AASHTO re:source Q&A Podcast Transcript

Season 4, Episode 5: Paving with Recycled Plastic – Hawaii’s Pilot Project - Part 4

Recorded: December 6, 2022

Released: June 27, 2023

Hosts: Brian Jonson, AASHTO Accreditation Program Manager; Kim Swanson, Communications Manager, AASHTO re:source 

Guest(s): Dr. Jennifer Lynch, Co-Director at Center for Marine Debris Research & Research Biologist at the National Institute of Standards and Technology

Transcription is auto-generated. 

[Theme music fades in.] 

00:00:02 ANNOUNCER: Welcome to AASHTO resource Q & A. We're taking time to discuss construction materials, testing, and inspection with people in the know from exploring testing problems and solutions to laboratory best practices and quality management, we're covering topics important to you. Now here’s our host, Brian Johnson.

00:00:20 BRIAN: In order to get some background information on this plastics issue, we've invited Doctor Jennifer Lynch, who's a research biologist from the National Institute of Standards and Technology, or NIST. And is Co-director of the Center for Marine Debris Research at Hawaii Pacific University. Welcome to the podcast.

00:00:38 JENNIFER: Thank you. Great to be here.

00:00:40 BRIAN: Yeah, now the. Fact that there is a Center for marine debris research tells us that there is a big problem going on that needs to be studied. Jennifer, what's going on in our oceans?

00:00:50 JENNIFER: Yeah, well, the statistics out there say that about eight million metric tons of plastic enters our ocean every year. It's a big, hefty number and the Center for Marine Debris Research was intentionally created here in Hawaii. Because this remote island state of the US receives giant magnitudes of plastic pollution washing in from distant places here in Hawaii. And of course, you know, many people love to come to Hawaii because of our beautiful beaches and reefs. And unfortunately, this plastic pollution is impacting. This beautiful natural environment.

00:01:34 BRIAN: What kind of plastics are we talking here?

00:01:36 JENNIFER: So, the plastics that. Are washing into Hawaii. We are mostly floating polymers, so the polymers that are less dense than seawater can make it here. Anything that's heavier than seawater will sink right where it gets littered or dropped into the ocean. So, what we're talking about primarily is polyethylene and polypropylene as the polymers go what those two polymers? Are used for in consumer goods range from your milk jug, right? That's high-density polyethylene. But that's the exact same material that makes up. Troll Nets, so fishing Nets it's the same material. It floats on the sea surface and when nets get lost, abandoned or ripped off while trawling, they will eventually find their way back, floating to the surface and float around into the garbage patches. And then Hawaii is unfortunately. Downwind of the great Pacific garbage patch, the biggest and worst one in the world. And so we actually receive over 100 metric tons per year washing ashore in the Hawaiian Archipelago.

00:02:50 KIM: Those numbers are scary to me. So, the things that are floating, is there a way to classify? Because I've heard like microplastics, and I've heard other terms. Is there like a classification of the plastics?

00:03:00 JENNIFER: yes. All plastic pollution are particles, right? So they're solid materials of long polymer chains of chemicals, and we classify plastic pollution into bins of size category. Tries from nano Plastics all the way to mega Plastics, so fishing Nets a giant fishing net would be a mega plastic. Anything over 1 meter. In size would be mega and then you get to your macro which would be about the size of a milk jug. Then you get to your meiso which is the size of a bottle. Then you get to micro, which so many people are talking about today. Microplastics are a big thing, and those are plastic particles smaller than 5 millimeters. So, about the size of a pencil eraser and smaller. Is a good analogy.

00:03:54 JENNIFER: And then there's this nano plastic world that's really hard for scientists to even measure and quantify. We're getting closer to being able to do that, but those are particles typically below 1 micrometer, so one 100th the width of a human hair. You can't see them. It's even in microscopes like regular microscopes, you can't see these particles. And each size class of plastic pollution has different ecological. Full impacts in the ocean. And so, when you're dealing with the bigger things, you're talking about entanglement of marine animals and drowning, touching fish that aren't going to get eaten by humans. So, ghost fishing. And then when you're in the nano to microplastic range, you're talking about things that animals are ingesting. Because they have small little mouths, they can actually eat those particles. And then what does that do? When they go through. The gut and the body of an animal because they deliver a cocktail of chemicals with them. Once they're eaten.

