Direct membrane-carbonation photobioreactor producing photoautotrophic biomass via carbon dioxide transfer and nutrient removal

An advanced-material photobioreactor, the direct membrane-carbonation photobioreactor (DMCPBR), was tested to investigate the impact of directly submerging a membrane carbonation (MC) module of hollow-fiber membranes inside the photobioreactor. Results demonstrate that the DMCPBR utilized over 90% of the supplied CO₂ by matching the CO₂ flux to the C demand of photoautotrophic biomass growth. The surface area of the submerged MC module was the key to control CO₂ delivery and biomass productivity. Tracking the fate of supplied CO₂ explained how the DMCPBR reduced loss of gaseous CO₂ while matching the inorganic carbon (IC) demand to its supply. Accurate fate analysis required that the biomass-associated C include soluble microbial products as a sink for captured CO₂. With the CO₂ supply matched to the photosynthetic demand, light attenuation limited the rate microalgal photosynthesis. The DMCPBR presents an opportunity to improve CO₂-deliver efficiency and make microalgae a more effective strategy for C-neutral resource recovery.