Can we throw away “biodegradable plastics” as they will naturally degrade? Stop…

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Can “degradable plastic” be naturally degraded if just thrown away?

In order to solve the plastic problem, "degradable plastics" have appeared on the market in recent years. Many people think that they can be thrown away at will and these plastics will degrade naturally in nature.

Rumor Analysis

This statement is not appropriate.

The degradation conditions of "degradable plastics" are actually very harsh. The decomposition rate of most degradable plastics in the natural environment is much lower than market publicity, and may even bring new pollution problems.

In recent years, plastic pollution has become a major problem for the global environment. The plastic waste that can be seen everywhere and blows in the wind is not only unsightly, but also poses a threat to our earth's ecosystem and even affects human health. In order to solve this problem, "degradable plastics" have appeared on the market in recent years, and are often promoted by businesses as the ultimate solution to plastic pollution.

However, is this really the case?

The name "degradable plastic" actually misleads most ordinary consumers. People often think that this is an "environmentally friendly material" and these "degradable plastic" products can be thrown away after use. In fact, many people do not know that the degradation conditions of so-called "degradable plastics" are actually very harsh. A report by the United Nations Environment Program (UNEP) pointed out that the decomposition rate of most degradable plastics in the natural environment is much lower than market propaganda, and may even bring new pollution problems.

Biodegradable plastics are not really “biodegradable”

"Biodegradable plastics" is a class of plastic materials that includes dozens of materials and can be decomposed into small molecules (such as carbon dioxide, water, methane or biomass) under specific environmental conditions (such as microbial action, light, moisture, oxygen, etc.).

According to different degradation methods, degradable plastics mainly include: biodegradable plastics, photodegradable plastics and oxidative degradable plastics. Based on different raw material sources, these materials can be divided into bio-based degradable plastics made from biomass and fossil-based degradable plastics made from fossil raw materials.

These different types of degradable plastics have different properties and degradation requirements. Different countries also have different standards and requirements for such materials, making them difficult to unify.

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In real life, many people think that as long as it is "degradable plastic", it can be thrown away at will. These plastics can disappear quickly and are truly environmentally friendly materials. But the fact is that different degradable plastics usually require specific degradation conditions to achieve degradation. Taking the common polylactic acid degradable plastic (PLA) as an example, PLA needs to be in an industrial composting environment, such as high temperature (above 50°C), high humidity and the action of specific microorganisms, for a period of time before it can be degraded.

In the natural environment, such as the ocean, soil or ordinary landfills, PLA degrades almost as slowly as traditional plastics. A 2017 scientific study confirmed that in marine and freshwater environments, the degradation rate of PLA, which is currently common in the market, is almost the same as that of our common traditional plastic materials (PET).

May bring more serious microplastic pollution

Even if biodegradable plastics begin to decompose, they may not disappear completely. Instead, they may turn into smaller plastic particles - microplastics .

In 2010, the Agricultural University of Athens studied the degradation behavior of polylactic acid (PLA) films and fibers in a natural Mediterranean soil environment. The experiment lasted for 11 months. The results showed that the PLA samples only partially physically decomposed and slightly fragmented. These disintegrated microplastics easily enter the water and are ingested by marine organisms such as fish and shellfish, and may eventually appear on our dining tables through the food chain.

Another study in 2019 showed that each person in the world may ingest about 50,000 microplastics through food and drinking water each year, and incomplete degradation of biodegradable plastics may make the problem worse.

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Reducing waste from the source is the fundamental solution

"Degradable plastics" is a positive exploration to solve the plastic problem. Perhaps one day we will see plastics that can really degrade quickly in nature. But as far as current technology is concerned, current degradable plastics do not really solve the fundamental problem, and may even bring new environmental burdens and health risks.

In addition, we should note that "degradable" plastic does not mean it is "disposable". Degradable plastic can also be recycled. Scientific and standardized recycling may reduce the generation of plastic waste.

Reducing the use of plastics at the source, increasing the possibility of reuse, properly recycling and reusing, and changing the linear model of continuous consumption through the practice of circular economy may be a better way to deal with plastic pollution at present.

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As ordinary consumers, we should avoid unnecessary use and waste of plastic products as much as possible, reuse shopping bags, tableware, water bottles and other daily necessities as much as possible , and reduce the use of disposable plastics from the source in our lives. This is the most direct and effective environmental protection measure.

Looking in the mirror of rumors

Some rumors come from the deviation between scientific concepts and our understanding of concepts. For example, the term "degradable plastic" was created to distinguish it from traditional plastics, but it does not mean that it can be quickly degraded in any environment. We should pay attention to the context and meaning of some words and not simply take them literally.

References

[1] UNEP, From Pollution to Solutions: A Global Assessment of Marine Litter and Plastic Pollution, 2021 https://www.unep.org/en/resources/congwurandaojiejuefanganquanqiuhaiyanglajihesuliaowuranpinggu

[2]Fate of So-Called Biodegradable Polymers in Seawater and Freshwater https://pubmed.ncbi.nlm.nih.gov/31565274/

[3]Human Consumption of Microplastics https://pubs.acs.org/doi/abs/10.1021/acs.est.9b01517

[4] WWF, Tackling plastic pollution through accountability https://www.wwfchina.org/content/press/publication/2019/%E6%9C%80%E7%BB%88%E7%A1%AE%E8%AE%A4%E7%89%88WWF%20PLASTIC%20REPORT%20FINAL(8.29).pdf

[5] Greenpeace, Decoding “degradable plastics”: definition, production, application and disposal https://www.greenpeace.org.cn/2020/12/30/degradable-plastics-report-20201230/

[6]E. Rudnik, Department of Agricultural Engineering, Agricultural University of Athens, Iera, Degradation behavior of poly(lactic acid) films and fibers in soil under Mediterranean field conditions and laboratory simulations testing https://www.sciencedirect.com/science/article/abs/pii/S0926669010003511

Author: Eric Popular Science Creator

Reviewer: Wang Xinhong, Professor of the School of Environment and Ecology, Xiamen University

Planning丨He Tong

Editor: He Tong

Proofread by Xu Lailinlin

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