Wax worm chewing through plastic (Photo Credit: Federica Bertocchini, Paolo Bombelli, and Chris Howe)

Though plastic shopping bags are incredibly cheap and useful, their disposal causes widespread pollution. That's because the non-biodegradable polyethylene takes centuries to decompose and is also detrimental to wildlife who often mistake the colorful debris for food. Now, we may have an unlikely ally to help clean up our trash – a small wax worm bred primarily for use as premium fish bait.

Federica Bertocchini, a developmental biologist at the Spanish National Research Council, stumbled upon the grub’s hidden skills by accident. About two years ago, the amateur beekeeper was cleaning out her hives that had become infested with the Galleria mellonella, or honeycomb moth, caterpillars. The larvae are the bane of beekeepers worldwide because of their voracious appetite for the wax that bees use to build honeycombs.

The researcher says, "I removed the worms and put them in a plastic bag while I cleaned the panels. After finishing, I went back to the room where I had left the worms, and I found that they were everywhere. They had escaped from the bag even though it had been closed and when I checked, I saw that the bag was full of holes. There was only one explanation: the worms had made the holes and had escaped.”

The caterpillars break polyethylene down into ethylene glycol, a compound used as an antifreeze. (Photo Credit: César Hernández/CSIC)

Realizing she may have stumbled upon an important discovery, Bertocchini teamed up with Paolo Bombelli and Christopher Howe from Cambridge University to conduct further research. They began by placing 100 worms on some polyethylene and discovered that each was able to create about 2.2 holes per hour. Over a 24-hour period, the worms managed to gnaw through 92 milligrams of plastic. The researchers estimate that at this rate, the group of worms could decompose an average-sized 5.5-gram plastic bag within a month.

To rule out the possibility that chewing was causing the degradation, the researchers spread the soft pulp of some recently deceased worms on a sheet of plastic. Sure enough, even the liquid larvae were able to eat through the material, confirming that the worms have a plastic-digesting enzyme. Further tests revealed that the only residue left behind was ethylene glycol, a biodegradable chemical compound commonly used in antifreeze. The researchers believe that the worm’s ability to digest plastic is a coincidence and stems from its diet of beeswax that comprises the same carbon bonds as polyethylene.

While the news is certainly encouraging, not everyone is convinced the grubs can help reduce our ever-growing mountains of trash. University of Michigan’s Ramani Narayan believes the tiny pieces of microplastics released by the plastic-eating caterpillars would pick up toxins and transport them up the food chain, causing, even more, harm to the environment and human health. The skeptical researcher quips, “Biodegradation isn’t a magical solution to plastics waste management.”

Plastic biodegraded by 10 worms in 30 minutes. Credit: César Hernández/CSIC

Susan Selke, director of Michigan State University School of Packaging, is concerned that the caterpillars will not be able to survive in an oxygen-free landfill environment. Additionally, it is unclear if the worms are chewing through the plastic to escape or because it provides them with energy. According to Bombelli, “If they just want to escape, they are going to get fed up very soon. But if they’re munching it to use as an energy source it’s a completely different ball game. We are not yet able to answer this, but we’re working on it.”

However, Bertocchini is not planning to deploy worm armies to landfills. Instead, the researcher wants to identify the enzyme that helps degrade the plastic. The researcher says, “Maybe we can find the molecule and produce it at high-scale, rather than using a million worms in a plastic bag.”

This is not the first time scientists have discovered wax worms that eat human-generated trash. In 2014, a team from China's Beihang University discovered that the larvae of Indian meal moths, the most common pantry pests, also consume plastic. However, the bacteria in the wax worm’s stomachs took much longer to digest the material then Bertocchini’s worms. Then, in 2015, the Chinese researchers collaborated with scientists from California's Stanford University to investigate mealworms that enjoy eating styrofoam. Whether any of these organisms are strong enough to help eliminate our trash remains to be seen. Meanwhile, the only way to solve this self-inflicted problem is by reducing plastic bag usage — so be sure to always carry a recyclable bag with you.

Resources: nationalgeographic.com,scientificamerican.com,guardian.co.uk