Sustainable Valorization of Solid Wastes into Functional Technosols: Enhancing Aggregate Stability, Bacterial Networks, and Plant Growth

The escalating challenge of solid waste disposal necessitates innovative recycling strategies. This study aims to constructed technosols from bulk solid wastes (fly ash, straw and sewage sludge) for the dual purpose of sustainable waste management and the rehabilitation of degraded land. Following a 150-day incubation period, six resulting technosols were systematically evaluated for aggregate stability, bacterial community structure, and biological safety to assess their viability as functional soil materials. All constructed technosols had a pH of 7.44–7.71 and were enriched in soil organic matter, nitrogen, and phosphorus. Aggregate stability (R0.25: 46.6–64.0%) surpassed that of typical Chinese soils. Bacterial analysis revealed a stable consortium of 165 core genera, accounting for 92.93–98.11% of the total relative abundance, and were dominated by six phyla (Proteobacteria, Bacteroidota, Planctomycetota, Gemmatimonadota, Firmicutes, Actinobacteriota). The addition of straw modulated phylum structure, elevating Bacteroidota and reducing Proteobacteria. The bacterial communities exhibited clear functional hierarchy at class and order levels, with dominant groups forming a complementary carbon–nitrogen–phosphorus cycling network. Functional prediction further indicated distinct differentiation in carbon and nitrogen metabolic pathways. The technosols were non-phytotoxic and significantly enhanced the growth of Portulaca oleracea, increasing plant height (4.9–86.7%), dry weight per plant (67.3–605.4%), and SPAD values (8.1–15.9%), respectively. This study provides a sustainable strategy for repurposing solid wastes into functional technosols, aligning with circular economy principles and offering a viable solution for the ecological restoration of degraded lands such as mining areas.