Food and feed safety of Tenebrio molitor reared on yet to be legally authorised residual streams in the European Union

Abstract Yellow mealworm ( Tenebrio molitor , YMW) is a potential new source of protein for food and feed. YMW farmers are looking for more sustainable, circular, and economical substrates than those currently allowed for all livestock; but safety concerns are cause for maintaining legal barriers. YMW were reared on broiler manure; category 2 meat-and-bone meal from animal rendering; biodegradable municipal waste; former foodstuffs sourced from supermarkets, of both vegetable and animal origin; and a standard wheat-based chicken diet. Performance in terms of survival and larval biomass yield were determined, and larvae and frass samples were analysed to determine nutrient composition and assess chemical and microbiological safety. Highest mean larval biomass yields were observed for chicken feed and category 2 meat-and-bone meal. Substrate-specific results showed accumulation of Cd, Se, Cu, and Zn; and dioxins; but larval concentrations did not exceed legal maximum levels. The biodegradable municipal waste, supermarket mix, and chicken feed contained residues of pesticides; some were transferred to the larvae. Supermarket mix contained residues of nicotine, assumed to originate from improper handling, suggesting a need for continuous control of the material as being crucial for safety. Since a municipal-waste stream implicitly offers less opportunities for control of the material composition and associated safety, in current collection systems, this limits its suitability for use at this time. Broiler manure was high in several elements and contained residues of coccidiostats; these were carried-over to the larvae and resulted in non-compliance with applicable limits. High microbiological contamination for this stream also raises concerns on its safety although post-harvest processing is anticipated to be capable of reducing contamination to acceptable levels. Larval performance on the category 2 meat-and-bone meal was equivalent to the wheat-based chicken feed and food safety parameters were all acceptable, presumably due to extensive processing. We conclude that when appropriate control measures are applied and substrate materials are mixed for optimized composition and growth; tested residual streams could be a nutritious, safe and sustainable substrate for insect rearing.