Analysis of yellow mealworm (Tenebrio molitor) frass as a resource for a sustainable agriculture in the current context of insect farming industry growth

With the ongoing rapid growth of the human population, the industrial development of mass insect rearing for feed and food is gaining momentum. This approach has proved to be a more efficient and effective alternative to traditional livestock to produce animal protein. In this context, the Tenebrio molitor production sector emerges as highly promising in the edible insect market, being among the most commonly bred species in the large-scale insect rearing industry. A recent modification of the European regulatory framework in this matter has authorized insect-produced feed for pigs and poultry, which will boost the creation of new insect industries, resulting in huge quantities of frass, the insect excrement, that could be valorized. This by-product holds substantial amounts of nutrients and advantageous microorganisms that have enormous potential for organic farming. It typically exhibits high organic content and an abundance of essential nutrients like nitrogen (N), phosphorus (P), and potassium (K), alongside a narrow carbon (C) to nitrogen (N) ratio. In addition to providing plants with essential macronutrients, frass has been discovered to boost soil microbial biomass and introduce biomolecules and microbes that foster plant growth. The study of utilizing frass in sustainable agriculture is a relatively new and actively researched field in recent years. By conducting a comprehensive review of peer reviewed works, this article highlights the advantages associated with the effects of its use as organic fertilizer. Among these, the effect of frass as (1) a plant growth promoter and productivity enhancer and as (2) phytofortifyer against biotic and abiotic stresses, has been underlined in recent studies. With regard to its promoting effect, it has been observed that the effects of frass depend very much on its dose and the type of crop, with remarkably favorable results in many of the tests carried out. Hence, frass derived from the mass rearing of yellow mealworm for feed and food, could serve as an important and potent source of organic fertilizer in intensive horticultural crops or in high-value woody crops, contributing to a more sustainable agriculture, which can decrease the use of conventional synthetic agrochemicals.