Various CO2 Aeration Conditions

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This study investigated microalgal CO2 fixation at the CO2 concentration ranging from 5 to 40% and the CO2 loading rate of 14.4 to 57.6 L/L-d. Chlorella sp. (AG10133) was selected as the optimal strain for CO2 fixation among examined algal strains. The microalgal CO2 fixation was highly dependent on the CO2 loading rate as well as CO2 concentration. In batch culture, the highest CO2 fixation rate of 1.785 g/L-d was obtained at the CO2 concentration and the CO2 loading rate of 15% and 43.2 L/L-d, respectively. The high CO2 fixation performance was maintained at CO2 40% with the same CO2 loading rate. On the other hand, CO2 loading rate over 43.2 L/L-d at CO2 15% deteriorated CO2 fixation along with the decrease of microalgal growth. In continuous culture, the CO2 fixation rate of 2.25 g/L-d was achieved at the pseudo-steady state. The microalgal CO2 fixation would be suitable for high-strength CO2 gas stream such as biogas by providing proper CO2 loading rate.