Microorganisms in soil are breaking down an alternative plastic, new research shows, potentially suggesting a future role in tackling plastic pollution.
Millions of tons of plastic end up polluting the planet's oceans and soil every year, threatening the stability of ecosystems crucial to life.
The demands on farmers mean that they often use special plastic mulch films on their soils to maximise their crop yields.
But these films can be difficult to collect afterwards and the debris from them ends up in the soil, where it accumulates as it is not biodegradable.
But now, researchers from ETH Zurich, the Swiss Federal Institute of Technology, have shown how microbes are able to break down an alternative mulch film.
Their work, published in the journal Science Advances, revealing for the first time a form of plastic that is biodegradable in soils.
Hans-Peter Kohler, an environmental microbiologist and one of the leaders in the research, said that not all "biodegradable" materials were really deserving of the name – as many just disintegrated into smaller particles.
"By definition biodegradation demands that microbes metabolically use all carbon in the polymer chains for energy production and biomass formation," said Mr Kohler.
For a plastic to be biodegradable, its carbon atoms need to be recycled and enter into the biomass of the environment.
"Many plastic materials simply crumble into tiny fragments that persist in the environment as microplastics-even if this plastic is invisible to the naked eye," Mr Kohler said.
The research shows to a scientific standard that the alternative polymer poly (butylene adipate-co-terephthalate) (PBAT) is actually biodegradable.
Although it is not clear how long it would take for PBAT to degrade outside of a laboratory environment, the research could hint towards a much cleaner future.
"Unfortunately, there is no reason to cheer as of yet: we're still far from resolving the global environmental problem of plastic pollution," said senior scientist Michael Sander, who also helped coordinate the study.
"But we've taken a very important first step in the direction of plastic biodegradability in soil."
At the same time, Mr Sander warned against people developing an unrealistic expectation of how PBUT could affect the build-up of plastic in the environment.
"As we have demonstrated, there is hope for our soils in the form of biodegradable polymers.
"The results from soils should, however, not be directly transferred to other natural environments.
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"For instance, biodegradation of polymers in seawater might be considerably slower, because the conditions there are different and so are the microbial communities."
:: Sky's Ocean Rescue campaign encourages people to reduce their single-use plastics. You can find out more about the campaign and how to get involved at www.skyoceanrescue.com
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