Mechanism of clay minerals in promoting organic matter sequestration and humification during chicken manure composting.

To accelerate the humification process and promote organic matter sequestration during aerobic composting, this work assessed how various clay minerals facilitate organic matter sequestration and humic acid synthesis in chicken manure composting. A composting trial was set up, including a control and three treatments incorporating montmorillonite , halloysite , and sepiolite , respectively. A water-permeable membrane encapsulation technique was employed to isolate the clay minerals from the composting feedstock in order to monitor their adsorption behavior towards organic matter. Montmorillonite treatment group demonstrated the most significant effect on organic matter sequestration. It achieved the lowest organic matter loss rate (22.14%), the highest HA content (68.81 mg/g), and the lowest fulvic acid (FA) content (8.28 mg/g), indicating effective FA-to-HA conversion. Montmorillonite enriched humification-related taxa (Actinobacteria, Firmicutes) and formed clay-organic complexes via hydrogen bonding. Structural equation modeling revealed that clay minerals promoted the synthesis and accumulation of humic acid by regulating the synergistic interactions among microbial community structure, organic matter components, and microenvironmental factors. In summary, montmorillonite exhibits excellent performance in enhancing organic matter retention, stabilizing the microbial community, and promoting humic acid formation. This provides a theoretical basis for improving compost quality and achieving efficient resource utilization of organic solid waste.