Light in a Photobioreactor

Abstract. A photobioreactor (PBR) can be used to produce biofuels by growing microalgae in a controlled environment where pH, CO2, light and nutrients are controlled. Light plays an important role in microalgal growth and production. How light attenuates with the PBR depth, different air flow rates and different biomass concentrations was determined. An equation which relates these three factors was developed. The experiment was carried out in two sections. In the first section, light measurements were made for light paths through water depths of 102mm, 127mm, 203mm, 254mm and 305mm (4”, 5”, 8”, 10” and 12”) and different diffuser/sparger air flow rates (0 to 10 lpm) in lab scale PBRs. The second section of the experiment was conducted with different PBR depths (102mm, 127mm, 203mm, 254mm and 305mm) and different biomass concentration (0 – 2 g/l) with no air flow in the PBR. The light intensity was reduced a maximum of 35% with PBR depth, 35% with air flow rate and 97% with biomass concentration.