Very hungry caterpillars could be the answer to the Earth's massive plastic bag problem

A Spanish biologist and amateur beekeeper may have discovered a way to deal with some of the trillion plastic bags humans use and toss annually — and the answer lies in the humble caterpillar.

Or, more specifically, the Galleria mellonella, or wax moth.

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Federica Bertocchini, from Spain's Institute of Biomedicine & Biotechnology of Cantabria, was actually working away at her side hustle—beekeeping—when she made the discovery that could make a huge dent in Earth's plastic problem.

Finding a bunch of wax moths in her hives, where they were busy munching on the wax that her bees need to make honeycomb, she dumped the pesky critters in a plastic bag. On her return, she discovered they'd eaten their way out of the bag.

Teaming up with biochemists Paolo Bombelli and Christopher Howe, she aimed to find out if—and how—the creatures were truly digesting the plastic. Their results were published in Current Biology Monday, and could have important ramifications in the fight against environmental waste.

Essentially, the team discovered "the fast bio-degradation of polyethylene (PE) by larvae of the wax moth Galleria mellonella, producing ethylene glycol."

When a film of PE was left with wax worms, holes started appearing within 40 minutes. As the graphic below shows, a high street grocery bag was riddled with holes after just 12 hours in the presence of some 100 worms. Overall, 92mg of plastic disappeared—far more than the previous record for bacteria, 0.13mg. The team also smeared the unsavory-sounding "worm homogenate" onto PE films, which showed the special enzymes produced by the worms helped break down the plastic.

"What allows the wax worm to degrade a chemical bond not generally susceptible to bio-degradation?" the study asks.

"The answer may lie in the ecology of the wax worm itself. They feed on beeswax, and their natural niche is the honeycomb; the moth lays its eggs inside the beehive, where the worms grow to their pupa stage, eating beeswax. Beeswax is composed of a highly diverse mixture of lipid compounds, including alkanes, alkenes, fatty acids and esters."

In other words, these worms are built to devour compounds similar to those found in plastic bags. But forget notions of huge armies of worms unleashed into your discarded grocery bags. 

"The idea would be to not use the worms," Bertocchini says. “Maybe we can find the molecule and produce it at high-scale rather than using a million worms in a plastic bag.”

However, not everyone is impressed with the discovery. Marine biologist Tracy Mincer from the Woods Hole Oceanographic Institute told National Geographic he believed reducing plastic production and increasing recycling was more important than finding ways to break it down after the event. 

“Polyethylene is a high-quality resin that can be up-cycled in many ways and can fetch up to $500 per tonne,” he told the publication. “In my opinion, although this is an amazing natural history story and wonderful academic exercise, it is not a solution for disposing of polyethylene as this is throwing away money.”

Another researcher from Michigan State University also voiced concern. Ramani Narayan told The Atlantic the evidence that waxworm paste produces ethylene glycol is "tenuous at best."

The fight against our plastic infestation continues.

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