Abstract

Hydrogen, a potential and high-energy green fuel, offers a solution to the environmental concerns arising from the imprudent use of fossil fuels. As an alternative energy carrier, it can be produced using various conventional and advanced technologies, aiming for a decarbonized energy future. Currently, H 2 production heavily depends on fossil fuels, which results in carbon emissions and makes the process energy -intensive, posing a significant risk.This review article discusses the commonly employed hydrogen production approaches, their current opportunities, and their strategic design towards a global hydrogen economy. Various reforming methods are also explored, along with the specific raw ingredients used in the generation process. Additionally, the production of biohydrogen is addressed, with a special focus on fermentation (dark and photo -fermentation), direct bio-photolysis, and indirect bio-photolysis. Bio-hydrogen is gaining popularity due to its environmentally friendly nature and the wide range of feed materials available for its production.The review provides comprehensive information on the biological conversion processes for H 2 production. While numerous researches have been reported, there is still room for improving the efficiency of large-scale H 2 production to meet the growing demand. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.