00:04:59 BRIAN: I wasn't thinking about this before, but the nanoparticles are those small enough to be respirable.

00:05:06 JENNIFER: Nano certainly, and also microplastics. Yeah, the human exposure to micro and nano plastics is most certainly through inhalation. And then we you know. The mucus membrane. Will push those back up and then we swallow them. So, while we're bringing it in through our noses, we end up pushing it down to our stomachs and ingesting them that way. So human exposure is thought to be mostly through inhalation of micro and nano plastics, but also through food and drinking water.

00:05:40 BRIAN: OK. Well, that certainly lays out quite a problem that we're all dealing with here. Now how does? The DOT how did the Hawaii dot get involved? In helping to deal with some of this problem.

00:05:52 JENNIFER: Well, they reached out to me back in January of 2021, saying that they were very interested in recycling plastic into the local roadways here in Hawaii. And since I was studying plastic and plastic waste, they found me on the Internet and. We striked up a conversation that went we want to put some plastic in the roads. Do you have any plastic? I said ohh. Do I have some plastic I have? We've studied 18 metric tons of derelict fishing gear that we've pulled out of the ocean. We know it's polymer. We can sort that mixed bag of fishing gear out by polymer type, which helps with the mechanical recycling. You need to separate all the polymers to know what you're working with so that your machines work properly. And I was really excited about the collaboration because. When you think about metric tons of plastic washing ashore in Hawaii and what on Earth are we going to do with it?

00:06:56 JENNIFER: Right, the state has. An issue with. We have landfilling. We have a recycling stream, and all of our plastic recycling gets shipped to Southeast Asia and we're not quite sure what happens to it once it gets there. Does it actually get recycled or not? We're not quite sure. And you know now on top of that we have this massive amount of plastic. Trash washing towards us that we did not create. We have to pay to remove and now we have to pay to dispose if the state of Hawaii could find a way to. Make that material into something valuable and useful, especially for long term infrastructure. That would be a win-win for get it out of the ocean and put it into something that the public can benefit from.

00:07:46 BRIAN: So where are we in that process of dealing with that fishnet plastic and getting that into transportation products?

00:07:55 JENNIFER: I think the short answer is we're in the infancy stage of that. The process of doing. That includes a very long workflow that starts with detecting marine debris out in the ocean, then going and intercepting it and retrieving it and removing it. That alone is its own. Field of work, right? That's salvage work out. In the ocean, here at the center, we're trying very hard to build that capacity here in Hawaii. That is pretty much taken care of only by nonprofits, many of which are funded by some government funds. A lot of private donations. And so, it's really good Samaritans that are out there doing this cleanup work. So, we're trying to build that capacity to increase and really stimulate the removal aspects from the ocean.

00:08:56 JENNIFER: That's a very expensive endeavor. So, there's that component. But then. We would love to link that component of taking it out of the ocean to the actual recycling and converting it into something useful. I mentioned that there is no conversion facility in the state of Hawaii and so we're really lacking that infrastructure to be able to physically turn. The sopping wet, salty fish Nets into something that could be useful in machines that are paving roads and then are the companies that are paving the roads willing to put this plastic in their machines, right? That we have to go through all kinds of research and development before. Anyone and everyone is comfortable doing such a thing.

00:09:44 BRIAN: Yeah, absolutely. Because I know there are so many considerations that have to be made, including performance of whatever is being produced.

00:09:52 JENNIFER: That's right.

00:09:53 BRIAN: How it interacts with the equipment, like you said you know, is it going to gum up their equipment? Is it going to be unworkable? What's the you know, there are a lot of conditions, but they're probably other uses beyond that that might factor into something. A DOT might be interested. I'm thinking I know they use corrugated pipe. You know that's made out of HDPE.

