Industrial Photobioreactors and Scale-Up Concepts

Unlike other more classical bioprocesses for heterotrophic growth (typically yeasts and bacteria) where mixing tanks have standard geometries, microalgal culture has no single standard geometry. The main reason is the need for a light supply, which (1) has spurred various technologies designed to maximize light use and (2) greatly increases process complexity, as light is a complex parameter to handle. However, in-depth and long-term modeling efforts have now yielded engineering tools to design, optimize, and control photobioreactors in a predictive and rational way. Here we discuss the parameters to consider when designing and operating microalgal cultivation systems and how appropriate engineering rules can support optimal system design and operation. Once the practical and economic constraints of the final application have been appropriately factored in, it becomes possible to set a rational design of effective technologies. This is illustrated later in this chapter in examples of successful developments, some of which are commercially available via AlgoSource Technologies. The examples chosen serve to highlight the many applications of photobioreactors from lab-scale fundamental studies to large solar industrial production, and to illustrate how a handful of engineering rules frame the various photobioreactor design options (artificial light or natural sunlight, external or internal lighting, high-cell-density culture, and more).