Biological hydrogen production is becoming important in the renewable fuels panorama and quite promising in the succession of fuels evolution with several technical, socio-economic and environmental benefits. Among the biological approaches, dark fermentation represents a promising and environmental process to achieve hydrogen from a wide variety of low-cost renewable feedstock. This book, can be useful to understand the basis of the process for a real scale application considering energy and practical aspects. To reach this goal, it was followed an experimental approach to find out the biological parameters and dynamics which influence the hydrogen production. Then, to obtain the energy sustainability of the whole process, the attention was focused into the integration of dark H2 bioreactor with other biotechnologies, in order to valorize the end liquid products. These attracting proposed systems can be taken in consideration as alternatives to develop cost- effective energy generator by organic refuse treatment.