Production of concrete, the worlds most used building material, is a major contributor to total global carbon emissions each year. On this episode of Policy Outsider, Matt Adams, a Richard P. Nathan fellow at the Rockefeller Institute, and Nicola Armacost, major of the village of Hastings-on-Hudson, in Westchester County, New York, join host Alexander Morse to discuss a local policy initiative in Hastings-on-Hudson aimed at promoting low-carbon concrete. The conversation, which builds on a recent policy brief, also touches on the role local, state, and federal governments can play in reducing carbon dioxide emissions from concrete.


Matthew Adams, Richard P. Nathan Fellow, Rockefeller Institute of Government

Nicola Armacost, Mayor, Village of Hastings-on-Hudson

Learn More:

Concrete Solutions to Climate Change


  • Transcript

    Transcript was generated using AI software and may contain errors. 

    Alexander Morse 0:04

    This is Policy Outsider. I’m Alex Morris. Production of concrete, the world’s most used building material, is a major contributor of total global carbon emissions each year. Over the past few decades, engineers and scientists have developed techniques to develop concrete with a lower-carbon footprint. Among procurers and suppliers, however, a lack of technical understanding of new technologies, concerns about costs of new materials, and a lack of funding have hindered adoption. On today’s episode, we have two special guests Matt Adams, an assistant professor in the John A. Reif Jr. Department of Civil and Environmental Engineering at the New Jersey Institute of Technology and a Richard P. Nathan fellow here at the Rockefeller Institute. We are also joined by the honorable Nicola Armacost, mayor of Hastings-on-Hudson, a village in Westchester County in New York State. Both will join today to discuss the concrete problem and a local policy initiative in Hastings-on-Hudson aimed at promoting low-carbon concrete. The conversation will also touch on the role local, state, and federal governments can play in reducing carbon dioxide emissions from concrete. Coming up next.

    Alexander Morse  1:50

    Today, I’m joined by Matthew Adams and the honorable Nicola Armacost. Thank you both for joining today.

    Matthew Adams 1:56

    Thank you.

    Nicola Armacost  1:57

    Thank you for having us.

    Alexander Morse  1:58

    So we’re here to talk about infrastructure, specifically, concrete. A vital material used for major infrastructure projects such as roads, walls, buildings, and bridges. And then with the backdrop of the Biden Administration’s forthcoming infrastructure plan and billions of dollars flowing into the communities across the United States to rebuild and repair many parts of America’s infrastructure, we thought it would be a good opportunity to invite you both to talk about the environmental impacts of concrete and discuss the recent case study authored by you, Matt, and published by the Rockefeller Institute that examines the village of Hastings-on-Hudson’s newly implemented Low-Embodied Carbon Concrete Initiative. So to start off, Matt, let’s get a brief introduction to concrete. I’m sure most of us are familiar with what concrete is and its applications, using to build bridges, roads, etc., but what about concrete makes it an environmental concern?

    Matthew Adams 2:58

    So concrete is made up of a few main ingredients, you’ve got aggregates (like gravel and sand), water, air, and then cement. So cement is a fine grey powder that when mixed with water undergoes a chemical reaction and that will cause the system to harden. So you can think of it like a cookie, a chocolate chip cookie, when you first mix those ingredients. They’re wet and pliable, you’ve got the flour and eggs that sort of act as the binder. Those are like the cement and water, and so when you mix those and put them in the oven, they undergo a chemical reaction and they harden, just like in concrete. The water in the cement undergo a chemical reaction and harden and bind all of the system together. So we put aggregates into concrete to make it cheaper and use less cement, because cement is the most expensive component. But cement is also where all of our embodied carbon concrete comes from. The production of cement actually produces quite a bit of carbon dioxide through various processes.

    Alexander Morse 4:08

    You use the term embodied carbon concrete, what does that mean?

