Membrane photobioreactor is a term that is used to describe a membrane contactor that is integrated with a photobioreactor to enhance CO2 mitigation by microalgae. The membrane module can be externally or internally integrated with the culture vessel of microalgae. The membrane photobioreactor can be considered as a new development in the research field, since it was first mentioned in 1998 by Ferreira et al. (1998). The latest study of the membrane photobioreactor was in 2008 by Fan et al. (2008). Between these years, only a very few research efforts are described in the literature, showing that there is still much work to be conducted. Photobioreactors are seen as one of the most reliable ways to reduce the emissions of CO2 to the atmosphere, and this is accomplished by using microalgae to sequester CO2 and transform it into biomass for use as biofuel feedstock.

Gas-liquid mass transfer is an important feature of photobioreactors, and the biggest challenge is to design for high biomass productivity. Poor mass transfer increases the risk of CO2 stripping in the photobioreactor, and this inhibits the growth of microalgae (Hoekema et al. 2002). This is because the higher the photo­synthesis activity, the higher the DO. The DO is significant enough to inhibit the growth of microalgae. However, this cycle can be predicted by using a mathematical equation (Hai et al. 2000). The correct light regime also is important to allow high photosynthetic rates, and this can be estimated by using modelling equations (Zijffers et al. 2008). The most favourable photosynthetic rate is eight quanta for every one molecule of O2 (Brindley et al. 2011). Another alternative that can be used to maintain the uptake light is the lumostatic operation of a bubble-column photo­bioreactor (Choi et al. 2003). Photobioreactors also have high-efficiency utilization of CO2 (Chiu et al. 2008), whereas up to 82.3% CO2 removal efficiency can be achieved in an airlift bioreactor. Airlift bioreactors also are suitable for batch, con­tinuous, and semi-continuous culturing of microalgae (Kaewpintong et al. 2007).