Biodegradable plastic needs one more year to decompose than compostable plastic

Self an extremely commonly used plastic, labeled as “biodegradable”, resists unchanged for 14 months in marine ecosystems, perhaps it is appropriate to admit that there is some problem with the use and meaning of the adjective. This is highlighted by a study just published in the journal PLOS ONE by a group of scientists from the Scripp Institution of Oceanography at the University of California, San Diego.

The authors of the work, in particular, have tried to disambiguate the sense of the terms “biodegradable” and “compostable”, distinguishing between materials that can only be degraded in controlled industrial environments (the so-called Pla) and those that instead are destroyed in the natural environment. And showing, precisely, that often what we call biodegradable is not really.

The fact that pollution from plastics, microplastics and nanoplastics poses a serious threat to marine ecosystems and to the health of the entire planet has long since ceased to be a mystery. One of the main problems connected to the question lies in the fact that, precisely, plastic is very resistant to degradationand its fragments persist for a long time in ecosystems: for this reason, in recent years scientists have developed various substitutes for “traditional” plastic, the one synthesized from petroleum, with the double goal of reducing dependence on fossil fuels and making waste products more environmentally friendly.

One such substitute are the Pla, lactic acid polymers derived from the fermentation of sugars and starches, able to decompose at the high temperatures reached in composting sites; and the authors of the newly published work tried to understand what their fate is when instead they are in the natural environment.

To do so, they placed several samples of PLA, petroleum-based materials, cellulose-based materials, and petroleum-cellulose-based materials in submerged cages off the coast of La Jolla, California, monitoring them every week. to understand its degradation: in this way, they found that cellulose-based materials actually decompose quite quickly, within a month; none of the others, on the other hand, showed signs of degradation during the entire 14 months of the experiment.

“Our results,” he explained Sarah-Jeanne Royeone of the authors of the article, “indicate that the term ‘compostable’ commonly associated with Plas does not imply actual degradation in the natural environment. So, Claiming that compostable plastics are biodegradable is misleading, as it can convey the idea that the material degrades in the environment. Pla-based plastics, on the other hand, only degrade in industrial facilities. Our work is one of the few studies that deals with the comparison of the biodegradability of different materials (from completely synthetic to completely biological ones) under controlled conditions: in the light of our results, we believe it is necessary to define standardized tests to label a material as actually ‘biodegradable’, so that consumers are adequately informed about what they use and buy”.