Comprehensive assessment of two Diptera species in the resource utilization process of swine manure

To advance sustainable swine manure management through insect-mediated bioconversion, this study implemented a comparative evaluation of the flesh fly Boettcherisca peregrina (Robineau-Desvoidy) (Diptera: Sarcophagidae) and the blow fly Aldrichina grahami (Aldrich) (Diptera: Calliphoridae). We quantified: (i) larval viability and bioconversion efficiency under manure-fed conditions, (ii) nutritional profiles and heavy metal accumulation in larval biomass, and (iii) agronomic value and residual heavy metal speciation of processed residues. B. peregrina exhibited higher adaptability, achieving a 95% survival rate and maximum biomass within 72 h, achieving a 35.6% swine manure mass reduction, slightly outperforming A. grahami (34.3% over 84 h). Both species produced nutrient-dense larvae (56.2% to 56.4% crude protein, 24.5% to 25.2% lipid) and pupae (61.3% to 63.8% protein, 18.4% to 19.1% lipid), with balanced essential amino acid profiles suitable for animal feed. However, arsenic accumulation in larvae approached EU feed safety limits, highlighting the need for substrate optimization. Processed residues showed enhanced agronomic value, with available phosphorus increasing by 24% to 29%, while most heavy metals remained below phytotoxic thresholds; however, chromium approximately doubled after bioconversion. From an application perspective, the short development time (3 to 5 d) and relatively high conversion efficiency of both species suggest economic advantages over longer-cycle insects such as black soldier fly, although successful scale-up will require careful management of substrate variability, biosecurity, and trace-metal risks. Overall, these findings identify B. peregrina and A. grahami as promising candidates for circular agriculture systems.