Podcast Episode 1.31

Trash to treasure: One man’s journey to make CO2 waste a useful product

What does it take to turn an idea that could help fight climate change into a self-sustaining business? We often hear the glamorous stories of startups that have made it, but little about the struggles, the learning, and the luck required to get there.

Pol Knops, Founder and Chief Technology Officer of Green Minerals, joined Climate Now to share his ongoing journey to design, develop and market a process that transforms carbon dioxide emissions into a useful product.

Green Minerals speeds up the natural process of mineralization, in which CO2 chemically reacts with iron, magnesium or calcium-rich minerals to form a new mineral, permanently trapping the CO2.

The Green Minerals mineralization process uses olivine to react with captured CO2 to create feedstocks for the concrete and paper industries.


Pol Knops
Founder of Green Minerals


Pol Knops

Founder of Green Minerals

Pol Knops is the Chief Technology Officer and Founder of Green Minerals, a tech company using olivine to mineralize CO2 and turn it into functional products like concrete and paper.

Hosted By:

James Lawler
Climate Now Host


James Lawler

Climate Now Host
James Lawler is the founder of Climate Now. James started Climate Now as a way to learn about climate change and our energy system. Climate Now’s mission is to distill and communicate the science of our changing climate, the technologies that could help us avoid a climate crisis, and the economic and policy pathways to achieve net zero emissions globally. James is also the founder of Osmosis Films, a creative studio.

Katherine Gorman
Climate Now Host


Katherine Gorman

Climate Now Host

Katherine Gorman is a podcast host for Climate Now. She has worked for terrestrial public radio stations across the US, and is also co-host of the podcast “The Talking Machines”. She is excited to democratize the climate conversation and to learn and share knowledge from experts in the field.

Date: 10.25.2021 Running Time: 20 min


James Lawler (00:03): You are listening to Climate Now. I’m James Lawler.

Katherine Gorman (00:07): And I’m Katherine Gorman. And today, we are talking with Dr. Pol Knops, the Chief Technology Officer and founder of a company called Green Minerals. 12 years ago, Pol had a PhD in physics and a career in converting waste products into energy and construction materials, when he decided to create an entirely new product for a market that didn’t really exist yet.

Pol’s plan was to develop a technique that turns CO2 into a solid mineral that could be used as a feedstock in industrial and manufacturing processes. On the path to realizing this plan, he has become one of the world’s top experts in the carbon dioxide removal technique called mineralization.

JL (00:46): Mineralization of CO2 is the process by which carbon dioxide reacts with certain rocks and minerals to form solid and stable carbonate rocks – turning the CO2 to stone so that it cannot be re-released into the atmosphere. This process already occurs naturally, removing somewhere between 0.6 and 1.5 gigatons of carbon dioxide per year[1,2].  Pol’s company, Green Minerals, is one of a handful of companies working to create this process artificially.

KG (01:17): Pol, welcome, and thank you so much for joining us.

Pol Knops: Thank you. I’m very much delighted to be here, indeed yes.

KG (01:24): I would like to just jump right into the science. How does your mineralization process work?

Pol Knops (1:31): Yes, indeed. Yes. Olivine is a mineral. It is an alkaline mineral and CO2 is an acid, carbonic acid. And you might remember from high school that acid reacts with base. And the olivine is a base, an alkaline material, it reacts with acids. So that’s in essence, the reaction.

KG: So you use Olivine to react with CO2, forming a new solid.

Pol Knops: Indeed yes.

JL (1:58): So of all of the different, you know, CDR possibilities, why do you find mineralization to be as compelling as you do? You are like the, the mineralization guy at this point.

Pol Knops (2:09): Unfortunately yes, indeed, yes. My background is physics and the process is a bit physics, chemistry, geology. So therefore, I happened to be stuck in, this process. I quite like it because you are permanently binding CO2 and you make valuable materials where you have the CO2 converted and it won’t be released again anymore. So, yeah, so that’s one, I think also being honest it’s also partially the stubbornness, indeed yes, to keep on, I think, indeed yes.

KG (2:39):  Pol has certainly been persistent, he’s been working for over a decade to get Green Minerals off the ground.

JL (2:47): He got the idea when he was working at a sewage treatment company using a high-pressure high temperature reactor to treat sewage, and he read that mineralizing CO2 would require high temps and high pressures and thought the reactor for sewage could also work for CO2. Makes sense, CO2 is really just a different type of sewage, right?

KG (3:06): Yeah, it’s our energy sewage.

