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ScienceOctober 17, 2023

What is nano-recycling, and why is it so important?

the recycling sign that is green-tinted
Image: Tina Tiller

To celebrate Recycling Week, Vanessa Young explains the essential role of nano-recycling in making the most of the tiny-scale but potentially harmful waste from batteries, circuit boards and more.

For most of us recycling means cans, jars, bottles and tins – and the sprint to get the bin out as the truck comes up the street. If we get fancy, we might think about the different types of plastic and what can and cannot be recycled. Beyond that we don’t generally give it much thought. 

But there’s a whole world of recycling that we literally can’t see: nano-recycling. Although not yet in the Oxford Dictionary, nano-recycling is happening in labs all around this country. And no, it isn’t when your neighbour only recycles a small amount of their waste. We’re talking about upcycling the lithium from battery cathodes, pulling the gold out of e-waste, recycling proteins from hoki fish eyes into corneal tissue and recycling acid waste from the galvanised steel industry. 

What these all have in common is that they involve materials science and the nanoscale.

Working with hoki fish eyes, a waste by-product from the fishing industry, Dr Laura Domigan extracts sufficient quantities of nanoscale crystallin proteins to look at using these to repair or replace corneal tissue in human eyes, and to make transparent biomaterials – namely thin films, gels and adhesives.

Dr Laura Domigan (Photo: Supplied)

The cornea is the exquisitely composed tissue that covers the eye. It can tear and malfunction for a variety of reasons, and need replacing or repairing. “Over 250 corneal transplants are performed in New Zealand every year, but as with all organ transplants, the number is limited by donors. There simply aren’t enough of them,” says Domigan. 

Domigan, a MacDiarmid Institute and University of Auckland researcher who was a finalist in this year’s KiwiNet Commercialisation awards, says her dream is to be able to construct or repair a structure that nature has taken billions of years to design: the eye.

She is collaborating with her colleagues in the department of ophthalmology at the Faculty of Medical and Health Sciences to make synthetic or naturally derived surgical products and implants. “It’s like any materials science problem – we need to look for the properties we need, and then search and experiment with materials till we find the right one,” she says.

It’s not the only nanoscale work going on in her lab. Each month a couple of her students head to a slaughterhouse in Auckland’s Great South Road to collect blood in 2L bottles. Back at the university, they extract haemoglobin from the waste and nano-recycle it, electrospinning it into nanofibres for fibrous scaffolds to mimic natural tissue, with potential applications in medicine.

“These biomaterials, like the hoki fish eye proteins, may be good for tissue engineering, or could be turned into bio-based inks for 3D printing,” she says. 

The eyes have it (Photo: Supplied)

Currently most electronic waste (e-waste) heads into landfills, where it becomes a modern-day buried treasure. The gold discarded as e-waste worldwide is estimated to be worth an estimated NZ$37 billion per year alone. 

Mint Innovation is reclaiming high value elements from e-waste, using smart chemistry and natural biomass to pull out gold, copper and palladium from the green printed circuit boards in old computers, and recycling the other components including plastic, ceramics and glass fibres into building materials.

The concentration of gold in printed circuit boards is 50-100 times higher than in gold ore, says R&D lead Dr Rob Staniland. As he explains it, Mint Innovation’s process dissolves the elemental gold, after which the natural biomass then acts like a molecular sponge, sucking up the gold ions selectively.

This clean-tech company reached commercial-scale success this year, with the world’s first “biorefinery” operating in Sydney, Australia, to service PCB waste collected and recirculate the “green” metals collected back into the Australian economy. Mint’s next steps are to rapidly scale their low-carbon technology to other urban locations around the globe to significantly reduce the excessive amounts of e-waste currently sent to landfills. 

There are well-paved roads to the company itself from university labs, with five MacDiarmid Institute PhD alumni (including Staniland himself) now working for the company.

The growth in EVs presents a need to find better ways of recycling their batteries (Photo: The Warehouse Group)

A significant amount of research is being done to prevent batteries becoming the next plastic waste crisis. A battery dies because the electrode loses functionality. Batteries can be smelted down – but this leaves a huge carbon footprint.

The Ministry of Transport predicts New Zealand will have 1.9 million EVs by 2039/40 and this presents a huge need to find better ways of recycling batteries. Peng Cao, a MacDiarmid Institute researcher and associate professor in chemical and materials engineering at the University of Auckland says smelting and extracting valuable metals is viable only for the first generation of batteries, as the second generation have much less or even no cobalt and are therefore less valuable.

“Considering that car batteries have an 8-10 year lifespan, with EVs increasing in number so much, in ten years’ time this will be a problem,” says Cao. “Car batteries will become another plastics disaster if we don’t start working right now.”

Cao is part of a Vector Energy-led battery innovation working group of New Zealand companies and researchers. He is working at the nanoscale to upcycle lithium from cathodes, and refurbishing the electrode with lithium, nickel, cobalt and manganese. A new class of chemicals called metal-organic frameworks (MOFs), is able to sieve out carbon dioxide from gas streams. The carbon dioxide can then be easily released from the material, and the MOF materials recycled for another round of carbon capture.

MacDiarmid Institute and Massey University researcher Professor Shane Telfer, who has spun out startup company Captivate Technologies to develop a new material that captures CO2, says that MOF research at the Institute is focusing both on the capture of carbon and using it as a feedstock for valuable products such as fuels and polymers and other things we use every day.

“The idea is to turn this carbon capture process into a cyclic system – like a circular economy. There is the potential to combine carbon dioxide with green hydrogen to make methanol or to use electrochemistry to convert it to other compounds.”

He acknowledges that there is a big challenge to scale up production of the new materials, and that new engineering systems will need to be deployed so the materials can be effective on a large scale.

“But in the meantime, carbon capture is one part of the whole equation and one of many pillars (along with tree planting, geochemical storage and changing our agricultural processes) that we need to simultaneously deploy to meet the challenge of climate change.”

Zincovery’s Thomas Hughes melting and molding some recovered zinc (Image: Supplied)

New Zealand companies are leading the way in ensuring industries are making better use of their waste. Zincovery is a new startup that recycles the waste from the steel industry’s electric arc furnace process for reuse as valuable raw materials. Aaron Marshall, lead researcher and Professor at University of Canterbury‘s Department of Chemical and Process Engineering Centre, and Jonathan Ring developed a process which recovers high purity zinc from material that would otherwise become expensive landfill waste. The University of Canterbury and MacDiarmid Institute-affiliated company joins other New Zealand startups like Mint and Avertana that mine industrial wastes into valuable commodities.

Jonathan Ring co-founded Zincovery – winner of the 2020 C-Prize for environmental tech innovation – based on research for his Masters degree in chemical and process engineering. Ring also won the Breakthrough Innovator Award for Zincovery at the 2022 KiwiNet Commercialisation awards. By  recycling zinc, the Zincovery technology reduces and cleans up pollution, while also producing other commercial benefits. 

“I want to drive change in the way industries think about waste,” he says.

So as we make our weekly dash for the recycling truck, we know we’re all small parts of a big puzzle when it comes to recycling. As nano-recycling shows, even the very tiny can make a big impact. 

Keep going!