Mealworms and superworms may nibble at one of the world's most stubborn plastics, but new research from The University of Western Australia shows they can't actually break it down.
In a study led by PhD student Zahra Mohammadizadeh Tahroudi, researchers from UWA's School of Molecular Sciences tested whether mealworms and superworms (insect larvae of Tenebrio molitor and Zophobas morio) could metabolise polyvinyl chloride (PVC), a highly chlorinated plastic widely used in pipes, flooring and consumer goods.
While the larvae readily consumed PVC, especially when it was softened with the common plasticiser dioctyl phthalate, detailed chemical analysis revealed no signs of biochemical degradation. Instead, the PVC proved actively toxic, with larvae showing reduced growth and survival.
"Our results show a clear disconnect between consumption and degradation," Ms Tahroudi said.
"The larvae were able to chew and ingest the PVC, but they didn't derive any nutrition from it. In fact, it harmed them. This challenges the idea that they can help us deal with PVC waste.
Co-supervisor Professor Rob Atkin said the team took extra care to rule out confounding factors that had clouded earlier studies.
"We housed every larva individually to eliminate cannibalism and tracked their health over long timeframes," Professor Atkin said.
"That gave us a definitive answer: insect larvae like mealworms and superworms can't solve the PVC problem."
The PVC study, published in the journal International Biodeterioration and Biodegradation, builds on the team's earlier work on expanded polystyrene, which similarly found no genuine chemical degradation.
Together, the two studies underscore that while insect larvae can chew through plastics, they lack the enzymatic machinery to actually digest them.
Co-author Dr Georg Fritz, who leads the UWA Fritz Lab, said the findings reinforced the need to pursue more advanced solutions.
"Mealworms and superworms have become poster children for plastic biodegradation, but our work shows their limits," Dr Fritz said.
"While they can help us understand how plastics are processed mechanically, true solutions will come from biotechnology, chemistry and systems approaches to plastic waste."
The study was supported by the Australian Research Council, UWA and Woodside Energy Ltd.
