For most of us, hearing the world plastic makes us think of single-use plastics like plastic bags or disposable plastic water bottles, but plastic covers a much wider variety of materials than that.
- Plastics are versatile, flexible, durable and cheap
- These benefits become problems when we are trying to dispose of them
- Dealing with plastic waste requires both scientific and social solutions
They’re everywhere and have become an inescapable part of our lives, due to their versatility, flexibility, durability, affordability and because they’re relatively lightweight.
“The thing which I feel the public miss, is just how ubiquitous plastics are,” said chemist Michelle Coote of the Australian National University.
If we threw away all plastics, we wouldn’t have smartphones or insulation on our wires, Professor Coote pointed out.
“I think people don’t realise for example, all the plastic that goes into an aircraft, is in part what makes it possible for it to fly.”
Most plastics play a useful role by taking pressure off natural materials like wood, metal, leather, natural rubber and ivory, she said, and are in many ways cheaper and less harmful to the environment that their natural alternatives.
“It is not clear to me that the environment could sustain our current population without synthetic materials.”
What is plastic?
- Plastics are a type of polymer, a molecule made of small repeating units which join up to become a very long, larger chemical molecule
- Scientifically speaking not all polymers are plastics, although the terms are often used interchangeably in common parlance
- Cellulose, proteins and silk are all examples of naturally-occurring polymers
- Plastic polymers, along with chemical additives added during the production process to improve the performance, functionality or life of the plastic, give us the vast range of materials we use today
Tons of plastic
This isn’t to suggest that plastic is a good thing for the environment.
Since we first started mass producing it in the 1950s we’ve produced 8.3 billion tonnes of plastic, a 2017 Science Advances paper calculated.
And the bad news is that most of this plastic is still with us.
The authors found that, as of 2015, 6.3 billion tonnes of plastic waste had been generated, but only around 9 per cent of that had been recycled.
The rest had either been incinerated (12 per cent) or left to accumulate in landfill or the environment (79 per cent).
In 2016 alone, we produced 396 million tonnes of plastic, equivalent to 53 kilograms for every person on the planet.
Another study found around 40 per cent of that was for single-use products.
World Bank figures quoted in a recent report by Royal Society Te Aparangi (the Royal Society of New Zealand) on plastics in the environment showed Australians produce 117 grams of plastic waste per person per day.
That might not sound like a lot, until you realise that’s over 42kg per person per year.
The problem is many of the properties we fete in plastics when we’re using them are a curse when we want to get rid of them.
Most conventional plastics are made from fossil fuels, a non-renewable resource.
Chemical additives added during the manufacturing process to improve the performance, functionality or life of the plastic, can leach out into the environment and pose a potential hazard to health.
Scientists have identified environmental and health hazard ratings for different types of plastics.
Making new plastic is cheap, so they are not always cost-effective to recycle. And the huge variety of plastics makes the process of recycling them more complicated.
Plastic’s durability means it often persists in the environment rather than breaking down, as most aren’t biodegradable, and some you wouldn’t want to biodegrade anyway because of what they would break down to.
“What we know is that plastics don’t go away, they pretty much continue to break up not down,” said ecotoxicologist Scott Wilson of Macquarie University.
Which leads to the whole issue of microplastics and even nanoplastics.
As Sangwon Suh, professor of life cycle assessment at the University of California Santa Barbara said in a recent presentation, we can’t separate the benefits of plastics from the problems they create.
Professor Suh was also the co-author of a global assessment of plastic’s carbon footprint.
It found that if we continued on our current course, “greenhouse gas emissions from plastics would reach 15 per cent of the global carbon budget by 2050”.
So, what can we use instead?
We haven’t yet discovered a wonder material we could directly substitute for plastics that would give us all the benefits without the disadvantages.
“Many applications of plastics have natural alternatives,” Professor Coote said, “but… replacing everything we do now with these would cause an environmental disaster of its own.”
“The real question is can we make smarter plastics?”
Depending on what we would want to use them for, these could include plastics made from waste products that degrade into safe things in the environment, or last forever so they don’t need replacing, or are fully recyclable.
“If you think about it, the most environmentally friendly thing you can do is make a material last longer so you need less of it. And then control what happens to it after that,” she said.
Bioplastics are a group of plastics that are either bio-based, biodegradable or both, and are a potentially good alternative, Dr Wilson said.
“There needs to be a commercial-scale collection, processing and treatment for these products. Unfortunately these only exist on a small scale,” he said.
Compostable bioplastics can carry logos to show they meet the Australian standards for either industrial scale composting or home composting.
Other terms like “environmentally friendly” or “green plastic” are not regulated, Dr Wilson said.
Oxo-degradable bags, in particular, do more harm than good, firstly because they degrade into microplastics, and secondly because additives that were added to the bag to accelerate this degradation are also released into the environment, he said.
We are seeing an increase in the amount of bio-based plastics being produced.
Made from renewable resources like agricultural waste, sugarcane or corn, they generally produce less greenhouse gas emissions than conventional plastics, particularly if you use renewable energy to make them.
In 2017, we produced 2.05 million tonnes of bio-based plastics globally and that’s expected to grow by 20 per cent over the next five years.
A report in 2009 estimated that bio-based plastics could replace 90 per cent of their conventional counterparts.
While they don’t currently cover every application, with continual technological improvement Professor Suh predicts that bio-based plastics could replace all conventional plastics by 2050.
A social solution
In many ways, plastic waste is as much a social problem as a scientific one, Professor Coote said.
We need to look at how we can change our behaviour and recycle, re-use and reduce our demand for plastics, particularly single-use plastics, rather than only looking for a scientific solution.
“As a population, we need to not litter… we need to stop them entering landfill, but from an industry perspective we need to make them last longer, we need to make them easier to recycle,” she said.
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In cases when we can replace plastic with something else, like stainless steel, paper, wood or cast iron, we may find the replacement provides poorer technical quality, is more expensive or less durable.
“With any alternative there also needs to be a weighing up of the comparative environmental footprint of that process, including carbon usage and end-of-life outcomes,” Dr Wilson said.
For example, a European Commission report looked at single-use plastics and their alternatives.
It found that one use of a single-use polypropylene straw was responsible for less carbon dioxide emissions than one use of a single-use paper straw, or one use of a reusable steel or silicon straw.
Although the report did not consider what happened to these products at end of life.
“We’re never going to eliminate plastics, but we can be obviously more sensible about what products we use plastics for,” Dr Wilson said.