Optimizing Carbon Dioxide Utilization for Microalgae Biofilm Cultivation

The loss of carbon dioxide (CO2) to the environmentduring microalgae cultivation is undesirable for both environmentaland economic reasons. In this study, a phototrophic biofilm growthmodel was developed and validated with the objective to maximizeboth CO2 utilization efficiency and production of microalgae inbiofilms. The model was validated in growth experiments with CO2as the limiting substrate. The CO2 utilization and biomassproductivity were maximized by changing the gas flow rate, thenumber of biofilm reactors in series and gas composition. Based onsimulations, the maximum CO2 utilization efficiency that wasreached was 96% based on a process employing flue gas. Thecorresponding drop in productivity was only 2% in comparison tothe non-CO2 limited reference situation. In order to achieve this, 25biofilm reactors units, or more,must be operated in series. Based onthese results, it was concluded that concentrated CO2 streams andplug flow behavior of the gaseous phase over the biofilm surface areessential for high productivity and CO2 utilization efficiency