Periodic CO2 Dosing Strategy for Dunaliella salina Batch Culture

A periodic CO₂ dosing strategy for D. salina 19/30 batch culture is proposed. A model of periodic CO₂ dosing including dosing time calculation, dosing interval estimation and final chlorophyll yield prediction was established. In experiments, 5% CO₂/95% N₂ gas was periodically dosed into D. salina culture. Two different gas dosing flow rates were tested. The corresponding dosing time for each flow rate was estimated via the model (10 min·d⁻¹ for 0.7 L·min⁻¹ and 36 min·d⁻¹ for 0.3 L·min⁻¹). Daily pH measurements showed that the pH of these cultures dosed periodically was always kept between 7.5 and 9.5, which highlights that periodic gas supply can maintain a suitable range of pH for microalgal growth without expensive buffers. Notably the culture dosed for set daily intervals was seen to have similar growth to the culture supplied constantly, but with much higher CO₂ capture efficiency (11%–18%) compared to continuous dosing (0.25%). It shows great potential for using periodic gas supply to reduce cost, wasted gas and energy use.