Enhancing hydrogen yield from biomass and plastic co-pyrolysis through mechanistic understanding and catalytic design

The co-pyrolysis of biomass and plastic waste has emerged as a promising approach for sustainable hydrogen production, offering simultaneous waste valorization and renewable energy generation. The synergistic interactions between oxygen-rich biomass and hydrogen-rich plastics can significantly enhance hydrogen production compared with individual feedstocks, with several studies reporting substantial improvements in hydrogen yield and syngas quality. This review provides a comprehensive assessment of the fundamental mechanisms governing hydrogen production during biomass–plastic co-pyrolysis, with particular emphasis on reaction pathways, synergistic interactions, catalyst performance, process optimization, and reactor technologies. Literature reports indicate that optimized operating conditions and catalytic systems can produce hydrogen-rich syngas containing more than 50 vol% H₂, while catalyst-assisted reforming and water–gas shift reactions further improve hydrogen selectivity and reduce tar formation. The roles of operating conditions, feedstock composition, and catalyst design in influencing hydrogen yield and syngas quality are critically evaluated. In addition, recent advances in catalyst development, catalyst deactivation mitigation, reactor configurations, and integrated process strategies are discussed. Particular attention is given to challenges associated with feedstock variability, catalyst stability, hydrogen purification, process economics, and large-scale implementation. By integrating mechanistic understanding with practical considerations, this review identifies key research gaps and highlights future opportunities for process intensification, catalyst innovation, carbon management, and industrial deployment. The insights presented provide a comprehensive framework for advancing biomass–plastic co-pyrolysis as a viable pathway for sustainable hydrogen production within a circular and low-carbon economy.