Plastic shopping bags: facts vs perception

“It used to be everyone was entitled to their own opinion, but not their own facts. But that’s not the case any more. Facts matter not at all. Perception is everything.” So said American writer and TV host Stephen Colbert and I agree.

Many people don’t appreciate being told that what they fervently believe to be true, actually isn’t.

The “gluten intolerant” folk turned on me, and not the bakery owner who was found — by a series in indisputable lab tests — to be passing off plain wheat rolls as gluten-free coconut flour ones, for example.

No amount of evidence will ever convince them that they’ve been duped. Try telling those who demonise plastic in any form that in many cases it’s the most environmentally friendly option and you are likely to be shouted down, no matter the evidence you produce.

With that in mind, the Council for Scientific and Industrial

Research (CSIR) recently released findings of a life cycle sustainability assessment (LCSA) of 16 different types of grocery carrier bags in SA, including the standard “single use” carrier bag you are given at around 75c each by the supermarket cashier if you don’t take your own.

Using funding from the department of science & innovation, the CSIR team looked at 21 environmental, social and economic impacts of the bag throughout its life cycle, like water and land use, global warming , plastic pollution impact as well as impacts on employment and affordability.

They concluded that reusable plastic carrier bags are the best option in SA, as they have a substantially lower environmental impact compared to single-use bags — provided consumers do re-use them.

The winner was a bag sold by Shoprite — their 70 micron HDPE “Planet” bag which retails for R3. Customers receive a 50c discount on their shopping each time the bag is reused.

And here’s the surprise for those who assume that brown paper bags are the most environmentally friendly option: generally, biodegradable plastic and paper carrier bags perform badly overall — except in terms of plastic pollution, of course — due mainly to their land and water use impacts.

So those brown bags may seem earthy, “natural” and retro, but their environmental impact may surprise some.

In this study the paper bag was rated the worst of all 16 bags in terms of land use and 12th in terms of water use.

And biodegradable bags — especially those made from a combination of imported polybutylene adipate terephthalate (PBAT) and starch — only outperform the standard 24-micron single-use plastic bags if the latter has a recycled content of 50% or less. Most supermarkets are moving towards 100% recycled content, if they are not there already.

“This study shows that ‘biodegradable’ doesn’t necessarily mean better — at least not for carrier bags,” says Anton Nahman, a principal environmental economist at the CSIR, who led the research team.

“Taking into account environmental and socio-economic impacts across the full product life cycle, the best-performing bags are all made from conventional plastics. In particular, the reusable ones are best — but only if they are reused as many times as possible.”

The single-use bags are best from an employment perspective. In particular, single-use paper bags perform well in terms of job creation, followed by 24 micron HDPE bags with 100% recycled content.

Those standard supermarket carrier bags are not supposed to be for single use. That was the whole point of legislation introduced back in 2003 forcing retailers to provide thicker plastic bags — at a cost, so consumers wouldn’t discard them.

“The other reusable bags — made from other types of plastics, such as polyester (recycled PET) and polypropylene — also perform well,” the report states. Pressed for examples, Nahman was happy to oblige. There are two kinds of polyester bags — woven and non-woven, that is spun bond and stitched.

While single-use bags rank lower, the best performing among them is the standard 24 micron HDPE plastic bag with 100% recycled content.

The higher the recycled content, the better the overall performance of the bag.

“The results of this research are important in evidencing how we manage single-use plastics in SA,” Dr Henry Roman, director of environmental services and technologies said.

“Though single-use plastics provide many benefits, there are also many avoidable plastic products that negatively impact our environment. Developing capability in life cycle sustainability assessment allows us to make informed decisions on the most appropriate material for product design.

Increasing the recycled content of products will also help to create a demand and a market for waste plastic, typically collected by informal waste reclaimers, helping to improve their livelihoods during a difficult time,” Professor Linda Godfrey, manager of the CSIR Waste Research Development and Innovation Roadmap Implementation Unit said.

So there you have it. Sciencebase facts versus perception.

We consumers get to choose what we do with that information, and the grocery retailers get to choose which bags they stock in their stores.

GET IN TOUCH: Contact Wendy at consumer@knowler.co.za or on Twitter @wendyknowler