Use of organic materials to obtain valuable products through bioconversion

Bioconversion is a biological process by which organic materials are converted in products with higher biological and commercial value. During its larval stage, the Black Soldier Fly (BSF), Hermetia illucens (L.) (Diptera: Stratiomyidae), is extremely voracious and able to feed on a wide range of organic materials, ranging from fruits and vegetables to animal manure. This ethological characteristic is particularly interesting for an innovative waste management treatment. The bioconversion process is highly efficient, as the organic substance the larva feeds on is reduced up to 65%-70% and converted into larval biomass. At the end of bioconversion of the waste, the larvae are suitable for pet food as they are rich in proteins and lipids. High energy content meal, deriving from appropriately dried and ground larvae can also be used as feed for select species by the aquaculture industry, according to recent European regulation. Resulting larval frass can be used as soil conditioner for crop fertilization. Furthermore, chitin and its derivative, chitosan, are relevant for medical, pharmaceutical, agricultural fields. In order to study the effect of different substrates from the agri-food chain on several parameters such as insect growth, final larval yield, protein and lipid content, substrate reduction and bioconversion values by the BSF, 10000 larvae were reared on 7,0 kg of six substrates (watermelon, kiwi, a mix of cabbage/savoy cabbage, strawberry, tangerine, orange) and on a standard diet, used as control. The results highlight that BSF is able to successfully feed on all the tested diets, although development time, growth rate, final larval biomass and larval components (ashes, proteins and lipids) impacted by different substrates. Although the standard diet is considered balanced in all nutrients and the best diet for BSF development, strawberries turned out to be more suitable substrate, among the analysed substrates, that are by-products from the agri-food chain. Although larvae fed on a mix of cabbage/savoy cabbage achieve the worst growth and bioconversion performances, BSF consumed this substrate, still accumulating high protein content, and confirming the BSF extraordinary ability to feed and reduce different kinds of substrates. Preliminary research was carried out also on zootechnical wastes (dairy mature and fresh manure). BSF is able to correctly feed also on manure, favouring their disposal and total recovery. This research project shows that waste management through the BSF bioconversion processes can represent a new economically important resource for companies belonging to agri-food and zootechnical fields and opens new perspectives for a sustainable and environmentally friendly industrial development in which by-products and wastes from these industries could be disposed and enhanced in this unconventional way.