Valorization of Sewage Sludge via Co-Composting with Iron Ore Tailing Enhanced Formation of Aggregated Soil-Like Compost

Co-composting sewage sludge with industrial mineral residues
offers
a promising strategy for integrated waste valorization and the development
of functional soil-like materials. In this study, two representative
inorganic wastesiron (Fe) ore tailings and fly ash, were individually
incorporated into a sludge composting system to evaluate their effects
on soilification performance and compost quality. The results showed
that Fe ore tailing addition enhanced compost soilification, increasing
the level of composting-induced aggregation by 8.1%. However, fly
ash initially increased particle size by 10.5% before composting but
ultimately hindered composting-based soilification by suppressing
microbial richness and organic matter (OM) transformation. High-resolution
mass-spectrometry-based molecular analysis revealed that Fe ore tailings
promoted the removal of amino groups through deamination reactions,
accelerating the breakdown of sludge-derived proteins. During the
cooling stage, dealkylation and decarboxylation processes became dominant,
generating lipid- and protein-like small molecules. These compounds
subsequently formed stable mineral-binding organic matter (MOM), facilitating
the formation of aggregated, soil-like structures. Microbe–dissolved
organic matter (DOM) network analysis further confirmed that Fe ore
tailing addition enhanced microbial-mediated conversion of key molecular
components, with Pseudoxanthomonas dominating the
thermophilic phase and Aminobacter enriched during
the cooling stage. Finally, compost quality assessments indicated
that Fe ore tailing addition enhanced the germination index (GI) and
nitrogen retention capability without leading to heavy metal accumulation.
This study demonstrates the feasibility of co-utilizing iron ore tailings
and sewage sludge to produce soil-like bioresources, advancing sustainable
waste co-treatment and land application.