Garbage in gold: circular economy research makes plastic more sustainable

October 14, 2021

Since the 1950s, plastics have changed our lives. But these amazing materials are mostly made from fossil hydrocarbons like oil, gas, and coal – and none are biodegradable. Thus, the vast majority of 18 trillion pounds plastic never produced is now litter in landfills and the oceans.

While plastic recycling efforts began in the 1980s in the United States, as of 2018, the plastic recycling rate is only 8.7%.

Arizona State University professor Timothy Long (right) works with chemistry doctoral student and graduate research assistant Boer Liu (left) and materials science and engineering graduate student and Graduate Research Associate Clarissa Westover (center) at ASU’s Center for Biodesign for Sustainable Macromolecular Manufacturing and Materials. , which Long directs. Photo by Andy DeLisle / ASU
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“The sustainability of plastics remains a huge challenge; it is an impending national and global crisis ”, says Timothy Long, professor at the Ira A. Fulton Engineering Schools and the School of Molecular Sciences at Arizona State University. “People have to take care of it now. There is a sense of urgency now. ”

One way to reduce the challenge of plastic waste is to introduce circularity: the idea that whatever has been created is sent back to the manufacturing system without anything going to landfill.

“It’s the idea that waste turns into gold,” says Long, who also heads the Biodesign center for the fabrication and fabrication of sustainable macromolecular materials. “How do we recover these plastic waste streams and bring them back to a raw material that has value? Right now, this is a very important research area, not only for universities but for all the major industries that make plastics. “

Developing a viable plan for a circular plastics economy is a key goal of a National Science Foundation Emerging frontiers in research and innovation, or EFRI, the Long project is carried out with an interdisciplinary team of researchers. This team includes ASU and Virginie Tech – two first university members of the Ellen MacArthur Foundation, a global hub and leader in advancements towards circular economies – in addition to National Laboratory of Renewable Energies, Oak Ridge National Laboratory and Adidas.

EFRI projects are chosen to advance transformative ideas that can change knowledge and have long-term impacts on big challenges or other societal needs.

“The ideas are new, the engineering is a challenge and the team is the right one to solve them. I think that’s a big part of why we were chosen, ”says Long. “We are not only addressing science and engineering, but also the humanistic elements of technology. “

Long and his team of researchers are working to eliminate end-of-life plastics in their $ 1.89 million EFRI projectthe “molecules to manufacture” approach to optimize and standardize processes to achieve a circular economy for at least one type of plastic: polyurethane foams, or PUFs.

Graduate researchers Ren Bean and Jose Sintas discuss chemical structures of monomers at ASU Biodesign Center for Sustainable Macromolecular Materials and Manufacturing.

Graduate research assistants Ren Bean (left) and Jose Sintas discuss monomers represented as chemical structures in ASU’s Biodesign Center for the fabrication and fabrication of sustainable macromolecular materials. Timothy Long and other researchers will study these monomers as part of the National Science Foundation’s Emerging Frontiers in Research and Innovation project. It is important to combine molecular science and engineering expertise to synthesize new monomers that will help improve the functionality and performance of polymers used in many plastics. Photo by Andy DeLisle / ASU

Bringing new life to waste foam

Long and the other researchers plan to literally go to mattresses in the fight against plastic waste. The main component of polyurethane in mattress foam represents the sixth largest family of polymers manufactured in the world; mattresses may have easier collection paths than other sources of foam, including sneakers, seat cushions, and insulation.

At ASU, Long relies on a team of scientists from ASU Biodesign Institute and the School of Molecular Sciences as well as engineers from the Higher School of Matter, Transport and Energy Engineers and Polytechnic school, two of the seven Fulton schools.

“The interdisciplinary culture that exists at ASU is really essential for this project,” he says.

long research group chemists and materials scientists and engineers get back to basics and examine how UFPs are made and explore their molecular structure.

As Long and his team move down to the molecular level, Kailong jin, assistant professor of chemical engineering, and his research group create a new solvent-free process that transforms PUFs directly into other polymers using enzymatic catalysts.

