Hydrogen Production from Biomass Through Conversion Pathways and Energy Efficiency Analysis—A Review

Hydrogen is increasingly seen as a viable energy carrier in the transition to low-carbon energy systems, mainly because of its high gravimetric energy density and the absence of carbon emissions at the point of use. In this context, producing hydrogen from biomass represents a practical and sustainable option, as it allows the use of renewable and waste resources while supporting circular economy principles. This work examines the main pathways for hydrogen production from biomass, considering both thermochemical and biochemical routes, with a focus on their energy performance and practical limitations. The analysis shows that thermochemical processes, particularly gasification, remain the most developed and scalable solutions for converting solid biomass into hydrogen-rich gas, although their performance depends strongly on feedstock properties, reactor design, and operating conditions. By comparison, biochemical processes such as dark fermentation and photofermentation are more suitable for wet biomass but are limited by lower hydrogen yields and issues related to process stability. From a thermal engineering standpoint, system performance is influenced by heat transfer constraints, the energy demand of endothermic reactions, and the efficiency of gas cleaning, while parameters such as temperature, steam-to-biomass ratio, and equivalence ratio play a key role in optimization. Advanced approaches, including catalytic and sorption-enhanced gasification, show potential for improving performance. Overall, efficient hydrogen production requires a system-level approach, as no single technology can be considered universally optimal.