    Matthew Adams 4:13

    The embodied carbon of something is all of the CO2 and oftentimes, we will include other types of emissions in there and just tie them back in and is what we would call a CO2 equivalent. But basically, the embodied carbon is all of that carbon that was produced during the production of the material. So, you can think of smooshing down all of the carbon that was produced during all the various phases of production into a single number and you say that okay, this block of concrete had this much carbon produced to make this block of concrete.

    Alexander Morse 4:54

    And what are some of those factors, like transportation?

    Matthew Adams  4:57

    Yes, we can think of transportation as a big one. So transportation burns fuel and releases carbon dioxide into the atmosphere. But also, cement production is quite carbon intensive. When we produce cement, we take raw materials. We take limestone and clay, for the most part. We crush them up, we put them into a kiln, and they get heated up to around 2500 degrees Fahrenheit. And that requires a lot of energy. We burn fuel for that. Burning the fuel to get up to that temperature releases carbon. But the main source of carbon from concrete comes from the limestone. When you heat up limestone to that temperature, you break it down. Limestone is calcium carbonate or CA CO3 from a chemical formula standpoint. When you heat that up, it breaks down into calcium oxide and carbon dioxide. And so right now, most of that carbon dioxide that’s produced during the cement making process just gets released to the atmosphere. We don’t have good processes in place yet for capturing it.

    Alexander Morse 6:07

    Okay, so how much concrete is produced and used in a given year?

    Matthew Adams 6:11

    There’s about five billion tons of concrete produced every year. You can think of it as a few cubic yards per person per year in the world. It’s produced on such a massive scale around the world. That is why it is such a big carbon producer in the world because we just make so much of it. It’s the second most used material in the world after water.

    Alexander Morse 6:41

    Wow, that’s incredible. So then, if its five billion tons produced a year, what’s the estimated carbon emissions then?

    Matthew Adams 6:50

    It’s about 8 percent of our total carbon emissions in the world, from anthropogenic or human-related activity each year. So that’s quite a bit. Concrete releases about .29 pounds of CO2 per pound of concrete that’s produced, which is actually pretty low compared to other building materials. But because we make so much concrete, it outstrips the other building materials in terms of total CO2 produced.

    Alexander Morse 7:20

    Yes, 8 percent is not an insignificant number. Why is concrete so abundant? Why is it so widely used?

    Matthew Adams  7:26

    So there’s three main reasons why concrete is so widely used. It is abundant and local, meaning that we can make concrete out of materials that are available just about everywhere in the world. So you don’t need to ship raw materials in from the other side of the planet to make concrete. And because of that, it ends up being fairly cost effective as a material. You don’t need to worry about negotiating with other countries or things like that. You can just make it at home. It can also be formed into any shape you want. It’s very easy because when you first mix it, it’s in a fluid state. So you can pour it into a mold and get a particular shape that you need. You don’t need to go through heavy processing to put it into a specific shape. And then finally, compared to a lot of materials out there, it’s relatively durable and resistant to environmental degradation. I know that we see and talk about concrete that is falling apart all the time, but in the grand scheme of materials, concrete is actually a very durable material.

    Alexander Morse 8:35

    Okay, so between its accessibility, ease of use, or applicability in across a lot of different projects, and it’s cost effective, so it makes it clear that it would be widely used. However, have there been improvements or efficiency gains in the development of concrete?

    Matthew Adams 8:55

    Sure, not too long ago when we were making cement, we used to take all the raw materials and grind them down into a wet slurry and introduce that into a kiln as like a wet mixture, which of course takes more energy, because before it can go through the chemical change process, you need to burn off all of that water. So we no longer really use wet slurries in concrete plants or cement plants anymore. We use dry slurries. And they’ve also done a lot of work to capture the heat that’s released from the kiln. So instead of just letting the heat bleed off out of the kiln into the environment, they now capture that heat and use it to preheat the materials. So there’s been a lot of energy efficiency gains on that end. But those gains really only impact the fuel efficiency of the kiln process. We have to remember that about 60 percent of the CO2 output of cement comes from the breakdown of the calcium carbonate. You only get so far with those fuel efficiency increases.

