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

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.