Advances in Bio-Hydrogen Production: A Critical Review of Pyrolysis Gas Reforming

Supplying the growing energy demand of emerging economies by utilizing available biogenic streams will be a key challenge in the coming years. Hydrogen is a promising alternative energy carrier to support the transition of the energy sector and other industries. In recent years, the use of biomass as a renewable energy source for bio-based hydrogen production has gained significant attention due to its potential to reduce environmental impact. Among the various thermochemical processes, biomass pyrolysis can be used to produce hydrogen, though the current use of this process is limited. Reforming the volatile fraction of biomass pyrolysis products has been only marginally explored, differently from gasification; the reforming of pyrogasses can then be seen as a viable method to enhance hydrogen yield. This review explores the key factors influencing hydrogen yield, including operating conditions and the role of catalysts. It is noteworthy that most of the studies evaluated in this review are in the laboratory and pilot scales, and the focus of this study is on the slow pyrolysis process in the first stage. Findings indicate that hydrogen production can be significantly improved with the proper choice of catalysts, with metal-based and nonmetal-based catalysts among the most effective. The outcomes of this review highlight the key effect of increasing the reforming temperature and steam-to-biomass ratio to enhance hydrogen production.