Saja Abu Znaimah

Black soldier fly (BSF) larvae are increasingly used in sustainable waste management, offering potential for the bioconversion of organic waste into insect-derived fertilizer and animal feed. This study investigates the impact of varied substrate mixtures percentages of sludge and chicken feed on heavy metal accumulation, pathogen reduction, and nutrient composition in BSF frass. Methods: The experiment was conducted with four substrate treatments (100% sludge, 75% sludge + 25% chicken feed, 25% sludge + 75% chicken feed, and 100% chicken feed) over a 20-day period. Chemical and microbiological analyses were performed on the feed mixture before adding larvae and on the frass produced in each treatment. Heavy metal concentrations, including cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb), pathogen levels (Escherichia coli, total coliform, and fecal coliform), and nutrient composition, including moisture content, pH, ash, nitrogen, phosphorus, calcium, potassium, sodium, magnesium, and chlorine, were assessed. Statistical analysis was used to determine significant differences across treatments. Results: Heavy metal levels in frass varied with substrate composition, with significantly higher concentrations of cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb) in sludge-dominant treatments (p < 0.05). Treatments with higher chicken feed content were associated with lower metal levels, indicating organic feed’s potential in limiting heavy metal accumulation (p < 0.001). Pathogen analysis showed high microbial levels in sludge-based treatments, while the 100% chicken feed treatment exhibited minimal contamination, highlighting its safety profile (p < 0.05). Nutrient characterization revealed that chicken feed-enhanced treatments produced frass with higher nitrogen and potassium levels, suggesting improved nutrient density and potential for agricultural use. Conclusions: Tailoring BSF substrates by combining sludge with organic feed can enhance the nutritional quality of frass while reducing environmental risks associated with heavy metal and pathogen presence. This study supports the potential of BSF as a sustainable bioconversion tool, promoting circular agriculture.

Background: The black soldier fly (Hermetia illucens) has emerged as a promising tool in sustainable waste management, owing to its larvae’s ability to efficiently convert organic waste into valuable biomass. Objective: This study investigates the impact of various substrate compositions on the growth, waste reduction efficiency, and bioconversion rate of black soldier fly (BSF) larvae (Hermetia illucens). The aim is to optimize feeding strategies to enhance the effectiveness of BSF larvae in sustainable waste management and protein production. Methods: A controlled experiment was conducted over a 20-day period, using four different substrate types: 100% sludge, 75% sludge + 25% chicken feed, 25% sludge + 75% chicken feed, and 100% chicken feed. Each treatment had three replicates with 100 larvae each. Larval growth metrics, including weight and width, were recorded bi-daily. The waste reduction efficiency and bioconversion rate were calculated based on the remaining substrate weight and larval biomass, respectively. Elemental analysis was performed to determine the impact of substrate type on the accumulation of various elements in the larvae. Results: Significant differences were observed in larval growth, waste reduction efficiency, and bioconversion rates across the different substrates. The 100% chicken feed substrate led to the highest larval growth (M = 0.0881 g/day, SD = 0.0042) and bioconversion rate (M = 7.52%, SD = 0.34), while the 100% sludge substrate achieved the highest waste reduction rate (M = 86.2%, SD = 2.15). ANOVA tests indicated that substrate composition significantly affected these outcomes (p < 0.05). Elemental analysis showed substantial variations in the concentrations of calcium, cadmium, and nickel among the substrates, with the 100% sludge substrate having the highest nickel accumulation (M = 0.2763 ppm, SD = 0.023), significantly different from the other treatments (p < 0.001). Conclusions: The results demonstrate that substrate composition is crucial for optimizing BSF larvae growth and waste reduction efficiency. Nutrient-rich substrates, such as chicken feed, significantly enhance bioconversion rates and larval biomass production, although careful consideration of elemental accumulation, especially heavy metals, is essential for safe application in animal feed.