    Alexander Morse 10:08

    So it sounds like there’s kind of a trade-off. By producing more concrete, we’re still burning off this limestone and we’re not really making a ton of efficiency gains in terms of emissions.

    Matthew Adams 10:20

    Right. And that’s assuming that you’re using full Portland cement concrete mixtures. But there are lots of options available for us to reduce the amount of Portland cement that we use in a concrete.

    Alexander Morse 10:33

    What is Portland cement?

    Matthew Adams 10:35

    So Portland cement is your everyday cement. Portland cement is part of a group of materials that we classify as hydraulic cements. And there are a handful of hydraulic cements out there, but Portland cement is the one that everybody’s really most familiar with. It’s what our driveways and roadways and buildings are mostly made out of. The other types of hydraulic cements we have are really more for niche applications. They have very specific properties that don’t lend well to being used everywhere but work for specific applications.

    Alexander Morse 11:07

    We’re talking about concrete, how carbon intensive it is under practices that we’ve been generally using throughout beyond the United States. Right, Matt?

    Matthew Adams 11:17

    Yes, this is worldwide.

    Alexander Morse 11:21

    Well, thank you, Matt, for giving us a little bit of table setting about concrete, what the components are, why it’s an environmental problem and concern and looking at where we can try to find approaches to improving the carbon profile of concrete. And so we’re going to take a quick break, but when we come back, we will invite Mayor Armacost to talk about the resolution that her village, Hastings-on-Hudson, had passed to identify an approach to decarbonizing the concrete process.

    Alexander Morse  12:25

    Welcome back to Policy Outsider. I’m with Matthew Adams and honorable Nicola Armacost, mayor of Hastings-on-Hudson in Westchester County, New York. We were just talking about the carbon profile within concrete and how it represents about 8 percent of all carbon emissions worldwide. And that there are several policy alternatives to trying to lower that amount of carbon and that the village of Hastings-on-Hudson proceeded to take a unique approach to limiting the carbon profile. So Mayor Armacost, could you please walk us through what this resolution is and what it does? And why it’s unique?

    Nicola Armacost 13:06

    Thank you, Alex. Yes, I’d be delighted to do that. In May of last year, our Board of Trustees passed a resolution committing our local government to promote the use of low-embodied carbon concrete products in buildings and infrastructure within the village. And we did this as part of a larger effort to reduce our greenhouse gas emissions. It turns out, we’re the first municipality in New York State to publicly commit to promoting the use of this technology. So that’s one area in which this is a unique resolution. But there are a couple of other things that are unique about it. Three things stand out for me. One is that we didn’t limit the type of technology. The second is that it doesn’t just apply to municipal projects. And the third is that we intentionally included a pedagogical component. And I’ll just quickly explain the way in which we didn’t limit the type of technology, so we specifically outlined in the resolution different ways in which the reduction of concrete could be achieved. It could be achieved through using less cement, replacing or substituting cement with other material—fly ash, slag, more slag, more fly ash or ground glass pozzolan—using cement that’s produced locally, very locally. And or, alternatively, some of the kinds of interesting cutting edge technology like embedding carbon in concrete as we’re seeing in some innovators that are operating around the country and in other parts of the world. So that kind of laying out of the different options is something we noticed as being unique.

    Alexander Morse 15:16

    Yes, I noticed that when I read the resolution that it was prescriptive, that the end goal was to limit the carbon profile and to have more energy efficient concrete. But it wasn’t prescriptive in the ways that you mandated that it had to be by using a different compound or a certain technology. I thought that was an interesting broad approach. And then there was the second aspect that was unique, which wasn’t limited to only municipal infrastructure. So how does that apply in the real world?

    Nicola Armacost  15:52

    So municipal infrastructure might be things like sidewalks or curbs or municipal buildings. Our view was, there’s lots of building happening in the municipality. For example, we have a large extension, a $20 million extension being proposed for our school. And by not making it just municipal, it means that we can be encouraging the use of green concrete in any other project that’s happening within the municipality that involves concrete.

