Study shows how slowly plastic decomposes

WSL studied the ability of microbes in cold Alpine soils to determine the time it takes for plastic to break down in nature.

For his research, researcher Joël Rüthi buried three types of plastic in soil samples taken from an altitude of 3,000 meters at Engadine: two biodegradable packaging, such as those used for compost bags, and a piece of polyethylene (PE). It is used to make ordinary black garbage bags.

After five months at 15 degrees Celsius, the two biodegradable materials showed tiny holes and a biofilm of bacterial and fungal fibers. PE, on the other hand, was intact.

“The compost bags were partially decomposed. But complete decomposition would have taken much longer, as Rüthi quotes in a WSL media release. Therefore, plastic waste should under no circumstances be disposed of in the Alps – or anywhere in nature – even those made of biodegradable plastic.

Genetic methods can be used to determine exactly which organisms grow on plastic. The genes for enzymes that can break down these long chains of molecules at certain points were located on the compostable plastic.

Bacteria that fix nitrogen in the atmosphere and are therefore important for healthy soils are also well developed. They apparently used plastic as an additional source of energy and carbon, because carbon is scarce in mountainous soils.

With his work, the scientist managed to prove that microbes that can decompose plastic exist and are active in the Alps, even if it takes years for them to completely break down.

At the same time, the researcher discovered numerous new DNA sequences from which plastic-degrading enzymes can be obtained, according to the study published in the “Journal of Hazardous Materials.”

(SDA)