00:10:12 JENNIFER: I think there's a gigantic opportunity to use waste plastic for things like what you're talking about, corrugated pipe that gets, you know, buried underground. No one's seeing it. It doesn't need to look pretty. It just needs to deliver water or a cable line or something through it. Obviously, it needs performance, but there is amazing thinking out there. There's amazing US innovation and manufacturing that can be harnessed in this recycling field I. I work for NIST in the circular economy program, and we are really trying to spur US innovation and manufacturing for turning waste plastics, which we use and make a lot of here. In the US, into. : Something that we can continue to use here in the US.

00:11:03 BRIAN: Yeah, that's exciting. What a great field to be in really solving problems that are meaningful. I also wanted to talk about microplastics. A little bit more. So, I was looking at something about how you test for microplastics and water, and I thought that was kind of an interesting test. Do you want to describe?

00:11:23 JENNIFER: That to go back to what we were talking about earlier; I think it's really important for the stage that we're at of putting plastics into roadways to also consider the environmental impacts. Right. Any decision we humans make will always have. Some kind of Environmental consequence, even when we're trying to do. The right thing. And I'm really happy to be involved with HD OT on the microplastic testing of what might be leaching from this asphalt Rd. I think it's really wise of them to include an actual test and we're testing it out in the field on the actual paved trail road. and we're testing it in the laboratory, combining our testing. With the UH engineering lab that's doing the mechanical testing performance and so we're getting the water samples from both that laboratory work as well as the field work.

00:12:23 JENNIFER: So, there are very few, I cannot say there are no standard methods for microplastic quantification. Because now there are ISO and ASTM are quite busy trying to come up with some standard methods for. This I know that there's one out on measuring microplastics from water, so it's coming along, but the field itself measuring microplastics and environmental samples, is still I was saying it's. Toddler phase if I had to give it a growth curve and still today most labs. Across the world, working on microplastics are using. Their own innovative ideas of what is on their shelf today to try to do this so everyone's still innovating. I don't think a gold standard has yet emerged, and so what we do here at the Center for Marine debris research, well, it starts with some very significant.

00:13:26 JENNIFER: QA, QC, quality assurance, quality control because. Because microplastics are everywhere, they're in our air, they're in the water, in our laboratory. We have to make sure we're not contaminating our samples with our air. I mean, they're everywhere. So, we start with using only metal and glass supplies. Avoid plastic like the plague. We work in clean air environments, so under a HEPA filtered clean hood as much as we can. Some of the operations like collecting stormwater off of this trail Rd. we can't bring along our help our air filter, but we will work as quickly as possible so that there is minimal atmospheric input. So, the process begins way before sample. Then we collect the water samples and. We will be bringing. Them back to the lab. This will start next week.

00:14:26 JENNIFER: Maybe so we've been gearing up for it for a long, long time, and now we're ready to go. We'll be bringing the water samples into our lab. We will be filtering those through. Sieve, first to catch the gravel, the big stuff. Then a filter to catch the about 20 micrometer sized particles on that filter and the water that flows through that filter. We actually are collecting to quantify not the particles, but the chemicals that can leach out of the plastic itself, which is the. Bigger toxicity concern. And so those plastics before they were converted into a pellet to go into the asphalt binder mix. They already had chemicals in them. Plastic additives are they're required almost to make any kind of plastic products. So, they're going to be in there and those are the things that were on the search for that could possibly be leaching out of the small amount of plastic into the water that then drains, right.

00:15:34 JENNIFER: To the ocean here in Hawaii. So, I've taken you on the journey of filtration, right. So, going back to that filter of the 20 micrometers, we will take that filter and then we will put that through additional sample processing. Most likely we will be putting it through a density separation. Device that we designed novel, brand new. Everyone wants it across the world. And basically, we put a really dense solution in there and then the rocks and the minerals are going to fall to the bottom and the plastic particles are going to float to the top and then we can close that off with the ball valve and take the top part off. Refiltered that onto a very expensive. Gold plated filter. Then we put that filter underneath an instrument called a microscope FTIR. And what that instrument does is it scans the entire filter looking for individual particles.

