Converging pathways in biomass‐to‐biohydrogen conversion: A review on hybrid systems, nanotechnological interventions, and sustainable integration frameworks

The worldwide shift toward low‐carbon energy systems has heightened the academic interest in biohydrogen generated from renewable biomass, positioning it as a viable and sustainable fuel alternative. This review provides a critical analysis of biological pathways, namely dark fermentation (DF), photofermentation (PF), and microbial electrolysis (MEC), in conjunction with thermochemical methodologies, including pyrolysis, gasification, and supercritical water gasification (SCWG). Biological routes generally produce 1.8–2.5 mol of H 2 per mol of hexose‐equivalent substrate, which necessitates reduced energy input and results in minimal carbon emissions. Conversely, thermochemical conversion can yield over 10 mol H 2 kg −1 of dry biomass at elevated temperatures (>600°C), albeit with issues surrounding catalyst degradation. Hybrid systems, particularly DF‐PF and DF‐MEC configurations, exhibit enhanced carbon conversion efficiencies, achieving up to 5.2 mol H 2 mol −1 of substrate under optimized laboratory‐scale conditions that align with Technology Readiness Levels (TRL 3–4). Novel advancements, including microwave‐assisted pyrolysis (MAP), magnetic nanoparticles (MNPs) catalysis, and artificial intelligence (AI)‐driven optimization frameworks, indicate significant potential for improving yield, flexibility, and real‐time process regulation. Comprehensive techno‐economic analyses (TEA) and life cycle assessment (LCA) evaluations reveal pathway‐specific compromises, emphasizing the necessity for standardized sustainability metrics, adherence to environmental health and safety (EHS) regulations for nanomaterials, and supportive policy frameworks to promote the advancement of biohydrogen toward commercial feasibility and climate‐resilient implementation.