The conventional management of hatchery residues is associated with greenhouse gas and unpleasant odor emissions, the presence of pathogens and high disposal costs for producers. To address these issues, on-farm alternatives like composting, fermentation, and insect valorization are promising approaches. This study aims to characterize hatchery residues and define critical quality thresholds to identify effective processes for their management. Hatchery residue samples were collected bi-monthly over a year (N = 24) and were analyzed for proximate composition (dry matter, ash, energy, crude protein, crude lipid, crude fiber, carbohydrates), pH, color (L*a*b*, Chroma) and microbiological loads (total aerobic mesophilic counts, coliforms, lactic acid bacteria). Volatile fatty acid composition was also measured (N = 8). Significant correlation coefficients were found between TAM and LAB loads and residue characterization (pH, chroma, crude fibers, carbohydrates, and temperature). On a dry matter basis, residues were high in energy (2498 to 5911 cal/g), proteins (21.3 to 49.4 %) and lipids (14.6 to 29.1 %), but low in carbohydrates (0 to 15.3 %) despite temporal fluctuations. Ash content varied widely (8.6 to 49.1 %, dry matter) and is influenced by eggshell content. Microbiological loads were high for total aerobic mesophilic bacteria (6.5 to 9.1 log cfu/g), coliforms (5.4 to 8.5 log cfu/g) and lactic acid bacteria (6.7 to 9.0 log cfu/g). Valorization of hatchery residues on the farm will depends on the optimization of effective upstream stabilization processes. The critical points are discussed according to the valorization potentials that could be implemented on the farm from composting to upcycling by insects.

This study explores the optimisation of rearing substrates for black soldier fly larvae (BSFL). First, the ideal dry matter content of substrates was determined, comparing the standard 30% dry matter (DM) with substrates hydrated to their maximum water holding capacity (WHC). Substrates at maximal WHC yielded significantly higher larval survival rates (p = 0.0006). Consequently, the WHC approach was adopted for further experiments. Using these hydrated artificial substrates, fractional factorial designs based on central composite and Box–Behnken designs were employed to assess the impact of macronutrient composition on bioconversion efficiency. The results demonstrated significant main, interaction, and quadratic effects on bioconversion efficiency. Validation with real-life substrates of varied protein content, including indigestible feather meal, affirmed the predictive model’s accuracy after accounting for protein source digestibility. This research underscores the importance of optimal hydration and macronutrient composition in enhancing BSFL growth and bioconversion efficiency.