Polymer Injection Technology: Turning Old Tires into Steel

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When we think of transportation, images of vehicles big and small might come to mind. Cars, trucks, planes, ships, all with their own strengths and weaknesses when it comes to choosing the right vehicle to move your products (or yourself). Though when it comes to sustainability, the focus is on the emissions of these vehicles. Rarely do we think of how some of the parts might cause environmental problems of their own. Come to think of it, how many sets of tires does a single car go through during its entire life?

Every year, roughly 765 million tires are left to sit in landfills, stockpiled somewhere, or dumped illegally around the world. As the United States is currently the largest producer of tire waste with 290 million a year, increased vehicle sales in China and India are closing the gap and piling onto the problem, which looks a little something like this:

Neverminding rubber’s inability to break down well (especially with all the chemical and metallic additives when making modern tires), tires pose a huge health hazard. While water pooling in old tires to foster the growth of disease-carrying insects like mosquitoes is a classic example, garbage fires involving these rubber harbingers of doom are especially toxic.

In most cases, tire fires spew thick, black smoke into the air usually for days, across dozens of miles, poisoning whatever it comes in contact with. The 1983 tire fire in Rhinehart, Virginia even polluted local water sources with lead and arsenic — in other words, stuff you really don’t want to be drinking.

But let’s shift gears to another car component: steel. In the United States, our steel industry accounts for approximately 2% of all energy consumed. On top of carbonaceous cokes (that is, high-carbon, low-impurity coal-derived fuels) and the greenhouse gas emissions associated with them, the automotive industry is really in need of some sustainable help. Luckily for them, a professor from the University of New South Wales and her research team might turn these two negatives (tire waste and energy requirements for steel production) into a positive.

Reinventing The (End-of-Life) Wheel

Professor Veena Sahajwalla at UNSW is no stranger to the world’s waste tire problem. As she said in a recent interview with The Hindu:

“My ambition to transform waste into valuable resources goes back to my childhood in India. Growing up in Mumbai, I used to walk past huge mountains of garbage on the way to school which supported communities of rubbish pickers. I imagined what it would take to convert ‘rubbish’ into something more valuable, like a resource for steel-making. Rubbish pickers would then have something more valuable to sell and we could improve the environment and reduce costs for steelmakers. That was part of my drive to first study Material Sciences in India, and to then go onto post-graduate and post-doctoral research in Canada and later in Australia, where I have worked at the UNSW in Sydney since the mid-1990s. […] To realize this ambition, I knew that we needed to do something really significant; we needed to revolutionize recycling science.”

At UNSW she’s taken part in finding that answer: polymer injection technology (or PIT for short). While waste tires are used to create new steel, it isn’t as simple as converting one into the other. In fact, it’s not a conversion at all.

PIT is simply a new take on old processes, specifically electric arc furnace (EAF) steel-making; instead of using cokes derived from coal or petroleum, granulated waste tires are injected as a substitute. The World Steel Association sums up the process:

“To minimize energy use, electric arc furnace steel-making facilities use coke or anthracite to insulate molten steel, keeping it hot for longer. These are injected into the steel-making process to produce a foaming slag that forms a blanket over the steel. The University of New South Wales has demonstrated that polymers (for example, rubber from tires) can replace some of the coke within the EAF steel-making process to increase the volume of foamy slag.”

OneSteel, Australia’s largest steel manufacturer, has seen quite a bit of success with polymer injection technology. In a case study surrounding their Sydney mill, electrical energy consumption fell from 424 kWh per billet ton to 412 kWh, “reduced the amount of carbon injectant required from 464 kg/heat to 406 kg/heat, and improved the number of liquid tons per power on time minute from 2.12 to 2.20 tons/minute as demonstrated through controlled condition trials.”

Rolling Out a Revolution

Now, waste tires are a part of commercial operation at two of OneSteel’s EAF mills. Based on the increased efficiency and partial replacement of conventional coke with injected waste tires, the lowered emissions from annual production equates to the removal of roughly 4,000 cars from the road. Pressing the initiative, they’re looking to get a third facility on board with PIT.

On the other side of the world, OneSteel’s collaborating with Celsa Armeringsstål, a steel manufacturer in Norway since last year. As the technology spreads, Sahajwalla looks forward to bringing PIT to India. Given the country’s scale and size compared to Australia and Norway, to see polymer injection technology spread throughout India would be a huge (and interesting) case study for the new process.

As this technology is still relatively new, it’ll be interesting to see how steel mills across the globe take to the process. While OneSteel’s results seem promising, it’s still a ray of sunlight in the black smog of burning tires wafting through the atmosphere. But what’s great about polymer injection technology is that it strips businesses of an excuse of sustainability being too costly. We need more initiatives and inventions like this that not only save our environment, but convince even the stingiest of business owners they’ll save money and resources too.

With the Earth as our greatest resource, Sahajwalla’s team is one group among many doing its best to preserve it.



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