Photobiological hydrogen production process

This review will discuss the development of photobiological hydrogen production processes, where microorganisms (algae or cyanobacteria) function as living... 

The engineering of (micro)organisms and of processes for direct photobiological hydrogen production without biomass as an intermediate at high themodynamic efficiency and high kinetic rates. 

Photobiological hydrogen production is a theoretically more efficient process, but significant fundamental molecular research is needed to identify and improve the limiting factors in order to evaluate fully this approach for hydrogen production. 

Filamentous cyanobacteria have been used in bioreactors for the photobiological conversion of water to hydrogen. However, the conversion efficiencies achieved are low because of the competing processes of hydrogen production and consumption within... 

Alternative methods of hydrogen production are thermochemical water decomposition, photoconversions, photobiological processes, production from biomass, and various industrial processes where it is a by-product. 

A plate loop or sandwich reactor for photobiological processes using purple nonsulfur bacteria has been designed at the RWTH Aachen (Fig. 5-12, right). The reactor is separated by a central plate on which the bacteria are growing. Solar insulation triggers a natural convection of the nutrition suspension to flush around the bacteria. In outdoor experiments, a hydrogen production rate of 2 l/(h m ) was achieved [63]. 

Many other methods for hydrogen production, suitable for coupling with solar or other renewable energy technologies, have been investigated and developed to at least a pilot demonstration stage. These include direct thermal decomposition or thermolysis [24], thermochemical cycles [25], and photolysis (photochemical, photoelectrochemical, and photobiological processes) [26,27]. Unfortunately, all of these processes have severe technical difficulties, many of them have been abandoned, and all of them are far from industrial use. 

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