Balancing energy efficiency and biomass yield through Computational Fluid Dynamics of a commercial scale bubble-column photobioreactor

Abstract Microalgae biomass derived fuel need to maximize production with minimal energy input to cultivation and harvesting operations. The mixing/circulation comprises an essential step in the expensive microalgae cultivation process. Additionally, prevents cell settlement and increases exposure to light and nutrients. Nevertheless, it is responsible for at least one-third of total cost to produce lipid from microalgae. Regulating air input is an effective way to save energy, but it can compromise production. Computational Fluid Dynamics was used to determine the percentage of dead-zones in 330 L photobioreactors (aspect ratio of 4.54) for production of the microalgae Nannochloropsis oceanica with different airflow. Three numerical cases were selected for growth experiments. The airflow rate of 0.0024 vvm allowed satisfactory production and low energy input. It is noteworthy that experiments with the highest Energy Return On Investment values were also observed in this airflow rate (0.0024 vvm). The complementary application of the tools (Energy Return On Investment and Computational Fluid Dynamics) have shown high potential to reach the economic viability of microalgae biofuel.