Turning old Plastic into Soap with Guoliang “Greg” Liu

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Travis

There are very few scents that are more recognizable in the very worst way possible than burning plastic. So I was quite surprised when I first heard that Virginia Tech's Greg Lue had figured out a way to burn plastic and turn it into soap. Naturally, I had all kinds of questions ranging from the process and the chemical breakdown to does it in fact smell like country breeze and what exactly is that anyway? And thankfully Greg was kind enough to answer these and more.

Greg is a professor of chemistry, chemical engineering, material science, and nanoscience. And his research focuses on novel ways to integrate materials in order to solve energy and environmental problems. Greg and I chatted a little about how his passion for sustainability motivates a lot of his research and what specifically inspired him to take on this project.

He explained the chemistry behind the change that occurs in plastic when it becomes a soap, described how he sees this fitting into an overall picture of sustainability when it comes to plastics, and even gave a little product review having used this soap to clean instruments in his own lab. I'm Travis Williams and this is Virginia Tech's Curious Conversations.

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Travis

Have you always been interested in trying to find a use for old plastic and has it always been so? Not really.

Greg

It's actually a journey of scientific pursuit. And I have always been interested in sustainability and that's for sure. And since I started my career, I have always been interested in either sustainable energy or sustainable environmental science. And I have a training in polymer materials. So I'm always interested in polymer science and engineering. And roughly around the time about, I think it's 2018, it's just slightly before the pandemic time. And I started to question myself what I can do in this new domain of sustainability. And then I started thinking about plastic waste. And that's like how I started the journey about turning plastic waste into soap. So soap was like one...that we came up with, but I'm always interested in turning plastic into more valuable materials and chemicals. What is it about soap that makes you able to create soap out of plastic? It was actually an inspiration that I got when I was questioning myself what to do during the Christmas time. And what I realized was that soap is a molecule that is made of a relatively long chain comparative to 12 to 15 carbon or maybe even longer and attached to a functional group at the end. So, and when we look at the molecules like plastics, for example, polyethylene, it's very similar except that it's much, much longer chain. We're talking about thousands and thousands of atoms of carbon linked together. So there's many similarities there that we can potentially utilize polyethylene and truncate the polyethylene molecule into shorter chains that will mimic the chain lengths of a surfactant, in this case soap molecule, so that we can have a little bit of control over the functionality and chain lengths and that in principle, we should be able to make soap or detergent out of the plastic waste. So that's kind of the idea come from.

Travis

Okay. And so what was the, I guess, what was the big challenge in figuring out how to go about doing that?

Greg

The major challenge, and even today, this is still the challenge, and that's why we have attacked here, is the control over the product that we can make out of the plastic waste. Especially if we are targeting surfactant in this case. the chain-length control is the most important problem that we must address. Because polyethylene, by definition, is a very long chain of carbon and how do we truncate that chain of carbon linkages together into shorter chains? That's the biggest challenge here. And how can we control the chain links in the range that is relevant to this affected industry? That's the big problem.

Travis

Okay. I think I had read a story that one of your inspirations for the way that you're going about doing this, and I think you referenced this earlier, had to do with you looking at a fire or a fireplace? And I found that very fascinating. What was it about the fire? What did that, pardon the pun, what did that spark in your mind?

Greg

So I have this hobby, During the winter, I really like fireplace. And I find it very peaceful to sit next to the fireplace. And I was staring at a fire. And what I realized was that when we burn the firewood in the fireplace, we're basically running a chemical reaction inside our house. And that reaction is basically a simple combustion that we think we understand fully already, but in reality, we don't fully understand the process yet. And there many people studying this process right now. But what I understand is that when we're burning the firewood, we are turning biomass, which is basically a long chain of molecules, like long chain molecules we break them all into small pieces and then we combust. And as we break their biomass molecule into small pieces, even we can figure out a way to burn them and actually truncate them in a way that is much more controlled than in principle, we making smaller molecules. And this is the process that we came up with. if I can burn with a quote, my plastic waste in a way that I can control the chain length of my product. I can follow a similar way to make detergent out of this process.

Travis

Okay, and is that the process by which you all have started to make soap? Or maybe a better question is what is the process by which you all are doing this now?

Greg

So the process that we're doing now is inspired by the firewood and actually candle as well. So The way we do the combustion is that we turn those molecules into small molecules and then we combust it. But what we're doing here is that we can turn a non-chain molecule of polyethylene into a smaller chain of molecule of say a wax or liquid. And we can control the reaction in a reactor we designed in our laboratory. It's called a temperature gradient semantics.

So this temperature gradient of somatosis allows the molecules to follow a series of reactions, breaking into smaller chains. And then we quench the reaction, and then we stop the reaction there. And then we basically allow the molecules to break apart, but they don't break apart all the way down to gaseous molecules. And then we make it into a relatively shorter chain molecule that can be useful for detergent use. And in the detergent industry, the most important ingredient is the olefin or the alpha olefin. So the key here becomes how do we control these molecules to break it apart and form those alpha olefins. It sounds like what you're doing is you're burning this and there's a chemical reaction and you're trying to catch it at just the right moment so that it could be used for soap.

Travis

What are some examples of the types of plastics that you have been converting or can convert now into soaps?

Greg

So the molecules or the plastics that we have tried so far include mostly polyolefins. Now we're going to get some technical juggernauts about polyolefins. And the mostly used polyolefins are polyethylene and polypropylene. So if you look at any product that has a label of the plastic type on the package, typically with the number two, number four and number five. Those are molecules of polyethylene and polypropylene. So typically what we do here is that we can turn molecules two, four, and five into short chains using our thermal gradients analysis process. that makes a lot of sense.

