An efficient Photobioreactors/Raceway circulating system combined with alkaline-CO2 capturing medium for microalgal cultivation.

High efficiency of microalgal growth and CO 2 fixation in a Photobioreactors (PBRs)/Raceway circulating (PsRC) system combined with alkaline-CO 2 capturing medium and operation was established and investigated. Compared with a pH 6 medium, the average biomass productivity of Chlorella sp. AT1 cultured in a pH 11 medium at 2 L min −1 circulation rate for 7 days increased by about 2-fold to 0.346 g L −1  d −1 . The maximum amount of CO 2 fixation and CO 2 utilization efficiency of Chlorella sp. AT1 could be obtained at a PBRs to Raceway ratio of 1:10 in an indoor-simulated PsRC system. A similar result was also shown in an outdoor PsRC system with a 10-ton scale for microalgal cultivation. Under the appropriate circulation rate, the stable growth performance of Chlorella sp. AT1 cultured by long-term semi-continuous operation in the 10-ton outdoor PsRC system was observed, and the total amount of CO 2 fixation was approximately 1.2 kg d −1 with 50% CO 2 utilization efficiency. [ABSTRACT FROM AUTHOR]