As the world seeks to curb the use of single-use plastics, Stanford University researchers may have found a way to create value from plastic food packaging waste. The latest research published in Environmental Science & Technology showed that tiny mealworms are not only able to eat and digest various forms of chemical-laden plastic waste, but they also remain safe as a protein-rich food source for other animals.
“Previous research had shown that [the mealworms] could eat polystyrene,” said Anja Malawi Brandon, PhD candidate in environmental engineering and science at Stanford. “In our lab, we then discovered that they could eat polyethylene as well.” This discovery is significant because polyethylene is a plastic that is chemically dissimilar from polystyrene, meaning that these insects could break down multiple types of plastic.
“When thinking about how these discoveries can be used, we learned that mealworms are already widely used as a feed supplement for agriculture and aquaculture,” Brandon said. Her team sought to test whether plastic-fed mealworms could safely be used as a food supplement for other animals, such as shrimp.
Many of the chemicals added to plastics, such as the flame retardant hexabromocyclododecane (HBCD), are known to be persistent and bioaccumulative, which makes them toxic. After consuming the polyethylene containing HBCD, the mealworms excreted about 90% of the HBCD within 24 hours and almost all of it within 48 hours. All that was left of the polyethylene was partially degraded fragments and carbon dioxide. The researchers then fed the mealworm biomass to Pacific white shrimp and found no evidence of bioaccumulation or toxicity in the shrimp.
Mealworms’ ability to digest these plastics without becoming toxic means they can still be used as safe food for other animals and they can be used to help break down plastic. “It was very surprising that these chemicals passed through the mealworms without bioaccumulating, meaning that the mealworm biomass remained free of chemicals,” Brandon said.
This research may be a positive step towards recovering value from plastic waste. However, the researchers noted that further studies are needed to evaluate the possibility of nanoscale toxicity. Additionally, the researchers acknowledged that the excreted fragments of polyethylene and carbon dioxide still pose an environmental hazard that requires further efforts to solve.
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