There is growing recognition that microalgae are among the most productive biological systems for generating biomass and capturing carbon. Further efficiencies are gained by harvesting 100% of the biomass, much more than is possible in terrestrial biomass production systems. Microalgae's ability to transport bicarbonate into cells makes them well suited to capture carbon. Carbon dioxide— or bicarbonate-capturing efficiencies as high as 90% have been reported in open ponds. The scale of microalgal production facilities necessary to capture carbon-dioxide (CO₂) emissions from stationary point sources such as power stations and cement kilns is also manageable; thus, microalgae can potentially be exploited for CO₂ capture and sequestration. In this article, I discuss possible strategies using microalgae to sequester CO₂ with reduced environmental consequences.