Carbon negative construction with engineered bamboo w/ Amir Mofidi

Geoff Capelle: The perfect building material doesn’t exist. 

Concrete is fast, durable, and fire-resistant, but it’s not as easily recyclable. Steel is recyclable, strong, and flexible, but it’s energy intensive to produce.

Timber is green, and uses five times less energy to produce than concrete and twenty-four times less energy than steel—but it can take many years to grow a forest.

So what if we looked at something different? Something with a proven track record but also, the potential to become superpowered with the right engineering.

Bamboo.

Though it isn’t perfect, it has a lot of green flags. 

For starters, it’s one of the fastest-growing plants in the world. Some species can grow up to a meter a day, and take only five years to mature.

It’s also a carbon sequestering powerhouse. 

Amir Mofidi: During that 4 to 5 years that it reaches its maturity level, for every one kilogram of bamboo that you're going to produce, half a kilogram of CO2 is going to be sequestered. So that is huge.

Geoff Capelle: This is Amir Mofidi, Associate Professor at Brock University.

Amir Mofidi: My major is structural engineering and construction materials. Part of my research is on the use of bamboo in construction and also I work on rehabilitation of infrastructure using innovative materials.

Geoff Capelle: And where some have been bamboozled on how to incorporate this lightning-fast grass into their project plans, Amir’s been looking at composites that could help tackle some of bamboo’s shortcomings.

Amir Mofidi: Compressive strength is the weaker property of bamboo compared to concrete. The reason why I started with bamboo was basically because we can actually use the existing structure, improve it, and we tested them—we now have engineered bamboo that is stronger than concrete, stronger than brick, and stronger than timber.  

Geoff Capelle: If we’re going to meet our Paris Agreement commitments by 2050, we’ve gotta start moving.

Amir Mofidi: Thirty-nine per cent of carbon emissions goes to the construction industry. So, not only we are producing a construction material that you can build with, but in the meanwhile, you're actually sequestering the CO2—carbon emissions— from the atmosphere, so that's basically a direct approach that we are going to need so that we can meet our Paris Agreement promises by 2050. 

Geoff Capelle: Back at home, it might even become a solution for tackling the Canadian housing crisis.

Amir Mofidi: We now know that in terms of housing, especially in Ontario and the rest of Canada, you’re short 3. 5 million houses. So if you want to use concrete and steel and other not very sustainable materialsl to address this housing shortage, we are going to be even further from the Paris Agreement promises. However, if you actually can use a responsible construction material like bamboo, building a house can actually cancel the effects of carbon emissions—like thousands of cars, for example, in a year.

Geoff Capelle: Today on Building Good, we’re talking about a material that’s already been holding up scaffolds in Asia for centuries—but has been slower to take hold in Western construction. 

 What inspired you to focus on the structural properties of bamboo? 

​​Amir Mofidi: That's a very good question and has an interesting story behind it. So basically I did a lot of research during my Masters, PhD and post-doctoral program on advanced composites. And all my research is on rehabilitation or lifetime extension of existing concrete infrastructure. Basically, I had a good knowledge of fibers and how you can actually put them in the right matrix, for example, a resin, so that you can shape your construction materials.

I was an assistant professor at Newcastle University, and there were two undergraduate students coming to me and asking to be supervised by me on use of bamboo in construction. And I just kind of laughed at them in the beginning, and I said, okay, come on, bamboo is like poor timber, and there is nothing much to research.

And then they told me about the mechanical properties of bamboo and the renewability. Then I got curious and then I read more about it and realized that there's a lot of potential. With my background in advanced composite, I realized that the strength of fiber in bamboo that we’re talking about 400 megapascal in some species. I realized that there's a lot of potential in there. Ever since then, my research has grown quite fast, and all doors are open in that direction, and hopefully in the future, it's going to be even more.

Geoff Capelle: Bamboo has been used in construction for thousands of years in Asia because of availability, strength, familiarity working with it. I remember wandering around Hong Kong just being so surprised to see the scaffolding and how it's built out of bamboo. So why has bamboo been slow to be adopted by the global construction industry?

Amir Mofidi: There's good reason for that. In terms of geometry, it’s inconsistent, not only between two different columns of bamboo, but also even throughout the length of it. That makes it a little bit challenging. In the meanwhile, it's a hollow cross section. And the connections can be a little bit challenging to make, you know, between the post and the beams. So the thing is that if you want to do multi-story buildings with natural bamboo, it's not really easy to make. We are actually getting there with engineered bamboo. There is a six story high rise fabricated and constructed in China.

In Zhejiang University, there is a group led by Professor Xiao that they are working on engineered bamboo for several years and considering the history you mentioned, because they're working on this material for thousands of years, and they know the properties of the material, so they don't need to convince anyone on the beneficial approaches and advantages that bamboo can bring into the table, whereas in North America, we still have to do a lot of convincing, and the only thing that can facilitate that or expedite that is developing some prototypes.

