The Future Of

Sustainable Buildings

Episode Summary

Concrete is the second most-consumed resource on earth but has a big carbon footprint. Hear how Curtin researchers are developing a self-healing and sustainable biocement using natural microbes that could be used in a range of building construction and restoration applications.

Episode Notes

Concrete is the most consumed resource on earth next to water. Curtin researchers are developing a self-healing and sustainable biocement using natural microbes that could be utilised in a range of building construction and restoration applications.

In this episode, David is joined by civil engineer Professor Abhijit Mukherjee and construction biotechnologist Dr Navdeep Dhami to explain what biocement is, how it works and how it can help us to build better in the future.

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You can read the full transcript for the episode here.

Episode Transcription

Jess (intro): 00:01 This is The Future Of where experts share their vision of the future and how their work is helping shape it for the better.

David: 00:10 I'm David Blayney. Concrete is the most consumed resource on earth next to water, but it also has a massive carbon footprint, accounting for eight per cent of the world's CO2 emissions. Curtin researchers, Dr Navdeep Dhami and Professor Abhijit Mukherjee from the School of Civil and Mechanical Engineering at Curtin are exploring greener alternatives to concrete. They're developing a self-healing and sustainable biocement from natural microbes – that is – living organisms. Thank you very much for joining me today. 

Dr Navdeep Dhami: Thank you.

Professor Abhijit Mukherjee: Our pleasure. 

David: Navdeep, are we soon going to be inhabiting living buildings?

Dr Navdeep Dhami: 00:52 Thank you very much for this wonderful question. So, if you ask me that – will we be inhabiting the buildings in future? – I'll say that we have been doing it even in the past without knowledge about it. So if we talk about, one of the examples I would like to mention here is the Great Wall of China. So the construction of the Great Wall of China included the addition of a couple of materials along with the modern clay, which were molasses, eggs, blood. So without even knowing that what we are doing there, we were actually doing biomineralisation. So we have living walls ever since we know construction. So in the future, yes. So now we will have better buildings. They will have living buildings. These living buildings will have living organisms, which we call bacteria. So yeah.

David: 01:38 What are bio minerals and what are the key processes involved in biomineralisation?

Professor Abhijit Mukherjee: 01:46 Well if I have to get an example from, say, the culinary world, it requires a cook and ingredients. And the cook, has a wonderful recipe and that recipe changes from place to place from different environment to environment. The cook, they are the bacteria, they cook calcium carbonate, which is a wonderfully durable material and most abundant in the natural world, and therefore it requires calcium, carbon and oxygen. A wonderful source of carbon and oxygen is carbon dioxide that's already there in the atmosphere. So if you go, to say Lake Clifton or, um, the [inaudible] which are near the Indian Ocean, you have calcium in the water, dissolved in water, and carbon dioxide in the atmosphere, and there are living rocks, calcium, carbon, is being deposited by the cook, the bacteria there, and you're getting, you know, growing rock every year. So that's what, in short, biomineralisation is.

Dr Navdeep Dhami: 03:04 Can I add something more? So, if you ask the definition of biominerals, I would like to explain it as the minerals which are produced by living organisms. So these living organisms, they can vary from bacteria, fungi, Metazoa, algae. So the formation of these biominerals is all around us. So they are ubiquitous. So as Abhijit explained, they can be seen in the form of stromatolites, in the formation of beach rocks, in the formation of caves, which we are very fortunate to see ourselves in Western Australia. So, yeah, maybe the process is what you just explained.

David: 03:41 Right now you're working on ‘microbial induced calcite precipitation’. Bit of a mouthful! Could you tell us more about this, and where are you applying the process? 

