Analysis of heavy metals in the conversion of lake sediment and restaurant waste by black soldier fly (Hermetia illucens)

Abstract

The risk posed by heavy metals makes it difficult to dispose of sediment contaminants from dredging lakes in China. Black soldier fly (Hermetia illucens) can convert organic waste, such as restaurant waste and lake sediment, to high-value-added protein feed and fertilizer. Experimental groups were formed in this study to explore the conversion of heavy metals present in the mixture of restaurant waste and lake sediment by black soldier fly larvae (BSFL). The results demonstrated that BSFL could survive in pure sediment with an 84.76% survival rate. Relative to the substrate, BSFL could accumulate 70-90% zinc (Zn), chromium (Cr), copper (Cu), and 20-40% cadmium (Cd) and lead (Pb). The experimental group 2:3, with 40% lake sediment and 60% restaurant waste, was the best group after conversion for 15 days, which showed a 95.24% survival rate of BFSL, 82.20 mg average weight of BFSL, 8.92 mm average length of BFSL, with varying content of heavy metals such as Cu (43.22 mg/kg), Zn (193.31 mg/kg), Cd (1.58 mg/kg), Cr (25.30 mg/kg) Cr, and Pb (38.59 mg/kg) in BSFL. Furthermore, the conversion residue conforms to the relevant standards of organic fertilizer in China and can be used as organic fertilizer. Overall, the present study shows that black soldier flies can improve the resource utilization of lake sediment, especially by reducing the effect of heavy metals.

Biogas Digestate and Sewage Sludge as Suitable Feeds for Black Soldier Fly (Hermetia illucens) Larvae

“…By contrast, although the digestate contained a higher concentration of heavy metals than the food waste, the accumulation in the larvae did not exceed the limits, making it a potentially suitable feed for larvae for future use. Our findings align with similar studies for various food waste [ 54 , 66 , 67 , 68 , 69 , 70 ], where the levels of Pb in larvae for food waste range from 0.08 to 1.5 mg/kg, while Cd ranges from 0.02 to 7.9 mg/kg, and Cr ranges from 0.08 to 3 mg/kg. Previous studies have shown that Cd and Pb can accumulate in larvae [ 18 , 28 ].…”

Mitigation Strategies against Food Safety Contaminant Transmission from Black Soldier Fly Larva Bioconversion

“…BSFL do bioaccumulate heavy metals and other elements depending on what is present in the feed, meaning some studies find no bioaccumulation of certain elements that other studies do. The bioaccumulation factors for cadmium and manganese are consistently the highest, followed by arsenic, lead, iron, zinc, mercury, copper, chromium, magnesium, potassium, and tin; these factors are consistently below 1 (no bioaccumulation) for aluminum, cobalt, molybdenum, nickel, selenium, silver, or vanadium [ 6 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. While this could reduce the suitability of the insects for use in feed, it does serve to decontaminate the substrate and produce a cleaner residue for downstream uses [ 8 , 54 , 57 ].…”

“…The bioaccumulation factors for cadmium and manganese are consistently the highest, followed by arsenic, lead, iron, zinc, mercury, copper, chromium, magnesium, potassium, and tin; these factors are consistently below 1 (no bioaccumulation) for aluminum, cobalt, molybdenum, nickel, selenium, silver, or vanadium [ 6 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. While this could reduce the suitability of the insects for use in feed, it does serve to decontaminate the substrate and produce a cleaner residue for downstream uses [ 8 , 54 , 57 ]. Some evidence suggests heavy metal contamination negatively affects the natural BSFL gut microbiome and leads to the enrichment of pathogens in the gut [ 56 , 59 ].…”