Background: Hydrogen is a clean, versatile fuel and energy carrier which can be produced by a range
of renewable technologies for combustion, use in fuel cells, or as a manufacturing feedstock. Despite
its attraction and significant technological innovation, commercial feasibility of photobiological
hydrogen processes is far from demonstrated.
Objective: This review examines direct photobiological biohydrogen systems, with a particular focus
on the main obstacles that must be overcome to deliver commercially viable, net energy positive
systems. As part of this process the interactions between future photobiological biohydrogen systems
and other parts of a renewable energy economy are examined to analyse potential technology
Results: The primary driver for renewably produced hydrogen is the potential for CO2 emissions reductions. Renewable
hydrogen is largely solar driven, either directly (e.g. natural photosynthesis, or bio-inspired devices) or indirectly (e.g.
fermentation, electrical hydrolysis). A large market for hydrogen already exists and is supported by extensive
infrastructure providing significant opportunities for emerging renewable hydrogen streams. Several key physiological
obstacles to efficient photobiohydrogen production have already been overcome, with oxygen tolerance as the most
significant remaining problem.
Conclusion: A much deeper understanding of photosynthetic biology is required before existing knowledge can be
integrated with real world systems. Cross-fertilisation between engineering and biology represents the best path forward
for implementation as a robust biotechnology.