Apr 29 2019
According to a new study, compostable and biodegradable plastic bags can carry full loads of shopping even after being subjected to the natural environment for three years.
Plastic bags (Image credit: University of Plymouth)
Now, the degradation of five plastic bag materials, which are extensively available from high street retailers in the United Kingdom, has been investigated by scientists at the University of Plymouth.
The plastic bags were subsequently exposed to sea, soil, and air—environments which they can possibly come across if disposed of as litter. At regular intervals, the bags were tracked and deterioration was regarded in terms of visible loss in disintegration and surface area and also assessments of more subtle variations in chemical structure, surface texture, and tensile strength.
Following their exposure to the open air for nine months, all the materials had fully degraded into fragments. Yet, the oxo-biodegradable, biodegradable, and traditional plastic formulations continued to be functional as carrier bags even after being exposed to the marine environment or the soil for more than three years.
Within a period of three months, the compostable bag fully vanished from the experimental test rig in the marine setting. However, it was still present in the soil after a period of 27 months while exhibiting some signs of deterioration.
The scientists from the University’s International Marine Litter Research Unit, stated that the study, published in Environmental Science and Technology, poses several questions. Among them, the most relevant is whether biodegradable formulations can be depended upon to provide an adequately sophisticated degradation rate to offer any genuine solution to the plastic litter problem.
After three years, I was really amazed that any of the bags could still hold a load of shopping. For a biodegradable bag to be able to do that was the most surprising. When you see something labelled in that way, I think you automatically assume it will degrade more quickly than conventional bags. But, after three years at least, our research shows that might not be the case.
Imogen Napper, Study Lead and Research Fellow, International Marine Litter Research Unit, University of Plymouth
Napper headed the study as part of her PhD.
In the study, researchers cited a European Commission report in 2013 which indicated that approximately 100 billion plastic bags were being released each year, despite the fact that numerous governments (including the United Kingdom) have introduced charges designed to deal with this problem since that year.
It is believed that a majority of these items enter the marine environment, and earlier studies performed by the University of Plymouth have studied the impact of these items on coastal sediments and demonstrated that marine creatures can break them down into microplastics.
Professor and Head of the International Marine Litter Research Unit, Richard Thompson OBE participated in those studies and provided proof to the government inquiry which resulted in the introduction of the 5p levy.
This research raises a number of questions about what the public might expect when they see something labelled as biodegradable. We demonstrate here that the materials tested did not present any consistent, reliable and relevant advantage in the context of marine litter. It concerns me that these novel materials also present challenges in recycling. Our study emphasises the need for standards relating to degradable materials, clearly outlining the appropriate disposal pathway and rates of degradation that can be expected.
Richard Thompson OBE, Professor and Head, International Marine Litter Research Unit, University of Plymouth