Professor Abhijit Mukherjee: Well, you're right, it's quite a mouthful. So we would possibly use a simpler term – biocement – that means cement produced biologically. I would like to give a few examples from this country. We have huge quantities of cement used for road base stabilisation, so when we have million kilometres of roadways in Australia, and to stabilise those road bases, we use cement. So the usage of cement in stabilising road bases and similarly, um, the [inaudible] just next to concrete, uh, which is a huge quantity. And there, if we can use the bacterial system, the bacteria present in soil already, so you don't really need the cook, the cook is already there, you just need to give a few ingredients and the cement is produced and we can avoid usage of engineered cement almost entirely. 

David: And Navdeep do you have anything to add?

Dr Navdeep Dhami: 05:00 Yes. So you have been asking that…MICP yes, microbial induced calcite precipitation. So I would like to tell more about MICP that there are different kinds of microbes which are involved in the process of cement formation in nature. So these micro-organisms can vary from, I just explained, cyanobacteria. There are others which can be urea-lactic. There are some sulfate reducers. So these are slightly technical terms I'm using here, but what I can give is some examples here. So like cyanobacteria are the one which utilise which form calcium carbonate in the presence of light. So there are certain others which have some other sources out there. Energy. So these can be urea, this can be sulfates, this can be methane. So in nature there are different kinds of microorganisms which are involved in the formation of calcium carbonate or limestone. So what we are doing in the labs now is that we have shortlisted urea-lactic bacteria, which can utilise urea as a source of energy and they can give us calcium carbonate. So we utilise MICP via urea-lactic bacteria in the labs. So we are forming limestone cement utilising urea-lactic bacteria. 

David: What are the benefits and the uses of biocement? What are the challenges? How does it differ from the engineered cement? 

Dr Navdeep Dhami: So one of the major benefits of a biocement is the sustainability factor it gives us. So because it's farmed at very low energy inputs and at ambient room temperature conditions. So we say that this is a highly sustainable material. Second term benefit of this biocement is that most of the reagents are soluble in water. Because of this, I mean, it's a very low viscosity solution and it has the ability to get into deeper cracks, find cracks where the ordinary cements don't work. So another top point we can say is that all the materials are natural, renewable, recyclable, which is not the case in case of chemicals.

Professor Abhijit Mukherjee: 07:00 Maybe once again I’ll come up with an example. Australia faces a huge problem of coastal erosion at this point of time due to more frequent occurring of extreme weather events. Australian beaches are at risk of getting wiped out. One of the ways of solving that problem is to beach renourishment. That means, all the eroded sand is put back on the beaches and this is an expensive proposition – imagine every two years you're going, and pumping sand back onto the beach. You can cement that sand a little bit more to give more resistance to erosion. We can't use a engineered cement there because you change the chemical composition of water, it will be more alkaline. You can also, you are going to have problem of changing the natural flora and fauna of the beach. And therefore, you need to use something which is naturally occurring. And biocement is the one that is naturally occurring. You have enough food for the bacteria in the form of, say, seaweeds there. You have dissolved calcium in the seawater and therefore you can just, you know, have the little bit of, you know, chemistry that you would energize the bacteria. And finally, you would have more durable beaches in Australia. Uh, I believe that's a wonderful solution for a really difficult problem all over the world.

Dr Navdeep Dhami: 08:41 So one of the benefits of biocement is the sustainability factor. So the ordinary Portland cement that we are using, I mean, I'm sure that some of us are already aware of this, that the temperatures involved in the formation of the cement goes up to 14 hundred Celsius, while in the case of biocement, the cement is formed at room temperature conditions. So there is a huge difference between the kind of energies involved in both the processes. So this sustainability factor of biocement is one of the driving factors for us to introduce that to the world now.

Professor Abhijit Mukherjee: 09:13 The four key points on sustainability is higher durability of the material because it's like, you know, in the introduction you said it's a self-healing material. It's a living material which heals itself. Second it uses very low quantity of carbon or no carbon at all. It’s not toxic. And finally, what Navdeep said in the beginning that it actually takes us back to the traditional methods of building our homes where used a rammed earth or mud or stone with mud mortars. So we are back there and we would live sustainably and solve the global challenge of housing.

