- Biodegradable bags can actually survive three years in the natural environment, according to a new study.
- Researchers at the University of Plymouth found that while air broke up bags into fragments, in soil and sea environments they lasted a lot longer.
- Biodegradable, oxo-biodegradable, and conventional plastic bags were all functional as shopping bags after being in the soil and sea environments after three years.
- The team said their results raise several questions, including whether environmental and weather conditions are a realistic means of decomposing bags that are thrown away.
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You might want to think twice about buying “biodegradable” plastic bags if you’re environmentally-minded. A new study from the University of Plymouth, UK, has found that when bags labelled as biodegradable are thrown away, they can actually survive three years in nature – and they are intact enough to hold your shopping.
The researchers examined how well five plastic bag materials that are all widely available from UK retailers decomposed when exposed to air, soil, and sea environments – whether there was any loss of surface area, or changes in strength and chemical structure.
In the air, all the bags broke up into fragments. The compostable bags disappeared from the sea environment within three months, and were still present in the soil after 27 months.
But it was the biodegradable, oxo-biodegradable, and conventional plastic bags that were the most intact. They were all functional as shopping bags after being in the soil and sea environments after three years.
“After three years, I was really amazed that any of the bags could still hold a load of shopping,” said Imogen Napper, who led the study as part of her PhD.
“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.”
The team said their results raise several questions, including whether environmental and weather conditions are a realistic means of decomposing bags when they are thrown away, even if they are labelled as “biodegradable.”
Professor Richard Thompson OBE, the head of the International Marine Litter Research Unit, said the results of the study show that “biodegradable” materials don’t seem to show a “consistent, reliable and relevant advantage.”
“It concerns me that these novel materials also present challenges in recycling,” he said. “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.”
Even cotton shopping bags might not be as environmentally friendly as you’ve been led to believe. According to a Danish study, you may need to reuse yours for 11 and a half years before making any noticeable impact.
Also, according to the UK government, tote bags have a larger carbon footprint because of the resources needed to manufacture and distribute them.
About 100 billion plastic bags are issued every year, so every little change helps. But rather than looking for quick fixes, like buying biodegradable or cotton bags, it may be a better idea to try using any bags you have more than once, instead of simply throwing them away.
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