Podcast Episode 5.1

The Science Behind Making Pipe: Part 01

With Guests:
  • Jason Ahrenholz of Prinsco
  • Dr. Michael Pluimer of the University of Minnesota

Jamie discusses “The Science behind making pipe” with Jason Ahrenholz, Director of Engineering at Prinsco and Dr. Michael Pluimer, Director of the Advanced Materials Center at the University of Minnesota, Duluth. In part one, the conversation focused on the material blends that go into making pipe, including the use of recycled content.

Episode 5.1 | 32:39 min
About 1 billion pounds of polyethylene material is used in corrugated drainage pipe...of that, about 50% is recycled."
— Dr. Michael Pluimer

Guest Bios

Jason Ahrenholz

Jason Ahrenholz is the Director of Engineering at Prinsco, Inc. Ahrenholz has been in the industry for about 15 years, previously working for the Department of Roads as an engineer in the State of Nebraska. Ahrenholz joined the Prinsco team 9 years ago and currently serves as the Chair of the PPI research committee. 

Dr. Michael Pluimer

Dr. Michael Pluimer owns and operates Crossroads Engineering and is the Director of the Advanced Materials Center at the University of Minnesota, Duluth. His engineering firm focuses on helping clients develop sustainable engineering solutions for pipes and other underground infrastructure applications. His company has expertise in areas of product design and development, polymer processing and materials, composite materials, testing, and the responsible incorporation of recycled materials into pipes.

Jamie: 

This is the water table.

Kent: 

The chance to hear the agricultural side of these issues.

Jamie: 

A place for people to go find information and education.

Matt Helmers: 

Water management which is just going to become even more critical into the future.

Jamie: 

how missunderstood what we do is.

Kent: 

I would encourage people to open their minds and listen to this dialogue.

Jamie: 

Welcome to the water table podcast. Today we have a couple of great guests with us and some interesting topics about material, plastic material, recycled material. And we want to talk about that with a couple of people I would consider experts in in this field. With me today, I have Jason Ahrenholz. Jason and I work together at Prinsco. Jason is our Director of Engineering. He’s been in the in the industry in the workforce for about 15 years working for the Department of roads as an engineer in the state of Nebraska for a few years. And then for the last nine years, he has worked with Prinsco in the engineering department and currently holds the role of Director of Engineering. Jason is involved in our industry on different committees. He’s on the PPI research committee. He’s actually the chair of that committee right now. He’s also involved with organizations like aashto ASTM, and he is also the secretary of a subcommittee that is the land drainage where we do all the land drainage and the agricultural drainage work through ppi. So welcome, Jason, glad to have you. Also with us today as Dr. Michael Pluimer. Michael is a friend of ours for many, many years, and we’ll talk about that a little later, too. But Michael owns and operates Crossroads Engineering, and he’s also the Director of the Advanced Materials Center at the University of Minnesota, Duluth. He’s a PhD teaches there, his engineering firm Crossroads focuses on helping clients develop sustainable engineering solutions for pipes and other underground infrastructure applications. His company has expertise in areas of product design and development, polymer processing and materials, composite materials, testing, and the responsible incorporation of recycled materials into pipes. And that’s an area that we’re gonna kind of focus on today. So welcome, Michael. An interesting side note to all this is, the three of us here, grew up in the same small town in central Minnesota, rural Minnesota. It’s pretty neat now that later in life in our mid years, we can share our interests and our expertise in materials together. So I’m pretty proud of you guys. And the fact that we all grew up in a town of 500 people. And now we can share some insights with the public on plastic materials. Pretty neat.

Michael Pluimer: 

It is pretty amazing, actually, if you think about it. Because we’ve kind of diverted and gone in our separate directions with our careers and other things like that. But when it comes down to it, those friendships have lasted for a long, long time. And we have our each of our own different components, I guess, we’re contributing to help benefit these areas that we’re interested in,

Jamie: 

For sure, for sure. So, Jason, any thoughts on that before we get going?

Jason Ahrenholz: 

I’ve known about Prinsco my whole life growing up in Prinsburg. And having the opportunity to move back around home and work for a company like Prinsco has been extremely rewarding. And it’s been a good strong career that I will continue to grow in.