00:16:38 JENNIFER: When it sees one, it tells us what size is that particle. So, we can say oh micro meiso nano sized plastic, we can categorize it. It tells us the shape is. It a long fiber? Or is it Fragment like a and the miracle of the machine is that it collects a chemical fingerprint of each particle that will tell us, is it polyethylene? Is it polypropylene? Is it PVC? Is it polystyrene or is it hair or some other? Kind of natural material that we aren't looking for, right? So, we exclude the majority of the particles are natural particles, right? Because that's the world that we live. Then, and we're trying to pull out and identify those small microplastics, so those will be counted, they will be identified to their polymer composition and sized, and then we'll be able to say the stormwater coming off of the road paved with plastic in it. Had so many plastic particles. Versus the road that got paved the same week that did not have the recycled plastic in it has this many particles and we want to compare those two.

00:18:01 BRIAN: That is really fascinating. So, you've got standard practices for sampling. You've got standard practices for filtration and reducing the size of the samples and chemical analysis, and you've got the use of the FTIR. I mean, this is quite an analysis process.

00:18:18 JENNIFER: It takes 2 weeks to analyze 1 sample for a full-time technician. So, it's a very labor-intensive process right now. Microplastic research is, like I said, in the toddler phase, which means we're still nitpicking the small decisions that make giant impact on the data, right? We're still nitpicking those decisions. And then. Once we've knit, picked all of that and we know what is the right thing to do, then we can think about high throughput. We're nowhere neither talking. About high throughput. Yet right now we're just brute force. Lots of people, lots of students, lots of student volunteers doing this very labor-intensive work.

00:19:05 BRIAN: Yeah, that's exciting. So, you've got physical microplastic problem and then the chemical, you know, the leaching that you described. Can we talk about how the physical debris comes off a roadway? i see a roadway, it's paved. Everything looks good other than like it you know, overtime if you have issues with freezing and thawing or compaction issues, whatever you could have potholes. But let's assume no potholes. Where does that microplastic come from? From the roadway, the physical part?

00:19:35 JENNIFER: Well, out there in real life on a road. The number one kind. Of microplastic that we're expecting to see in the stormwater or tire wear particles. Actually, because you think about you've got rubber tires grinding on the top of asphalt and they're made to shred away with time so that you're not destroying the road, right. You've got the tires. Are the things that are less permanent. And so that is leaving small little. Polymer particles all over the road surface and. Tire wear particles have been identified as one of the most contaminating source of the planet for microplastic pollution. So, what we expect to see is a whole lot of tire wear particles from the field trials now from the engineering lab, there should be no tire wear particles, so we can.

00:20:35 JENNIFER: Eliminate them with these two different tests that we're doing, which is really awesome for the scientific side, we can exclude those and not have those interfering with the. As far as the plastic that is recycled in the pavement itself, the field doesn't quite fully understand what the three-dimensional structure looks like of the plastic coating the aggregate or is it melted? And mixed fully and homogeneously with the binder. First, there's all this unknown and it also very much depends on which process you use, whether the wet process or the dry process. So, as a road gets used, you know you see gravel bits flake off even if you don't have potholes, there's some abrasion of that surface of the road and the plastic will be in all those layers, at least in the road that we paved here in Hawaii and so.

00:21:41 JENNIFER: The smallest little particle could contain the plastic the road is made of a very tiny percentage of this recycled plastic product. And so way less than the binder itself and way way way less than the rock and the sand. And the aggregates. But the rocks in the sand and the binder, you know, it does crack off. And those particles could come with it or could crack off on their own. When we're dealing. With 20 micrometer sized particles, it's very possible that microplastics could be shedding off of those roads. But when you put it into context of the tire wear particles, the tire where particles will. Swamp the data.

00:22:31 BRIAN: That's what I was kind of wondering about because I know that that's an issue and it's just it's made they're made that way like you said and you've got all these different tire manufacturers with. Blends of rubber and you've got other contaminants that get you know other oils and greases and sealants and all sorts of stuff kind of getting in there that really creates a complication for the researcher trying to isolate those, but it's great that you've already gotten to the point where you're like we already know, that we have to. Basically, tear our results for the existing contaminants that we've got.

00:23:05 JENNIFER: Yeah, that's right.

00:23:06 BRIAN: But yeah, that sounds like such an interesting process trying to figure out. That you have. Are you getting a signal on the roadway itself after it's been paved to get, like, an initial reading before you start getting the other readings?

