Biohydrogen is the most promising and eco-friendly energy source. It is having high energy yield of 122kJ/g, which is 2.75 times higher than that of fossil fuels. Hence this fuel can defend the world against energy crises. When combusted, it only produces water which could result in reduction of GHG and also it is the pre-eminent choice as energy carrier. Production of biohydrogen from biomass through biological pathways is an emerging and eco-friendly technology. This book will be helpful for the other researchers who are working in the field of fermentation technology.