Tunable Pd-Based Multilayer Membranes for Hydrogen Production from Biomass and Organic Waste: Materials, Reactors and Real-Environment Challenges

Hydrogen production from biomass and organic waste offers a route to combine renewable energy generation, residue valorization, and circular carbon management. However, the resulting H2-containing streams are chemically complex and may contain CO, CO2, CH4, steam, light hydrocarbons, tars, sulfur species, and particulates, making hydrogen recovery and purification major process bottlenecks. This review critically assesses the role of H2-selective membranes in biomass- and waste-derived hydrogen production, with particular emphasis on supported Pd-based multilayer architectures and their integration into separation units and membrane reactors. The conversion routes examined include gasification, pyrolysis-derived reforming, reforming of glycerol, bioethanol and biogas, aqueous-phase reforming, and water–gas shift conditioning of the resulting product streams. A route-specific comparison based on hydrogen partial pressure and permeation driving force indicates that direct Pd-membrane integration is most technically credible for conditioned reformate and water–gas shift streams. By contrast, gasification- and pyrolysis-derived streams generally require more extensive upstream cleaning and conditioning, whereas aqueous-phase reforming is better suited to downstream purification or hybrid separation schemes because of its comparatively low operating temperature and pressure. Across the reviewed studies, membrane performance is governed by the complete support/interlayer/selective-layer/seal/reactor assembly rather than solely by the intrinsic permeance of the Pd-based film. Architecture–process co-design, validation under realistic multicomponent mixtures, contaminant-tolerance assessment, reproducible and scalable fabrication, and integrated techno-economic and life-cycle evaluation are identified as the principal priorities for industrial deployment.