Mechanism of synergistic hydrogen production from agricultural and plastics waste co-gasification: A ReaxFF molecular...

Steam co-gasification of mixed agricultural and plastic wastes in a single reactor for hydrogen production represents an effective pathway for waste valorization and clean energy generation. Yet the underlying synergistic mechanism remains unclear, which limits process optimization and large-scale application. In this study, the ReaxFF molecular dynamics method was employed to systematically investigate the interaction mechanism during co-gasification by constructing a co-gasification reaction system comprising hardwood lignin and polyethylene molecules. The results show that co-gasification promoted H₂ production, with the most significant synergistic effect observed at a feedstock mass ratio of 1:1, where the actual H₂ yield was 29.3 % higher than the theoretical value. High-temperature conditions enhanced the hydrogen production pathway, whereas excess steam inhibited tar dehydrogenation reactions. In the reaction pathway, active hydrogen radicals generated from polyethylene cracking promote H₂ production by inducing deep dehydrogenation of tar; in contrast, hydrogen atom recombination and hydrogen transfer reactions involving H₂O and CH₄ make a relatively minor contribution. This study elucidates that the synergistic mechanism underlying hydrogen production via co-gasification stems from the enhancing effect of active ∙H radicals on the dehydrogenation pathway of tar, thereby providing a theoretical basis for optimizing the hydrogen production process by co-gasification of waste biomass and plastics.