Black soldier fly larvae (Hermetia illucens) reared on conventional and emerging agri-food by-products: the case of olive leaves, olive pomace, and quinoa husk

• Black soldier fly larvae can feed on olive oil and quinoa by-products effectively. • Performance is adequate with 15% olive leaves and 50% olive pomace or quinoa husk. • Larvae conserve nutritive levels of proteins and lipids but increase chitin. • Olive pomace remarkably reduces lauric acid while increasing oleic acid content. • Circular economy, converting by-products into sustainable livestock feed is shown. Black soldier fly larvae (BSFL) is one of the most popular edible insects authorized for feed and an excellent bioconversor of agri-food by-products. Thus, the ability of BSFL to valorize by-products from olive oil production (olive leaves, OL, or full-fat dry olive pomace, OP) and quinoa husk (QH) is explored. OL up to 15%, and OP or QH up to 50%, allowed successful bioconversion of by-products, with larvae performance comparable to control. These levels did not affect protein, lipid or ash content, though chitin increased. Mainly OP feeding resulted in more unsaturated lipids of BSFL, with lauric acid decreasing from 43% in control larvae to 23% in OP50 and 2.5% in OP90, while oleic acid rose as the major one to 32% and 55%, respectively. However, higher inclusion of OL (>15%) and OP (>50%) reduced protein and ash contents, increasing lipids and chitin. QH-fed larvae showed similar composition to control. Correlation analysis suggested that unbalanced diets at high levels of OL and OP influenced the results. Diets rich in carbohydrates and proteins also correlated with the saturated profile of BSFL, while high lipids and fiber led to more unsaturated ones, particularly with OP. Therefore, BSFL can successfully valorise olive-oil and quinoa by-products when used at limited levels, maintaining similar nutritive composition of the larvae but improving their fatty acid profile.