To rid the world of plastic dishware, the worm’s the word
By Stav Ziv
More than 1 million tons of plastic foam cups and plates—most made of polystyrene resin—were discarded in the U.S. in 2013, says the Environmental Protection Agency, and the stuff can languish in landfills for many years. But there may be a simple solution: mealworms.
Two papers published in the journal Environmental Science & Technology in September found that the larvae form of the beetle Tenebrio molitor can eat and rapidly break down Styrofoam and other forms of polystyrene generally thought to be nonbiodegradable. After roughly 10 days adapting to a new Styrofoam diet, the mealworms could degrade the plastic in their guts in less than 24 hours, turning 47.7 percent of what they ingested into carbon dioxide and most of the rest into fecal matter.
Several forms of analysis showed that the mealworms’ guts had depolymerized the polystyrene molecules—in other words, they could break apart the links among the molecule’s components. The Styrofoam-eating mealworms completed their life cycles—from larva to pupa and finally adult beetle—just as those subsisting on a normal diet of bran do, though their weight didn’t increase as much as that of a bran-fed control group. The researchers, from Stanford University and Beihang University in Beijing, also looked more closely at the microbial environment of the mealworm gut and the key role it plays in the plastic degradation process.
After giving their insect subjects antibiotics for 10 days to suppress the activity of gut bacteria, the scientists found that the creatures could no longer degrade the plastic. They isolated one bacterial strain and demonstrated its degrading effect on polystyrene even when outside the gut—albeit at a much slower pace. The ultimate goal of the project, says Wei-Min Wu, a senior research engineer at Stanford and an author on the papers, is to turn this into tech that can “accelerate remediation of plastic contaminated sites.”