Photobioreactor

Closed photobioreactors are flexible systems that can be controlled to the physiological requirements of the cultured organism, resulting in optimal growth rates and purity levels.

However, they offer an insufficient control of reaction conditions due to their reliance on environmental light supply and carbon dioxide, as well as possible contamination from other microorganisms.

[5] All modern photobioreactors have tried to balance between a thin layer of culture suspension, optimized light application, low pumping energy consumption, capital expenditure and microbial purity.

However, light attenuation and increased carbon dioxide requirements with growth are the two most inevitable changes in phototrophic cultures that severely limits productivity of photobioreactors.

[8] The simplest approach is the redesign of the well-known glass fermenters, which are state of the art in many biotechnological research and production facilities worldwide.

The tubes are oriented horizontally or vertically and are supplied from a central utilities installation with pump, sensors, nutrients and carbon dioxide.

[10] Due to the recent prices of the photobioreactors, economically feasible concepts today can only be found within high-value markets, e.g. food supplement or cosmetics.

A combination of the mentioned glass vessel with a thin tube coil allows relevant biomass production rates at laboratory research scale.

[12] An alternative approach is shown by a photobioreactor, which is built in a tapered geometry and which carries a helically attached, translucent double hose circuit system.

From the pool of different concepts e.g. meandering flow designs or bottom gassed systems have been realized and shown good output results.

This new procedure reduces by a factor of up to one hundred the amount of liquid needed for operation compared to the current technology, which cultivates algae in suspensions.

The discussion around microalgae and their potentials in carbon dioxide sequestration and biofuel production has caused high pressure on developers and manufacturers of photobioreactors.

New approaches test e.g. dripping methods to produce ultra-thin layers for maximal growth with application of flue gas and waste water.