As cities grow, so does waste. And to cope, smarter solutions are required to build sustainable solutions and turn trash into a range of new products.
Veena Sahajwalla is the founding director of the Center for Sustainable Materials Research and Technology and has received international recognition for her work, which focuses on the sustainable use of materials. Environmental and community benefits are a focus of her work. Sahajwalla has developed new techniques to turn waste into innovative and useful materials — end-of-life plastics and rubber tires into steel, unwanted electronics into valuable metal alloys, and shells from macadamia nuts into a replacement for fossil fuels in the production of high-performance manufacturing materials.
“Any solution that reduces or avoids waste to simultaneously deliver economic and environmental benefits is ‘smarter’ than conventional wasteful processes that we know are depleting our virgin resources at an unsustainable rate and contribution to devastating environmental damage worldwide,” Sahajwalla told Devex.
Sahajwalla sat down with us to discuss her inspiration, solutions and goals, which she hopes will help developing cities become smart and sustainable cities of the future. This interview has been edited for length and clarity.
Tell us about your journey to becoming an engineer, scientist and eventually inventor.
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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, such as resources for industries. Rubbish pickers would then have something more valuable to sell, which could improve their lives. I knew if I wanted to pursue this broader goal of ‘upcycling’ waste I needed a very good education, and the only chance I had was through scholarships — so that drove me to work very hard at school.
When I started my engineering degree at the Indian Institute of Technology it turned out I was the only girl in my class. As socially isolating as it was at the time, I not only survived but I came out believing nothing could ever be as tough again. This was a great preparation for the challenges ahead. I had set myself a very ambitious personal goal: I wanted to achieve industrial scale recycling. I soon realized that I would also need a very good international education, so I then sought out scholarships to go onto postgraduate and post-doctoral research in Canada and the U.S.
At the University of New South Wales I have had fantastic opportunities to pursue my goal. I am director of the Center for Sustainable Materials Research and Technology (SMaRT) and the ARC Industrial Transformation Hub for Green Manufacturing. This means I can devote all of my energy to working with our research teams to revolutionize the science of recycling.
This sounds ambitious — how does it work?
Conventional recycling involves laboriously sorting through the world’s rubbish to extract single streams of the same materials, then reprocessing them back into the same form, such as recycling glass back into more glass. However, as our waste is becoming more and more complex and toxic — such as waste tires, mixed plastics, e-waste and auto waste, for example — much of it simply cannot be recycled using such conventional approaches.
We are overcoming the technical and cost barriers of conventional recycling — and so revolutionizing recycling science — by looking at waste at its elemental level. The world’s waste mountains are packed with useful elements — such as carbon, hydrogen, silica, titanium and materials such as silicon dioxide, titanium dioxide and various metals that we would otherwise source from mined materials. We are working out how to reuse them.
You are the inventor of a world-first environmentally friendly process to recycle end-of-life plastics and rubber tires for steelmaking. How did the idea of ‘green steel’ first came about?
Steelmaking is one of the world’s most important industries. Steel is ubiquitous, it is the backbone of our built environment, our transport systems and our industries. However, steelmaking is also one of the most carbon intensive industries, and many steelmakers understand the need to reduce their carbon footprints. In electric arc furnace steelmaking, non-renewable coke has been used as a carbon source for decades. There are many other good sources of carbon, and many very problematic waste streams are carbon rich. These include waste tires, waste plastics and high volume agricultural wastes.
Waste tires are particularly challenging. Worldwide, over 1.2 billion used tires are thrown away annually and at least 4 billion or so have accumulated in landfills and stockpiles. In the U.S., for example, only some 40 percent of the approximately 300 million tires discarded last year were processed.
In the European Union, where more than two decades of regulations, targets and extended producer responsibility schemes have likewise greatly increased recycling rates, almost one-third of waste tires in some E.U. nations continue to go to landfill.
In Australia, some 20 million passenger tires require disposal annually, of which only 23 percent are recycled, 64 percent go to landfills and the remainder are dumped illegally, despite bans on disposal in landfills in some Australian states.
