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Cows’ stomachs can break down hard-to-recycle plastic, study finds

By Sara Spary, CNN

Researchers in Austria may have found an unlikely solution to the problem of plastic pollution: cows, and the microbes found inside their stomachs.

Researchers from the University of Natural Resources and Life Sciences (BOKU) in Vienna, the Austrian Center of Industrial Biotechnology and the University of Innsbruck found that common plastics could be broken down when exposed to rumen, the matter found in the largest part of a cow’s stomach.

The microbes and enzymes found within rumen can break down common plastics — including those widely used for plastic bags, bottles, textiles and food packaging, they found.

The study, published in the scientific journal Frontiers on Friday, looked at samples of rumen from Alpine cows in an abattoir in Austria.

The researchers tested the effect of rumen on three types of plastic — polyethylene terephthalate (commonly known as PET), polybutylene adipate terephthalate (PBAT) and polyethylene furanoate (PEF).

Trained to digest

Professor Georg Gübitz, from BOKU, told CNN that rumen could break down plastics in “several hours” — and that it could break down some of the plastics entirely when treated with it long enough.

This is because cows’ stomachs are already “trained” to break down difficult-to-degrade food matter, including the plant polymer cutin — a waxy substance found in plants, including in apple peels and berries, Gübitz said.

Cutin is “a polyester, not identical, but similar to PET (the most common type of plastic, found in plastic bags and food packaging),” he said.

He said more research was needed but that the findings were significant because they could help find a solution to degrading otherwise “difficult to recycle” plastics.

Research into how microbes and enzymes affect plastics is already a current field of study, he said, but he believed the potential role of cows had not been explored until now.

“It (rumen) was quite efficient when compared to other enzymes tested in the last 10 years,” he said.

If manufactured at scale, rumen could initially be collected as a byproduct of the meat and dairy industry, he said.

“But longer term it will make more sense to produce the responsible enzymes and even further enhance their activity by using genetic engineering,” he added.

Professor Richard C. Thompson, head of the International Marine Litter Research Unit at the University of Plymouth, England, who wasn’t involved in the study, told CNN that using microbes from cows was novel but that the wider concept of degrading plastic using organic matter was not new.

“Most conventional plastics are very resistant to biodegradation and that on one hand creates a benefit. While the plastic is being used — like the mobile phone I’m using now, or lightweight parts in an airplane, or even a bottle of lemonade, we want the plastic to last.

“But the challenge is then what happens when you finish with the item — and that’s where biodegradation often comes in as part of the answer.”

The problem of plastic pollution is widely documented.

In Europe, “widespread consumption of plastic waste (has) led to the accumulation of 25.8 million tons of waste,” the researchers said in the study.

Last year, a separate study predicted that the world will have 710 million metric tons of plastic by 2040 — and that’s taking into account efforts to reduce, reuse and recycle plastic products.

Plastics have also been found in some of the most remote places on earth.

There are estimated to be 14 million metric tons of microplastics sitting on the ocean floor, while plastic was found in the gut of a small invertebrate in a remote island in Antarctica in 2020.

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