Article

Microalgal Reactors: A Review of Enclosed System Designs and Performances

Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal.
Biotechnology Progress (Impact Factor: 2.15). 12/2006; 22(6):1490-506. DOI: 10.1021/bp060065r
Source: PubMed

ABSTRACT

One major challenge to industrial microalgal culturing is to devise and develop technical apparata, cultivation procedures and algal strains susceptible of undergoing substantial increases in efficiency of use of solar energy and carbon dioxide. Despite several research efforts developed to date, there is no such thing as "the best reactor system"- defined, in an absolute fashion, as the one able to achieve maximum productivity with minimum operation costs, irrespective of the biological and chemical system at stake. In fact, choice of the most suitable system is situation-dependent, as both the species of alga available and the final purpose intended will play a role. The need of accurate control impairs use of open-system configurations, so current investigation has focused mostly on closed systems. In this review, several types of closed bioreactors described in the technical literature as able to support production of microalgae are comprehensively presented and duly discussed, using transport phenomenon and process engineering methodological approaches. The text is subdivided into subsections on: reactor design, which includes tubular reactors, flat plate reactors and fermenter-type reactors; and processing parameters, which include gaseous transfer, medium mixing and light requirements.

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    • "However, issues associated with PBR include oxygen removal and reactor overheating. As a byproduct of photosynthesis from algae, oxygen can inhibit the photosynthesis process at concentrations beyond air saturation (Carvalho et al., 2006). To overcome the overheating issue, cooling water spray may be necessary and the water consumption associated can be significant (Pate, 2008). "
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    • "Photobioreactors (PBRs) are closed systems for microalgae cultivation and there are currently three main design groups available (Carvalho et al., 2011). These designs are tubular (Molina et al., 2001), flat panel (Issarapayup et al., 2009) or fermenter-type (Carvalho et al., 2006). Tubular and flat-panel PBRs are designed for the efficient harvest of sunlight and are therefore based on the principle of high area to volume ratios. "
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    • "PBRs are thus known to display significantly higher biomass productivities, also enabling the culture of sensitive strains (Ugwu et al., 2008). High investment and operational costs (e.g., capital, maintenance, and energy; Carvalho et al., 2006) are important economic constraints as far as their widespread use is concerned. However, further developments in PBR design, and implementation of large-scale facilities, mainly driven by the research in the field of biofuels, are expected to decrease these costs, enabling the culture of microalgal biomass for the exploitation of high-value products, such as PUFA. "
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