Jamie: 

Sure. Mike, do you have any more thoughts on how I introduced you? Or do you have anything that you think that that would be helpful on this podcast for the listeners to know before we start pounding you with questions about materials?

Michael Pluimer: 

I can give a little bit of additional background information. As some of you may know, who are listening to this, I started my career at the Toro company in Bloomington, Minnesota as a mechanical engineer. I spent a number of years working at Toro and and that’s actually where I met, for a second time, Prinsco because Prinsco was supplying some blow molded parts to Toro. And they approached me in my in my Toro design process and said would you be interested in coming in helping us out at Prinsco with some of our plastics, technologies and materials properties and things like that. So actually, I left my work at Toro to join Prinsco and was their Director of Engineering for a number of years. And from that I went on to a position as Director of Engineering of the Plastics Pipe Institute. And that really led me to my consulting career later on in life. So I’ve, I’ve got quite a bit of experience in various industries from mechanical engineering, operations and design, to management and then over into the civil engineering world with my work with pipes and infrastructure. And then the other thing I think that would be important to note is that I went back to get my PhD rather late in life. I was about 40 years old when I went back to get my PhD. And the sole purpose for going back for my PhD was so that I could teach in the University setting. That’s really where my passion is. Is helping educate this next generation of scientists and engineers to to help make our world a better place. In order to do that, it was really necessary for me to go and get my PhD. So my bachelor’s and master’s degrees were in mechanical engineering, but I chose civil engineering for my PhD. And after completing that, about two years after that is when I started my employment at the University of Minnesota Duluth, where I’m now an assistant professor there. And then, as you mentioned, the Director of the Advanced Materials Center. The Advanced Materials Center is a brand new Center at the University of Minnesota Duluth. And it’s a we’re very, very excited about this program. Basically, the purpose of the Advanced Materials center is to focus on more advanced materials, but specifically, materials that are related and of interest to Minnesota. So we focus on our natural resources, we focus on crushed stone, for example, and other materials, that we feel that we have a direct benefit to working with these materials in Minnesota. And we also are very interested in preserving our natural resources. So any new research that’s materials related that can impact the state of Minnesota positively, and then hopefully, lead to some positive impacts in the rest of the world are the areas and materials that we’re focusing on. And the materials industry is basically a combination of several different fields. So we have scientists, we have chemists, we have physicists in the department, we have mechanical engineers, civil engineers, and, and really, that the common unifying subject that we all deal with is materials. That’s a component of all of these different science and engineering disciplines. And that’s really what I’m involved with in my role as director of the AMC.

Jamie: 

Great, thank you for that. And, you know, one of the things you said and there was and I in just from knowing you, as part of your passion is just making the world a better place. And I think that’s kind of where we want to jump off here is, is that’s, that’s what we want to do here, too. And what the water table podcast is about is explaining to the general public, explain helping our customers with their questions that they can answer for their, for their end user customers, for their friends in their in their communities, around water quality in agriculture. Part of the water quality in agriculture is how it’s conveyed. It’s conveyed through plastic pipe. That water is conveyed through plastic pipe. And a lot of times we’ll hear, you know, just in the general public and even in today’s society around banning plastics and plastics are bad and, and that kind of thing. And we just want to talk about the type of plastic we use. And the recycled plastic that we use. That’s what we want to talk about today. But first off, you know, probably a question both of you guys can jump in on but let’s just real basic here. What kind of plastic do we use in agricultural drainage pipe?

Michael Pluimer: 

Agricultural drainage pipe is made up of polyethylene, specifically, high density polyethylene. So when we talk about plastics, there’s lots of different plastics out there. There’s polyethylene. There’s polypropylene, there’s PPT, there’s PVC. A lot of different plastics, and they’re not all the same. Not all plastics are the same. So the materials specifically used in corrugated drainage pipe for agricultural drainage, are high density polyethylene materials. And what do we mean by high density polyethylene? Well, there’s different densities of polyethylene. There’s low density, medium density, and high density typically are the main categories that we talk about. The reason why high density polyethylene is used is because it’s a little bit stiffer material, a little bit more rigid, it’s going to provide a better structural performing product than medium density or low density for those applications.

