Efficient CO2 capture from the air for high microalgal biomass production by a bicarbonate Pool

Direct air capture (DAC) of CO2 from ambient air based on alkaline sorbents has great potential, but regenerating sorbents with physiochemical methods is energy-intensive. With free solar energy, however, sorbents can be regenerated with the consumption of CO2 during photosynthesis by microalgae, but this regeneration is limited by the low efficiency of CO2 capture from air, which is also the primary reason for the high cost of microalgae production. In this study, 100 - 500 mmol L-1 bicarbonate with a pH of 10.0-12.5 was used to efficiently capture CO2 from the air, store it as a bicarbonate pool, and rapidly supply CO2 during photosynthesis. The initial pH and bicarbonate concentration significantly affected biomass productivity and the carbon-capture rate, with maxima of 1.00 and 0.81 g L-1 d(-1), respectively, indicating the high efficiency of this process. This process that can be completely driven by renewable energy in future, such as wave energy, will significantly reduce costs and facilitate both carbon capture and microalgae production in an environmental friendly manner.