00:23:20 JENNIFER: So, we only have planned one sampling campaign out on the roadway, but what's really great is that HDOT was willing to set up an experimental. It has three sections to it, and they all pave the same week and one section is our traditional asphalt. I'm not an expert on what that is, but its polymer modified SBS binder and so it already contains polymers, right? Most of our roads here in Hawaii already contain polymers and you know, for decades we've been using that across the US, and no one's really been concerned about microplastic leaching from that. But we'll be testing that section as our control and we'll see if SBS microplastics leach out of that section of the road and then we have a section that is polymer modified with the SBS, but we've added on top of that the recycled plastic.

00:24:20 JENNIFER: We do know the polymer that was added. So, we know what we're looking for in that section and then we have a third section which is just the recycle plastic, no LSBS modified binder. So, we have these three things that we can compare. We'll take multiple samples on each section only at one time point. That's definitely a disadvantage of the project and the labor intensiveness of the project. Going to go. Out at three months after the road is paved, 3 to four months. And see what the road gives us, but we will not be comparing it to time 0. Instead, we'll be comparing between these three sections that were all paved at the same time that have different things in them.

00:25:08 BRIAN: OK, that makes sense too. I mean, there's a lot of ways you can do it and like you said, this is a burgeoning field right now. There's going to be so much more study done as you learn more about what you're dealing with there. Kim, did you have a question?

00:25:22 KIM: Yeah, I was wondering if because you're in Hawaii. Will that skew the results, or would you expect the same results or different results in other parts of the country?

00:25:32 JENNIFER: It's hard to answer that question because, well, the research would have to be done in different climates with the same pavement, and I'm told that the pavement here in Hawaii is different from pavement on the mainland because our aggregate is mined from right here in the islands and our aggregate. Would be different than your age. And then our climate is different. So, there's so many apples to oranges that it's a great question, but I don't think I. Have an answer for it.

00:26:04 BRIAN: But in doing so, you just you just brought up a bunch of potential research. It could be done to figure out what's happening.

00:26:12 JENNIFER: The sky is the limit on. The R&D. That can and should be done if plastics are to be recycled into roads, because no, we don't want potholes and we don't want microplastics. And those are the two things that are almost competing against each other. And to find the win-win in that is sort of the Holy Grail of this field.

00:26:37 BRIAN: And I think the way things are going, there's not, it's not reasonable to assume that we'll ever get to a point where we eliminate this microplastics problem, but I wanted to ask you, what could we do to help reduce the amount of microplastics that are getting into our waterways?

00:26:56 JENNIFER: I think for the general public to be become more aware of the environmental issue and to make small, inconvenient changes in your lifestyle and your habits and to become more aware of what your habits really are. For example, if you have clean drinking water that comes out of a tap in your house. Maybe don't buy disposable plastic water bottles, right? So, reducing your use of plastic will reduce microplastics out. In the environment. Because the less we use, the less can get fragmented into those sizes. Some other things that. Lead to microplastics in the environment that most people are thinking about are textiles and their tires. And so when?

00:27:52 JENNIFER: You wash your clothes at home, and you scrape off all that lint out of your dryer lint catch. That is microfibers that that is microplastics that you're holding in your hand because a large fraction of the clothing that we wear today are polyester, nylon. Other synthetic polymers just an interesting aside, is that polyester clothing is the exact same plastic as the disposable water bottle. Same plastic spun in a different way, blown in a different form, so things that you can do. To make a small change. Adds up when you. Think about billions of people on the planet, right? So. Reduce, reuse and recycle. I mean those are the, those are the 3R's that we've heard for decades. Right. Start with the reduce, then encourage recycling. Mechanical recycling is the lowest. Greenhouse gas emitting option for disposing of plastics. And so encouraging that here in the US, instead of exporting it off to other countries, let's make the value worth it here and encourage that in your local community.

00:29:16 BRIAN: Oh, that's great message. I appreciate that.

00:29:19 KIM: Topic adjacent you made a point of saying mechanical recycling is the lowest greenhouse gas emitting option. So, can you just like really quickly explain that there's different ones about that?

