Photobiological hydrogen production: Bioenergetics and challenges for its practical application

• We review photoproduction of H2 by purple bacteria, cyanobacteria, and green algae.
• We focus on bioenergetics of photobiological H2 production.
• We discuss some strategies for improving H2 production.
• We discuss technological aspects such as the cost of nutrients and bioreactors.

Photobiological production of hydrogen is considered to be one of the most promising technologies for replacing or complementing fossil fuel-derived energy. This review focuses on the bioenergetics of photobiological hydrogen production by various phototrophs, namely purple non-sulfur bacteria, green sulfur bacteria, cyanobacteria, and green algae. We discuss the improvements in hydrogen production efficiency and the advances in related technologies that are needed before phototrophs can be used for economically-viable hydrogen production. We also discuss some technological aspects such as the cost of nutrients and bioreactors, which should be taken into consideration in designing future plans for the application of photobiological hydrogen production.