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

Abstract: 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. Graphic Abstract: [Figure not available: see fulltext.]