    Alexander Morse 16:28

    Now, is this a mandate? Or is it just an encouragement?

    Nicola Armacost 16:31

    It’s an encouragement for now. My view on policy change is that you have to woo people and you have to educate. You educate and you woo and then eventually you mandate. But if you mandate from the very beginning, there’s a feeling of it being oppressive because people don’t really understand what’s involved. You have to have persuaded them and done some pilots and explained that this is going to be something that’s beneficial and prove through action that it’s something that’s beneficial at the end of the day.

    Alexander Morse 17:08

    So that leads nicely into the third component of this resolution, which was the educational aspect of being able to communicate what your successes, your findings, and your best practices are to neighboring municipalities or other engineers. Why did you find that to be an important concept to include?

    Nicola Armacost 17:28

    Well, from the very beginning, in order to get it adopted, we had to engage in a pedagogical process. We had to explain to the trustees who were going to adopt it that it was something that they should be adopting. We had to assuage any concerns they had. We had to persuade the village staff who were going to procure it that it was something that made sense for them to procure. We had to persuade our engineer that it was equally safe or equally durable as anything that he would otherwise be procuring on behalf of the village. So there was an education process that had to happen with the core stakeholders that were needed to actually… and our building inspector, we had to persuade our building inspector that he was not going to violate any building rules by implementing this policy for us. There was a process we went through in terms of building the buy-in of key stakeholders within the municipality. And it was clear to us that if we wanted to leverage the impact of this resolution, we needed to have many other municipalities adopted. We’re a relatively small municipality, we have 8,000 residents. And if we want to seriously reduce CO2, we need big cities, we need states, we need the federal government, we need other countries to be adopting a similar set of resolutions and mandates and laws in order for that impact to occur. So we were leading by example. And we were showing municipalities close to us, sharing our resolution freely with them. We held many webinars. We held seminars. There were lots of chitchatting on the phone. There was a long ongoing process. We did interviews with the local media. There was a lot of work involved and it’s ongoing in terms of sharing this idea and helping to spread the word. We felt that was something that was very important to do with something that is so new to people and helping to demystify it. Helping to make it something that is interesting and exciting for them to do and also not scary or dangerous.

    Alexander Morse 20:01

    Good policymaking is typically done through a collaborative community approach. So it sounds like there was really a bottom-up approach ensuring buy-in throughout the entire community and all the stakeholders. How did the village identify concrete as a path towards decarbonization?

    Nicola Armacost 20:20

    It’s a kind of an interesting story. So I had been invited to the Bloomberg New Energy Finance Summit in Manhattan by a friend of mine, whose head of the Americas for the NEF. And one of the things that BNEFS does is it showcases interesting businesses and technologies that are on the cutting edge in terms of sustainability. And I heard Rob Niven, who is the CEO of CarbonCure, speak and I found it fascinating. I had filed it away in the back of my head as something that might possibly be interesting for the municipality. At that time, I was a trustee. And by coincidence, a few years later, a dear and long-standing friend of mine, Chris Neidl, who’s worked very closely with the Open Air Collective, and I were catching up. And he told me, he was working on this very topic. And so I said, “Look, I’ll offer my new municipality as a place for us to explore how this can be done in a way that could be leading edge in New York State.” He said that he was working on a legislative approach at the state level. And often to get something passed at the state level, you need to see examples of municipalities that are smaller that have actually proven the case. And through Chris, we met Matt, who was incredibly useful to us because he could speak engineer-to-engineer to our engineer and persuade him that we weren’t all completely out of our minds, but were actually relatively sensible here. And we also met eon Simoni Dez, who it turns out grew up in Hastings, but was working with the Open Air Collective. And so we ended up pulling him in not only to our green concrete activity but into a bunch of other activities. So there was there was a little bit of luck, there was a little bit of magic, there was a lot of hard work. That’s sort of what built it up. But a lot of community engagement is different people pooling their ideas together. It’s got us to where we ended up.

