Australian scientists have successfully used backyard mould to break down one of the world's most stubborn plastics — a discovery they hope could ease the burden of the global recycling crisis within years.
Experiments conducted by researchers at the University of Sydney, published in science journal npj Materials Degradation, found that two types of fungi could be harnessed to attack small samples of polypropylene, which is used to make items like takeaway containers, ice-cream tubs and cling film.
The fungi — Aspergillus terreus and Engyodontium album — are usually found in plants and soil.
It took 90 days for the fungi to degrade 27 per cent of the plastic tested, and about 140 days to completely break it down, after the samples were exposed to ultraviolet rays or heat.
Chemical engineering professor Ali Abbas, who supervised the research team, said the findings were significant.
"It's the highest degradation rate reported in the literature that we know in the world," the professor said.
Despite being recyclable, an estimated 13,500 tonnes of polypropylene ends up in Australian landfill every year because it is contaminated or mixed with other materials.
Professor Abbas said he was "very confident" the technology could be scaled up to process thousands of tonnes of plastic a year, because the same techniques were already being used in different fields.
"It is scaling up which is very much similar to any kind of fermentation process," he said.
"That technology already exists for those processes and we're able to now borrow that learning from chemical process engineering and bring it into this particular process here."
The challenge for researchers will be expanding any possible solution to address the nation's mounting piles of soft plastic.
The collapse of the national REDcycle scheme last year exposed big problems with Australia's plastic recycling systems and left most Australians without a way to recycle soft plastic.
Researchers will now try to make the degradation process faster and more efficient by tweaking key aspects of the process such as temperatures, the size of plastic particles and how much fungus is used.
Professor Abbas said scaling up the process could take between three to five years.
"Or even sooner should the investment be ready and available for us to accelerate that," he said.
Could we really see a solution within five years?
Yes we could, according to environmental scientist Paul Harvey, an expert on global plastic pollution who was not involved in the research.
"That is a fairly standard time frame for standing-start research through to commercialisation," Dr Harvey said.
He said it could and should be even sooner.
"There's really no reason why this type of research can't get expedited, given the enormous issues that we have globally, in terms of waste management and plastic pollution management," Dr Harvey said.
So does this mean I can use as much plastic as I want?
Absolutely not, say the experts.
While the technology may be a few years away, Dr Harvey said Australia still needed multiple ways to manage waste and plastic pollution because the environmental crisis continued to worsen.
A 2020 paper published in ACS Sustainable Chemistry and Engineering found that humans were generating 400 million tonnes of plastic waste per year.
About 175 million tonnes of that is sent to landfill or pollutes the environment. That amount would be enough to rebuild a 6,000km stretch of the Great Wall of China every 12 months.
"We have an addiction to plastic and we're not getting any better at kicking that addiction," Dr Harvey said.
"We, as a country, don't seem to get the enormity of the plastic pollution problem that we are facing.
"And we don't seem to get the fact that we need to be reducing our plastic waste because we don't have the room for it in landfills, we don't have the strategies in place for managing plastic waste and we're generating far, far too much of it."
Professor Abbas, who led the University of Sydney team, agreed.
"We can't afford to wait, we do need to act," he said.
"The technology itself may be ready, as we said, within the next few years. That however will not solve the problem alone.
"We need the behavioural issues, we need the social issues, we need the business issues, all of these need to be resolved around the plastics problem. The technology is only half the solution."
What's the next step?
The University of Sydney scientists are now working on something called proof of concept, which is evidence that their solution is feasible.
They will do this by building a "bench-scale prototype", which tests chemical processes on a small scale.
"That's the chemical engineering work that we do in scaling up and allowing us to prove the process at scale technically, economically, environmentally and then we can carry that out into the commercial scale," Professor Abbas said.
"So as we develop the technology over the next, say, five years, we're able to see clearer how close we are to a commercial-ready plant."
What could this solution look like?
Dr Harvey said the fungi were unlikely to become an off-the-shelf solution that consumers could buy at the hardware store.
"But you might see them being used in large-scale industrial applications or commercial applications, and so that might be in municipal waste management facilities," he said.
And that technology could have major implications for regional Australia.
"If you've got a town that has very limited waste management infrastructure but is able to use a fungus or a bacteria or an enzyme to treat their waste stockpiles and they can turn that waste stockpile into a lower mass stockpile … then that's a great thing," Dr Harvey said.
"It also means that they can process their waste in their regional location.
"One of the biggest challenges outside of the metro and city areas is how do you process and treat the enormous amount of waste that is produced in areas where there's very low population, but a substantial amount of waste that still needs to be managed."
Is this the only solution scientists are working on?
There is a lot of research being conducted in this space.
The experiment from the University of Sydney adds to a growing body of research around things like algae, bacteria, enzymes and fungi to break down plastic.
But a lot of work is also being done on pyrolysis and incineration, which is the burning of materials.
"That's concerning in and of itself because while, yes, we're producing energy from burning the waste, it's not really a sensible use of resource because it's a bit like burning fossil fuels," Dr Harvey said.
"Once it's gone, it's gone but it also creates a by-product which is problematic in and of itself.
"And so while, yes, that will help to combat the amount of waste that enters into the environment, for me it's not a long-term solution."
That should also be a consideration for scientists in the fungi experiment, according to Colin Jackson from the Australian National University.
Dr Jackson, who is also the chief science officer at a private company that uses enzymes to break down plastics before remaking them, said there needed to be a conversation about whether plastic should be recycled or metabolised by fungi.
"This is because of the greenhouse gases that could be ultimately released if the plastic goes from being in a solid form where all the carbon is sequestered to being essentially, eventually turned into CO2," Dr Jackson said.
"That again has to be balanced because you're stopping the production of new plastic which also generates a huge amount of carbon dioxide as well, so it's not necessarily that it's a bad thing, it's just that more circular solutions where the carbon is returned back into plastic might be better in terms of greenhouse gases."
