How Many Worms Would It Take?

If 100 wax worms can devour 92 milligrams of polyethylene in 12 hours, how many wax worms would it take to consume 100 plastic bags per day? Assume each bag weighs 8 grams (I weighed one), and the worms eat constantly at the same rate for 24 hours. Read to the end of this post for the answer.

Wax worms – the larvae of wax moths – usually end their lives as fish bait. But perhaps their existence could serve a higher purpose. In the wild, wax worms eat beeswax, much to the chagrin of beekeepers and anyone who cares about the importance of bees to our ecosystem. As Spanish scientist and amateur beekeeper Federica Bertocchini found out accidentally, the worms also enjoy polyethylene, the plastic in plastic grocery bags. According to an article in The Guardian, Bertocchini found wax worms in her beehive and captured them in a plastic bag. They ate through the plastic and ran amok.

Americans use 100 billion plastic bags each year (that’s over 250 million per day), and our country is certainly not the only source of plastic trash. Polyethylene waste is especially troubling because it is difficult to recycle. Many recycling facilities do not want it because the material clogs up machinery, and they have no end market into which to sell it. Despite being told not to discard plastic bags into recycling bins, lots of individuals and businesses in the U.S. and Europe are doing just that, creating a headache for recyclers.

But there is a bigger problem with plastic. Far too many plastic bags – and other types of plastic trash – are ending up in rivers, lakes, and oceans. According to the Ellen MacArthur Foundation, at least 8 million tons of plastic enters the ocean each year, the equivalent of a garbage truck full of plastic trash every minute. This statistic should alarm everyone, but it is easy to get complacent if we don’t personally see the damage.

Henderson Island, a remote island in the South Pacific, is now making international news headlines because Australian researchers just published results of a study showing that Henderson’s beaches are covered in over 37 million of pieces of trash, much of it being discarded plastic items. This is an uninhabited island comprising only 14 square miles! Currents have been washing trash ashore from locations as far flung as China, Japan, and Chile.

Plastic bags are only part of the problem, but they are a good target to address. We need a global effort to educate people and convince them not only to recycle bags rather than throwing them away, but to separate plastic bags from the rest of their recycling. If such efforts are successful, plastic bag recycling drop-off spots (grocery stores, for example) may be able to collect more of these bags and send them to facilities that can recycle them. Researchers are working on methods to efficiently recycle the material. The optimal recycling process is likely to take advantage of bacteria that consume plastic.

Bacteria in the guts of wax worms may indeed be responsible for their ability to consume polyethylene. Researchers are trying to figure out whether the worms are eating through the plastic just to escape, or if they are using is as a food source. If it is the latter, that is much more promising, because it suggests that wax worms may have a continuing appetite for the material. If so, they may be able to eat constantly at a rate approaching that observed in the lab, which I quoted at the beginning of this post.

The answer to the math problem? 434,783 worms. Breeding the billions of worms required to make a dent in our plastic trash problem comes with its own set of concerns, so any practical solution is likely to lie in manufacturing enzymes resembling those that the wax worms produce.