Optimized aeration by carbon dioxide gas for microalgal production and mass transfer characterization in a vertical flat-plate photobioreactor

To optimize the aeration conditions for microalgal biomass production in a vertical flat-plate photobioreactor (VFPP), the effect of the aeration rate on biomass productivity was investigated under given conditions. Air enriched with 5% or 10% (V/V) CO2 was supplied for the investigation at rates of 0.025-1 vvm. The CO2 utilization efficiency, change of pH in the medium, and the optimum aeration rate were determined by evaluating biomass productivity. To investigate the VFPP mass transfer characteristics, the overall volumetric mass transfer coefficient, k(L)a, was evaluated for several different flat-plate sizes. Increasing the height of the VFPP could improve both the mass transfer of CO2 and the illumination conditions, so this appeared to be a good method for scaling up. Based on a comparison of the kLa value at the optimum aeration rate with previously reported results, it was confirmed that the range of CO2 concentration used in the experiments was cost-effective for mass culture.