Evaluating Sawdust as a Bulking Agent to Enhance Black Soldier Fly Larvae ( Hermetia illucens ) Performance and Survival in Potato Peels

The rearing of black soldier fly larvae (BSFL) offers a sustainable approach for producing high‐protein larvae for animal feed, contributing to waste reduction and nutrient recovery. While BSFL‐rearing is well studied, the role of non‐nutritive bulking agents such as sawdust remains unclear. Sawdust was added on top of the base substrate at 0% (control), 5%, 10% and 15% of the total substrate weight to evaluate its effect on BSFL survival and growth. Sawdust did not significantly impact survival, with all treatments maintaining a percentage above 65%. However, it enhanced biomass yield, with 15% yielding 682.97 g and 10% yielding 648.91 g on a dry basis, while 5% showed minimal effect. Growth rates followed a similar trend, with Sawdust15 (0.1233 g/day) outperforming Sawdust10 (0.1189 g/day) and the control (0.1005 g/day). The results indicate that sawdust inclusion prolonged the feeding period of BSFL, as larvae in sawdust treatments continued feeding longer than those in the control group, which depleted the substrate more rapidly. These findings indicate that sawdust application at 10%–15% significantly enhances BSFL growth and biomass yield, with the 15% inclusion level yielding the highest larval weight and biomass conversion efficiency. However, the 5% sawdust application did not significantly improve performance from the control, suggesting that lower inclusion rates may not be optimal for BSFL rearing on high‐moisture substrates. Therefore, sawdust likely enhances movement flexibility for the larvae, allowing them to conserve energy for later utilisation during the metamorphosis process between the 4th and 5th instars.