Jamie: 

Jason a little bit so when we’re talking when Mike’s explaining high density polyethylene, and we use a lot of recycled plastic at Prinsco and I’ll let Dr. Pluimer explain a little bit more about recycling in a minute. But you know, what are what what kind of recycle? Where’s that coming from? In regards to where are we buying it? But also what products are recycled to get into pipe and made into pipe?

Jason Ahrenholz: 

Yeah, so like Dr. Pluimer mentioned, we use a lot of high density polyethylene. And if you look at consumer products, it’s it’s really anything that has the triangle with a two that’s considered high density polyethylene. So a lot of times we use post consumer or post industrial HDP materials. So that can be you know, a lot of laundry detergent bottles or large blue barrels or drums and things like that. So, the ability to recycle that material allows that to get reprocessed, or it allows it to be cleaned and in flaked, and then we have the ability to purchase that and bring that into our process.

Jamie: 

When we think about materials and recycle materials, how much recycle material gets used in the pipe industry in the plastic pipe industry for agricultural use,and probably for all uses as far as storm, sewer, and residential also?

Michael Pluimer: 

It’s a good question, Jamie. And I’ll give you some approximate numbers that are that I’ve obtained. To the best of my knowledge. The plastic pipe industry does a surveys where they survey all pipe manufacturers and producers. And so we get an idea of how many pounds of materials are used in this industry in the corrugated drainage industry. As in other industries as well. So a ballpark figure that we’ve been hovering at for the past decade or so with regards to the overall amount of pounds of materials used in the corrugated industry is about a billion pounds. So about a billion pounds of polyethylene materials are used in corrugated drainage pipe for all applications. That would be storm sewers, culverts, highway drainage, as well as agricultural drainage. So we’ve been hovering around about a billion pounds. Of that about 50%, believe it or not, is recycled materials. So over 500 million, somewhere in the range of 500 to 600 million pounds, and that fluctuates year to year, but it’s been steadily increasing for the most part. We’ve seen it level off a little bit over the past couple of years now. But about half of that volume is post consumer and post industrial recycled materials. Which is pretty astonishing. In fact, the corrugated pipe industry is one of the largest consumers in North America, if not the top, it’s in the top three or four of high density polyethylene recycled materials.

Jamie: 

So as we talked about that probably, you know, a question for both of you again. But you know, over the years, over the last I’ve been working at Prinsco for 24 years now, this month, it’s changed a little bit over time, but we still get this and definitely earlier in my career around, you know, “you can’t make a good quality product out of recycled material” from some customers and from some of our competitors. We still have a few competitors that that have chosen just to make their product out of virgin materials. And that’s, that’s where they brand themselves. And that’s fine. But talk about the confidence that a consumer should have that a customer Prinsco or a customer of others that makes product out of recycled plastic. And we’re really talking about right now about a agricultural drainage pipe since this is an agricultural podcast. But what kind of confidence should they have in the products that we make at Prinsco that are made out of recycled plastic?

Jason Ahrenholz: 

So really all of our products are made to specifications in our world specific to ag drainage we meet ASTM specifications. And those are national specifications that all pipe manufacturers follow. In within those specifications, there’s requirements for physical properties, as well as material properties. So some of the physical properties are your pipe outside diameter, your inside diameter, your crush strength, impact resistance for cold weather, things like that. But more importantly, that the material streams that come into that product and that are used to produce that product are all analyzed. So thinking real high level of of how pipe is produced, you know, we source recycled material, we bring that in house. And we go through a number of testing procedures to analyze that material. Essentially, we’re wanting to fully understand the density and other properties of that material and how it will perform in a finished product. And then we have the ability to take that material and blend it together with other materials of known properties to arrive at what will meet the finished product requirements.

Jamie: 

Does that Dr. Pluimer on, you know, kind of what Jason said, should that give our customer and even suppliers the confidence that a product can be made out of recycled plastic, very consistently, high quality product?

