Dark fermentation is a biological process that involves the breakdown of organic matter in the absence of light to produce hydrogen gas, carbon dioxide, and organic acids. This process is typically carried out by certain anaerobic bacteria and archaea, and is seen as a potential sustainable method for producing biofuels and other valuable products. Dark fermentation is considered a promising alternative to traditional methods of hydrogen production, as it is less dependent on expensive inputs and can utilize a wide range of organic substrates, such as agricultural residues, organic waste, and wastewater. Additionally, dark fermentation can be integrated with other bioenergy processes, such as anaerobic digestion and microbial electrolysis, to increase overall efficiency and productivity. Research in the field of dark fermentation focuses on optimizing process conditions, such as temperature, pH, substrate composition, and microbial consortia, to enhance hydrogen production rates and yields. Additionally, efforts are being made to develop new strains of bacteria and archaea with improved hydrogen production capabilities, and to explore novel reactor designs and operating strategies to scale up dark fermentation for industrial applications.