We need plastics — how do we avoid choking the planet with them?
Technologies for biodegradable and more easily recyclable plastics could help solve our plastic problem
Originally published on May 18, 2019.
Plastic's unique combination of durability and disposability is turning out to be a deeply problematic issue for our planet.
In recent years a disturbing amount of research has catalogued the degree to which discarded plastic has contaminated every ecosystem. Plastic debris and microplastic particles have been found in oceans, lakes and rivers all over the world, on the highest mountaintops, embedded in arctic ice and in agricultural soil.
But researchers are developing new technologies that could reduce its persistence and increase our ability to reuse it, which could reduce the amount of plastic that's escaping into the environment.
Underlining this was a report in May that an explorer in a submarine descended into the Marianas Trench — the deepest part of the Pacific Ocean, 11 km below the surface — and found plastic debris.
"It's not just the plastic itself that is inside of our products. There's also different additives," said plastics researcher Love-Ese Chile. "Some of those additives are toxic. And when the plastic does get out into the environment, you end up also adding some of those different toxins into the environment as well."
The future is in plastics
The bright side of plastic is that it's an incredibly useful material that has become essential to our modern lifestyle. We eat from plastic plates with plastic cutlery and drink from plastic cups and bottles. We wear clothes made of or with plastic fibres.
Our vehicles contain plastics, and our homes and offices are filled with plastic, from our electronics to our furniture to the carpets beneath our feet. Life-saving medical technologies from blood bags to artificial joints are made of plastic.
To a certain extent we can wean ourselves from the wasteful uses of plastic, but we can't eliminate the ones that have become essential.
That's why researchers are hoping to make this wonderful, terrible material a little more environmentally benign.
Bioplastics: From nature, to nature
One approach is to try and reduce the problem of persistent plastics in the environment. And a key material being developed to help with this is bioplastic.
Most plastic we use is petroleum-based, which is inexpensive, but carries a significant environmental burden both in manufacture and in disposal. One of the valuable features of these plastics is their durability as they typically don't break down in the environment. Micro-organisms that break down materials like wood or natural textiles, typically can't break down plastics, and they're often immune to the chemical reactions that break down materials like metals.
Chile, a bioplastics researcher and consultant with the Vancouver-based Grey To Green Sustainable Solutions, told Quirks & Quarks host Bob McDonald that bioplastics have important differences from petroleum-based plastics.
"They try to solve the problem of how plastics are made or where they come from. Many bioplastics are made from biological sources so you can use things like corn husks or agricultural or food waste to make it plastic," she said. "But then, on the other side of the coin, some bioplastics try to solve the problem of plastic pollution. And so instead of being really persistent and quite long-lasting, they are biodegradable."
Redesigning for recycling
Another major problem we face with plastics is the difficulty of recycling them.
Recycling traditional plastics can be difficult for many reasons. An essential one is that plastic is not one material. There are a range of different types with different properties, and they're further altered with additives like glues, flame retardants and colours. These mixed materials are very hard to separate, and so recycled plastic is often a low-grade, low-value material, said plastics researcher Peter Christensen.
"The recycled material can have a significantly lower value in terms of how you could reuse it to make new products. Grinding up old plastic and melting it down and turning it into a new shape actually chemically degrades the material and for that reason you can only reuse a certain percentage and that percentage is typically very low," he said.
Christenson, a a postdoctoral researcher at the Lawrence Berkeley National Laboratory in California, has been working on developing a new kind of plastic that is designed to be recyclable.
The new material, called polydiketoenamine, or PDK, has bonds between the individual chemical building blocks, or monomers, that can be easily broken down using a process that involves water and a type of strong acid. The disassembled building blocks can then be reconstituted into pristine new material.
The disassembly process also separates out any other additives that had been integrated into the plastic.
"You can remove all of the colour, you can remove all of the additives, the flame retardants carbon fibre or fibreglass or everything that's added to the plastic to make it the product," said Christensen.
"Then you make that same plastic again without ever losing any of the properties. … You could recycle a very hard plastic into something that's very stretchy or something that's very stretchy into something hard."
One key benefit of this this material is the way it might impact the recycling system. Discarded PDK plastic could be recycled into a more valuable material. In this way, the disassembled plastic "creates an incentive for the recovery of this material from its end of life," said Christensen.
However, PDK has some way to go before it makes it out of the lab and into large scale production, he said.
"We have to figure out how to make this stuff with the lowest level of environmental and human toxicity as possible, the lowest carbon footprint possible the lowest water usage. Then the exciting part is to be able to work with designers to build actual products that also have a very low carbon footprint [and] low water usage, and are not harmful to people in the environment."