Dr Navdeep Dhami: 10:02 So one, another benefit, of biocement is that very little maintenance is required. So with the most conventional cements are the chemicals that we use for repairs, so every time the shelf life of the chemical is gone, we have to apply it again. But in case of biocement because the living organisms or the living microbes are already in the building and they're going to be there for 200 years as per the stats. So with the biocement, so we can save a lot of money on maintenance and repairs. So that's another benefit that we don't have to do the repairs again and again because our substrate is within the building. 

David: So it's it seems there are lots of benefits of biocement. Are there any drawbacks, any challenges in terms of cost or time or complexity?

Dr Navdeep Dhami: 10:50 So yes, if we talk about natural biocementation processes, it takes years, hundreds of years or millions of years in certain cases. But in case of the bio engineered cement that we have created, we have shortlisted the times to just a couple of days. So the time is not a factor I'll say. But a cost, yes. At this stage we are trying to minimise the cost or economise the cost to the level that it is competitive with the conventional Portland cement. Though there are a couple of challenges ahead for us, and one of the challenges is the newness of this technology, which is sometimes not easily acceptable to the engineers, civil engineers outside. So because they have been used to Portland cement and the grouts and conventional chemicals for so long that bringing in a new technology which utilises bacteria, which we are known, like we know bacteria for their bad habits. We know that, okay, if it's bacteria, it's going to cause a disease or it's going to cause some infection, but very little we know about the good side of the bacteria that it can also help us in formation of cements. So yes, newness of the technology is one of the challenges we are facing at this stage. 

Professor Abhijit Mukherjee: 11:59 I think it’s the classic problem of, uh, news that bad news spreads far faster than good news and therefore we know more about disease-causing bacteria ad very little about the good bacteria. We know more about antibiotics than probiotics and, the same way engineers have completely ignored the living material that they work with really. So I remember one of my first papers when we sent it for review, a comment was that ‘I can't believe that the cement that I used so far is full with, you know, dirty creatures like bacteria.’

David: But of course we’re full of bacteria, so we're all filthy. 

Professor Abhijit Mukherjee: Yeah – so ninety percent of our genes are bacterial genes. So yes, we are as puerile or as filthy as the bacteria are.

David: 13:06 In terms of the research that's being conducted with MICP and other biocements, well, actually that's the same thing – are we seeing the increased longevity for new and pre-existing building materials, lower carbon footprints, in the research that's been done right now?

Professor Abhijit Mukherjee: 13:25 I will possibly answer that question a different way. Where do we see the lowest hanging fruit with this technology? Now what we have noticed is that repairing old structures is one area where a living material can make a huge difference. Our latest Australian Research Council project is on that – how to create a self-healing material but at the field scale, not in the lab scale. So that's one area where we think there is a lot of immediate gains to make. We are working with a start-up company in Western Australia to commercialise the biocement as a product that is like a, it's not really a coating, it's more like something that gets absorbed into the substrate, which could be concrete or it could be soil, and seals it and therefore the pollutants from that atmosphere cannot go in and therefore it increases longevity.

Professor Abhijit Mukherjee: 14:37 So you get a huge bang for the buck where you are using very little quantity of the biocement and getting a huge benefit. Uh, similarly for dust suppression, you know, we are a mining state and therefore dust is a huge problem. You can cut the dust down tremendously with a very natural product in this case, with a biocement, so you cement the dust particles just a little bit so that they cannot, cannot fly off easily. They are interlocked and they cannot, you know, move away from each other easily and therefore you suppress dust. So these are some of the areas that, along with the coastal erosion problem that we talked about already, these are the three areas that we think biocement has a huge scope.

