Optimizing Carbon Dioxide Utilization for Microalgae Biofilm Cultivation

The loss of carbon dioxide (CO2) to the environment
during microalgae cultivation is undesirable for both environmental
and economic reasons. In this study, a phototrophic biofilm growth
model was developed and validated with the objective to maximize
both CO2 utilization efficiency and production of microalgae in
biofilms. The model was validated in growth experiments with CO2
as the limiting substrate. The CO2 utilization and biomass
productivity were maximized by changing the gas flow rate, the
number of biofilm reactors in series and gas composition. Based on
simulations, the maximum CO2 utilization efficiency that was
reached was 96% based on a process employing flue gas. The
corresponding drop in productivity was only 2% in comparison to
the non-CO2 limited reference situation. In order to achieve this, 25
biofilm reactors units, or more,must be operated in series. Based on
these results, it was concluded that concentrated CO2 streams and
plug flow behavior of the gaseous phase over the biofilm surface are
essential for high productivity and CO2 utilization efficiency.