Travis

And I think if I'm understanding correctly, a lot of those are the ones that cannot be just commonly recycled.

Greg

Yes, we definitely face quite a bit of challenge there to recycle these molecules. the recycling rate right now is pretty small. So I think this can give us some alternative ways to recycle the content. But from my perspective, I think this is more like a way to use the end of a life plastic waste. from my personal opinion, or my personal philosophy, is that if I can reuse and reduce the content that we use today, that was the best way. But if I have used them many, many times and then become, this material to become no longer reusable, then I think would be the best way to treat them through this process to generate a different product for different applications.

Travis

Yeah. What are some examples of some different materials or objects that you would you would use or reuse until it gets to this kind end of life stage where you're going to turn it into soap.

Greg

Right. So for example, So polyethylene, I just showed you an example of a PESCA bag, a grocery bag. That's a typical example of polyethylene. Another common example that we see almost daily is that a milk jug, which is also made of high density polyethylene. Other examples can be PESCA wraps.

Those are typically made of polyethylene too. And for many of these products, right, so we will try to find our best way to reuse them. For example, milk jar. Like you want to reuse those materials as much as possible because the high quality polyethylene. But let's say if you use it so many times and the quality will degrade, that's why after so many reprocessing, the quality of the plastics will degrade and then we will no longer be able to use them for a different...cycle again, then we started to consider, what if we turn them into something that can be different and useful for some other people?

Travis

Yeah, that makes a lot of sense. Well, kind of on the other side of what you're doing, the soap that you're creating, is it a liquid soap? Have you been able to make it into like a block, like a bar soap? What does that look like?

Greg

So we actually have figured out two kinds of products that we can make out of the passive waste. So if we can control the chain length to be little longer, so we will have a solid wax that we make at the end. And that wax can be converted into solid soap. And now in our new process, we have learned a method to control the chain length to be shorter. For example, in the range of C12 to C15 range that you commonly see in the deuteron bottle, now we can make it into liquid detergent. So we have the capability to tune our process in a way that we can control our end product.

Travis

That's awesome. So there's a little bit of variety there for people's different soap preferences, it sounds like.

Greg

Absolutely. So that's the important breakthrough that we have here is the control over the product chain names and the functionality so that we can gain the different needs of different customers. Does it smell good? It's the same ingredient that we use to make our detergent and soap today. So I don't see any differences in terms of smell, but if you want to add additional smell that you make more opinion, I think that's doable.

Travis

Yeah, I was curious because I don't know how traditional soap is made. I don't know if it has its own smell or you add smells to it later. Like if you want it to smell like the rain or something like that.

Greg

I would say that's probably beyond my domain of knowledge. And I would guess that we probably need to add some ingredients to make them smell better.

Travis

Yeah, that makes sense. Have you used the soap yourself?

Greg

So we have made some prototype soap and detergent in our laboratory. And my students haven't tried them in a daily basis, like hand washing yet but we have some tried to watch the lab glassware in laboratory.

Travis

Has that been successful?

Greg

Yes, it was pretty good.

Travis

I know you kind of started down this journey with sustainability in mind and plastics, but doing this work, I'm just kind of curious, what in this space just simply gives you hope?

Greg

There are multiple reasons behind this. And to me, number one, the plastic waste is a huge problem we face right now there are potentially many solutions to this problem, but I think it's not a one-way street. There's only one solution to this problem, and I think there will be many solutions that we should encourage. And the plastics to high-grade chemicals, I think is one way to solve the end-of-life plastic waste problem. That's one. So there's a need from the source part about the feedstock, about plastic waste.

But there's also a need downstream. And today, if you notice, the detergent industry, there's a huge push for sustainability. And we want to make our materials or chemicals more sustainable. So almost anything that we use in the future, we would like to be more sustainable. Either we use renewable feed stocks or we use materials that is more sustainable and can help to make our planet better.

And this is something that we have received from unknown individuals. Basically, they just mail me postcards and send me emails and ask me, hey, I want you to make some soap or detergent that we can help mitigate the problem we face right now. So there's a huge push and demand out there from the end-to-use customers. They want to use their soap in a more sustainable way. So that gives me hope and there's a huge demand out there. We want to solve this problem together. And I'm very happy to see there's a huge push in this direction.

Travis

Yeah. Do you think eventually you will be able to take this soap to market in some form? Like, will you be at one of the festivals with soap? Like those little stands or what do you see? Where do see this going?

Greg

I personally, I would really love to see this coming to fruition in the future and somebody can commercialize this process. That would be lovely. I'm not sure if I'm the best person to do that, but I would definitely try my best if I have to do so. And I would also encourage anybody who is interested in this area to join us and work on this problem together.

Travis

Yeah. Well, that's awesome. It sounds like that there's just a lot of possibilities for the future. And I think one thing that I've also taken away from this conversation is It's good to go spend some time sitting and thinking by your fireplace.

Greg

I cannot agree more. And I, to me, I think sometimes right now we work in a really fast paced environment. Everything is so fast paced and we want to the results sooner and faster. But sometimes I think it's also worthwhile to just sit down and relax a little bit and think about what we really want to do in the future.

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Travis

And thanks to Greg for talking to us about the process by which he's figured out how to convert plastics into soap. If you or someone you know would make for a great curious conversation, email me at traviskw at vt.edu. I'm Travis Williams and this has been Virginia Tech's Curious Conversations.