Evaluation of growth rate and biomass productivity of Scenedesmus quadricauda and Chlorella vulgaris under different LED wavelengths and photoperiods

Cultivation has been identified as an essential stage for biofuel production. This research has examined two important parameters for the industrial production of microalgae, namely microalgae growth rate and biomass productivity. Chlorella vulgaris and Scenedesmus quadricauda were cultivated using a closed photobioreactor (PBR). A novel approach for cultivation and energy input reduction was developed by incorporating periods of darkness during cultivation, as would happen in nature. Three different LED light sources (white, red, and green) were used to determine the conditions that result in the highest growth rate and biomass productivity. C. vulgaris and S. quadricauda responded differently to lighting conditions. It was found that, depending on the LED source and light period, different growth rates and biomass productivities were obtained. Overall, experimental results obtained in this study indicated that a white LED is more effective than green or red LEDs in increasing microalgae growth rate and biomass productivity. A maximum growth rate of 3.41 d⁻¹ and a biomass productivity of 2.369 g L⁻¹d⁻¹ were achieved for S. quadricauda under a 19 h period of white light alternating with 5 h of darkness. For C. vulgaris the maximum growth rate of 3.49 d⁻¹ and maximum biomass productivity of 2.438 g L⁻¹d⁻¹ were achieved by continuous white light with no darkness period.