The application of a membrane contactor for the carbonation of the microalgae culture was reported in the late of 1990s for the purpose of utilizing CO2 emissions to prevent them from entering the atmosphere. The hydrophobic membrane is capa­ble of enhancing CO2 transfer per area of membrane surface by a factor of 10 com­pared to silicone tubing (Ferreira et al. 1998) and 1.48 x 10-2 min-1 compared to 7 x 10-3 min-1 of plain bubbling and higher by a factor of two (Carvalho and Malcata 2001).

Membrane hydrophobic is also capable to enhance CO2 fixation rate from 80 to 260 mg L-1 h-1 or more than three times greater than a reactor without a membrane (Cheng et al. 2006; Fan et al. 2007). The DO dropped by a factor of 30 (Cheng et al. 2006) and the O2 evolution was enhanced (Fan et al. 2007). Besides their use for carbonation and deoxygenation, membrane contactors also can be used to integrate with the microalgae harvesting system (Bayless and Stuart 2009), thus could reduce the production cost of microalgae biomass.

The effectiveness of membrane contactors for sequestering CO2 is affected mainly by the microalgae density in the reactor, feed gas flow rate, light intensity (in the case of using microalgae), and the properties of the membrane. The property ranges that suitable to be applied to achieve the maximum capability of the membrane to sequester CO2 are listed in Table 14.3 (Ferreira et al. 1998; Carvalho and Malcata 2001; Cheng et al. 2006; Fan et al. 2007). These are the values that are used in the membrane contac­tor research field when using microalgae for the bio-mitigation of CO2.