Sustainable cultivation of microalgae by an insulated glazed glass plate photobioreactor.

Microalgae growth in closed photobioreactors is greatly inhibited by elevated temperatures caused mainly by the infra-red portion of light. Current passive evaporative cooling systems for temperature control in outdoor photobioreactors are neither economical nor sustainable. Here we built a novel flat plate photobioreactor with its illumination surface customized with insulated glazing units (IGP). The IGP design enabled transmission of more than 50% of visible light while blocking 90% of ultraviolet and infrared radiations. The growth and productivity of Nannochloropsis sp. (MUR 267) in the IGP was compared against conventional flat plate photobioreactors subjected to the full spectrum (HLP) and also externally modified spectrum (CLP) of halogen lights. High temperature (up to 42°C) resulted in no growth in the HLP. Biomass productivities of Nannochloropsis sp. grown in the CLP was significantly higher than the IGP due to higher light transmission and lower temperature profiles recorded in the CLP. Lipid content of Nannochloropsis was highest in the CLP (60.23%) while protein was highest in the IGP (42.43%). All photosynthesis parameters were negatively affected in the HLP. The IGP's ability to remove infrared (heat) makes this newly developed photobioreactor a promising and sustainable cultivation system for mass algal production especially for high value products.