Enhancement of microalgal CO2 fixation in photobioreactors by means of spiral flow vortices

Abstract

Microalgae have received a lot of interest as a sustainable solution for carbon dioxide fixation due to their great efficiency in capturing CO₂ and converting it into valuable biomass, making them a promising tool for mitigating climate change and expanding carbon capture technology. This study examines the efficacy of fixed shaped portable conical helix baffles (PCHB) in enhancing gas–liquid mixing to promote microalgal growth in column photobioreactors (PBRs). Flat (90° angle from cone surface), round, and inclined (60° angle from cone surface) baffles were compared for performance. Modeling the gas flow indicated that round PCHB produced more spiral vortices and achieved better mixing performance than flat and inclined designs. Increasing the baffle size from 3 to 7 cm resulted in a 21% higher mass transfer coefficient. The simulation was verified by experiments. Notably, the implementation of a PCHB with a round helix-shaped structure (5 cm) led to a 33% (2.102 ± 0.08 g/L) and 17% (2.419 ± 0.07 g/L) dry mass increase of Limnospira fusiformis when compared to flat and incline-shaped baffles, respectively. Our study revealed that using a round-shaped PCHB resulted to higher spiral movement, which in turn increases CO₂ utilization and cell proliferation. Our approach demonstrates high potential to further optimize industrial PBRs, thereby facilitating CO₂ sequestration during microalgal cultivation to combat global warming.