Michael Pluimer: 

Yeah, absolutely. I think there’s a couple of things to add to what Jason said as well. I agree with everything what Jason said. Beyond that, the ASTM process itself is pretty rigorous. So the the process of developing an ASTM standard and getting that standard to be published involves several rounds of balancing. There’s about 700 members of ASTM-F17, which is the ASTM committee that governs plastic pipe products. There’s about 700 members of that committee. And those members all have an opportunity to vote affirmative or negative on various standards. So in order to get a standard passed and develop through the ASTM process, it’s very rigorous. And so we’ve got a lot of vetting on that side as well. So in other words, if somebody is opposed to the requirements at a certain ASTM standard they can vote negative throughout the process and those negatives have to get resolved. So I would just say that should give consumers a lot of confidence with regards to the products because if any manufacturing is stamping the ASTM number of that specific product on onto their pipes, they can rest assured that it meets those stringent requirements that were developed and categorized in that standard itself. So that’s the first thing that I think should give consumers confidence. And then the second area really is we need to understand what are the primary concerns or failure mechanisms of pipes. And so as long as we’re developing materials that are going to be resistant to those failure modes, consumers should have great confidence. So can we make products consistently with recycled materials? Absolutely. And the reason that we can do that is because the industry has learned how to properly filter out contaminants, for example, have the materials. They’ve learned how to properly select the materials that are going to be the highest performing for a given application. We could make a corrugated drainage pipe out of 100% virgin materials that performs much, much worse than a product made out of 100% recycled materials. And that may sound counterintuitive to some. But the reason is it all comes down to the selection of those materials. What types of polymers are we using for the design? And so therefore, if you choose higher quality recycled materials, one can make a very, very good product and very consistent product that’s perfectly suitable and applicable for agricultural drainage applications. As well as highway drainage applications, to be to be honest, and we’ll talk maybe about that a little bit later.

Jamie: 

And I think that, I appreciate you saying that and that’s important to note that, you know, all high density polyethylene is not the same, even if it’s if it’s new if it’s a virgin product. It has to meet a certain spec for it to work in the application in which you’re using and the application of a drainage product used in rural America. You know, and the rigors that it goes through where it gets made, it gets put outside, it’s out in the elements, it’s loaded on a truck, it’s all to a job site, it’s dropped off the job site, sometimes on corn stocks are bean stubble. It’s then uncoiled, you know, to go into the machine, and it’s uncoil that could be you know, 10 degrees above zero. And that type of rigor on the product needs to have meet a certain spec in order for it not to crack and not to have issues. And that’s what you’re what you’re referring to there. And I just want to share that with with the listeners that just to give a little bit more context that if you don’t choose the right spec on that product and virgin you’re not going to have the product that you desire to have.

Michael Pluimer: 

So yeah, that’s exactly right.

Jamie: 

Any more thoughts on that, Jason?

Jason Ahrenholz: 

So yeah, at Prinsco we do a tremendous amount of testing on the material. You know, we pride ourselves on the work that we’ve done, the processes that we’ve set up to ensure that the finished products are going to perform. As part of the ASTM, there are specific requirements and intervals for doing that testing. And so we look at all those on a regular basis. The finished product performance, the materials. And so, like we’ve talked about here, already, customers have the ability to rest assured knowing that it does have that ASTM stamp on it that it will perform to their requirements.

Jamie: 

Great, great. Another thing that we do within that to get to a high quality product, recycle wise, is we blend our material. And you want to talk a little bit about that, Jason? And Dr. Pluimer you can you can add to that if if you have anything to add.

Jason Ahrenholz: 

Sure. So like we talked about, there’s different streams of material. There’s different levels of quality of material. And in when we when we get new material and we want to understand what are the properties? What are the capabilities of that material? So we take all the different materials in, we do our analysis on it and we really want to understand and essentially fingerprint those materials. And then we look at some materials are going to be a higher performing, some materials are going to be a lower performing. And how do we make sure that we utilize the materials in the proper way to satisfy the end use, the application of the installed pipe. And so, we make sure that we have the appropriate materials blended together that will far exceed the the minimum requirements in those stringent ASTM specifications. So, we do have a large blenders that are different facilities that not only blend the materials together, but they also reduce moisture, take out the moisture, and then go into the manufacturing process to extrude and mix and blend those materials into the final product.

