Unveiling the potential of pyrolysis-gasification for hydrogen-rich syngas production from biomass and plastic waste

•Biomass has emerged as a renewable energy to replace fossil fuels.•H2 is regarded as a possibly zero-emission, efficient, economical, andclean fuel.•The water–gas shift reaction and Boudouard reactions promote the H2 yield.•H2 can be increased in pyrolysis-gasification using different catalysts.•Biomass and plastics co-processing is a sustainable way to improve the H2 yield. The paper highlights the emerging importance of hydrogen as a clean and sustainable energy with a focus on biomass and plastic waste feedstocks. The effectiveness of different gasification operations, including co-gasification, pyrolysis-gasification, and co-pyrolysis-gasification in producing hydrogen-rich syngas from biomass and plastic wastes, has been explored. The paper also probes the catalytic characteristics of the process, examining the functions of various metal catalysts, including alkaline earth metallic catalysts, and natural mineral catalysts for enhancing the hydrogen-rich syngas generation. Further, the effect of key operating factors including the synergy in co-gasification reactors, the influence of gasifying agents, temperatures, pretreatment effects, and types of gasification reactors on hydrogen yield and quality were extensively examined. The pyrolysis-gasification of biomass and plastic waste not only solves waste management issues but also creates new opportunities to produce clean energy, which is a major step towards a circular economy. Biomass and plastic waste feedstocks, various types of gasification techniques and their reactions and mechanisms, the effects of catalysts, as well as the effects of other parameters influence the overall hydrogen production during pyrolysis-gasification. The review offered a novel approach to improving the sustainability and efficiency of hydrogen production from waste by incorporating recent advances in reactor design and process optimization. It also identifies future research directions and practical applications.