Monday, December 28, 2015

Can Mealworms Digest Plastic?

Earlier this fall the following headline caught our attention:

“Plastic-eating worms may offer solution to mounting waste, Stanford researchers discover.”

In this article, scientists discover that the common mealworm, Tenebrio molitor can eat Styrofoam and process it into ordinary, non-plastic frass (bug feces). When most animals eat plastic, it usually remains in their bodies – like the items found in the whale stomach on exhibit at Pacific Science Center.

Sometimes the plastic interferes with digesting other things. Even when animals seemed to digest plastic, in fact, it was simply broken up into smaller pieces –still plastic – that are passed as waste. This does not cut down on the amount of plastic waste in the environment. Mealworms, however, are able to reduce the amount of plastic around by breaking apart the plastic in their guts and using it for food.

Scientists hope to replicate the digestive processes in a lab on a large scale to deal with the mountains of discarded packaging.

Scientists are also looking for an aquatic organism capable of breaking down plastic to prevent scenes such as this:

There are huge islands of plastic debris in the Pacific Ocean

The idea of a natural solution to cleaning up plastic trash is enticing.

After reading this article, Animal Caretaker Amanda Plemmons immediately thought of the mealworms we rear for feeding our carnivorous and omnivorous animals. Could we replicate the experiment and demonstrate this exciting development? Yes. We could. All we needed, really, were mealworms and Styrofoam.

For a few weeks we kept some of our mealworms in a small enclosure with foam packing material and moist cardboard as a water source. We noticed them surviving and thriving. We could tell they were flourishing because they were healthy enough to shed their skins and grow. The next step was to move a larger number into a larger enclosure with a variety of polystyrene shapes.

After a week “backstage” they were brought out on exhibit and we were pleased to see them visible on the surfaces of the foam. They still have moist cardboard and cellulose sponge as a moisture source and although we have seen them eating it, they are also eating the Styrofoam with gusto.

Best of all the foam is going in as plastic and coming out as frass! The mealworms aren’t just chewing and swallowing. They seem to be digesting and excreting. This story is much more complex than just a Grossology® connection, but we have rarely been more excited to watch insects poop!


  1. Has anyone done an analysis of the mealyworm poop to see if it really truly is completely "plastic free"? In other words, are mealyworms really able to 100% digest it? Is this due to some kind of microbial activity in their guts? I would really love to know more!!!

  2. Hi Miriam,

    Because we did not perform the original experiments, I think the best answer would be found in the link above. The details on how the waste is analyzed seem to make it sound like it is broken down into organic material; it's not 100% clear that it was plastic free. I'd always rather refer to the source material. It's a good read!