Cosmos » Engineering
30 September 2023
Marie Low is a regional and rural journalist based in Gunnedah, NSW.
Towers of tyres at landfills across regional Australia, along with coffee grounds and waste hydrogen are becoming the steel of tomorrow.
The polymer injection technology pioneered by 2022 Australian of the Year Professor Veena Sahajwalla and her University of New South Wales team 15 years ago, uses end‐of‐life rubber tyres and waste plastic to substitute some of the coking coal to produce high quality steel.
The team from the university’s Centre for Sustainable Materials Research & Technology (SMaRT) originally worked with OneSteel and now with Newcastle-based steel maker MolyCop to produce what has become known as “green steel”.
So how does it work?
Polymer injection technology (PIT) injects shredded end-of-life tyre rubber and other high-density polyethylene plastic, into the electric arc furnace (EAF) that has already been heated to a high temperature.
The polymer reacts rapidly to produce the foaming slag usually produced by coke or anthracite, and does so with greater electrical energy efficiency.
In the past few years, the UNSW SMaRT Centre has published three papers showing waste coffee grounds and hydrogen from other wastes can also be used as part of the green steel technology.
According to Molycop, using PIT technology in producing steel leads to environmental advantages including: an improved carbon footprint through reduced CO2 emissions; a solution for end-of-life rubber products; reduction of slag ferrous oxide resulting in an improved steel yield; and high temperature reactions in the slag layer with no noxious fumes and a reduction in dioxin emissions.
“This project proves that Australia can develop and, critically, commercialise new and innovative ways to address waste and emissions that also benefits steelmakers’ bottom lines and the environment,” Molycop’s President of Sustainability, Ian Tooze says. “Through AMGC [the Advanced Manufacturing Growth Centre] we have bridged that commercialisation gap, developing a product, process and system that can now be offered to global EAF steelmakers.”
What’s happened so far?
In 2014, the University of New South Wales announced tyres diverted from landfill by the technology “could reach as high as the International Space Station”. OneSteel had used more than two million end-of-life tyres for green steel. -.
The move coincided with other uses for old tyres Australia-wide, including in road barriers, rubber asphalt, pavement – even racetracks.
In its 2023 report Tipping the Balance, Tyre Stewardship Australia (TSA) found that while about 90% of Australian automotive tyres were recycled in some way, fewer than 10% of off-road tyres – used mostly in mining and agriculture – were recovered.
“Across Australia 130,000 tonnes of off-the-road tyres reach their end of life each year,” the report notes. “Add to this up to another 115,000 tonnes of rubber tracks and conveyors, that’s up to 245,000 tonnes of rubber products we’re throwing away every year.”
TSA CEO Lina Goodman says there is still a long way to go.
“Data provided by Snap Send Solve shows that, on any given day, there are at least eight reports of tyres dumped on the side of the road, in a creek, or the bush around Australia, with local government and communities bearing the brunt of costs and risks,” Goodman says.
“Here’s the reality for local councils and communities: 10% of passenger, bus and truck tyres unrecovered equates to 5.7 million passenger tyres not being collected each year.”
At the start of the cementing of a green steel partnership with Molycop earlier this year, Molycop announced the technology would reduce its reliance on imported carbonaceous materials by up to 20%, and remove up to 90,000 tyres from landfill.
Molycop now has worldwide rights to sub-licensing the green steel technology.
“The average EAF steel mill has the potential to consume approximately 200,000 passenger tyres annually,” Molycop says.
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Originally published by Cosmos as Coffee grounds, tyres and plastics part of new green steel technology
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