Concept of electrochemical conditioning of biohydrogen produced during dark fermentation process

The production and accumulation of food waste is growing annually, posing a threat to humanity and the environment. Food waste is also a potential renewable source for producing green hydrogen through dark fermentation (DF). Recent studies on DF intensification have demonstrated the high potential of the process, comparable in efficiency to electrolysis. However, despite the efficiency of the DF process, one of the obstacles to its implementation is the significant (up to 94%) carbon dioxide (CO₂) content in hydrogen-containing biogas. Therefore, for further use of biohydrogen, it must be purified from CO₂. This article demonstrates that the use of a chemical adsorbent is most suitable for purifying hydrogen-containing biogas. However, this method needs to be improved through the application of green chemistry principles, with the possibility of further use of the improved purification method within the framework of a circular economy. The objective of this study was to develop a concept for the electrochemical conditioning of biohydrogen obtained through DF using the principles of a circular economy and green chemistry. The concept involves purifying biohydrogen while reducing CO₂ emissions into the atmosphere using an intermediate carrier of carbon dioxide for subsequent utilization in a photobioreactor. A material balance was developed based on the process chemistry. A pilot plant was designed to experimentally validate the feasibility of biogas conditioning according to the presented concept. The average CO₂ removal rate was 68%, with a biohydrogen content of 84.9% after electrochemical conditioning. The obtained data indicate the feasibility of using the developed system for purifying biohydrogen obtained during dark fermentation. However, modernization and optimization of individual system components is required, which is planned for future research.

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