00:29:30 JENNIFER: Yeah, absolutely. So, there's mechanical recycling and then there's chemical recycling and mechanical recycling is simply shredding and extruding that plastic material into a new form shape product. So, it usually does downgrade the plastic. Quick, so if you had a pricey item, you're not going to end up with the same pricey item being extruded at the end of that chemical. Recycling is literally taking the plastic itself and breaking it down into its elemental and molecular forms to then rebuild it. Up so bringing it. Down to carbon. Dioxide bringing it down to individual oligomers. That then can be. Repolarized into a different plastic, a different chemical. But yeah, most of our plastics today are just carbon and hydrogen. So, you can break that chemically down and then rebuild.

00:30:34 KIM: All right. Well, thank you for clarifying that because I honestly didn't realize I'm like as you said, it was like, well, that clearly makes sense. But like and if. You don't think about it. I was.

00:30:43 JENNIFER: Right, chemical recycling is very energy intensive. You're breaking molecules and. You need temperatures and pressures and chemicals and things to do That.

00:30:55 KIM: So, what was the type of recycling method used for the project with the DOT? Was it a mechanical or?

00:31:05 JENNIFER: It was mechanical, yes. So the polymers that went into the road were purchased from a supplier and they used post industrial waste and mechanically ground that and extruded that into a pellet size that was easy to work with. At the production plant for asphalt.

00:31:27 BRIAN: OK.

00:31:28 KIM: So, I just have one more question. What's something that has surprised you, if anything, about this project or working with the dot?

00:31:37 JENNIFER: We don't have results yet. So I think once we have our findings and our results, then I'll have so many surprises and exciting things to talk about. But until we have that data in hand, I guess the surprising. That's how many people we've had to collaborate. With to get this. Project off the ground and working and that's. Been a really fun. Then, exciting process and you know, just getting the people talking from these various fields. I never thought I'd be talking to the paving industry and the learning curve of understanding asphalt and how it's made. I was like a kindergartener going to the asphalt production plant. You know, when the kindergartener gets to see the fire engine pull up and they get to, like, touch it and talk to the firemen. That's exactly how I was.

00:32:27 JENNIFER: I was like, can I take? Pictures. What's that thing? What's this doing? Like it was so fascinating. To me and you. Know the production plant workers are like. Why is she so excited about it? So, no, just the learning curve of learning about the production of asphalt and. How all of this can be linked together, but you've got to bring together this very diverse feel to make this happen.

00:32:57 BRIAN: Yeah, I love that because that I think one of the things that I've learned through this process of trying to put. This it was originally going to be one episode on a totally different subject together is the collaboration and the partnerships, the little outside the box thinking and collaborative approach that was taken by the DOT and all of the other people who got together and how everybody has been talking to each other. Yeah, we'll set up an interview with somebody and they'll say, oh, yeah, we know that you already talked to this person or you're going to talk to this person. Like you guys are all still talking to each other regularly about this stuff and I I think it as much of AA story is this is about innovation. It's also a great story about collaboration and cooperation.

00:33:45 JENNIFER: I agree with that 100% yes.

00:33:48 BRIAN: Yeah, that's been great. So, I know we've taken up a lot of your time. I want to thank you so much for your time today. Doctor Jennifer Lynch. I appreciate it. And if people want to get more information, where should they go to learn more? About this topic.

00:34:00 JENNIFER: You could Google HPU Cmdr. And the top hit will come up. It's a long website, but. Hawaii Pacific University Center for Marine Debris research. We have a lot of exciting news that we post on our website.

00:34:16 KIM: All right, I'll put a link to that in the show notes. For people as well, so they don't have to Google it.

00:34:21 JENNIFER: Perfect.

00:34:22 BRIAN: All right. Thank you. So.

00:34:24 JENNIFER: All right. Thank you so much.

[Theme music fades in.] 

00:34:27 ANNOUNCER: Thanks for listening to AASHTO re: source Q & A. If you'd like to be a guest or just submit a question, send us an email at podcast@aashtoresource.org or call Brian at 240-436-4820. For other news and related content, check out AASHTO re:source's social media accounts or go to aashtoresource.org.