Biohydrogen: Chapter 2. Fundamentals of Biohydrogen

A variety of methods are available and under study for the biological production of hydrogen, each with its own advantages and challenges. These include two light-dependent process: biophotolysis with wither green algae or cyanobacteria or photofermentation with photosynthetic bacteria. Here the major challenge is how to harvest the requisite light energy effectively and efficiently. Two processes that do not depend on light—dark fermentation or microbial electrolysis cells (MEC)—have the advantages of being able to use a variety of waste streams as substrate and a wide variety of different types of microbes as catalysts. However, these suffer either from low yields (dark fermentation) or low volumetric hydrogen productivities and challenges in reactor configuration (MECs). Here, the fundamental principles underlying these different processes are reviewed and recent progress in each are highlighted.