The plastics industry is growing, and it’s a growing problem. Greater Sydney will run out of landfill capacity by 2030 unless major action is taken. Soft plastics — highly susceptible to fire as they are made from crude oil — are stockpiled in warehouses across Victoria following the demise of RedCycle and they have now become a serious fire hazard.
Concerningly, the use of plastic is showing no signs of slowing. Plastic use is poised to double globally by 2040*, in a sector valued at three times Australia’s GDP.
Plastic figures paint worrying picture on land and at sea
Plastics are tipped to outnumber fish in the ocean in just over a quarter of a century. Here in Australia we’re consuming plastic in huge quantities — including 70 billion pieces of ‘soft’ plastic such as shopping bags, trays and punnets. Of the 84% of used plastic we send to landfill, we’re only recycling – wait for it – less than 13% (which is predominantly PET and HDPE**).
Australia, we have a soft plastics problem
And the scale of the problem couldn’t be bigger in the area of soft plastics – – plastics known as Polyethylene and Polypropylene.
Soft plastics recycling is often in the too-difficult to-process basket,” says Dr Vipul Agarwal, UNSW Senior Lecturer – Cluster for Advanced Macromolecular Design (CAMD), School of Chemical Engineering.
The challenge of waste plastics recycling and the road ahead
“The recycling of soft plastics have traditionally been challenging for several reasons. Products made from soft plastics are often made from multiple layers of different polymers, which are combined together to deliver specific properties such as flexibility, strength, and moisture protection, for example.”
“Among the main issues with most widely used plastics recycling methods is that the process typically requires very high temperatures and therefore high energy use, and release greenhouse and toxic gases. Additives and dyes cannot be removed from plastics – such as those added for different applications.”
“Also, repeated heating leads to the breakdown of individual polymer chains in the plastic — which is one of the reasons why same waste cannot be recycled an infinite number of times, because each time the process is conducted, the polymer degrades resulting in loss of intrinsic properties making them unusable for value added product manufacturing.”
Contamination is another issue where the existing recycling methods predominantly rely on clean waste sources. The contamination could be the combination of mixed polymers, additives, dyes and residual material and dirt.
Not all doom, or gloom in the world of waste plastics recycling
Researchers from the University of NSW, Sydney (UNSW) have devised a novel, low-energy method for recycling plastic — an approach that has the potential to retain most of the intrinsic properties of the polymer by significantly reducing the degradation of the plastic (polymers) during recycling.
The new technology has been successfully translated to pilot scale using industrial scale processing.
The recycled soft plastics from this new technology can be used to manufacture virtually all kinds of value-added products including packaging materials, toys and automobile parts.
“Our method has the potential of causing no mechanical or chemical degradation of the polymer, so we believe it may be possible to recycle the plastic a higher number of times than using existing recycling processes,” says Dr Agarwal.
“In addition, there is no need for extensive cleaning of the waste plastic before it is recycled. This process also has the potential to separate the polymer from various additives such as dyes, eliminating one of the stages currently required in current recycling processes,” explains co-inventor Prof. Per Zetterlund (UNSW).
“The other advantages of this new technology are tolerance to mixed plastic waste allowing segregation of different waste plastics during the recycling process such as LDPE from HDPE and PP, and recycling of chemicals used in the process,” said Dr Agarwal.
“This is a completely new approach — any kind of waste plastic is processed polymer to polymer to resemble an ‘almond milk’ substance that can be processed and made into pellet-like materials that can be used to produce rolls — used to manufacture value added products.”
Australia: an untapped global recycling hub?
It has been estimated $419 million per year could be returned in economic value to Australia if it recovered all PET and HDPE, figures from the CSIRO indicate. This estimated figure does not include other soft plastics, LDPE and PP.
“By recovering and recycling all soft plastic waste, Australia has the potential to become a global recycling hub adding significant economic value both as a consumer of global waste and producer of recycled clean plastics,” says Dr Agarwal.
“We’re not just sitting on a pile of rubbish — we’re sitting on untapped potential.”
Watch a video about this innovative low-energy method to recycling plastic at https://www.youtube.com/watch?v=Xa3NGp-U_Ic
*Sources: Advanced recycling technologies to address Australia’s plastic waste; CSIRO 2021
**PET = polyethylene terephthalate
HDPE = high-density polyethylene
LDPE = low-density polyethylene
PP = polypropylene
Dr Vipul Agarwal is a Senior Lecturer at the University of New South Wales (UNSW). He joined UNSW in 2018 on a prestigious Australian National Health and Medical Research Council (NHMRC) Research Fellowship in the School of Chemical Engineering. Prior to this, he was awarded a SERB-DST National Postdoctoral Fellowship to undertake postdoctoral training at the Indian Institute of Science, India. Dr Agarwal graduated with a PhD in Chemistry from The University of Western Australia in 2015.
Dr Agarwal’s current research interest is in materials chemistry focusing on development of synthetic and fabrication strategies towards two- and three-dimensional polymer nanocomposites for a range of applications including neural tissue engineering. He has received a range of awards including a 2024 NSW Young Tall Poppy Award.
Picture courtesy Minna Sophia Manu