    Alexander Morse 22:47

    And so you ended up with passing this resolution in May of 2020. So it’s been a little bit over a year now since that resolution has passed. What projects has the village undertaken utilizing green concrete?

    Nicola Armacost 23:00

    Well, almost immediately, we knew we needed a showcase project. We had a fairly terrible thing that had happened in the village, which is that a truck lost its brakes and slid down and hit a beautiful old wall and crumbled the wall at a place called Cliff Street. So we decided in the rebuilding of that wall that we would use low-embodied carbon concrete. And it was quite interesting because we had to explain what we meant to our engineer. We had to explain what we meant to the contractor. And everyone got it, everyone understood the concept and everyone saw that using less slag in this case, or I guess, more slag and less concrete in this case, was going to be able to reduce the CO2 and create a perfectly lovely and solid wall. So that was our first project. The second project was for what we call the Vest Pocket Park, which is a really lovely little park opposite one of the favored coffee shops in the village. The wall was unstable and the park had been unusable for several years. And so in the process of rebuilding the retaining wall, we used low-embodied carbon concrete. So those two projects are actually completed. And we have already planned a major sidewalk project, which is something that we are doing with Westchester County. We’ve already committed $350,000 to sidewalks and we have about, I think, $2 million worth more of sidewalks we intend to implement, and we intend to use use low-embodied carbon concrete for each of those projects.

    Alexander Morse 25:04

    Now, are there estimates for how much concrete was avoided or maybe how much carbon was displaced as a result of utilizing this?

    Nicola Armacost 25:15

    For the Cliff Street project, we were able to reduce the global warming potential of the concrete by about 16 percent. And for the Vest Pocket Park wall project, we were able to reduce the global warming potential of the concrete by almost 19 percent, which was an improvement of 3 percent on the Cliff Street project. So it’s gradually improving with each new project.

    Alexander Morse 25:50

    It’s great to hear that there have been a couple of success stories and more projects coming down the pipe. We hope that this podcast can help satisfy the pedagogical component and help give municipalities an opportunity to learn from your case study and success stories.

    Nicola Armacost  26:08

    Yes, it will be fantastic. The more the merrier.

    Matthew Adams 26:12

    Well one thing, I think, that is interesting that I want to add in and, maybe correct me if I’m wrong, when working with the concrete producer, the first went to the concrete producer, and they said we want low-embodied carbon concrete, we want green concrete, he didn’t really know what that meant. But as soon as they explained it, it was a product he was already using. The slag replacement was something he was already using and was familiar with. Just wasn’t using it in this particular purpose. I think it’s really interesting that there’s lots of these solutions that are already in use out there just not being used in this in this manner.

    Nicola Armacost 26:56

    Absolutely. I think it’s quite interesting, because some people, when you say, you know, were promoting green concrete, they want to understand why the concrete is actually physically green. And of course, it isn’t green, it looks exactly the same as every other concrete. But you know, there’s a, there’s a five or 10 minute conversation about colors that you have to go through before you can actually have the rest of the conversation. And, as Matt says, it is when you are able to explain it in language that is familiar, or in terms that are familiar to an engineer or to a concrete producer or to a contractor, they totally get what you’re saying everyone understands, you don’t need to have the same amount of concrete in a sidewalk, which is just going to hold up, you know, one of the three of us as you might in a bridge, which has to hold up an articulated lorry, you know, so you, you know, the kind of durability that’s required, or, you know, everyone can see that you can, in fact, substitute ground glass puzzle and and that’s not going to make any difference to any of those safety or security type concerns that people might have about a project.

    Alexander Morse 28:15

    I think it’s pretty fascinating. This has been a great conversation. Is there anything that no one wants to touch on that we haven’t?

