Interval observer for Chlorella vulgaris culture in a photobioreactor

Microalgae present a very promising alternative for carbon dioxide mitigation strategies. These unicellular photosynthetic microorganisms fix carbon dioxide efficiently, converting it into biomass and high-value compounds. One of the control system challenges is to maximize carbon dioxide consumption by maintaining the cellular concentration to an optimal value in the exponential phase. In this paper, we propose a software sensor for the biomass concentration of Chlorella vulgaris culture in a continuous photobioreactor with uncertain model parameters. From Total Inorganic Carbon measurements, the interval observer can provide a guaranteed upper and lower bound for the cellular concentration using the available interval of the uncertain initial condition, model parameters and measurements. Numerical simulations and experimental validation are included to illustrate the performance of the proposed estimation strategy.