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Change Agent: Aaron Sadow, finding the chemistry to add value, utility to plastic waste

Posted Aug 4, 2021

This is the latest entry in a series of articles telling the personal stories of Iowa State University faculty and scientists whose work is changing the world for the better. Click here to read about previous Change Agents.

Aaron Sadow, patiently going through the origin story of his plastics research, was explaining how glass and aluminum can be melted, reformed and recycled into materials with the same properties as the original.

“That doesn’t work so well with plastics,” said the professor of chemistry at Iowa State University and senior scientist at the U.S. Department of Energy’s Ames Laboratory.

The problem with plastics is the carbon-carbon bonds break down when heated.

“So they don’t reform in the same way as the original,” he said. “And over time, the material properties degrade. So you can’t recycle plastics infinitely.”

Take PET, polyethylene terephthalate, the stuff of rigid, impermeable plastic soda bottles. Try to melt, reform and recycle that bottle after one use, and Sadow said the material is too weak to work as a bottle.

“They’re much better for carpets,” he said. “All plastic bottles end up with one more life as a carpet – assuming you don’t have my dog chewing it up.”

But, does it have to be that way? Could there be a way to upcycle that plastic into something more valuable? Or is that idea nothing but unicorns and alchemy?

Sadow and his colleagues are going to find out. With the support of a four-year, $12.8 million grant from the energy department’s program to establish Energy Frontier Research Centers, they’re building a multi-member Institute for Cooperative Upcycling of Plastics (iCOUP) based at the Ames Laboratory.

It’s important work happening in iCOUP’s labs – important for science, certainly, but also essential for the world.

“Plastic waste is a national and international issue, with consequences affecting energy, manufacturing, and transportation industries, our conservation of natural resources, and global environmental health,” said Adam Schwartz, the director of the Ames Laboratory. “Aaron Sadow and his team are leading the charge to develop new technologies needed for efficient processing of plastics by advancing basic science, and then applying those innovative discoveries to recover, reuse, recycle, and repurpose used plastic materials.”

The Road to Chemistry

Sadow grew up in Unionville, Pennsylvania, about 45 miles southwest of Philadelphia. (He’ll even rattle off the directions: Interstate 95 past the Philadelphia International Airport to U.S. 322 to U.S. 1 to Pennsylvania 82.) His parents, Sandy and Gerry Sadow, are still in Unionville.

“It has a relatively small town high school,” he said.

But there was a chemistry teacher (and winner of 474 games as a girls lacrosse coach), Lee Krug, who made an impression on Sadow.

“I liked him and I liked the class,” he said. “I decided I’d go to college and start with chemistry, and if I found I liked something better, I’d switch.”

Well, he didn’t switch at Penn State, went on to graduate school at the University of California, Berkeley and then post-doctoral work at ETH Zurich.

After joining the Iowa State faculty in 2005, Sadow’s mother ran into Mr. Krug and (“being a mom”) talked up her son’s new job as an assistant professor of chemistry at Iowa State.

What? It turned out Krug attended Iowa State in the late 1960s.

“So my connection to Iowa State goes all the way back to my high school teacher,” Sadow said. “The odds of that I think are kind of small.”

It’s great that connection somehow happened, said William Jenks, professor and chair of Iowa State’s chemistry department.

Because of Sadow’s work and the new plastics research center, Iowa State chemistry has one more thing for its recruiting pitch and many more opportunities for students and faculty.

“While it will be hard for us to directly measure some of these effects, we are thrilled to see Aaron’s group be so successful, both on its own scientific merits and because of these secondary benefits to our department and university,” Jenks said.

‘They’re Trying to Break it’

Sadow’s experience with polymer chemistry goes back to his undergraduate days working in research labs, including some work to synthesize polyesters.

Aaron Sadow in his Hach Hall lab.

Graduate work at Berkeley included searching for efficient ways to make polyolefins, very common plastics used for drinking straws, food containers, bags and many, many more products. Then, in a quest for more distinctive chemistry, Sadow turned to working with the basic materials of silicon production, including polymers that conduct electricity. That included some study of making – and breaking – silicon-hydrogen bonds.

While at Berkeley, Sadow heard a graduate student make a presentation about a new paper out of France: “It was a depolymerization paper – a paper on catalyzed deconstruction.”

Sadow remembers his reaction: “Everyone is trying to make it, they’re trying to break it. They were deconstructing polyolefins.”

Fast forward a few years and Sadow, now at Iowa State and the Ames Laboratory, was working with Cynthia Jenks, then the lab’s division director for chemical and biological sciences, to identify a project for the energy department’s “Big Idea” program that addresses major problems and challenges.

A team of national lab scientists, with Jenks, started pushing the idea that there’s “energy everywhere,” including in waste. Chemists just had to find effective ways to turn it into a usable resource.

“In the back of my mind, I’m thinking of the polymer problem and remembering that paper from grad school,” Sadow said.

Later, at an energy department scientific meeting, Sadow; Jenks, now of Oak Ridge National Laboratory in Tennessee; Massimiliano ​“Max” Delferro, of Argonne National Laboratory and Northwestern University in Illinois; and Susannah Scott of the University of California, Santa Barbara; all agreed to work together to develop a research center devoted to upcycling plastic.

“This was basic, fundamental research that we thought needed to be done,” Sadow said.

On a Mission With iCOUP

Now, just about a year after iCOUP launched, the institute’s name is showing up in the acknowledgement section of research papers.

The journal Chem, for example, published a paper last May (Sadow is the corresponding author) that reports on the discovery of a catalyst that chops up long chains of molecules in polyolefin plastics, which make up more than 50% of plastic waste.

The chopped up pieces can be turned into biodegradable fatty alcohols that are useful in detergents and other applications, “providing high-value, end-of-first-life applications for the (connected) chains of single-use polyolefins,” the paper’s authors wrote.

And, they report, producing fatty alcohols from waste plastic isn’t any more expensive than conventional synthesis of the compounds.

“Thus,” the authors wrote, “this process could ameliorate economic and environmental challenges of the plastic-waste crisis.”

It is a crisis – the Environmental Protection Agency estimates nearly 27 million tons of plastic waste generated by Americans in 2018 ended up in a landfill.

That’s heavy motivation for Sadow and all the iCOUP collaborators to bring their new ideas and their diverse scientific backgrounds to the institute and its cooperative mission:

All that plastic waste, says the institute’s mission statement, “is full of energy and carbon value, which is currently lost. We are determined to transform discarded single-use plastics into more valuable products, providing the economic incentive to transform used plastics into renewable resources.”