Generalities
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1.1.7.1. Open systems: raceway
In recent decades, the industrial cultivation of microalgae has mainly relied on the opensystem operating system, which refers to a system in which microalgae are grown in an open
environment using natural light exclusively and thus eliminating the need for artificial lighting
expenditure during the growth of microalgae (Razzak et al., 2013).
The raceway pond (figure 5) is mainly used for cultivating microalgae: scenedesmus sp,
Chlorella sp and Spirulina platensis. The idea is to circulate the algae over a long distance, but
with a shallow width. Paddle wheels are used to facilitate mixing and circulation (Tebbani et
al., 2014).
Figure 5:Raceway pond (Dalgleish, 2017).
1.1.7.2. Closed systems: Photobioreactors
Biological growth systems known as closed photobioreactors were used to grow
microalgae indoors, isolating them from the outside elements.
They were often tubular in shape (Figure 6) to maximize the surface/volume ratio so that
microalgae cells could receive sufficient light. Although these controlled environments allowed