Michael Pluimer: 

I just add add to that, Jason. It’s a very interesting process. And I think a lot of people may assume that, you know, manufacturing manufacturers are just taking plastic pellets and turning them into products. And it that is a simplistic way of thinking about it. But beyond that, there goes there’s a lot of science that goes into the blending of the different materials to make sure that they are appropriate for the given application. And so when we talk about blending, we’re really talking about taking two or three or four or more components sometimes, and blending them together to get some desired finished properties. And so when we want to talk about what types of components we’re going to blend, and why it’s important to do that, some of the things we want to consider are the long term performance of that material. So for example, one of the biggest things that we want to pay attention to in the corrugated pipe industry, as in all plastic pipe industries, is how the material behaves relative to stress cracking. So in other words, we don’t want premature failures of the product that are gonna result in cracking 20, 30, 50, 100 years down the road. So we have to there’s there’s very strict requirements within ASTM to develop materials that are going to be resistant to that stress cracking. And the interesting thing is we can formulate the blends of materials to far exceed the ASTM standards, if we know a little bit about the molecular characteristics of each constituent component. And that’s really what Jason was talking about is when they’re testing and characterizing the materials in Prinsco’s lab, they are understanding the behaviors of that material from a molecular standpoint and knowing which material to blend with which one to optimize its performance relative to stress cracking, or any of the other parameters or structural properties of interest. And so it is a pretty significant amount of science that goes into blending of materials and determining the proper blend ratios to make sure those finished product requirements are met. But if we understand those blend ratios properly and understand the science, it’s easy to see that these products can be developed that are going to last and well in excess of 100 years in these given applications.

Jamie: 

Well, that was I was just writing down to ask, you know, how long will these products last? I think I get I get asked that question, you know, periodically from farmers, people that have invested in an agricultural drainage system. And just just wondering, you know, how many generations of my farmers are going to be able to benefit from this system? And so, you know, excess of 100 years is what our industry usually uses. And I appreciate you mentioned that, Dr. Pluimer, but also the other question that comes along with that is and gets asked periodically would be, I’m using a product that is made out of more than 50% recycled plastic, will that product last as long as a virgin product in the, you know, in its service life?

Michael Pluimer: 

And that’s a good question too. And to give a little bit of background information on on my answer to this question is, I mentioned earlier on in the podcast that I went on later in life to do my PhD. A PhD in civil engineering from Villanova University. The topic of my dissertation was around the service life of corrugated pipes manufactured with recycled materials. So this was a topic of interest to many State Department’s of transportation, as well as actually the railroad industry. And that’s the railroad industry was a funder of some of my research over at Villanova University, where we installed a pipe made with 50% post consumer recycled content underneath one of their active railway lines to demonstrate its durability and longevity. So anyway, that’s a lead into answering this question is that my research really was focused on determining the service life of pipes manufactured with recycled content. And so the very short answer to your question is yes, a pipe manufactured of 50% or even 80% or even 100%, to be perfectly honest, recycled content can be made to last in excess of 100 years in most applications and wouldn’t have an adverse effect on its service life compared to virgin materials. But the longer answer to that is it really comes down to the types of recycled materials that are used, as well as the the application, the loading conditions and application that it’s that these pipes are being placed in. So the service life model that I ended up developing as part of my PhD dissertation was basically doing a test to determine how long these products will last relative to the slow crack growth phenomenon that I listed mentioned earlier, stress cracking. And developing a test that would accelerate stress cracking, and then applying that test to the finished product itself to make sure that it meets those minimum requirements to ensure that stress cracking does not occur prior to 100 years of service.

Jamie: 

I think it’s important for people to know that this is not this podcast, and we mentioned this before, but the water table podcast is all about education. It’s not about about Prinsco, it’s not about who we are at Prinsco and trying to sell anything for Prinsco, it’s about telling the truth. And that’s the truth right there. You can have confidence when when you put in a product. And you know, I’m listening to Dr. Pluimer and I’m thinking, and I know the answer but I’ll ask him the question anyway. And the question is, you know, if you were sitting here right now and you were going to invest in an in a water management system for your farm, and you had the choice, would you feel just as confident putting in product that was made out of recycled plastic as you would out of virgin plastic?

