Biomass Enrichment and Scale-up Implications for Dark Fermentation Hydrogen Production with Mixed Cultures

Biohydrogen (H2) production via dark fermentation (DF) is a promising renewable energy technology. In the process, the enrichment of microbial communities producing hydrogen is very important as their activities considerably affect the overall performance. To this aim, spore-forming microorganisms as e.g. Clostridium species, which are commonly present in anaerobic digestate and wastewater sludge are suitable for enrichment, although pre-treatments of these biomass sources are needed. This work evaluates the following pre-treatment methods: acid treatment, heat shock (at 95 °C and 105 °C) and load shock pre-treatment, keeping into account the scale-up of DF systems. The effectiveness of pretreatment methods was assessed by conducting bio-hydrogen potential (BHP) tests fed with glucose and comparing the following H2 production performance parameters: (i) cumulative H2 production; (ii) H2 production rate; (iii) length of the lag phase; (iv) process intermediates production. The analysis of results showed that the load shock pre-treatment is the most efficient. Hence, further insights are also given on the safety aspects concerning the production and storage of H2, and on the importance of operational costs and feasibility of the pre-treatment methods.