Effects of salinity in food waste on the growth of black soldier fly larvae and global warming potential analysis

Cultivating black soldier fly larvae (BSFL) has proved to be a potential technology to realize simultaneous recycling of food waste (FW) and production of biofuels or proteins. Due to different dietary habits, the FW salinity usually varies in regions and, thus, could affect the biotransformation of BSFL. The current study investigated the effects of FWs salinity on the BSFL growth and composition distribution in the salinity range of 0.2–6 %. Results showed the final body length, final body weight, and crude protein content of prepupa reached the maximum with 1 % salinity, which was 22.06 ± 0.18 mm, 198.18 ± 3.23 mg, and 40.93 ± 3.82 %, respectively. FW with 0.5 % salinity was the most favorable for BSFL to accumulate lipids, with crude lipids content of 34.76 ± 1.60 %. Due to the unique salt metabolic mechanism, salt can be effectively excreted by BSFL, which enabled it to grow normally in a 2 % salinity culture substrate. However, when the salinity exceeds 4 %, the growth parameters, such as the growth time and survival rate, were reduced by more than 50 %. BSFL treatment has more environmental value than landfill, and the salinity adjustment was beneficial to further reduce the global warming potential (GWP) net impact. In summary, the salinity of food waste has been established as a critical factor. Appropriate modulation of salinity will enhance the utilization of substrates by BSFL and contribute to the alleviation of global warming. This study offers valuable guidance for the efficient and sustainable rearing of BSFL.