While anaerobic digestion has regained a lot of interest with intensive industrial development in the field of waste treatment, fermentation processes represent a great potential way of innovation, particularly for the production of hydrogen, as emerging energy carrier. The main objective of the ProBHyM project is to study and evaluate the optimal parameters of fermentation process operation with a view to intensifying the production of hydrogen as an additional mean of energy recovery in waste AD plants. In particular, the fermentation process will be investigated on : (i) the mechanisms of inhibition (metabolic and/or populational) in relation to the accumulation of these by-products, including H2 in the medium (ii) the long-term operation and the impact of fermentation step on downstream AD, (iii) the upscaling and (iv) an economic and environmental analysis. The ProBHyM project will provide essential answers on the potential and limits of the production of H2 by dark fermentation.