A Norwegian study has raised concerns over the use of fish sludge as feed for insects and worms, highlighting potential risks associated with heavy metals and environmental toxins. The research, part of the SecureFeed project, was conducted by SINTEF, the Norwegian Veterinary Institute, and the Institute of Marine Research to determine if these contaminants could enter the food chain.
Fish sludge from aquaculture farms can be used to feed polychaetes and black soldier fly larvae, which in turn provide protein-rich feed for fish and livestock. However, the sludge may contain harmful substances such as heavy metals, PCBs, and dioxins, which can be absorbed by the animals.
The study analyzed approximately 50 sludge samples from various Norwegian aquaculture facilities. The Institute of Marine Research found that the levels of metals such as cadmium, arsenic, copper, and zinc in the sludge were comparable to those found in fish feed, with some samples exceeding the limit values for feed ingredients. While some metals remained within acceptable levels, others raised concerns, particularly regarding the accumulation of pollutants in the larvae.
The research also noted gaps in knowledge about the transfer of organic pollutants from sludge to insects, with some substances, like PCBs and dioxins, found to increase in black soldier fly larvae, potentially exceeding regulatory limits. SINTEF researcher Andreas Hagemann emphasized the need for further analysis to ensure the safety of using fish sludge in bio-circular feed production.
The findings point to the importance of monitoring fish sludge for contaminants to ensure its safe use in the animal feed supply chain. Further research and regulatory adjustments are necessary to establish safe practices for this growing industry.
