Design of microalgal biomass production in a continuous photobioreactor: An integrated experimental and modeling approach

The industrial production of microalgae in continuous photobioreactors (PBRs) was investigated using an integrated experimental-modeling approach. A lab-scale PBR was assembled for microalgae cultivation, in the shape of thin-layer flat-vertical panels of 250 mL, in order to minimize the effect of cell self-shading and optimize the light use. Two microalgal species, one from marine and the other from freshwater environments, were cultivated in continuous mode in this PBR. They were grown under non-limiting CO2 supply and with excess nitrogen and micronutrients availability. Steady-state operating conditions were achieved and the effect of partial recycle on biomass concentration and productivity was investigated. Light energy was supplied at a constant rate, and the net flux of photons absorbed by the culture was measured and correlated to the average internal biomass concentration. The reactor performances were evaluated in terms of photosynthetic efficiency, and the possibility of increasing the productivity of the system was discussed. The light attenuation along the culture depth was modeled to fit the light absorption and backscattering coefficients. The growth model proposed by Pruvost et al. (2011b) was applied to reproduce the experimental behavior of the lab-scale PBR and to simulate the performances of a pilot unit both without and with recycle, i.e. as a function of the axial mixing, under both transient and steady-state conditions. The optimized model parameters were used to predict the microalgal growth in a pilot-scale closed raceway-pond PBR. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.