Estimation of carbon dioxide sequestration potential of microalgae grown in a batch photobioreactor

• High algal growth rate observed with continuous flow of 10% CO2 enriched air.
• Moles of CO2 sequestered was determined by mass balance and graphical integration.
• Both strains exhibited maximum carbon sequestration at gas flow rate of 40 ml/min.
• Good correlation observed between moles of CO2 sequestered and algal growth rate.
• Chlorella pyrenoidosa sequestered CO2 more effectively than Scenedesmus abundans.

The carbon dioxide (CO2) sequestration potential of two microalgae, Chlorella pyrenoidosa and Scenedesmus abundans was evaluated in a tubular batch photobioreactor with provision for continuous flow of 10% CO2 enriched air through the headspace. CO2 sequestration and biomass growth was affected by gas flow rate over the range 20–60 ml/min and 40 ml/min was found to maximize algal growth and CO2 sequestration. Moles of CO2 sequestered over 20 h at a gas flow rate of 40 ml/min was estimated using a novel rapid screening approach as 0.096 and 0.036, respectively, for C. pyrenoidosa and S. abundans. At this gas flow rate the maximum growth rate was 4.9 mg L−1 h−1 and 2.5 mg L−1 h−1 for C. pyrenoidosa and S. abundans, respectively. The CO2 sequestration and growth rate were comparable at height/diameter ratio of 8 and 16.