    Nicola Armacost  28:22

    On my side, one of the things that I’d really love to see is some of our system municipalities adopt similar resolutions. So the village right next door to us, oddly, has already adopted a similar resolution. It would be really fabulous to have more and more municipalities going up the Hudson toward Albany adopting this kind of a resolution. To have the county adopt a resolution for the governor to sign it in New York State that really will make such a palpable difference in terms of CO2 reduction. It’s a really serious action that has genuine impact. One of the concerns that some of our trustees had initially had to do with is this greenwashing? This is not greenwashing, this is really, really something that will have genuine impact that will affect one of the areas that produces the most CO2. And so I think that for a municipality that cares about climate change or for residents, or stakeholders that care about climate change, this is actually an action that’s completely simple accessible to do that will make a real difference.

    Alexander Morse 29:53

    Just going go back one second, what is greenwashing?

    Nicola Armacost  29:56

    So the idea that it sounds good but actual the impact is not that substantial. And the concerns that our trustees had were that this was something that sounded kind of attractive but wasn’t going to have any impact whatsoever. And we were able, through a lot of the research that Matt had produced and the Open Air Collective had produced, we were able to show that this was something that was going to have huge impact locally, but also potentially, in the county and at the state level and broader if the application was picked up by some of those other entities.

    Alexander Morse 30:41

    It appears or it sounds like it’s… I don’t want to necessarily say low-hanging fruit but it might be small results in a single village. But as the application is adopted more widespread, those small incremental approaches will eventually yield significant results.

    Nicola Armacost  31:03

    Absolutely. It’s about aggregating the power of these municipalities. We, for example, are part of a consortium on river town/villages. So there are six of us within this group called the Local Village Officials Committee. My fantasy is that when we next procure concrete, the sidewalks, we all do it together. And it’s one of these versions of green concrete that we’ve discussed. There are all of these different kinds of consortia where mayors and elected officials can share these ideas with one another. We actually passed this in record time, it was really one of the quickest pieces of legislation for us to adopt. And I think it had to do with preparing people well in advance so that they could understand the benefits of it. And they could see that it was not going to create anything more onerous for the village and was going to be something that would be cost effective, which makes it a no brainer at the end of the day, from a policy perspective.

    Alexander Morse 32:14

    Especially as you improve your economies of scale. When you’re collaborating with other municipalities, like you said, you want to build a sidewalk with a neighboring sister village, sharing labor, sharing purchasers, and equipment costs, that’s going to drive prices down while simultaneously achieving a dual goal of reducing carbon emissions.

    Nicola Armacost 32:34


    Matthew Adams 32:35

    The government, whether it be federal, state, or local, is the largest procurer of concrete. So obviously there are private entities that have been very forward thinking in terms of sustainability and that has extended to their own construction projects. You can think of companies like Apple that have spent a lot of time making sure their new construction is sustainable but in in reality that’s a very small amount of concrete that is procured. If we can move this idea into the government procurement sphere that’s really where we’re going to see the big impact because that’s where most of the concrete is being purchased and made for.

    Alexander Morse 33:25

    Well, Mayor Armacost, Matt, thank you so much for joining me today. This is a great conversation.

    Matthew Adams 33:31

    Thank you for having me.

    Nicola Armacost 33:33

    Thank you, Alex. It was a pleasure.

    Alexander Morse 33:45

    Although Hastings-on-Hudson was the first municipality in New York State to have such a resolution involving green concrete, there has been some activity at the state level. The New York State Senate and Assembly recently passed a bill that would apply a low-carbon concrete standard to all procurement contracts with state agencies and departments. The legislation awaits the governor’s signature before it becomes law. We here at the Rockefeller Institute will follow along with the developments and keep you updated about this initiative. So be sure to follow along with us. Thanks again to the Honorable Nicola Armacost and Matt Adams for joining today. And thank you for listening. I’m Alex Morris, until next time.

    Alexander Morse 34:46

    Policy Outsider is presented by the Rockefeller Institute of Government, the public policy research arm of the State University of New York. The Institute conducts cutting edge nonpartisan public policy research and analysis to inform lasting solutions to the challenges facing New York State and the nation. Learn more at or by following RockefellerInst on social media. Have a question or comment or idea. Email us at [email protected].

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