Michael Pluimer: 

I would go so far as to say I’d feel more confident. And that may sound a little bit counterintuitive as well. But the reason I would say I’d feel more confident is because actually the standard that we developed for the highway industry also was similarly adapted into the drainage industry. And the material requirements in the drainage products for products that contain recycled materials are actually higher, more stringent than the requirements for those that contain only virgin materials. And so I would feel more confident, to be perfectly honest, of a product made with recycled content in accordance with the appropriate ASTM standard than I would the virgin materials just because the requirements are greater. Now that said, many of the pipe manufacturers that make products with virgin materials well exceed the requirements of the standard and the same as those that make products with recycled materials. So ultimately, it comes down to what types of materials are being selected and used and and whether or not they exceed those requirements or meet or exceed the requirements of the standard. But certainly, I would feel very comfortable and would prefer, in my opinion, recycled materials over virgin materials for agricultural drainage applications. Not only for the durability, but also from a sustainability perspective. I mean, if we look at this from an approach of saying what are some of the problems in our world today?One of the biggest problems is environmental pollution. And you can find pictures all over the internet about plastics that are polluting the oceans and getting into places where we don’t want them and there’s overflow in our recycling system. So a lot of the plastics are being landfilled and those ultimately end up in our oceans and streams and start to pollute. And so when we think long term about what we can do to make this world make this planet a better place it’s finding ways to use those materials in a positive manner. And I can’t really think of a better application, to be perfectly honest, than putting those materials into corrugated drainage pipes that are going to be serving a function for decades if not over 100 years.

Jamie: 

Yeah, and when you start linking what you just said, and using recycled plastic to put into pipe that’s going to manage a water system and if you do that, manage a water table on a farm that’s going to produce more food that’s going to feed the world and if you do that you can add a water quality element to it which is what we’ve been talking about already on this podcast and we will continue it’ll be most of our episodes are going to be talking about how do we do this where we can ensure that the quality of that outlet that when the water’s coming out it’s it’s not affecting the environment negatively in any way. And so if you can do all that it can get really exciting around, you know, what we can do. You start talking about, as you mentioned earlier, Dr. Pluimer, around, you know, passion to change the world or to do good in the world and that’s exactly what can happen here and what what we already feel we’re doing. I personally have had the opportunity to travel some internationally and travel and in the Philippines and see what 7,000 islands and in a vast ocean, you know, in between the bays and coves in uninhabited areas that are just absolutely packed with garbage with, with a lot of it is plastic. And it’s not, you know, we have to be good stewards of that. But the other side of that is is that of much of the world doesn’t understand that the rural America and the amount of fresh water that we have here, we have such a privilege to have so much fresh water, and we can grow the crops we can grow here, it’s just unbelievable compared to most of the world. And we have to be good stewards of that and that’s what we can do with these products. And so, a little bit on my soapbox there, but wanted to share that because it’s it’s exciting. And we’d be happy to talk more about that. Jason, on that note, you know, where do you also see that you want to you want to share on some of these topics that we’ve been talking about?

Jason Ahrenholz: 

I guess thinking about the manufacturing process as a whole, you know, we’ve talked a lot about how we take incoming materials in and we put them through a rigorous test to understand them. And, I guess, thinking about end user with all of our manufacturing, we’re really focused on the ability to design and manufacture products that will last for generations. And that’s that’s really the foundation of what we do at Prinsco, but the foundation of what our industry is doing as a whole too. I think plastic in a buried infrastructure is really the sustainable future for our drainage industry. And, you know, there there’s other materials out there that have an appropriate place for different types of infrastructure. But when you think about burried infrastructure that’s that’s really where plastic shines.

Jamie: 

Great conversation that we’re having here today with Dr. Pluimer and Jason Ahrenholz. Thank you guys for joining us. I think this is a good place to stop for now. We will release another episode next week of the two part series here on materials and environmental impact of recycled material and recycled plastic. So stick with us. Join us next week for the second part of this series with Dr. Pluimer and Jason Ahrenholz. If you enjoy what you’re listening to you can find us on your favorite podcast platform. You can find us on Twitter or Facebook. You can also find us at watertablepodcast.com. Thanks for listening!