Such vast volumes of waste tires not only pose a risk to human health and the environment but represent a significant waste of a potentially valuable carbon-rich resource. In landfills, waste tires are not readily biodegradable and risk leaching toxic chemicals into the surrounding environment. Waste tires stockpiles are also significant fire risks, as they are long burning and emit hazardous fumes. Yet, despite considerable research and numerous technological developments, there are few ideal processes for the cost-effective recycling of waste tires.
This is where ‘green steel’ comes in. I wanted to find a way to use waste tires that was economically attractive to businesses, to ensure the process was implemented, and, at the same time delivered meaningful economic and social benefits.
What is the process of creating green steel and where does manufacturing occur?
The key to the success of ‘green steelmaking’ is the substitution of coke with an alternative source of carbon, for use as a carbon injectant.
The result is a novel recycling solution that requires only minimal modifications to the manufacturing process and retains the quality and performance of the end product.
PIT introduces a precisely calibrated mix of crumbed waste into the furnace to optimize outcomes. We spent a number of years researching and understanding the high temperature reactions that take place when waste tires partially replace coke, enabling us to optimize the operating parameters of the furnaces.
As the new polymer-coke mix improves the foaminess of the slag, it improves furnace efficiency, while absorbing an otherwise problematic waste streams destined for landfill. Worldwide we have absorbed millions of waste tires, reduced coke usage significantly, achieved savings in electricity and reduced toxic gases, as the polymers are completely consumed at the high temperatures used.
Our patented PIT ‘green steelmaking’ technology has been already integrated into commercial steelmaking operations in Australia, Thailand, South Korea and the United Kingdom with discussions in process for other locations. Our plans are to continue to promote its implementation worldwide due to its dual economic and environmental benefits. At the same time, we are exploring other options for electric arc furnace steelmaking using waste resources.
We are also continuing our research and development work so that we can offer similarly innovative solutions to safely transform other problematic waste streams, such as e-waste, into valuable resources.
How do you think green steel and other similar products can or should be used in smart cities being developed today?
The beauty of ‘green steel’ is that the integration of waste tires into the EAF steelmaking process enables steel of the same quality to be produced, while making economic savings and delivering environmental benefits.
My overriding goal is to transform waste to value. I see the depletion of natural resources around the world as an unnecessary waste, given the vast volumes of valuable material we have buried in landfills and other rubbish dumps. We can effectively ‘mine’ our rubbish to redirect much of what we throw away into new products and materials, and so build much smarter cities.
This ‘urban mining’ approach is especially relevant to cities, as we currently spend huge amounts of money and energy in collecting and trucking or transporting waste away from cities. Instead, we could reprocess much of our waste locally and redirect these resources into industries. That way we would also reduce the need for extractive industries that, likewise, require long distant transport to bring materials to factories.
At the SMaRT Center we are working on new waste solutions that bring the solution to the problem, not the other way around. This is based on using a microfactory model that can be deployed wherever waste is stockpiled.
‘Green steel’ is an ideal solution for smart cities because waste tires are available in very large numbers in the vicinity of steelmaking industries, and the urban areas that need steel for building and infrastructure are, likewise, nearby.
We believe that with our ‘green steelmaking’ process, we have introduced a real economic and environmental incentive for communities and businesses to value waste tires as an input into steelmaking, and so steer them away from landfill. When business and environmental incentives coincide in this way, recycling becomes very attractive. This is why, as researchers, we always look for solutions to waste burdens that take into account real world conditions. If we can demonstrate that our waste solutions return value to industry, business will be keen to implement them.
How do you hope your story will inspire others to seek innovative solutions to help developing countries?
I spend as much time as I can in the public arena talking about waste and the opportunities that lie within it. Waste can be a positive story, so we need to reimagine it as a potential source of wealth and value, not a burden.
In developing countries, poverty is a very powerful driver.
Informal waste picking communities already recover many valuable materials from waste for reuse, but this is rarely done safely and communities are exposed to a range of risks from methane to toxins and contaminants. We need to see these communities as valuable contributors to the future of the planet; they do play a really important role by recovering waste and they shouldn’t have to put their own health at risk to do so. With technical help, their lives can be transformed. This is one very important developing country issue our e-waste solution addresses.
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