“If successful, this research will develop a scalable approach to recycle waste cross-linked polyurethane into a library of valuable polymer products,” said Jin.

During this time, Matthew Green, associate professor of chemical engineering, and his Research Team are on what he calls “cleaning duty”.

“Taking a polymer apart doesn’t mean you’ve created a circular plastic economy. You have to demonstrate that you can recover these molecules, in high purity, and use them over and over again, ”says Green. “My job is to try to isolate and purify the flow components coming out of their deconstruction process, and to do so in a very energy efficient way. “

Kenan song, Assistant Professor of Mechanical Engineering, explores how to use advanced manufacturing techniques to process waste foam, from traditional molding to new additive manufacturing technologies.

“We are developing new manufacturing principles that will break new ground in the porous microstructure of foams for better performance in recycled products,” Song says of his Research Team in the Advanced Manufacturing Laboratory of Advanced Materials. “The use of additive manufacturing means that we will save materials and energy consumption compared to conventional subtractive processing. “

The efforts of ASU teams are supported by two national laboratories, which “bring some of the most advanced research tools we have to the country, and they bring national expertise essential to the equation,” said Long.

The Oak Ridge National Laboratory provides analytical tools to help researchers understand and measure the fundamental mechanisms of foam deconstruction and reuse.

The National Renewable Energy Laboratory brings expertise in chemical processes, reactor design, and purification strategies to help break down polymers in PUFs in a process called depolymerization.

The economic and social aspect of recycling technology

This research goes far beyond the science and engineering of polyurethanes. Jennifer russell, Assistant Professor of Sustainable Biomaterials at Virginia Tech, and her research team are making sure that the technologies developed by ASU researchers can actually be adopted around the world. This involves considering the economic, social and environmental implications of creating a circular system for PUFs.

Russell’s team will analyze waste PUF materials from industrial, commercial, institutional and residential sources – and confirm whether mattresses, compared to sneakers or another source, present greater and better waste management challenges. raw material for recycling.

Another important consideration for the Russell team is the environmental impact at every stage of the PUF life cycle. They will assess whether the diversion of PUF products and waste and their recycling leads to the desired environmental impact reductions.

“We don’t want to come up with new technologies or new systems that leave us in a degraded environmental situation,” she says.

The techno-economic assessment will help Russell’s team assess the economic performance of new technologies developed by ASU researchers, the infrastructure and systems needed to divert and recycle PUFs, and the economic gains that companies could benefit from using recycled PUF materials instead of new ones.

The Russell team will also create qualitative and quantitative forecasts of future conditions and material needs with relevant stakeholders representing management, manufacturing, government and industry “to ensure that infrastructure and systems solutions developed under this project are genuinely viable, appropriate and have been considered collectively. “

Adidas, a leading manufacturer of polyurethane-based textiles, including PUFs for use in athletic shoes and other equipment, will be a key industry player in this EFRI project.

“Adidas brings external validation of what we’re doing in terms of translational impact,” says Long. “It increases our chances of taking what we learn here at ASU and bringing it to market. “

The company also provides facilities and testing that will help evaluate the properties of recycled foams to ensure they meet the needs of Adidas and other companies.

Working for a more sustainable future

The entire EFRI team is excited to work together and learn from each other on a project with immense potential impact.

“Polyurethanes represent a huge fraction of the polymers we make and use, and at the moment we have no viable recycling strategy,” says Green. “If we are able to accomplish what we put in the proposal, it will have a huge societal impact.”

Russell says she is thrilled to have the opportunity to recognize that technological solutions must come along with sustainable behavioral and economic advancements and unintended consequence analyzes – and to demonstrate a model for addressing other challenges in the world. problematic but important sustainability.

“If we fail to get people to use the innovation we develop, then even the most perfect technological and innovative advancements will ultimately be useless,” says Russell. “We aspire not only to find technical solutions to the challenges of PUF depolymerization, but also to build a system vision that ensures these solutions will be economically viable, scalable and environmentally preferable. To achieve this, we had to take into account and involve the human dimensions of recycling and a circular economy from the start. ”

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