A multiwavelength model to improve microalgal productivity and energetic conversion in a red-blue light emitting diodes (LEDs) continuous photobioreactor

Highlights: • In continuous PBR, a comparable biomass productivity is achieved under R/B and white LED. • Acclimation to the light source is needed to obtain reliable kinetic parameters. • Biomass growth under tailored spectra can be predicted by the mathematical model. • R/B LEDs have advantage in terms of both photosynthetic and energy efficiency. Irradiation with light emitting diodes (LEDs) is proposed as a method to increase the photoconversion efficiency in large-scale microalgal cultivation. Although several authors have reported the possibility of using colored LEDs in batch systems and for many species, the overall energy efficiency of a continuous system integrated with fine-tuned LED technology is still not available. In this work, the cyanobacterium Arthrospira maxima was cultivated under a R/B (red/blue) LED lamp at increasing light intensities, in order to study the effects of light quality on microalgal performances. Kinetic growth parameters were retrieved from respirometric tests and implemented in a mathematical model to examine the effects of process variables on microalgal growth and to predict maximum biomass productivity in the multi-wavelength spectrum employed, which was also included in the simulation tool. The efficiency of both photosynthetic and LEDs were examined for energy evaluation. It was found that integrating tailored LEDs in microalgal cultivation increases process efficiency by reducing light energy waste. Moreover, integrating tailored LEDs was also found to be more efficient than white LED source, due to their higher energetic efficiency.