Bio-hydrogen production through dark fermentation: an overview

Recently, hydrogen gas is becoming the most prominent alternative fuel due to its clean and environment-friendly nature. It only delivers water as a waste product during the operation instead of emitting harmful greenhouse gases. It has a high heating value (142 MJ/kg), over 2.75 times that of other hydrocarbon-based petroleum fuels. Presently, the primary method of producing hydrogen is the steam reforming of fossil fuels, which is not economical and environmentally harmful, and fossil fuels are on the deadline to finish. Hence, alternative methods of hydrogen production are the topic of current research. Biological methods of hydrogen production were found the best for producing green hydrogen because they utilize plentiful available renewable sources as feedstock. The dark fermentation technique is becoming more famous among all biological hydrogen generation methods because of its light autonomous nature and functional ability. It has the facility to convert any type of carbohydrate-rich organic substrates into bio-hydrogen, but pure carbohydrate substances are not economical on a commercial scale. Hence, carbohydrate-rich organic waste can be easily harnessed for bio-hydrogen generation. This method yields hydrogen gas and different high-volatility fatty acids, which could be used for industrial purposes after separation or as a precursor for the bio-methanation process for biogas production. This paper defines mechanism, microbiology, affecting factors, various integration methodologies, and potential and limitations related to the dark fermentation method.