Life-history traits of black soldier fly reared on agro-industrial by-products subjected to three pre-treatments: a pilot-scale study

Agrarian production generates approximately 190 million tons of agro-industrial by-products (AIBP) per year that are often disposed of without proper treatment, causing health hazards and environmental pollution. The black soldier fly (BSF; Hermetia illucens) has gained popularity as an organic waste recycler owing to its suitability for large-scale insect farming. Despite their valuable components, AIBPs are rich in fibres with low digestibility and provide a breeding ground for potentially pathogenic microbes, which necessitates proper caretaking. This study focuses on a pilot-scale life-cycle analysis of BSF, comparing three different pre-treatments for agro-industrial wastes. We assessed the effect of the pre-treatments on larval and pupal biomass yield and development time of life stages, pupal and adult body properties, adult emergence and sex ratio, and oviposition and fertilization rates. A mix of residues from pasta production and wheat bran (basis substrate, BS; control treatment) was pre-treated using a chemical (with 0.15% potassium sorbate, BSSORB), an organic (with 10% biochar, BSCHAR), and a microbiological (with a 10-day lactic acid fermentation, BSFERM) approach. We report that the BSSORB treatment had the significantly highest larval and pupal biomass yield as well the significantly largest pupae and adults, and the most successful adult emergence but had low oviposition success. BS and BSFERM were similar in terms of larval and pupal biomass yield, BSF development time, pupal and adult body properties, adult emergence, and oviposition. Nonetheless, BSFERM had the highest share of unfertilized eggs. With BSCHAR, BSF developed faster. This study indicates that all treatments have advantages and disadvantages and that thus their application should be selected based on breeding strategy. By analysing and adapting methods that facilitate the conversion of AIBPs to BSF biomass, the treatment of agricultural wastes and by-products can be made more efficient and sustainable.