Dr Navdeep Dhami: 15:30 Dust is a big problem in Western Australia, especially in mining environments. So in this case, so the conventional process of dust suppression is spraying water six times a day, which is a huge amount of water and there's a lot of manpower required in the process. So when biocement we can minimise to one set of spray and it's good to go for the next five days. So how much we are preserving utilising natural materials? So that's a big benefit. So another benefit that we have seen just recently, we have got another project with the Mineral Research Institute of Western Australia in collaboration with mining industries including BHP, so there we are going to utilise this biocement for creation of barriers after [inaudible] recovery of metals. So that is also another benefit where conventional reagents or conventional materials have not been able to function to their best. So there biocement is going to be applied.

David: 16:29 Abhijit, you mentioned the lowest hanging fruit – the problems that we were able to solve more or less now with biocement – if we're looking in the, I guess the longer time frame, what are some of the higher hanging fruit, the bigger challenges that we can solve, the bigger problems that we can solve with this research?

Professor Abhijit Mukherjee: 16:47 Well the final aspiration is to completely avoid engineered cement and go back to the natural products that we have been using earlier. The world population right now is 7 billion, expected to go up to 10 billion. So if we have to build a house for each individual, if everyone has to have a roof over head with the present technology that we know had left, and therefore you need to come up with something that's sustainable. The present cement technology is definitely not sustainable, and that's the bigger challenge that you have that can we really make, you know, kind of transform engineering, civil engineering as it is today into something which recognises the huge benefit that the little microbes that were already around us, always around us, can give? 

David: And do you reckon we can pull it off? 

Professor Abhijit Mukherjee: Yes. Well as researchers we always remain optimistic. Well, of course, you know, when we are criticised sometimes, we feel really bad; we take a long walk and come back and say, ‘No, it's going to happen.’ And, and once again they're going to start working in the lab, you know, if you go to our lab right now, there are at least 15 students, you know, who think that they can pull it off. And I have great faith in them.

Dr Navdeep Dhami: 18:26 Yeah. So even this can be seen in the, like, the current projects that we have got, the funding that we have got, and we have been able to convince the industry, we have been able to convince the Australian Research Council. So that's one of the ways where we can see that, yes, we can pull it off because we have already been able to convince the experts in the area. So we definitely see a future in this.

David: 18:48 So the future is closer than we think it is? It could be that it might not be too long until we've, we've got this on building sites on a larger scale? 

Professor Abhijit Mukherjee: Well [inaudible] 10 years. Yeah that, that's my take. If I have convinced you today about the biocement.

Dr Navdeep Dhami: 19:06 So already this technology has been applied on certain historical monument repairs. So there is a good amount of research which was done in Europe, in the US, so their big field trials have already been done and historical buildings, monuments, have already been repaired utilising this technology. So definitely we would like to expand it further. 

David: How do we lower the costs of biocement?

Dr Navdeep Dhami: So with the current processes or the current technology is utilising very pure grade chemicals for growing bacteria. The cementation reagents that we are currently using, they're very, very pure forms of the chemicals. So the way forward is to utilise natural, low-grade, cementation reagents, as well as the nutrients to grow bacteria. So definitely we need to move from very fancy, pure grade lab chemicals to something which is available in nature in large amounts. And one of the ways by which it can be done is utilising industrial by-products, which are waste lying all around us.

Dr Navdeep Dhami: 20:06 So in one of the research studies conducted in our own group, so we try to utilise the waste product from lactose, from corn industry. So there we try to utilise that as a source of nutrients for bacterial growth. And we were successful in that. So another way to minimise the cost is utilising calcium and urea from natural sources. So in case of urea, there has been another study. We are the source of – sorry, not urea calcium, I'm sorry – so the calcium has been utilised from seawater. So that is another way to economise this technology by utilising natural sources.

