Evaluation of a Pilot-Scale Vertical Flat-Panel Photobioreactor for Indoor Mass Cultivation of Microalgae

Abstract The study assessed flat-panel photobioreactors (FP-PBRs) for superintensive microalgae cultivation. FP-PBRs were constructed with a metallic skeletal structure and galvanized metal grids for support. FP-PBRs were made with plastic bags with dimensions of 2.30 m × 0.75 m × 0.1 m and a useful volume of 150 L. The operation included a filtered aeration system, CO2 injection, and automated pH and temperature control. To start the FP-PBR operation, an aeration rate of 0.067 vvm and an overall mass transfer coefficient KLa(O2) of 54.29 h-1 were used. An irradiance of 400 µmol photons m-2 s-1 suitable for Nannochloropsis oculata cultivation was applied. Two surface-to-volume ratios (S/V) were used: 10.5 m-1 with one-sided illumination and 21 m-1 with illumination on both sides. At the end of 264 h (11 days), the FP-PBR system made with alternative materials proved to be efficient. The highest biomass of N. oculata biomass was achieved with a S/V ratio of 21.0 m-1 (1.91 ± 0.15 g L-1 day-1), compared to 1.13 ± 0.08 g L-1 day-1 in the S/V 10.5 m-1 treatment. By using a FP-PBR that cost around US$ 544.00, it was feasible to attain high productivity in cultures where the algal cells received increased light exposure, while still ensuring control and safety.