Developments and constraints in fermentative hydrogen production

Fermentative hydrogen production is a novel aspect of anaerobic digestion. The main advantage of hydrogen is that it is a clean and renewable energy source/carrier with high specific heat of combustion and no contribution to the Greenhouse effect, and can be used in many industrial applications. This review discusses fermentative hydrogen production from various points of view. First, the theoretical principles of the biological processes taking place in hydrogen production, as well as the organisms responsible for this process, are described. Second, practical aspects of fermentative hydrogen production are overviewed. Suitable conditions for the hydrogen-producers (pH and temperature), suitable substrates for hydrogen production and applicable reactor designs are discussed. Finally, the challenges faced by fermentative hydrogen production are discussed. Current research directions are listed together with the most important problems currently constraining full-scale application. (c) 2007 Society of Chemical Industry and John Wiley & Sons, Ltd