Uncoupling solid and hydraulic retention time in photobioreactors for microalgae mass production: A model-based analysis. (8th June 2020)

• Record Type: Journal Article
• Authors: Barbera, Elena; Sforza, Eleonora; Grandi, Alessia; Bertucco, Alberto
• Is Part Of: Chemical engineering science. Volume 218(2020)
• Publication Date: 2020-06-08
• Subjects: Bioprocess engineering -- Photosynthetic microorganism -- Productivity optimization -- Light utilization; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2020.115578
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: SRT is the key variable to maximize the biomass productivity. At the optimum value of SRT, the HRT does not affect the biomass productivity. Operating with SRT > HRT does not improve productivity in light-limited cultures. Operating with SRT < HRT allows to strongly reduce water and nutrients consumption. Abstract: In conventional continuous bioreactor operations, it is a common practice to decouple the hydraulic retention time (HRT) from the solid retention time (SRT). When dealing with photosynthetic microorganisms, light intensity plays a major role in the growth kinetics; thus, the effect of HRT and SRT on biomass productivity may differ from that in chemotrophic bioreactors. In this study, we assessed the role of uncoupled SRT and HRT on biomass productivity in continuous photobioreactors (PBRs) based on simple mass balances, light transfer, and kinetic models to highlight the specific features of PBRs. Under a non-limiting nutrient supply, SRT is the fundamental variable used to maximize productivity and control the biomass concentration and light penetration in a PBR. Operating at SRT > HRT does not enhance the productivity. If the goal is biomass production, it is instead convenient to operate at SRT < HRT, thereby significantly reducing the water and nutrient consumption.