LAUSR

ABSTRACT The industrialization of microalgae-based biofuel production has been hampered by low biomass productivity of conventional open ponds. In this research, a hybrid cultivation system that combined an open pond and photobioreactor (PBR), with broth circulating between both, was introduced. The hybrid system was tested under indoor and outdoor conditions using the oleaginous microalgal species Scenedesmus dimorphus. When the PBR(s) in the hybrid system reinforced the light supply to the carbon-replete open pond the biomass reached 1.34 g l–1, 116% higher than in the non-hybrid system. Subsequent studies showed that higher circulation speed and low volume ratio of PBR vs. open pond would further improve the hybrid effects. When applied outdoors at pilot scale, the biomass productivity of the hybrid system increased 46.3–74.3% compared with the open pond and in September was 12.5% higher than that of PBRs. These results indicate that hybrid cultivation might be a cost-effective way to improve the light usage efficiency of current open pond systems.