Robert Dillschneider and Clemens Posten

Abstract A variety of high value products have so far been produced with algae and the transition to algae mass cultures for the energy market currently arouses the interest of research and industry. The key to efficient cultivation of microalgae is the optimization of photobioreactors that does not only allow for efficient light cap­ture but also takes account of the specific physiological requirements of microalgae. Three fundamental reactor designs (bubble columns, flat plate reactors, and tubular reactors) are common and are discussed together with some elaborate derivatives in the following. Every concept excels with specific advantages in terms of light distri­bution, fluid dynamics, avoidance of gradients, and utilization of the intermittent light effect. However, the integration of all beneficial characteristics and simultane­ously the compliance with energetic and economic constraints still imposes demand­ing challenges on engineering.