Geoff Capelle: Looking at a building, looking at a construction site, what are some of the uses of bamboo on that? And can you tell us a little bit more about the characteristics of the bamboo fiber that make it well suited to that?

Amir Mofidi: Even in where I live in a condo in Toronto, I see engineered bamboo is used for flooring, for example, or used for aesthetics in the building.

But the thing is that we are planning to use it as a load bearing element. Canada was the first in terms of building high rises with engineered timber. Tallwood House at University of British Columbia was the first, and now you see that different companies across the world are trying to compete with each other to build the tallest engineered timber high rise.

Is it a sustainable solution to displace all our high rises made of concrete or steel with timber? So obviously on one side, we are going to actually use material that is renewable, it sequesters CO2 while it's alive. But we have a limited number of forests. Even the fastest growing softwood takes twenty years; this is like the fastest one. For example, white spruce takes like sixty years to get there. Bamboo, you can actually plant it and it's going to reach the maturity level in five years. Fibers are going to be strong enough so that you can use it in construction. 

Basically, when you cut one, you don't need to replant it. Basically, the rhizomes, which is a network of roots underneath the ground, are alive, and another shoot is going to come out, and it's going to become mature bamboo in five years.

Geoff Capelle: You're talking a little bit about how bamboo compares with timber. How does bamboo perform as a replacement for steel when it comes to concrete reinforcement and so on?

Amir Mofidi: Obviously steel is really versatile construction material. Everybody loves that. So there's nothing wrong with steel or concrete or any other construction material. They're all fantastic. They have been used for centuries. 

If you want to make a competition or a challenge or comparison between bamboo and steel, that's not going to be a fair comparison. But for example, now we're talking about sustainability that’s also not going to be fair. It's not going to be fair to steal because steel is going to be highly unsustainable in terms of the carbon emission corresponded to its production where bamboo is going to be highly sustainable and it's carbon negative. So that means that comparing between bamboo and steel, it's going to be comparing apples and oranges. But while we are going to need bridges, with two kilometers of free span, for example, then definitely nothing can really compete with steel in such cases.

It could be a good idea if you direct the usage of steel in the highly advanced structures that nothing else can be used. Same for concrete, so we can actually have longer span concrete bridges, pre-stressed cable-stayed bridges. It might be more smart and clever to use these construction materials like steel and concrete for highly advanced construction, which timber and bamboo are not going to be competitive material for that.

To give you some numbers, steel yields at 400 megapascal normally. They are different type of steel, but the construction steel we normally use yields in 400 megapascal, both in compression and tension. So this is the most impressive property of steel in my belief, that in tension and compression, it basically behaves the same.

We use steel bars even in concrete structures where we know that concrete has deficiencies in tension. So the thing is that that's 400 megapascal that we can actually rely on most of the time. Now we have met 42 megapascal for example in compression with bamboo and this is pretty much higher than concrete and timber, but not stronger than steel.

Maybe we're going to reach there at some point because the fiber has the potential. Maybe if we use the fiber's potential to the most, then we can meet that 400 megapascal, but we are far from that right now in terms of residential building, office building, even high rises now we can use bamboo and timber.

There might be some concern about that bamboo is going to be invasive. So for example, in Ontario region, there is a lot of vineyards, so we don't need to use the expensive grounds and fertile grounds that we use for vineyards to plant bamboo, but there's other lands that are not being used for farming and bamboo can be grown there.

So the only concern that comes to my mind is that in terms of the environmental impact bamboo forest has been successfully developed in a man made bamboo forest in China. It's growing super fast in Guanzhong, in Zhejiang areas, there are forest of bamboo. The effects of that in terms of how much carbon it was actually sequestered during this time and how it affects the environment, there are new birds came, new animals started to make completely new ecosystem over there where nothing else was there technically. 

Geoff Capelle: We'll be back with Amir after this. 

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When you use bamboo on a building, what is the current lifespan of that product?

Amir Mofidi: So that's a very good question. So we are looking at the same lifespan as timber. The properties, while not identical, but in terms of the durability, more or less, we can actually safely say that we can actually look at the same durability levels of bamboo.

And just keep in mind, you know, even if you have manufacturing processes, for example, prefabricated elements, that basically facilitates building bamboo, although rebuilding an existing structure prematurely in like five years, ten years, it's not really economical, but in terms of the sustainability and environmental impacts, it can actually can have positive benefits, considering the fact that constructing with bamboo can be carbon negative. So if you actually replace or demolish one bamboo building in five years or ten years and reproduce one, you actually helping the environment as a matter of fact, but obviously to prematurely replace a building is not economical, but definitely sustainable. In terms of to answer your question, I think we're looking at the same lifetime span as timber structures.

