Improving the CO₂ fixation rate by increasing flow rate of the flue gas from microalgae in a raceway pond

Residence time of flue gas bubbles with different solution velocities and the influence of NO_X and SO₂ from flue gas on pH values of culture solutions were analyzed based on large-scale raceway reactors. Microalgal growth and CO₂ fixation rates were also investigated with different gas flow rates. Bubble residence time was ∼1.1 s when the solution velocity was 20 cm/s. The NO_X and SO₂ effects on microalgal growth were negligible, although 66% NO_X and 95% SO₂ were captured by the microalgal solution. Microalgal biomass productivity increased from 10.3 to 14.1 g/m²/d when flue gas flow rate increased from 20 to 50 m³/h. CO₂ fixation and microalgae biomass productivity increased further from 26.3 to 31.9 g/m₂/d and from 14.1 to 17.1 g/m²/d, respectively, upon increase of flue gas flow rate from 50 to 150 m³/h.