"Unveiling the Hidden RNA Virus Diversity in Organic Wastes: Shaping and Reduction Effects of Black Soldier Fly Treatment" Environmental Science & Technology
People and animals create lots of waste that is usually sent to landfills, incinerated or stored in engineered ponds such as manure lagoons. Now, researchers publishing in ACS' Environmental Science & Technology Letters report a potential removal method using insects, specifically black soldier fly larvae. In experiments, the larvae ate spoiled food, sewage sludge or livestock manure, and removed most human-pathogenic viruses. The researchers say this demonstrates a step toward simple, environmentally friendly waste management.
"Viruses in organic wastes have rarely been studied in a systematic way, but our research shows that black soldier fly larvae can help reduce potential viral risks, highlighting the promise of this approach for future waste treatment," says Gang Luo, a corresponding author of the study.
Zhijian Shi, Luo and colleagues wanted to see how well black soldier fly larvae break down RNA viruses in three organic waste streams, or if viral material persists in their bodies or appears in their frass (tiny, nutrient-rich pellets larvae excrete). The researchers fed separate groups of black soldier fly larvae food waste, sewage sludge or pig manure. After eight days, all the larvae gained weight, with those that ate food waste growing the most, followed by those fed manure and those fed sewage. When the team members assessed the three waste streams, they found that the initial feedstocks contained a diverse array of RNA viruses that could infect living things such as bacteria, fungi, plants and animals, even humans.
Larvae that consumed food waste contained low amounts of insect-specific viruses, which the researchers consider to be of minimal ecological or human infection risk. In contrast, larvae that were fed sewage sludge or pig manure had higher viral diversity, and their frass contained RNA viruses that could infect humans. Although larval digestion significantly decreased the abundance of most human-pathogenic viruses (e.g., noroviruses) from the fecal organic matter sources to frass, some viruses (e.g., picobirnaviruses that can cause digestive symptoms) persisted in both the final larvae and frass.
The researchers conclude that black soldier fly larvae are a promising simple and natural approach for waste management, but larvae consuming fecal wastes may need additional treatment for safe use in feed or for their frass to be used in fertilizers. Future research will focus on whether viruses remaining in larvae or their frass are still active. Gang Luo says this is "key to safely reusing them in a circular waste management system."
The authors acknowledge funding from the National Natural Science Foundation of China.