Geoff Capelle: What are some of the limitations of using bamboo?

Amir Mofidi: Let's compare it with timber, because everyone knows about the wood, about how the trees grow. So we want to compare it with timber to make it simpler. The tree logs can be quite big in terms of the cross section.

So the different pieces of timber and lumber cross sections you can actually extract from one tree log, which is pretty much big and mature. And they're going to be all solid from the inside, and you can add connections nails in different directions through timber. 

This is not really the case for bamboo, if you want to compare it. So, for example, we prepare not to use nails or make any holes as much as possible in bamboo, because that's actually going to separate the fibers from one another. And currently in the older versions of bamboo construction, they used ties around the connections, which, it lasts, but if you want to have more reliable connections, we need to work on that so that the hollow cross sections can be connected quite easily. 

And this is an ongoing research. Multiple teams are working globally on that. So another major challenge with bamboo is that the hollow cross section is not completely circular. 

As it grows and it goes higher, the dimension changes, and the cross sectional diameters are going to become smaller and smaller as it goes higher. So the thing is that many people are working on research on raw bamboo, which is pretty much definitely a direction to go for a single story or maybe two story buildings. But if you want to have high rise, modern construction approaches, personally, I believe we need to go through the engineered bamboo direction. So moving through from raw bamboo to engineered bamboo, the challenges are going to be different. It's not going to be any more the geometry or inconsistent mechanical properties or hollow shape.

It's going to be the production process and how you're going to produce that so that it's maintained sustainable. For example, the adhesive that we are going to use is going to be bio-based, not very high carbon intensive. So these are the challenges to the production process. The production of the laminated bamboo lumber, which I'm sure you have seen engineered bamboo pieces on flooring, strips of, let's say, three millimeters to four millimeters by let's say ten millimeters are cut and all glued together and they provide a nice shape of cross section putting all these pieces and strip together like lego pieces and making the shape that we want out of it's going to be a square four by four for example and it's going to be like drawer covers, which thinner thickness, but spread all over the floor or on the wall.

And then the other technique is the scrimber. The cross section of bamboo are crushed, and then you compress all these cross strips or pieces or strands, let's call them, in the cast that you want to be the shape of your cross section. And you add your resin, then that first of all is going to be definitely in terms of the energy, it's a very energy-saving approach. And also in terms of waste is going to be a very positive, it’s going to have close to none waste. And it's going to be also very sustainable. And it actually showed that in terms of mechanical properties, it's comparable to the LDLs, which is the existing approach mostly used across the world.

Geoff Capelle: Can you talk us through some of the considerations before using bamboo as a component of construction?

Amir Mofidi: Obviously people are going to ask about the fire resistance of bamboo. Similar to timber, there are fire treatments that can be applied but the thing is that the main fire resistance system is within the timber, and similarly to bamboo, so that is the char that they are producing. None of these buildings that we have can resist fire indefinitely, right? So the only concern here is that for how long it can last so that people inside can escape in case of fire.

Geoff Capelle: So looking at future potential uses for bamboo, where do you see the industry shifting? What do you see the future as?

Amir Mofidi: We need to make the future. We need to make sure that we can do it locally. So now, in Niagara region, we are separating the cold-hardy bamboo species out of a thousand species that is out there, and we're planting them to make sure that they’re cold hardy. We also hand-picked the ones that are providing strong mechanical properties for construction as well.

So that's the beginning. We need to produce it. 

And then the next step is the standards or design sheets. So I have approached many construction firms and they were positive, but they're looking for design sheets for different cross sectional areas, different spans, different usages, different live loads. As soon as you have it, they are on board. 

Because the engineer bamboo, it's not going to be very far from the engineer timber. So it basically looks the same. It's what’s inside that’s a bit different, which is bamboo and not with fibers. In the beginning, we can use the hybrid bamboo and timber cross sections. And then later on, when we get advanced and the industry is ready for bamboo-based solutions, then you can even have hundred percent bamboo.

This shouldn't take like decades. We have the technology, we have people that can do research in Canada, but we need investment from the government, from the companies that can benefit later on, and even people are going to enjoy it when they can actually see that they have a positive impact on the CO2 emission challenges and greenhouse gas challenges that the world is facing. 

Geoff Capelle: That was Amir Mofidi. Thanks for listening to Building Good. We’re having conversations about changing construction for the better, so if you want to be part of those conversations – stay subscribed on any podcast app.

Building Good is a Vocal Fry Studios production in partnership with Bird Construction and Chandos Construction.

The producers are Jay Cockburn and Katie Jensen, with production assistance from Jessica Loughlin and Joanne Hignett.

I’m Geoff Capelle. Thanks for listening.