Breaking down what it truly means to be biodegradable
New research finds not all biodegradable shopping bags are born equal - but in SA we’re taking the right steps
How green is your valley, or in this context: how biodegradable is your shopping bag? According to new research, many bags marketed as “biodegradable” are only a slight improvement on conventional plastic carrier bags, because after three years they are still intact and a danger to the environment.
Lead author Imogen Napper, from the University of Plymouth in the UK, said “clear evidence” that single-use plastic bags were a menace to the environment prompted scientists to come up with healthier alternatives. This resulted in new products which manufacturers claim “deteriorate faster and have fewer impacts on the environment because their persistence is shorter”.
However, Napper’s study of different “biodegradable” bags in different environments over a three-year period had some surprising results – whether in the open air, buried in soil, or submersed in saltwater.
While the bags began deteriorating at different rates in the different environments, none of them truly biodegraded and some could even still hold a bag of groceries three years down the line.
“Collectively, our results showed that none of the bags could be relied upon to show any substantial deterioration over a three-year period in all of the environments,” said Napper. None of the formulations or products “provide sufficiently advanced rates of deterioration” compared to conventional bags.
The study, published in Environmental Science and Technology, raises questions about the marketing of “biodegradable” products, said Prof Richard Thompson, head of the research unit where the study was carried out.
“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.”
In SA, 90% of our flexible plastic products, such as shopping bags and food wrappings, are not biodegradable and cause havoc for the environment – but both private companies and government bodies are making strides to change this.
One such company is The Really Great Material Company (RGMC), which makes and distributes biodegradable shopping bags in SA after teaming up with an overseas company called Novamont.
Andrew Pollock, a co-founder of RGMC, said the bags are made from “non-edible plant-based materials”. Although they look and feel similar to plastic bags, their end-of-life journey “should be into a home compost system” but only after the bags have been used over and over again.
The bags are made from a variety of resins which break down and decompose naturally. They take weeks at the least and months at the most to do so, as opposed to the more than three years it took for the bags tested at the University of Plymouth.
The bags are already being picked up by some major retailers, while the governmental Council for Scientific and Industrial Research has also created a biodegradable bag and is looking to manufacture it.
Senior CSIR researcher Dr Sudhakar Muniyasamy said: “The environmentally friendly bioplastic products are derived from 100% renewable resources which are plant-based, and they can biodegrade in soil, compost and water within three to six months after end-of-life.”