Photobiological hydrogen production

The chapter reports evidence that photobiological hydrogen production by algae and cyanobacteria is also a possible option in addition to other potential clean sources of hydrogen such as photovoltaic electrolysis and wind electrolysis of water, thermochemical water splitting, photoelectrochemical production from water, dark microbial fermentation, and photofermentation processes. These organisms have some advantages over other techniques, since they can produce hydrogen directly using renewable energy resources (sun and water), are carbon neutral, operate at ambient temperature and pressure, self-assemble the working catalytic structure, and don't require an intermediary electricity infrastructure. However, low efficiency of solar light conversion, and particularly oxygen inhibition of hydrogenase function, coupled to the high cost of photobioreactors are preventing practical implementation of the process on an industrial scale. Preliminary experiments carried out with the microalga, Chlamydomonas reinhardtii, and the cyanobacterium Synechocystis PCC 6803 in photobioreactors outdoors have ascertained practical issues that might enhance the technology transfer readiness level of current applied research. Notably, it has now become clear that achieving the necessary conversion efficiencies and cost requirements that might allow the development of a practical system will require more advanced biotechnology and photobioreactor engineering research.