Introduction:
This study investigates the bioconversion efficiency and nutritional outcomes of Black Soldier Fly (BSF) larvae (Hermetia illucens) reared on substrates combining aquaculture sludge (AS) and brewers’ spent grains (BG). The objective was to identify the optimal AS inclusion level that maximizes larval growth and nutrient composition, offering a sustainable approach to waste valorization. Frozen aquaculture sludge was thawed at room temperature and thoroughly hand-mixed. Five experimental substrates were formulated:
Substrate moisture was adjusted to 70% (except for the control) by adding distilled water, aligning with findings by Bekker et al. that optimal BSF larval growth occurs at moisture levels between 65–75%. Larvae were reared under controlled conditions (28 ± 1°C, 70% RH) for 14 days. Growth performance metrics included larval weight gain, survival rate, and development time. Post-harvest, larvae were analyzed for proximate composition: crude protein, lipid, ash, and moisture content.
Results:
Results indicated that T2 (50% AS + 50% BG) achieved the highest larval weight gain (0.45 g/larva), survival rate (95%), and optimal development time (12 days). Proximate analysis revealed that T2 larvae had the highest crude protein (42.5%) and lipid content (28.3%), with moderate ash (8.2%) and moisture levels (10.5%). These findings suggest that a balanced 50:50 ratio of AS and BG provides an optimal nutrient profile and growth environment for BSF larvae.This study demonstrates the potential of integrating aquaculture sludge with brewers’ spent grains to enhance BSF larval production, contributing to sustainable waste management and alternative protein sources.