Efficient CO2 Capture and O2 Generation by Multiple Column-Type Photobioreactors with Arthrospira platensis

Sustainable CO2 capture can be achieved using photosynthetic microorganisms such as Arthrospira platensis. This work investigates CO2 capture and O2 generation efficiency by employing multiple column-type bubbled photobioreactors with Arthrospira platensis pre-adapted long-term to enhanced CO2 concentrations. Thirty photobioreactors (10 L each) were placed inside a sealed chamber (2 × 2 × 3 m). Three 12-day experiments under constant illumination (225 μmol/m2·s) and temperature (27 °C) and different CO2 concentration were conducted at 1.5, 3.0, and 6.0 vol.%. During the experiments, the gas composition within chamber, biomass accumulation, and chemical composition of the culture medium (pH, concentrations of carbonates, bicarbonates, nitrates and phosphates) were monitored. With an increase in CO2 concentration from 1.5 to 6%, the biomass growth rate increased from 321 to 344 mg/(L·day), while CO2 capture and O2 generation efficiency estimated from biomass accumulation changed from 432 to 480 mg/(L·day) and from 371 to 412 mg/(L·day), respectively. Increasing CO2 concentration effectively suppressed medium alkalinization (pH maintained at 8.75–9.30 at 6.0% CO2 vs. >9.8 at 1.5% CO2) and sustained bicarbonate availability. Microscopic analysis confirmed high culture viability (>85% live trichomes) at all studied concentrations. The obtained results can be used for Arthrospira platensis-based CO2-enhanced biofixation and accumulation of valuable biomass.