Biohydrogen for a Circular Economy: Progress, Challenges, and Net-Zero Pathways

Hydrogen will play a key role in decarbonising hard-to-abate sectors, yet the current supply is mostly fossil-based and carbon-intensive. Biohydrogen, produced from biomass and organic residues, offers a low-carbon alternative and can achieve negative emissions when integrated with carbon capture. However, its deployment is constrained by both feedstock availability and technology maturity. This review examines the global availability of different types of bio-feedstocks and their compatibility with biohydrogen production routes such as thermochemical and biological methods. Following PRISMA guidelines, it assesses the development status of the main thermochemical and biological routes, maps sustainable feedstocks to compatible technologies, and evaluates regional deployment potential. Thermochemical routes are at higher technology readiness levels (TRLs) and are better suited for large-scale centralised facilities, being compatible with dry lignocellulosic feedstocks. Conversely, biological methods are at lower maturity but are uniquely positioned for small-scale deployment and integration with wastewater and agro-industrial systems. Feedstock type critically influences performance, suggesting region-specific strategies. Future research should focus on technology demonstration in operational environments, regenerable catalysts, oxygen-tolerant enzymes, improved purification, and regional life-cycle assessments. Policy support on carbon pricing, hydrogen mandates, and streamlined permitting is vital to positioning biohydrogen as a cost-competitive complement to electrolysis-based hydrogen powered by renewable energy.