Hydrogen (H2) is a highly efficient and clean energy source with the potential for renewable energy. The production of H2 from biological routes such as biophotolysis, photofermentation, dark fermentation, and bioelectrochemical production is characterized as a renewable alternative to current production, which is mainly based on energy-intensive electrochemical and thermochemical processes and responsible for the emission of high amounts of environmentally harmful compounds. Dark fermentation is the most efficient and cost-effective method for producing biohydrogen, making it a key research focus. This article offers a comprehensive overview of the dark fermentation process with the aim of enhancing hydrogen productivity and yields. Aspects related to the main substrates used, the inoculum sources and their pretreatment, and physical-chemical parameters of the process are covered. Furthermore, this manuscript addresses topics such as process integration, genetic and metabolic engineering of fermentative microorganisms, and the main types of bioreactors aimed at greater yields and productivity of biohydrogen to enable its production through dark fermentation on a larger scale.