Professor Abhijit Mukherjee: 20:45 I'd probably look at cost from different angles. One is, of course, costs in terms of dollars. I think there the answer lies once again in the nature – nature doesn't really pay to, you know, make cement that you know, is happening in coral reefs and stromatolites and caves and across topographies. So what does the nature do? It actually, there's a cycle of mineralisation and demineralisation of calcium carbonate. So there are some bacteria that dissolve calcium carbonate into soluble forms and the other that re mineralises it. So right now we have actually broken the key of how to mineralise. We haven't seen enough of the other one that, how can I dissolve limestone into soluble calcium? If I can do that, limestone is everywhere, it's cheap, you can use it more easily. But there's another cost which is environmental cost and how to bring that down.

Professor Abhijit Mukherjee: 21:53 One of the challenges that we have right now is the technology that is most commonly used also creates ammonia. And ammonia is not a gas that we would like to release into the atmosphere. How to use it back you know, how to use it beneficially is another important component. So we can use it, you know, one example is one of my students is working on a river valley stabilisation in India. Now in that, when ammonia is produced, it's food for plant. It's the same plants that grow on the riverbank because we want to stabilise. This river starts from China and then goes, flows into India, flows through India into Bangladesh and becomes the largest Delta of the world. So it has the largest and the smallest Island on a river.

Professor Abhijit Mukherjee: 22:59 So the riverbanks break all the time. In monsoon, the river changes its course. So what we are trying to do is stabilise the riverbank so that the devastation is at least mitigated. Now, if you use the technology, the cementation technologies – it’s a long riverbank – so ammonia generation is huge. Now how do you cut down that ammonia going into the atmosphere? So it's soluble and so use it to grow the plants. So the plants also stabilise the bank. So how to, you know, once again convert the by-products of this process into product for something else so that you can really have a circular economy. So once you have a circular economy, you have really, you know, addressed the issue of cost.

Dr Navdeep Dhami: 23:53 And this ammonia can be also utilised as a fertiliser for plants. So we would like to – 

Professor Abhijit Mukherjee: 23:58 Yes, sorry, I didn't use the word fertiliser, that’s an important one. 

David: And research wise, what are you both up to? What fun-filled research is happening within the walls of this institution?

Dr Navdeep Dhami: 24:11 Okay, so there are, I'll say three components of this research. So the first component of this research from where we started initially it was studying natural formations, or studying natural cements. So in that, we started with understanding the formation of beach rocks, the formations of stromatolites, the formation of caves in Western Australia. And fortunately we had a couple of very interesting sites around us, which gave us a chance to collect these materials. So the second part of this research was to isolate the bacteria, which we can utilise for different applications in the current civil industry. So the second component was isolating bugs for a specific purpose. Like in case of concrete, we look for bugs which can work under high pH, high salt conditions with low oxygen. So they we need to get bugs from certain similar environments. So that's what we have been successfully doing for different applications. So the third part of the work, where Abhijit is exploring, is applying this biocement into different civil materials and he'll tell more about where he sees us in this.

Professor Abhijit Mukherjee: 25:23 Well, finally, everyone is a philosopher, right? So I was just trying to write down the answer to your question and what I came up with is, what's my aim? Unlock the mysteries of nature on how to leave peacefully with all creatures.

David: Gee, you're right. Everyone is a philosopher!

Dr Navdeep Dhami: 25:53 So I think we have been successful in unlocking maybe a few parts of the puzzle.

Professor Abhijit Mukherjee: There a few still missing, and we are searching all the time. 

Dr Navdeep Dhami: And if we can utilise it in the same way that nature is doing it, so that will be the ultimate goal for us.

David: 26:10 Cool. Well, I think that should, I think that should wrap everything up. Thank you very much Navdeep and Abhijit for coming in and sharing your expertise on this topic today.

Dr Navdeep Dhami: 26:19 And thank you very much for giving us this platform to share our research with everyone. Thank you.

Professor Abhijit Mukherjee: 26:25 Thank you. 

David: You've been listening to The Future of, a podcast powered by Curtin University. If you have any questions about today's topic, please feel free to get in touch by following the links in the show notes. Bye for now.