Impact of light quality and quantity on growth rate kinetics of Selenastrum capricornutum

Microalgal biomass produced in indoor photobioreactors can be used as inoculum for large‐scale outdoor cultures or directly for the production of high‐value bioproducts due to the higher control of these cultures compared with outdoor systems. One of the main costs of indoor microalgal cultures is the illumination. This work can be used as a basis for the optimization of the light source for indoor microalgal biomass production, based on the light source type, irradiance, productivity, growth rate, attenuation coefficients, and contaminant growth on the reactor's side‐walls. Four commercially available near 400‐W artificial light sources for microalgal cultures (metal halide (MH), high‐pressure sodium (HPS), Son Agro^®, and fluorescent) were compared. The light elevation and the surface scalar irradiance were shown to have a linear relationship. The attenuation coefficient in air (k_a) was highest with Son Agro^®. A linear partition of the attenuation coefficient between the water and biomass and an exponential relationship between average scalar irradiance and depth were found. An empirical overall scalar attenuation coefficient for each light source was obtained. The lowest maximum observed growth rate was obtained with fluorescent light (0.98 d^?1) and the highest with Son Agro^® (2.39 d^?1). The highest growth on the reactor's wall was obtained with Son Agro^®. Further studies resulted in a higher maximum specific growth rate and optimum irradiance for HPS (2.37 d^?1 and 460 μmol s^?1 m^?2) compared with those observed with MH (1.73 d^?1 and 391 μmol s^?1 m^?2).