Green Hydrogen Production Technologies and Feedstock Limitations: A Concise Review

Abstract Nowadays, intensive research is directed to green hydrogen production as an alternative to the depleting fossil fuel resources. Shifting from conventional hydrogen production routes, which rely on hydrocarbon reforming, toward cleaner and more sustainable pathways is a pivotal strategy to support decarbonization and minimize harmful emissions. Water and biomass are two abundant and sustainable resources that can serve as a promising green hydrogen feedstock. Water splitting into its constituents can be achieved by electrolysis, photocatalysis, and thermochemical techniques, while biomass can be converted into syngas through thermochemical processes, such as pyrolysis and gasification. Additionally, biomass has the potential to produce hydrogen through biological routes, like fermentation and microbial electrolysis processes. Electrolytic splitting of freshwater achieves a mass fraction of approximately 11.19% hydrogen (8.94 liters of water produces 1 kg of hydrogen). The highest energy efficiency of hydrogen (ηelectrolyzer) from the electrolyzer system has been reported in the literature to be 60–80% under a higher heating value with 3.35–5.6 kWh/Nm3 energy consumption. However, the utilization of desalinated water as an alternative feedstock is emerging as a strategic focus among global green hydrogen market participants. Integrating renewable energy resources, like solar and wind energy, into hydrogen production technologies is a critical approach that demands intensified research and development. This review discusses the major green hydrogen production technologies along with their fundamental characteristics, operating conditions, and the associated advantages and drawbacks. Furthermore, it provides an overview of recent concerns surrounding hydrogen production technologies and feedstock availability, while emphasizing the technical challenges that constrain the large-scale deployment of green hydrogen.