A review of sustainable hydrogen production using seed sludge via dark fermentation

In recent years, the production of hydrogen (H2) via dark fermentation has become increasingly popular because it is a sustainable approach to produce clean energy. This review presents an overview with a critical analysis of the technical challenges in obtaining high H2 yield through dark fermentation. Particular focus is given to the pretreatment methods that affect H2 production. We observed that heat pretreatment is the most frequently applied and the most effective method of eliminating H2-consuming bacteria (HCB) while preserving H2-producing bacteria (HPB). The pre-dominant HPB species after pretreatment belongs to the genus Clostridium and hence the fermentation conditions are optimized according to their preference for H2 production. Besides, we also reviewed fermentation conditions such as substrate, pH, temperature, oxidation-reduction potential (ORP), types of nutrient and inhibitor substrate, to obtain clearer insight on the influences of critical parameters in H2 production.