Experimental analysis and model-based optimization of microalgae growth in photo-bioreactors using flue gas

This study tested the growth of three algal species (Chlorella sp., Synechocystis sp. PCC 6803, and Tetraselmis suecica) using flue gas (generated by natural gas combustion). All the cultures showed poor biomass growth if they were exposed to continuous flue gas. To optimize the flue gas utilization in algal photo-bioreactors, we performed both model simulations and experimental analysis. First, we employed an un-segregated Monod-based model to describe the microalgal growth in response to CO2 in the photo-bioreactor. Via the dynamic optimization approach (DOA), the model profiled time-dependent CO2 concentrations (volume fraction ranging from 0.1 to 0.6%) to support maximal biomass growth. Second, we designed an oneoff flue gas pulse mode to reduce CO2 inhibition (a volume fraction up to 15% CO2) to the algal cells. Based on the reported algal kinetic parameters, our model predicted that gas-on (w10 s CO2 pulse) and gas-off (5e9 min) could achieve over 90% of the maximum theoretical algal growth rate predicted by the DOA. Third, we used mass flow controllers to apply oneoff flue gas pulses in photo-bioreactors, and the experimental results verified that the flue gas pulses could reduce flue gas inhibition and improve Chlorella growth compared to cultures exposed to atmospheric CO2. a 2012 Elsevier Ltd. All rights reserved.