Posted in | News | Pollution | Recycling

Comparison of Degradation of Biodegradable and Non-Biodegradable Plastic Bags in Three Natural Environments

The omnipresent plastic bag is easy to use for taking groceries and other items home from the store. But this convenience has an impact on the environment, with plastic debris spoiling waterways and land.

An oxo-biodegradable plastic bag could still hold 5 pounds of groceries without tearing after being submerged in the ocean for three years. (Image credit: American Chemical Society)

Although manufacturers provide compostable or biodegradable plastic bags, in several cases, these claims have not been investigated in natural environments. Currently, scientists reported in Environmental Science & Technology, an ACS journal, that the bags do not decompose in some places more quickly compared to regular polyethylene.

As per the European Commission, every year, approximately 100 billion plastic bags enter the European Union market. Many plastic bags are used only once and then discarded, rolled onto the ground or blown by the wind into oceans or lakes. Besides being unpleasant, plastic debris is harmful to ecosystems and animals. Some bag manufacturers provide plastics that decompose by microorganism actions, whereas others use oxo-biodegradable plastics carrying pro-oxidant additives to speed up the process.

Moreover, compostable plastics have the potential to degrade by microorganisms under controlled conditions. However, these promising solutions to the plastics problem have not been well studied in various environments for years. Hence, Imogen Napper and Richard Thompson decided to compare the degradation of various plastic bags in three natural environments for a period of three years.

The scientists placed plastic bags with labels as biodegradable, oxo-biodegradable or compostable, and conventional polyethylene bags in the open air, buried them in soil, or submerged them in seawater. Besides the compostable bag in the marine environment, which decomposed within three months, parts or whole samples of each bag type remained even after 27 months. After three years in the soil or sea, the conventional, biodegradable, and oxo-biodegradable bags had the potential to carry about 5 pounds of groceries without any damage.

The scientists came to the conclusion that no bags deteriorated for sure in all environments within a period of three years. The biodegradable bags did not deteriorate quickly in a consistent manner compared with the conventional polyethylene. As biodegradable bags could have the unexpected result of increased littering and are difficult to recycle in conventional waste streams, the scientists suggested that a better solution might be to motivate consumers to reuse shopping bags several times.

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