New research finds larvae of black soldier flies (Hermetia illucens) can eat and partially break down polyurethane, thanks to their gut microbes. It’s no silver bullet, but the findings suggest insects or their enzymes could someday help tackle stubborn plastic waste. (Photo by Rebekah D. Wallace, University of Georgia, Bugwood.org)

By Melissa Mayer

Melissa Mayer

Black soldier fly larvae are incredible recyclers. The wriggling maggots routinely transform food scraps and manure into feed and fertilizer. But can they survive on something far less appetizing—like plastic?

That’s what’s researchers from Henan University of Technology wanted to know, as reported in their study published in December in Environmental Entomology. In the study, black soldier flies (Hermetia illucens) devoured plastic foam at a steady rate and even gained weight. The findings add to growing evidence that insects and their gut microbes could help break down stubborn plastic waste.

A Plastic Buffet

The plastic in question is polyurethane, a common component of insulation and packaging. It’s notoriously difficult to recycle, thanks to strong chemical bonds that resist melting. Polyurethane regularly ends up in landfills or the environment, where it can persist for hundreds of years while slowly releasing harmful chemicals.

Other insect larvae can break down plastics, and black soldier flies were a promising and understudied candidate. Their robust gut microbes degrade other problematic substances like mycotoxins, pesticides, and antibiotics.

“Yet the ability of black soldier fly larvae to degrade polyurethane and the response mechanism of their gut microbiota remained unclear,” says Xifeng Wang, Ph.D., lead author of the study. “Our team had previous research experience in organic waste bioconversion and toxin degradation using black soldier fly larvae. This prompted us to explore whether they could also degrade polyurethane and to uncover the underlying microbial mechanisms.”

To do that, the researchers reared black soldier fly larvae on three diets: a standard feed, polyurethane foam soaked in water, and water alone. Over 16 days, the larvae chowing down on polyurethane consumed about 10% of the foam. Each larva ate 0.35 milligrams of plastic per day and gained 19 milligrams in weight total over the 16-day period. That’s far less than the larvae enjoying a normal diet, who packed on 96 milligrams, but it’s significantly more than those given no food at all, who steadily lost weight.

Chemical analysis of the frass the larvae left behind revealed that key bonds in the plastic had been broken.

New research finds black soldier fly larvae can eat and partially break down polyurethane, thanks to their gut microbes. It’s no silver bullet, but the findings suggest insects or their enzymes could someday help tackle stubborn plastic waste. The research team behind the study sampled the larvae’s gut bacteria and attempted to rear them on polyurethane. One bacteria strain—Delftia sp. A2—successfully broke down polyurethane powder, as illustrated in this comparison, as viewed via scanning electron microscope, of the surface of polyurethane powder without degradation by any bacteria (left) with degradation by Delftia sp. A2 (right). (Image originally published in Wang et al. 2025, Environmental Entomology)

The Tiniest Teammates

While the larvae chewed up and swallowed the polyurethane, the real work took place in the midgut, where a community of microbes broke down the plastic. When compared with larvae fed a normal diet, the composition of the gut microbiome shifted to adapt to the nutrient-scarce conditions. And those microbes secreted more enzymes known to break chemical bonds in plastics.

The research team sampled these gut bacteria and attempted to rear them on polyurethane. One strain—Delftia sp. A2—successfully broke down polyurethane powder and, to a lesser degree, polyurethane film.

However, don’t expect to see bins of black soldier flies at your local recycling facility any time soon. It’s a big job to find a feeding protocol that maximizes how much plastic the larvae break down while ensuring their health—especially if those larvae can do double duty as feedstock. Or, maybe researchers can extract those microbial enzymes and build biodegradation systems that way.

But uncovering this insect–microbe partnership is a good sign that plastic waste might one day meet its match—one small bite at a time.

Melissa Mayer is a science writer and the human behind Washington State University’s science cat, Dr. Universe. Email: [email protected].