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Making the most of waste

When Veena Sahajwalla sees garbage, her mind starts breaking down the material into the individual elements that make it up.

Coffee grounds? That’s carbon. Biosolids? Carbon in there, too. Used tyres? Carbon and hydrogen. Batteries? There might be some nickel, cobalt, manganese, zinc, lithium, copper.

And all of these are potentially valuable.

“What we're doing now is looking at potentially having that residue be utilised in many different ways, and one of the things that we are working towards is harnessing that into various manufacturing processes,” Sahajwalla told delegates during her keynote address on the final day of Ozwater’21.

“Ultimately, we don't see waste as waste, but as a resource where it could be channelled into manufacturing — something completely different.”

One example she gives is used tyres. As Director of the University of New South Wales’s Sustainable Materials Research and Technology — or SMaRT — Hub, Sahajwalla has devised a process that uses old tyres in steel production where it can be substituted as a more sustainable alternative to coke and coal.

For some steel producers, she said, such an idea raises concerns about whether using that alternative would cause problems in their industrial processes.

“But the question should be really, ‘How do I manage a resource that allows me to achieve the goals where I can tick off manufacturing as well as recycling?’,” she said.

“This is where the alignment of recycling and manufacturing can come in: identifying the value in every element, in every molecule, that you can actually harness. 

“So, in this case, the two key elements of carbon and hydrogen are very important. Carbon can replace a lot of traditional coal and coke in this process, and that's exactly what we've done in manufacturing green steel in electric arc furnaces.

“We've also now started to show that the presence of that hydrogen, if it's released under the right conditions inside the steel-making furnace, it can actually bring about a fantastic outcome that all metal producers want, which is carrying out the reduction of an oxide.”

Thanks to the SmaRT Centre’s research, 11 million tyres have now been used to produce steel.

“We're now starting to think very laterally,” Sahajwalla said. “We like to call this and think about this as lateral integration, not the traditional vertical integration, where you are thinking about one particular sort of group of materials and production capacity. Here you're thinking across different industry sectors.”

There are benefits, Sahajwalla said, to shifting our thinking so that we think about manufacturing in terms of value rather than size.

“When we say manufacturing and economies always have to be about economies of scale, I challenge us to think about economies of purpose,” she said. 

“What is the purpose here? Is the purpose about reciting our waste, creating jobs, creating new opportunities for towns and for people to look at their waste as a resource?”

That requires conceiving of our future as a collective one.

“Circularity and substantive solutions mean that we all have to collaborate and work together,” she said. We all generate waste. We all utilise products in our homes. We all wish to support manufacturing and local job opportunities.”

The advantage of such an approach is that it allows opportunity for broadly shared benefits.

“This is important because it's good for our environment, it's good for business, it's good for the country,” she said.

“You can actually achieve all the goals of delivering benefits to humanity, to our environment and to our businesses, and deliver resources in a way that can protect and preserve our environment.”

Sahajwalla said she saw it as an opportunity to come together and make a real difference.

“What excites me is some of the work that we're doing now is allowing us to look at more and more sustainable feedstocks to provide those simple necessities: water and housing, and all the things that we need as human beings.”