There's a Creepy-Crawly Solution for a World Drowning in Styrofoam

Scientists discover that mealworms can digest the indigestible—the plastic polluting the planet.

(Photo: Charles Mann/Getty Images)

Oct 5, 2015· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

Forget diamonds—Styrofoam is forever.

The polystyrene packaging that cushioned your latest online order for delivery may well sit in landfills for many decades without degrading. How big is the problem? Americans throw out 2.5 billion Styrofoam cups alone each year.

But researchers have now confirmed for the first time that mealworms can biodegrade petroleum-based plastic in just days, thanks to bacteria in their gut. The mealworm is the larvae of the darkling beetle, and it can survive on a diet of Styrofoam and other types of polystyrene.

“People talk about how Styrofoam takes decades to biodegrade,” said Wei-Min Wu, a senior research engineer at Stanford University and the coauthor of two new papers on mealworms and plastic published in the journal Environmental Science and Technology. “But we are confident there is a fast degradation, so this could eventually lead to a breakthrough for rapidly breaking down plastic in the environment.”

In a series of experiments, the researchers fed 100 mealworms a diet of Styrofoam. The worms ate 34 to 39 milligrams of plastic—about the weight of a small pill—per day. They converted 48 percent of the Styrofoam into carbon dioxide, and they appeared as healthy as worms eating other food.

Within 24 hours, the worms excreted 49 percent of the plastic as broken-down bits of Styrofoam. Wu said the droppings are believed to be safe in the environment but that more study is needed.

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The researchers were able to isolate the particular gut bacteria in the worms responsible for breaking down the plastic. That could be crucial for the future, said Wu, because it would be easier to use engineered bacteria than worms to clean up plastic. He noted that the team hasn’t yet tried to engineer the bacteria.

Worm guts are efficient bioreactors for breaking things down, not unlike the stomachs of cows or other grazing animals, the study authors noted. Future work will examine other potential plastic-biodegrading insects.

The approach could also help alleviate the ocean plastic pollution crisis, given that marine microbes have been found to digest plastic. Still, scientists are not sure if the presence of plastic-munching bacteria would be beneficial.

Microbes that eat ocean plastic may release toxins like flame retardants into the food chain or may break down larger pieces of debris that could be ingested by fish and marine mammals.