Coupling bio- and electro-chemical processes for hydrogen production from organic residues

Hydrogen is a carbon-free energy carrier and the research on alternative production methods, low energy-demanding and not based on fossil sources, plays a key role in the energy transition target. In that context, dark fermentation is considered a promising strategy for bio-hydrogen generation since it allows energy recovery from residual materials such as biodegradable waste. The present work addresses from different perspectives those which are currently believed to be the major challenges of the process. Firstly, a research study on the production yields and the assessment of long-term stability in continuous systems was performed; the results from the experimental campaign involving a number of combinations of operating conditions were reported. Secondly, the feasibility of combining the dark fermentation with electrochemical method was investigated with the aim to overcome the biochemical constraints associated with reduced hydrogen yields. To this purpose, an innovative integrated bio-electrochemical process was designed and tested under different configurations at lab-scale. Lastly, the concept of a multi-stage layout was investigated by means of two different bio-electrochemical systems serving as post processes for the dark fermentation effluent, with the overall aim of achieving a fully energy recovery from the starting substrate through bio-methane and electric current generation as well as providing an adequate level of stabilization of the residual organic matter.