Microalgal Reactors: A Review of Enclosed System Designs and Performances

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.

Design principles of photo‐bioreactors for cultivation of microalgae

“…This leads directly to the fact that at least one dimension is determined by the light path length, while the other two dimensions (width and height) are free for design and scale up. A detailed description of different geometries is given from [34].…”

“…The compromise between bubble residence time, bubble diameter for good gas transfer, and energy demand limits scale up seriously especially for inclined tubular devices. This has already inspired people some years ago to supply CO 2 by membrane diffusion e.g by hollow fibre modules in an external by-pass [34]. The principal advantage is shown in [64,65].…”

Placing microalgae on the biofuels priority list: a review of the technological challenges

“…More sophisticated closed PBRs are designed to offer shorter optical paths under external illumination (as shown in figure 5), mainly achieved using tubular or flat plate vessel configurations manufactured from transparent materials (reviews by Carvalho et al 2006;Eriksen 2008). These designs are intended to minimize light attenuation between the wall and the centre of the culture vessel, with typical tube diameters/ plate thicknesses of ca 0.05 m. Tubular PBRs vary in their configuration, including horizontal, vertical, helical and a-shaped designs, whereas flat plate PBRs are typically thin rectangular chambers oriented vertically or inclined towards the sun.…”

Surveying techno-economic indicators of microalgae biofuel technologies

“…A set of articles can be found in the literature evidencing the technical feasibility of growing algae for biofuel production [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], in which the majority of them demonstrate the absence of the major drawbacks associated with current 1st generation biofuels. For example, the most common drawback pointed out of 1st generation biofuels as being the affect on food prices due to massive arable land use.…”