Most people look at waste products – cooking oil from domestic kitchens, leftover sulphur from industrial processes – and see an ugly, insurmountable problem.
Associate Professor Justin Chalker, who’s a synthetic chemist at Flinders University, South Australia, looks at waste and sees opportunity.
Chalker is an expert recycler: by inventing entirely new polymers out of common waste products, he and his team at the Flinders Chalker Lab have already produced a bevy of solutions for complex sustainability problems.
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Their latest material creation, detailed on Tuesday in a paper published in Chemistry Europe, kills two birds with one stone: it can be used as efficient insulation (poor insulation is a significant driver of CO2 emissions), and is made up of waste materials discarded by the truckload each year.
The new polymer was created from the basic building blocks of wool offcuts, sulphur (nearly 80 million tonnes of which is produced yearly as a waste product from petroleum refineries), and canola oil, a common household waste product.
In a three-step process, the team employed a process called inverse vulcanisation to create the polymer from canola oil triglyceride and sulphur; then they mixed the powdered polymer with wool by binding it to the wool fibres using electrostatic attraction; and finally they applied heat and compression to bind it all together into a single composite material.
Chalker says the resultant material – which carries the low-flammable properties of the wool – could be used to insulate buildings, or for refrigerated food trucks and shipping containers, or even for insulating roads and walkways in countries with harsh winter conditions – so that they aren’t damaged by freeze-thaw weather patterns.
The new material builds on the Chalker lab’s previous work, namely the invention of a useful polymer made of canola oil and sulphur – materials which are cheap to access, easy to prepare in large volumes, and would otherwise go to waste.
“One of the goals for our lab is to work towards sustainability in all aspects of chemistry,” says Chalker. “All of the useful materials that we use in our everyday lives, we want to make sure that they’re sustainable, recyclable and they don’t just end up in landfill.”
There are numerous opportunities for using this inventive polymer to address environmental and sustainability flashpoints.
For example, it can be used to clean up oil spills, because the canola oil binds to other oils present in the water and repels water molecules. It can be floated in the ocean near major oil spills, which it sucks up, leaving behind clean water. The oil can then be drained from the polymer, disposed of safely, and the polymer reused.
The polymer can also be used to extract mercury from soil, water and air, because the sulphur molecules bond with mercury. This application could one day protect some of the more than 15 million people worldwide afflicted by mercury poisoning as a result of gold mining in low-income countries.
Another timely potential application is as a slow-release fertiliser. Nutrients can be embedded in the polymer and released over time, reducing the gallons of fertiliser runoff that are polluting the world’s soil and rivers.
The problem of fertiliser run-off is ubiquitous, plaguing even countries that boast significant green credentials: last year, a government report found that almost 60% of New Zealand’s rivers are polluted above acceptable levels.
Chalker’s powerful creation won him the 2020 Prime Minister’s Prize for New Innovators, and his lab is already scaling it up for commercial use. The team has partnered with Clean Earth Technologies, a Singapore-based company that has produced multiple tonnes of the polymer, which is already being used for mercury remediation and oil-spill clean-up.
It’s brilliant science – the kind of multi-pronged problem solving that comes from seeing waste products in a new light.
“In principle, everything we use as our building blocks is derived from waste,” says Chalker, “and we think that’s an intriguing idea, to get people thinking about making things from waste materials – valorising waste and converting it into valuable things.”
Amalyah Hart is a science journalist based in Melbourne.
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