**1. Introduction**

The first alternative to the traditional aerobic composting of organic waste was vermicomposting; however, according to Čičková *et al*. [1], Lindner already in the second decade of the last century (1919) had proposed the use of insects (in accordance to his experiments with the house fly (*Musca domestica* L), to recover nutrients (especially fat) from organic waste; this could have been the threshold for entomocomposting research, nevertheless, it is only a few decades later that some experimental work appears in the context of the disposal of potentially polluting organic waste.

Nowadays, suitable technologies have already been developed for a diverse range of target functionalities of entomocomposting, namely:


Whatever the main objective is, the entomocompost will always provide invaluable added value (as produced or, possibly, after suitable treatment) for safeguarding food security and the environment, due to its potential in the immediate and deferred fertilization of agricultural soils, so as in the recovery of exhausted soils and even in the inclusion of new unproductive land, as, for example, in the case of abandoned mining sites.

#### *The Insects as a Workforce for Organic Fertilizers Production – Insect Frass DOI: http://dx.doi.org/10.5772/intechopen.100144*

But when we talk about entomocompost we are referring to a product with a very diversified physical, chemical and microbiological composition, depending on the nature of the substrate to be digested and the species used to produce it; thus, the option to obtain an organic fertilizer by entomocomposting for pre-defined main purposes, requires taking the following into consideration, as regards the elements of the above mentioned "substrate-insect" interaction: On the one hand, knowledge of the nature of the substrates to be biodigested and the more adequate species to do the job; on the other hand, the eventual treatment of the substrate that may enhance more efficient bio-digestion and/or specific qualities of the frass, and the choice of the best insect species (or genotype within the elected species) in order to obtain most efficiently the entomocompost that is more suitable for fertilizing the soil and the crop for which it is intended.

This would be ideal, and to some extent feasible, at rural level, however, the production of entomocompost for crop fertilization is still in short supply, even counting on the compost obtained in a different context.

Organic bio-digestion by insects for the production of entomocompost also requires the choice of technology to be adopted, both for industrial production and for medium-scale production in rural areas (either at cooperative scale or at farm level), and in the case of agricultural and livestock holdings, it evokes the choice of a circular economy system.

This chapter deals with the knowledge that informs the decision to be taken for all the aforementioned options, by the some other, concluding with a compilation of the experimental results that we consider most relevant with regard to the relative fertilizing potential (immediate and deferred) for specific situations of the "soil–plant-fertilizer" triad interaction. Some notes on insects regarding food and feed are anticipated, as they are inextricably linked to the production of the entomocompost.
