As we mentioned, closed cultivation systems that house the growth of algae under con­trolled conditions are referred as photobioreactors (PBRs). Photobioreactors provide a more controlled environment than open ponds because these systems are closed and everything that the algae need to grow (carbon dioxide, water, and light) can be supplied with in the system (Weissman, 1987; Pulz, 2001). There are different types of PBRs reported for algae cultivation. PBRs facilitate better control of culture environment, such as carbon dioxide sup­ply, water supply, optimal temperature, efficient exposure to light, culture density, pH levels, gas supply rate, mixing regime, and so on (Mata et al., 2010). High mass transfer is one of the important criteria for PBR design, especially for CO2 sequestration (Ugwu et al., 2008). Ag­itations in PBR are done either mechanically or nonmechanically. Non-mechanical agitation can be observed airlift, bubble column, tubular reactor, and flat panel operations. PBRs spe­cifically designed for CO2 sequestration have the flexibility of using CO2-rich gas as a means of mixing as well as providing nutrients for the growth of algae (Hu et al., 1996). PBRs can be operated in both batch and continuous modes. In comparison with open culture systems, a closed photobioreactor is easy to control with regard to environmental parameters and can achieve high growth rates (Pulz, 2001; Sierra et al., 2008). Higher biomass of microalgae pro­ductivity is obtained in closed cultivation systems where contamination can also be prevented (Ramanathan et al., 2011). Fully closed photobioreactors provide opportunities for monoseptic culture of a greater variety of algae than open cultivation systems (Borowitzka, 1999). Various types of closed cultivation systems are studied to a great extent.