Hemp Waste as a Substrate for Hermetia illucens (L.) (Diptera: Stratiomyidae) and Tenebrio molitor L. (Coleoptera: Tenebrionidae) Rearing

SIMPLE SUMMARY: Growing insects on agricultural wastes is an approach to reduce the amount of waste produced by farming operations and convert it into valuable products such as protein (for food and feed) and fertilisers. The larvae of two insects were fed with substrates that contain hemp residues (welted flowers, old leaves, and stalks) and were able to grow. The produced black soldier fly larvae did not contain the psychoactive ∆-9-tetrahydrocannabidiol (∆(9)-THC) and contained beneficial cannabinoids such as cannabidiol (CBD), and the amounts were minimal in comparison to the amount found in the initial substrate before given to the larvae. Mealworms were grown on hemp material that is rich in bioactive compounds, none of which was detected in the produced larvae. This study demonstrates that hemp agricultural wastes can be used as feed for these two insects, and the produced larvae do not contain the psychoactive compounds of hemp. ABSTRACT: The proper treatment of cannabis agricultural wastes can reduce the environmental impact of its cultivation and generate valuable products. This study aimed to test the potential of cannabis agricultural wastes as a substrate for the rearing of black soldier fly larvae (BSFL) and yellow mealworms (MW). In the case of BSFL, replacing the fibre component (straw) in the substrate with the hemp waste can increase the nutritional value of the substrate and led to bigger larvae. The bigger larvae had lower P and Mg, and higher Fe and Ca. Crude protein also varied based on the size of larvae and/or the content of protein in the initial substrate, which was boosted by replacing straw with hemp material. No other cannabinoids than cannabidiolic acid (CBDA), cannabigerolic acid (CBGA), and cannabidiol (CBD) were found in significant amounts in the larvae. In the case of MW, the larvae grew less on the hemp material in comparison to wheat bran. Replacing wheat bran with the hemp material led to smaller larvae with higher Ca, Fe, K, and crude protein content, but lower Mg and P values. No cannabinoids were detected in the MW fed with the hemp material.