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Certain microbes in the stomachs of cows may be able to break down plastic

The discovery could offer hope at a time of growing concern about plastic pollution around the world.

© Marie Fontaine -

According to a study led by Dr Doris Ribitsch of University of Natural Resources and Life Sciences in Vienna, bacteria in the stomachs of cattle could break down plastic, reports The Guardian. These results are far from insignificant, given that more than eight billion tonnes of plastic have accumulated on the planet since the 1950s - a weight equivalent to one billion elephants!

Natural polyester

To carry out this research, the scientists started from the observation that natural polyester, present in tomato or apple peelings, can be degraded by certain microbes.

The fact is that the cows' feed is also composed of these natural polyesters. Therefore, the researchers hypothesised that the stomachs of the cows would contain bacteria capable of breaking down the plant material. And it seems that they were right.

To verify this, the experts collected rumen fluid - that part of the ruminant stomach that is similar to a fermentation tank - from a slaughterhouse in Austria. It should be noted that about 100 liters of rumen can be recovered from a cow.

"You can imagine the huge amount of rumen fluid that accumulates in slaughterhouses every day - and that's just a waste," says Dr Doris Ribitsch.

This liquid was incubated with all three types of polyester - PET (a synthetic polymer commonly used in textiles and packaging), PBAT (a biodegradable plastic often used in compostable plastic bags) and PEF (a biobased material made from renewable resources).

Each plastic was tested in film and powder form.

The laboratory results showed that all three plastics could be broken down by micro-organisms present in the stomachs of cows, with the plastic powders breaking down faster than the plastic film. - findings published in the journal Frontiers in Bioengineering and Biotechnology -

The next steps will be to identify the microbes crucial to plastic degradation from the thousands present in the rumen, and then the enzymes they produce. Once the enzymes are identified, they can be produced and applied in recycling plants.

At present, plastic waste is mainly burnt.

To a lesser extent it is melted down for use in other products, but after a while it is damaged and cannot be used again.

Another method is chemical recycling - turning plastic waste into basic chemicals - but this is not an environmentally friendly process.

The use of enzymes would be considered a form of green chemical recycling.


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