Section IV
Mass Production of Microalgae
15 | Open Cultivation Systems and Closed Photobioreactors for Microalgal Cultivation and Biomass Production |
C.K. Madhubalaji, Ajam Shekh, P.V. Sijil, Sandeep Mudliar, Vikas Singh Chauhan, R. Sarada, Ambati Ranga Rao, and Gokare A. Ravishankar
CONTENTS
Abbreviations
Introduction to Microalgae Cultivation System
Open Cultivation Systems
Circular Ponds
Raceway Pond
Closed Photobioreactors
Vertical Tubular Photobioreactor
Bubble Column Photobioreactor
Airlift Photobioreactor
Horizontal Tubular Photobioreactor
Flat Panel Photobioreactor
Helical Type Photobioreactor
Stirred Tank Photobioreactor
Soft-Frame Photobioreactor
Hybrid Type Photobioreactor
Comparative Account of the Performance of Various Bioreactors
Future Prospects
Acknowledgments
References
Box 15.1 Salient Features
Microalgae are considered valuable photosynthetic microorganisms for various applications, from CO2 utilization, to production of nutraceuticals, to wastewater treatment. Irrespective of the final application of microalgae, the process of cultivation remains the same. However, the production capabilities vary depending on the choice of cultivation system. Various kinds of open and closed photobioreactors are used for high microalgal biomass production. However, the design of a suitable photobioreactor depends on light availability and/or distribution, CO2 supply-mass transfer, environmental/cultivation conditions including temperature and solar radiation, and mixing. To provide the necessities of microalgae cells, various photobioreactors have been proposed. We have reviewed these open cultivation systems and closed photobioreactors in this chapter.
Introduction to Microalgae Cultivation System
Microalgae is an indispensable resource for various metabolites (Astaxanthin, β-carotene, omega-3, omega-6 fatty acids, proteins, carbohydrates, vitamins, and minerals) production with multiple benefits of its application in food, feedstock, medical, cosmetic, biofuel, and chemical industries (Fernandes et al. 2015; Ranga Rao et al. 2018a,b, 2014). This led to an increasing demand for the microalgal biomass. Growing microalgae in natural environments (pond, lake) cannot produce the quality of the biomass for intended uses. Various types of cultivation systems with different configurations are used for microalgal cultivation, such as simple open circular ponds, open raceway ponds, and complex enclosed systems referred to as closed photobioreactors. The open cultivation in contained reactor is widely used especially for growing extremophilic organisms such as Spirulina and Dunaliella free from contamination. Also this system is cheaper to construct and provides excellent utilization of solar light source especially in the equatorial regions of the globe. However there is constant innovation in design geometry of the open cultivation systems to maximize the solar energy distribution on the culture surface (Fernández et al. 2001; Sierra et al. 2008) to provide adequate light (Terry 1986; Grobbelaar 1994), fluid dynamics, and mass transfer to achieve high biomass productivities (Rubio et al. 1999; Posten 2009).
Closed bioreactors of various designs are being developed and adapted for controlled cultivation of the biomass with higher precision in providing the adequate quantity and quality of light...