Caterpillars that can eat plastic bags have just been identified, by a scientist and amateur beekeeper who noticed they’d munched through his trash.
The discovery was reported this week by Cambridge University and Spanish National Research Council researchers.
Is this the end of landfill, turtles with plastic-clogged stomachs, and streets with tattered shopping bags?
Experts urge caution. They point to previous attempts to clean up man’s mess with nature’s assistance, such as planting trees to soak up carbon dioxide, using micro-organisms to clean up oil spills, or introducing invasive species for pest control.
Like the cane toad, introduced to Australia in the 1930s to control crop pests, which found the local wildlife to their taste and gorged themselves on it as they spread across the continent.
The caterpillars are the larvae of the greater wax moth (Galleria mellonella). They can devour polyethylene, the main type of plastic found in waste, along with its close relative, polypropylene.
First, you’d need an awful lot of very hungry caterpillars to make a very small dent on the plastic waste problem.
The UK alone discards almost 2m tonnes every year. The researchers say one worm gets through about 2 milligrams a day, so you’d need billions of caterpillars eating constantly all year round. That’s quite a large farm, just for Britain’s bags.
Next, wax moths, which are found throughout the world, are called “wax moths” because they eat wax. Specifically, they love to eat the wax from which bees make their honeycombs – so they can devastate bee colonies.
Galleria mellonella is one of the two common species. They cause almost $7m of damage annually in the US alone.
Bees are already under severe stress from pesticides, habitat loss and predators, so breeding one of their enemies in huge numbers might not be such a bright idea.
Polyethylene sits around in the environment because its molecules are so hard to break down. Ordinary soil micro-organisms don’t have the resources for it.
Because these plastics are built up from the hydrocarbon molecules in oil, ideally we’d turn them back into oil after we had used them.
Chemists have been working to do that, but it’s tough, and they’ve only started to make progress recently.
Bacteria may be an easier and less hazardous solution. Some happily devour toxic chemicals, such as perchlorate (weedkiller), others live amid radioactive waste.
Last year Japanese scientists identified a bacterium existing in the wild that can feed on another common plastic, polyethylene terephthalate – the one used to make soft drink and water bottles.
These bacteria live in the digestive tract of another wax-eater, the Indian mealmoth and might also be the secret to Galleria mellonella’s plastic-busting abilities.
It may be those bacteria could brewed up in fermentation vats that would dissolve plastics without breeding vast wax moth colonies, or it might be possible to extract the enzymes the caterpillars use and put them to work on their own.
So it seems that, rather than watching vast armies of caterpillars marching to war against plastic bags, science will follow the clues from this discovery to come up with a practical solution, in time.
Just as well we have scientists prepared to march in 500 cities around the world to promote research and facts instead of loudmouth, shoot-from-the-hip, kneejerk reaction, isn’t it?