Towards a hydrogen economy: A comprehensive review of the full hydrogen value chain

As countries pursue deep decarbonization and energy system transformation, hydrogen (H 2 ) is emerging as a critical enabler for hard-to-abate sectors and large-scale energy storage. However, realizing a sustainable and scalable H 2 economy requires a holistic understanding of the entire H 2 value chain, encompassing production, storage, transportation, and end-use. This review paper provides a comprehensive assessment of the key technologies, infrastructure challenges, and policy frameworks that influence the development of a low-carbon H 2 ecosystem. The paper examines two primary production pathways: green H 2 , which is produced through water electrolysis powered by renewable electricity, and blue H 2 , which is derived from fossil fuels with carbon capture and storage. Their techno-economic characteristics, scalability, and regional applicability are compared based on recent literature and policy developments. In terms of storage and transportation, various options such as compressed H 2 , cryogenic liquid H 2 , ammonia, and liquid organic hydrogen carriers are analyzed for their efficiency and economic feasibility. On the utilization side, the paper explores both the direct use of H 2 in fuel cells and industrial processes, and its indirect use in the synthesis of e-fuels such as methanol and ammonia. The review emphasizes the importance of integrated system-level approaches that connect all stages of the value chain, supported by modeling of supply-demand dynamics, infrastructure optimization, innovation in H 2 carriers, and industrial deployment. Ultimately, this paper suggests that approaching H 2 technologies as part of an integrated system, rather than as isolated components, is the key to ensuring the sustainability and viability of the H 2 economy.