Effective CO2 capture by the fed-batch culture of Chlorella vulgaris

Microalgae are promising candidates for CO2 capture and concomitant biomass production. Chlorella vulgaris was grown in the batch and fed-batch cultures to develop a culture strategy targeting maximum CO2 capture and conversion to biomass. Growth at five different dissolved CO2 (dCO2) concentrations in the feeding media (atmospheric, 1.55, 1.62, 1.75 and 1.88 g L−1) was tested to assess the effect of dCO2 concentration on the growth, biomass productivity, and nutrients removal efficiency of microalgae. Results suggest that fed-batch culture outperformed "standard" batch cultivation with a higher algal growth rate (2.3 times). As expected, the algal growth was limited at low (atmospheric) dCO2 concentrations and inhibited at high levels (1.75 and 1.88 g L−1). C. vulgaris grown with medium containing 1.62 g L−1 dCO2 showed the highest growth rate (0.094 h−1) with the shortest doubling time (7.4 h), maximum biomass productivity, nitrogen and phosphorus uptake rates (222, 7.5 and 1.6 mg L−1 d−1, respectively). By pre-dissolving CO2 into the feeding media and using the fed-batch culture mode, a high CO2 removal efficiency could be achieved.