With ‘forever chemicals’ a risk to New Zealand’s drinking water, a team from the University of Auckland has had promising early results using the plant to remove chemicals from water.
David Barker was at his kids’ school helping out after some harakeke bushes had been cut down when he started wondering if there was more to the plant than met the eye. He was helping the children use harakeke to practice weaving, when he got talking to a Māori parent who told him how harakeke can clean water. While the living plants clean water with their roots, Barker, a chemical scientist and professor at the University of Auckland, started wondering if their leaf fibres might have the potential to treat water.
Initially, he tried to see if harakeke, which grows across Aotearoa and attracts tuī, would bind to nitrate and phosphate pollutants in water, but the substance didn’t pick up enough of these chemicals to be useful. But researchers at the University of Auckland spun their own project off Barker’s testing and started eyeing forever chemicals.
Fast forward and the researchers have conducted experiments that show the native plant outperforms other treatment methods in removing forever chemicals from water. “Its different chemical properties just seem to be a good match for the harakeke,” Barker says.
PFAS – short for perfluoroalkyl and polyfluoroalkyl substances – are known as forever chemicals because these molecules endure. They take so long to degrade that scientists can’t even measure the length of time it takes. Forever chemicals are used in the manufacture of smooth coatings for a variety of products, including non-stick frypan coatings, raincoat waterproofing and cosmetics like mascara. While not acutely toxic, the chemicals impede immune system function and due to their longevity, accumulate in the environment. They will be banned from use in cosmetics in New Zealand from the end of 2026.
Shailja Data, a PhD student at the University of Auckland, who has been working on the harakeke research, says forever chemicals pose a challenge. “The very same properties that make PFAS good [for manufacturing] mean it’s not good for the environment or human health, it can keep building up until it’s at a harmful level.”
Data says the team treated harakeke fibres to create a positive charge. They then shake water samples and the fibres attract negatively charged PFAS, removing 70% to 99% of them. Data puts it simply: “It pulls [the PFAS] off the water.”
Harakeke fibres are sturdy and rigid, which makes them ideal for immersion in water as they don’t degrade quickly, Data says. They also won’t create a source of microplastics, which might happen if a plastic filter was used.
The team has focused on short-chain PFAS, which are often used as a replacement when longer-chain PFAS are banned. While the molecules on short-chain PFAs are smaller, they last just as long in the environment. “It’s called ‘regrettable substitution’,” Data says. The short or ultra-short chain PFAS are super difficult to remove, she says, and most PFAS treatment has been developed for traditional, longer PFAS, so treating short-chain PFAS in drinking water supplies around the world is an important public health issue.
Testing has shown low amounts of PFAS in New Zealand waters, but PFAS-containing products continue to break down and enter the environment, and have been found in drinking water supplies. Data says this is why their research has focused on drinking water. “It’s an exposure route for PFAS in humans.”
So, if harakeke fibres catch the PFAS, what happens to them next? Data says petrochemical-treated single-use products have previously been used to remove PFAS from water, but the great thing about harakeke treatment is the chemicals can be washed off the fibres using a solvent. This results in a concentrated form of the chemicals which can be destroyed by breaking the carbon-fluorine bonds, instead of returning them to the water system. The harakeke fibres can then be reused for filtration, meaning a potential filter product is longer lasting.
While the experiments show harakake holds great promise, its use at scale is a long way off. As no PFAS are manufactured in Aotearoa, there are fewer present in the environment than in other parts of the world.
The scientists also acknowledge tackling water contamination is complex. “We have limited data about PFAS in New Zealand – we need to know how we’re getting exposed,” says Data. She says more information is needed about kaimoana, agriculture and PFAS in endemic species because international studies may not be relevant to New Zealand.
“While we can certainly reduce the practices that cause pollution, it’s probably not going to ever completely stop… especially for long-lasting pollutants like PFAS,” says Barker. “Having materials that can remove pollutants is critical for all our health.”
Data would like to see how harakeke works treating PFAS in low concentrations, and she wants to continue trialling more efficient ways to treat and reuse the fibre. “The experiments were in lab conditions – in the real world, there are different variables, different ions, more organic matter – it would be exciting to understand how it performs.”
Still, Barker thinks there are huge possibilities, particularly as harakeke grows across New Zealand, making it potentially an affordable, sustainable, regenerative industry. “We wanted to use fibres available locally so that if projects were successful then potentially we could develop locally, he says. “There is a growing group of farmers, small companies and iwi who are very interested in growing harakeke as a commercial crop.”
Harakeke is already being used innovatively. One company, Kiwifibre, is making carbon-fibre replacement materials and another, Biotenax, is creating yarns which could replace synthetic fibres.
Of course, for centuries Māori have used the plant and its inner muka fibres to make baskets, traps, cloaks and more. Barker says that working with matauranga has been fascinating. “Harakeke is a taonga species. Working with Māori researchers, I’ve understood how deep the connections with the plants are.”
