Scientists convert plastics into soaps and detergents

As an undergraduate student at Zhejiang University in eastern China, Greg Liu went with some of his classmates on a university-sponsored trip to tour a host of chemical industries within the area.

The tour gave students pursuing degrees in chemical engineering an opportunity to learn more about the manufacturing and production processes of chemicals within China at the time. Liu realized that day exactly what he wanted to do for a career—find ways to alleviate or stop the industry from polluting the environment.

“I realized that this was not going to be the sustainable way of our future. Pollution was everywhere; water, soil, road, you name it. Workers were in unbearable working conditions. I didn’t want to be in an environment like that, nor our future generations,” Liu said. “That basically drove me to think, ‘OK, I must pursue an advanced degree to change the way we work in the chemical industry.'”

Liu later came to the United States and earned his doctoral degree from the University of Wisconsin-Madison. Now, his zeal to use his knowledge of chemical engineering to create a more sustainable world has led to him developing a revolutionary way to deal with arguably one of the world’s most pressing issues—plastic pollution.

A long research project encompassing five or six years finally led to a breakthrough, with Liu, a professor within Virginia Tech’s Department of Chemistry housed in the College of Science, and his team of undergraduate and graduate students finding a way to convert certain plastics into soaps, detergents, lubricants, and other products.

Liu has written an article about the process and the feasibility and commercialization of it that was published in Nature Sustainability.

In simple terms, Liu’s system was two steps. It first involved using thermolysis, or breaking down a substance—in this case, plastic—by using heat. Plastic placed in a reactor built by Liu’s team and heated to between 650 and 750 degrees Fahrenheit broke down into chemical compounds, leaving a mixture of oil, gas, and residual solids.

The key to this first step was breaking down the polypropylene and polyethylene molecules that make up plastic within a certain carbon range, and Liu and his team were able to accomplish this.

The residual solids left behind were minimal, and the gas could be captured and used as fuel. The oil, though, was the product of the most interest here.

During his research, Liu was able to functionalize, or change the chemistry, of the oil into molecules to be converted into soaps, detergents, lubricants, and other products.

“These materials are stable,” Liu said, holding up a vial of soap. “This vial of soap has been in my office for, I would say, a year already. … You could use it to wash your hands and dishes. We have used it to wash our lab glassware in the laboratory.”

The process, which took less than a day, led to almost zero air pollution output, thus offering clues to a desperately needed solution to a global problem. According to the United Nation’s website, the world produces 430 million tons of plastic each year, with the equivalent of 2,000 garbage trucks full of plastic dumped into oceans, rivers, and lakes each day.

Plastic pollution leads to an increased choking of marine wildlife, the damaging of soils, the poisoning of groundwater, and is the cause of negative human health impacts. In addition, there are greenhouse gas emissions released into the air during production.

The United Nations expects plastic pollution to triple by 2060 if no action is taken. Unfortunately, according to the United Nation’s website, less than 9% of plastic actually gets recycled—though there is a reason for that, according to Amanda Morris, the head of Virginia Tech’s Department of Chemistry.

“We make plastics to last from the perspective that many of them have to hold a liquid inside them that you don’t want coming out of a bottle. So they have to be relatively strong materials,” Morris said.

“The bonds that hold the polymer together and give us that strength and give us the properties of the bottles that we use are also really hard to break, and so it’s just trying to come up with ways to do it in an energy efficient manner where you get clean product.

“The other thing is that those polymers can degrade into many different things. Are there ways that we can get it to one specific product that then could actually be used downstream again? I think those are some of the things that we’ve struggled with.”

Liu and his team have come up with a way to break those bonds, but now potentially comes the hard part—scaling up the system and making it a continuous one, while, more importantly, making it cost effective.

His is the plight of many researchers. They often find solutions to issues, but those solutions can come with hefty price tags, often resulting in the solutions remaining on the sidelines. Liu said industries have expressed interest in upscaling this process, but any effort, energy, and investment needs to result in profitability.

Liu said he is seeking help from the community to test a business model. This involves securing capital needed to build a reactor to run continuously in his lab, or perhaps creating a private offsite start-up company to test the ramping up of his process. Yes, soap can be created from a few pieces of plastic, but can tons of plastic generate soaps and detergents profitably?

“There will be a lot of demand on our end to further derisk the process,” Liu said. “We have to derisk it so they [businesses] can see real value out of it, and they can potentially adopt it.

“My estimate is in the hundreds of thousands of dollars range to test this. The good thing is that we’re training talented students and postdocs in this lab right now. They will be the ones who can potentially carry on this process in the future. But we definitely need more resources, especially funds, to build reactors and test the reactors.”

Back-end challenges aside, Morris remains optimistic about Liu’s findings and their future impacts. She welcomes opportunities to publicize his efforts tackling the plastics problem and discussing the chemistry department’s efforts in meeting this challenge as part of Virginia Tech’s Global Distinction ambitions.

“I think that any time that we can make our science accessible to the broader public, including our alumni and friends, it’s incredibly beneficial,” Morris said. “It’s beneficial for them to see the impact that we’re having not just as Hokies, but also that they can have by investing further in the Virginia Tech mission.

“The goal is really to take Greg’s technology, make modifications based on what we understand fundamentally about the process, and then make it even more energy efficient and more beneficial to industry. The other thing is that Greg’s technology is for a few polymer classes [with a recycle code of 2, 4, and 5], so can we apply that to other polymer classes? Are there ways where we can increase the reach of the technology? That has me excited as well.”

Liu doesn’t view himself as a pioneer, although, in this case, he truly is a pioneer of converting plastic waste to soap. Instead, he views himself as someone contributing a small piece to the solution of a global problem that requires everyone’s diligence. He said he welcomes more involvement from the scientific and industrial community.

In other words, science needs more collaboration on this problem. The stakes are too high without it.

“It’s no longer enough to be like, ‘Oh, I can play with my cool chemistry in the laboratory, and I can magically generate something out of it, and then I’m good enough,'” Liu said. “That is surely cool, but that isn’t the real solution to the pressing problem of the plastic crisis.

“I hope, down the road, we find a solution, and I hope plastic is no longer a problem to worry about. I hope, in time, society will take care of all these waste materials. We can generate useful chemicals and materials from waste, and hopefully we can close the loop of carbon and plastics. That is my dream. I believe we can achieve it, but it’s going to take a while. With everyone’s will, we will solve it.”