Use of black soldier fly (Hermetia illucens) larvae in orange peel waste treatment

• OPW provides high vitamins and sugar for the growth and a longer lifetime of BSFL • The volatile compounds, such as limonene, in OPW do not restrain the growth of BSFL • Shredding and dewatering of OPW helps to speed up the decomposition process In 2024, Vietnam was ranked 9th in global orange production, especially for the orange juice and essential oils industries, generating a huge amount of orange peel waste (OPW) annually. Numerous biological methods have been applied to treat the peel waste and gain by-products, yet the costs are still high, and there are leftovers to be treated. There is still a lack of studies on the application of black soldier fly larvae (BSFL) in treating OPW as a single-stream substrate under different preprocessing conditions. Thus, this study aims to bridge the gap between OPW treatment and the application of BSFL as a new waste treatment method and contribute to sustainable agriculture. Results from this study showed that OPW provides nutrients, vitamins and high sugar proportion that might help to increase the BSFL length (20.72 ± 1.13 mm) and weight (154.61 ± 4.78 mg), extend their lifetime in the larval stage (60 ± 2 days), with the waste treatment effectiveness was 82.1% (± 1.5 %). The highest growth was noticed in the OPW-NS-ND control (Tray 2). The volatile compounds, such as limonene in OPW, might not restrain the survival and growth of BSFL if a suitable feeding strategy is applied. Moreover, preprocessing of OPW (shredding and dewatering) helps to accelerate the decomposition process and maintain comfortable moisture content (79.23 ± 1.07 %), temperature (27.89 ± 1.20 °C), and pH (6.99 ± 1.73) conditions for the growth of BSFL rather than the unprocessed substrate. Besides, in treatment trays, the percentage of BSFL reaching pupae stage was 58.7% (± 2.8%) while this figure in the control tray was 85.4% (± 1.5%), meaning that the BSFL in treatment trays can continue to decompose the OPW as they are still in the larval stage.