Even if we stop producing them today, it will take millennia for plastics to be digested by the Earth

“Plastic is fantastic”… Except for our old planet. This practical, durable, multi-featured material has been a part of our daily lives for decades. However, in recent years, various scientific studies have shown that they are harmful to ecosystems. Be it for the oceans on the famous “plastic” continent, which has made its mark with its supporting images. Or microplastics, which have recently been found even in the clean air of the Pyrenees.

But no global study has investigated the global life cycle of this material, whether in the air, underground, or deep ocean. Nor as we know the 9.2 billion tons of plastic produced between 1950 and 2017, or one ton per person currently living on Earth, of which less than 10% is recycled.

Therefore, a group of Toulouse scientists began to work. The results of these members of the Laboratory of Functional Ecology and Environment and the Laboratory of Geology and Environment are not encouraging.

Millennia to “digest” microplastics

“Our research shows that even if we stop producing them in 2025, they will continue to be released into the environment, especially from the ground. And it will take decades for them to visibly disappear from terrestrial systems, and hundreds or even thousands of years to combine and digest these plastics in the deep ocean,” explains Gaël Le Roux, research director at CNRS and co-author of the published study. in a specialized journal Microplastics and non-plastics.

Projected distribution of plastics in land, oceans and atmosphere from 1950 to 20,000 years if production and release cease in 2025. – CNRS

To achieve this, they reviewed all available data on the presence of these plastics in all forms, from large plastics to nanoplastics, in urban areas, rural areas, remote areas of obvious pollution, deep oceans or oceans. but also in the atmosphere. They then assessed the reserves and reservoirs in these different areas, taking into account the progressive and slow degradation phenomena of this polluting material. And they ran their own mathematical model.

Land issues

So we can see that in 2015, according to their calculations, 3,500 million tons of plastic waste was “stored” on the ground, which is much more than the 82 million tons in the cliff, beaches (1.8 million) or coasts. surface of the oceans (0.3 million).

Diagram of the life cycle of plastics and microplastics between land, air and sea.
Diagram of the life cycle of plastics and microplastics between land, air and sea – CNRS

If public authorities have decided to act on the visible part of the problem, especially with decisions on plastic bags or household packaging, the challenge today is microscopic. “However, it takes a long time to eliminate them in the soil because they have to be eroded, transported to rivers and then to the ocean, which takes time to ‘digest’ and forces them to sink into the water. cliff In addition, some of the plastics that are present in the ocean are released back into the atmosphere, so we have a real cycle that takes time to diminish,” continues Gael Le Roux.

If awareness is anything to go by, France needs to do more than just ban plastic packaging. Especially since the trend in recent years has already gone in this direction, the planet has produced more plastic in the last twenty years than in the previous fifty years.

“Simple recommendations that can be adopted include not integrating plastic or waste into the soil without making sure that no micropollutants are already present. There are many process, such as sewage sludge, which tends to be applied to agricultural land and has no visibility. We also need to be able to predict where the pollution sources come from and what kind of plastics they are: polypropylene, polyethylene or blends of polymers,” concludes the scientist from Toulouse. For him, these questions can be the subject of a new study.

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