Originally published in NZ Life & Leisure magazine, Winter 2018
The problem of plastic in our oceans has suddenly become a mainstream issue but truly sustainable alternatives seem few and far between.
We are addicted to plastic in all of its guises – bottles, cups, food containers, cling film and general packaging, but the single-use plastic bag is the most insidious and damaging of the lot. They waft about on the wind, drift down rivers into the sea, smothering birds and strangling the insides of countless animals mistaking them for food.
A trillion bags are produced globally every year. If we could curtail the environmental disaster created by them alone, we’d be doing well. But where science initially showed a conscience-salving glimmer of hope in the form of biodegradable plastic bags, it has now revealed that we don’t actually have a clue whether these alternatives are any friendlier to the environment at all.
European researchers in May published a study in the journal Royal Society Open Science that reviewed a wide selection of published studies looking into the end-of-life fate of biodegradable plastic bags. It found them to be so wide-ranging in their protocols and the real-life testing so inadequate that they don’t give us any information that could usefully inform policies – such as whether a tax or ban on plastic bag use and incentives to use biodegradable or compostable replacements would make any difference.
The problem is that even biodegradable plastic bags that supposedly break down harmlessly within a few months in the environment, can perform very differently in landfill when mixed in with regular plastic and other household trash.
They can also leach acids or release gases in anaerobic marine habitats like salt marshes or brackish waters.
It is not as though there aren’t established standards for biodegradable plastics, which are typically made from plant-based materials featuring everything from corn starch to kiwifruit skins, rather than the petro-chemicals comprising disposable bags. The European Commission led the way in developing testing standards that measure things like disintegration of bioplastics, heavy metal concentration and “microbial respiratory gas evolution”.
The International Organization for Standardization (ISO) standards for bioplastics play a big role in regulating bioplastic production here in New Zealand.
A number of New Zealand companies are producing biodegradable plastics and even
compostable plastics that can break down to harmless mulch in as few as 90 days. The problem is that the materials need to be dealt with properly at the end of their life through dedicated composting and recycling schemes to perform as intended.
We don’t have the regulatory drivers in place to make that happen on a large scale, so a lot of bioplastics, produced with the best of intentions, are chucked out with regular rubbish ending up in landfill. Sadly, some of it misses the bin entirely, hence our current environmental dilemma.
“It would be risky to give the impression through a formal standard that plastic
biodegradation in the open environment is manageable if our underpinning knowledge still has significant gaps,” the researchers wrote.
Kiwi scientists agree.
“Biodegradable plastic bags are in many cases made from crude oil, requiring carbon-based production processes and are emitting CO2 or methane when degrading,” says AUT Professor of Engineering, Thomas Neitzert.
“A biodegradable plastic bag is potentially dangerous to marine life from the moment it enters the water until it dissolves into micro- or nanoparticles over many years,” he adds.
That’s a problem, because many retailers will understandably be looking at biodegradable plastic as a potential alternative as they respond to pressure to phase out standard single-use plastic bags, as the Warehouse Group, Foodstuffs and Countdown plan to do by the end of the year.
The stigma of plastic bags has led retailers and any business seeking a cheap giveaway emblazoned with their logo, to hand out free tote bags. I have a collection from various conferences I’ve attended. But even there, the research isn’t reassuring.
Extracting cotton consumes a lot of resources, particularly water, and a major UK study undertaken by the Department for Environment, Food and Rural Affairs, found that a cotton tote bag would have to be used 173 times to impact the environment less than a plastic bag used once.
Tote bags made from plant matter such as jute or hemp can have less of an impact, but it depends on how they are farmed and harvested. Still Professor Neitzert advises their use over plastic.
“On the way to a low carbon economy, we should carry a reusable bag made from cloth or jute, like our parents did,” he says.
New Zealand scientists aren’t giving up on bioplastics just yet. But we need to get smarter about how we produce them, and better manage them through their entire lifecycle.
“It would be best to design products from the outset with end of life in mind,” says Professor Kim Pickering, from the University of Waikato’s School of Engineering.
“Consider what additives are used in simple products like biodegradable plastic bags and films and look for ways to add value to waste plastic, taking more account of the environmental cost in their price so things are more likely to be used more than once,” he suggests.
It doesn’t help that recycling now has a tainted reputation, particularly since China recused itself as the dumping ground for the world’s used plastic, leaving pallets of bottles and containers piling up in recycling centres the world over.
A solution to all of this is fairly urgent. As I wrote this, associate environment minister Eugenie Sage was mulling over a levy or outright ban on single-use plastic bags.
The bag-stuffed pilot whale dying on a Thai beach, the floating garbage patch of plastic in the pacific, the pelican with a bag over its head. The evidence of our plastic littering is starting to serve to shame us into action. But it needs to be the right action for the planet.
On that front science, our government and we as consumers have a lot of work left to do to replace our plastic fetish with something far less destructive.