Different rearing substrates exhibit direct influence on growth and macronutrient composition of Hermetia illucens (L.) (Diptera: Stratiomyidae) larvae at an industrial scale

Black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), during the larval stage is able to feed on varied organic materials. This feature can be exploited for the application of innovative strategies for waste management at an industrial scale. The ability to accumulate high levels of proteins and lipids, allows the use of resulting larvae as animal feed or in technical applications. Approximately 10,000 larvae were reared on 7.0 kg of six substrates: apple, banana, spent grain from brewery waste, apple/banana, apple/spent grain, banana/spent grain. The effect of the diets on insect growth, larval yield, proteins and lipids content, substrate reduction was evaluated. Substrates’ pH value variations during the experiment were measured. High larval growth was observed in all the selected diets with significant differences among larval yield. The highest growth rate was measured in larvae fed on spent grain and banana/spent grain mix. The highest percentage of crude proteins was measured in larvae fed on apples/spent grain mix, while the highest percentage of lipids was found in larvae fed on apple and on apple/banana mix. The variation of the pH value was dependent from the substrate. This study shows that waste management through H. illucens represents a new economic resource and opens new perspective for a sustainable environmental friendly industrial development. Results indicate that diet influence larval performances, yield and content of macronutrients. Single diets or mix can be selected to produce insects with the desired nutrient profile to satisfy different needs and to address the product to different markets.