The big problem with plans to replace the supermarket plastic bag

As the world wakes up to the environmental disaster of plastic bags, shoppers are wondering what is going to replace them.

After Australian states and territories introduced plastic bag bans, supermarkets like Woolworths have recently begun offering alternatives such as paper bags.

But much to the chagrin of eco-conscious consumers, it’s hard to go into a supermarket these days and not be frustrated by the overwhelming presence of plastic. Whether it’s plastic bags for the vegetables or bananas and apples wrapped in the stuff, it’s clear our plastic problem isn’t disappearing any time soon.

A shopper is seen carrying bags at a Coles Sydney CBD. Source: AAP
Researchers are working on viable alternatives to the plastic bag. Source: AAP

The hunt to replace the plastic bag

But the fact that environmentally friendly alternatives aren’t more readily available, is not for a lack of trying.

“There are synthetic polymers which have properties that are great, but they’re much more expensive,” says Graeme George, Emeritus Professor at Queensland University of Technology.

One of those is known polyhydroxybutyrate, or PHB. It’s among a class of plastics which are bio-derived and biodegradable. Because PHB is made by microorganisms it decomposes when buried in soil.

“We’ve had this plastic since the 1970s, so coming up to 50 years now and it hasn’t been able to be fully commercialised,” Prof George explained.

“Why has it taken 50 years? It’s the same question of cost.”

Traditional plastic bags are made from ethylene, derived from petroleum or natural gas which does not degrade easily and as a result, they mostly end up in landfill. But the process of making them is highly automated, cheap and their properties are perfect for their purpose.

Biodegradable plastic bags too expensive

Despite all the work that has been done, biodegradable alternatives are still more expensive by a factor of about 10.

Prof George, who has made a career in macromolecular and materials chemistry and studying the environmental issues of plastics, says there is one material that has been getting a lot of attention due to its potential to replace standard plastic bags at a low cost: starch.

“We’re more familiar as starch as a food stuff than anything else,” he conceded, but starch-based polymers could provide a cheaper source of biodegradable plastic material, although so far it lacks the sturdiness of regular plastic bags.

Nonetheless, such alternatives have been trialled in Australia recently. Last year, light-weight “compostable” bags for fruit and vegetables made from 98 per cent corn starch were trialled in two south Australian supermarkets.

A picture of a compostable bags which are more expensive to make. Source: Facebook
Compostable bags are available, if consumers are willing to pay the extra cost. Source: Facebook

Do ‘biodegradable’ bags really break down?

There are options already on the market claiming to be biodegradable, but consumers should check the fine print. Many of them are quite likely oxo-biodegradable and break down and crumble not due to microbes but require heat and sunlight.

In many cases, they are just normal polyethylene and have an additive that has been included to accelerate the breakdown due to heat and light, Prof George said.

“They will break apart but the fragments are very slowly biodegradable … it might take decades.

“A true biodegradable material should not need heat and light to break down it should break down when it’s buried or in compost.”

Australia has strict standards on what constitutes a compostable plastic (which Prof George helped write) but there is a concern that consumers will believe such materials can be easily discarded and will break down in any environment, when in fact they actually need to be properly composted.

“Things are going to take a finite time to degrade no matter what,” Prof George said. “You’re not going to be able to get a strong plastic bag that you can flush down the loo.”

When disposed of correctly, genuine compostable plastic should biodegrade completely in about six months – a big improvement on the many centuries it can take for a normal plastic bag to break down in landfill.

“There are a number of material around which are able to meet the compostable standard. The whole issue is industry will step and up provide the material as long as people are prepared to pay the price,” Prof George said.

“If we wan’t to protect our environment, we have to spend money.”

Reports of Aldi introducing biodegradable bags in 2020 false

A number of reports circulating online in recent months claim that German supermarket giant Aldi is set to begin offering biodegradable bags at its stores in 2020.

However despite the enthusiasm of some environmentalists, Aldi told Yahoo News Australia that the supermarket chain has no immediate plans to replace reusable plastic bags with compostable ones next year.

Nonetheless, news of the move, albeit fake news, prompted customers this month to demand the same of supermarket giants Coles and Woolworths.

“'s time to bring these to your stores,” one customer demanded last week on the Woolworths Facebook page.

A seperate customer suggested the same for Coles. “An idea for your fruit and veg department,” they wrote. “Scrap the plastic for compostable bags.”

There seems to be little escape from plastic in the fruit and veg section. Source: AAP
There seems to be little escape from plastic in the fruit and veg section. Source: AAP

A Woolworths worker responded by saying it would take the feedback on board and that the company was “working hard to reduce the amount of plastic used across our stores”.

Meanwhile a Coles worker said it would pass the suggestion on to its Sustainability Team for consideration and pointed out that its plastic bags can be recycled in store.

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