The truth about ‘bio-degradable’ plastic bags

Our new and improved environmental saviour of the turtles and whales, the bio-degradable plastic bag apparently is not. Nor does the compostable bag compost that well. Oh dear!

Greenpeace got the west all stirred up over “single-use” plastic bags and had them banned. So the enlightened switched to bio-degradable and compostable bags to save the planet.

Unfortunately, according to a study from University of Plymouth published in Environmental Science and Technology, all is not as promised. The abstract of the paper reads: quote.

There is clear evidence that discarded single-use carrier bags are accumulating in the environment.

As a result, various plastic formulations have been developed which state they deteriorate faster and/or have fewer impacts on the environment because their persistence is shorter.

This study examined biodegradable, oxo-biodegradable, compostable, and high-density polyethylene (i.e., a conventional plastic carrier bag) materials over a 3 year period.

These materials were exposed in three natural environments; open-air, buried in soil, and submersed in seawater, as well as in controlled laboratory conditions.

In the marine environment, the compostable bag completely disappeared within 3 months. However, the same compostable bag type was still present in the soil environment after 27 months but could no longer hold weight without tearing.

After 9 months exposure in the open-air, all bag materials had disintegrated into fragments.

Collectively, our results showed that none of the bags could be relied upon to show any substantial deterioration over a 3 year period in all of the environments.

It is therefore not clear that the oxo-biodegradable or biodegradable formulations provide sufficiently advanced rates of deterioration to be advantageous in the context of reducing marine litter, compared to conventional bags. end quote.

ACS Publications


The lead researcher Imogen Napper said that she was really amazed that any of the bags could still hold a load of shopping after three years.

I guess that is a fail, then. Can we have our useful plastic bags back, please?

The approved Whaleoil suggestion is to be a tidy Kiwi and to not discard any bag into the environment, be it single-use, paper, multi-use, bio-degradable, compostable or Louis Vuitton.

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