CO₂-Derived Carbon Capture Using Microalgae and Sodium Bicarbonate in a <i>PhotoBioCREC</i> Unit: Kinetic Modeling

By converting bicarbonates via Chlorella vulgaris photosynthesis, one can obtain valuable biofuel products and find a route toward carbon-derived fossil fuel conversion into renewable carbon. In this research, experiments were carried out in the PhotoBioCREC prototype under controlled radiation and high mixing conditions. Sodium bicarbonate (NaHCO3) was supplied as the inorganic carbon-containing species, at different concentrations, in the 18 to 60 mM range. Both the NaHCO3 concentrations and the organic carbon concentrations were quantified periodically during microalgae culture, with the pH being readjusted every day to the 7.00 level. It was found that sodium bicarbonate was converted with a selectivity up to 33.0% ± 2.0 by Chlorella vulgaris. It was also observed that the reaction rate constant for inorganic carbon conversion was 0.26 ± 0.09 day−1, while the maximum reaction rate constant for organic carbon formation was achieved with a 28 mM NaHCO3 concentration and displayed a 1.18 ± 0.05 mmole L−1day−1 value