Scaling-up sustainable Chlorella vulgaris microalgal biomass cultivation from laboratory to pilot-plant photobioreactor, towards biofuel

Unicellular microalgal culture represents a new opportunity for producing significant biofuel quantities in the future along with other specialty products, due to several major advantages microalgae species present when compared to conventional crops, including much faster growth rates, cultivation in a variety of environments and photobioreactor systems, and almost 100% recycling of nutrients. In the current research, the scaling-up of the cultivation of Chlorella vulgaris microalgae to a 4 m3 pilot-plant photobioreactor is examined, compared to the performance of a 25 L automated laboratory bioreactor. Beyond the size and configuration, the main differences of the two bioreactors are the mode of operation, the illumination nature and depth, the temperature, and pH. Specifically, temperature and illumination are naturally varying from day to day and season to season into the pilot-plant photobioreactor that is set inside a greenhouse. The specific growth factor appears to be higher for microalgal cultivation in the laboratory bioreactor. It is also found that the growth kinetics is severely slowed down during the winter months. This is primarily due to the low temperatures and the poor illumination observed during winter.