Food loss, food waste and agricultural by-products have become key targets in the circular bioeconomy objectives in the EU. The exploratory project FLY4WASTE aims at assessing the benefits and risks of the insect-based bioconversion of these biowaste by the black soldier fly larvae (BSFL), Hermetia illucens. Indeed, it can convert a wide variety of biowaste and be used as a new feed source. In this experiment, BSFL were reared on EU-authorized agricultural by-products; wheat bran, carrot, apricot, salad and a wheat bran-apple mix used in the industry (standard) and unauthorized biowaste such as school canteen and supermarket waste. BSFL weights, total protein and lipid contents were measured. A total of 16 fat-soluble vitamins and dietary carotenoids were also screened: retinol, retinyl palmitate, cholecalciferol, ergocalciferol, ergosterol, α and γ-tocopherol, α and β-carotene, lutein, lycopene, zeaxanthin, β-cryptoxanthin, astaxanthin, phytoene and phytofluene. They were extracted using a double extraction with hexane and quantified by HPLC-UV. Fresh weights of BSFL significantly differed: BSFL reared on apricot and supermarket waste had lower weights (85 ± 4 and 90 ± 4 mg, respectively) than their counterparts (120 ± 7 mg for standard). However, the dry weight, protein and lipid contents of the larvae were similar in the different BSFL groups. Nine bioactive molecules were detected in the substrates and BSFL. For some molecules, bioaccumulation in BSFL was observed; up to 55 times the concentration in the substrate (β-cryptoxanthin in school canteen waste). Conversely, vitamin A, D and astaxanthin were neither detected in the substrates nor in the BSFL. Their absence could be explained by their too low levels in biowaste or their destruction during biowaste treatment. Thus, it is possible to enrich BSFL in fat soluble micronutrients by rearing them on EU-authorized and unauthorized biowaste containing these compounds without compromising on their macronutrient qualities. It is also a promising work on the use on yet unauthorized biowaste in the EU for the insect industry.