JL: And he found an angel investor, and they basically cobbled together the reactor on their own, in his basement. And then they needed more hands, they needed researchers, but they couldn’t find any universities or institutions in the Netherlands that would support their work so they ended up going to Belgium –

Pol Knops (3:24): We ended up going to Belgium. To the University of Leuven. We met a professor over there and, he said, okay, that’s a nice idea. If you supply the equipment, we supply the students and then we can get things moving. We put it in a van, from my brother. And we just drove over. And we installed it over there and then, I think a few students did their theses about it. One guy did his PhD about it. And that gave us, let’s say much more flexibility because we got much more access to university analytical equipment, after some time we got a big project with ArcelorMittal, which is a major steel firm. And with Sibelco. That was the first time I would get some money out of this project.

JL: And you’re how many years in at this point?

Pol Knops (4:10): I think something like three or four years or so, and the three or four years we are, of course, very tough because I was spending the savings of my children. I was doing some consulting in between just to pay the bills. And my angel investor, he paid for the equipment, but it didn’t pay my salary. You have to remember in Europe getting venture capital is much more difficult. And so therefore I was very glad to get a project with ArcelorMittal and Sibelco. That speeded up things. And also, I learned that you need to have industrial partners involved. That you got to focus on not only the technology, but on the market.

KG (4:44): So the first several years were rough but it was a learning process for sure.

Pol Knops (4:49): And then about, I think five or six years ago, the project ended because the guy said that’s not economically feasible.

KG: No!

Pol Knops:  And then I said, yeah, of course, it’s not feasible. We’re just getting started.

JL (5:03): Pol decided that in order to make his process more attractive to investors, he needed to figure out a way to use the chemistry involved to create a product to sell in the market.

Pol Knops (5:13): We just were focused at the academic stuff, at the chemistry, indeed. And then we slowly realized that we were making a product, we were making a powder. And the powder can be used for different uses.

JL: What is the powder that comes out of this?

Pol Knops (5:27): It is a mixture of, magnesium carbonate and silica and it’s a mixture of fairly small, very fine particles.

JL: So then what’d you do? You had no more project, no more money. You know, people were telling you it’s not possible to do this. And then what did you do?

Pol Knops (5:45): I went to an incubator program because I thought, okay, I know the academics, I know the process, but I think we should better focus on the business side. And, I had the hope that if I went to incubator program, I got into some kind of ecosystem, I could form a team.

JL: And how did that go?

Pol Knops (6:03): The program was very good. So I learned quite a lot about venture capital and all these kind of things. But during the program I happened to know the people from Heidelberg cement for a long time. And then they came over to me and said, okay, we got a proposal from the German ministry to look into mineralization. Do you mind helping us? And of course, as that’s my business and I said, yes, please. So, the cement guy of Heidelberg and me, put together a research proposal really on one afternoon, that was on a, on a Thursday. On Monday, we went to Berlin presented the program.

JL: And who were you – you’re presenting it to whom?

Pol Knops: To the German ministry of, Bildung und Forschung, how do we say? Education and research.

KG (6:49): OK so Heidelberg Cement came to you, you put together a research proposal with them on a Thursday afternoon, and the following Monday presented it to the German ministry of education and research. And what did they say?

Pol Knops (7:00): And she said, okay, you propose four year, make it three years. And she said, okay, you have to include German minerals. I said, the German minerals are not suitable. She says, that will be the outcome. And she said, go ahead. So we got 2.2 million euros.

JL: Wow.

Pol Knops (7:15):  Out of blue, indeed. Yes. That was on a Monday. And then we went to the University of Aachen on Thursday. And of course, if you go up with a budget from the German ministry, if you’ve got Heidelberg Cement, this is the number three major global cement player. So, then the doors at university opened and we were able to get this research proposal, let’s say converted into the academic reel. So we are able within one week to sit with five professors together and to make it into work packages and these kinds of things. So that was really a kickstart, indeed yes. And it was by far the biggest mineralization program in the Northern hemisphere. So that was quite a good start. Indeed, yes.

KG (7:58): So all this work, all this struggle, you lose your angel investor, you say, “I still can make this work!” you get into an incubator program, and then out of the blue this cement connection calls you, and boom, a week later you have 2 million euros and you’re the biggest mineralization project in the Northern Hemisphere.

Pol Knops (8:15): It was also for me, it was a complete, I was really shocked going in, and not a committee, not anything, just OK.

JL: Yeah, just here you go. Right. But ok, so that was how many years ago?

Pol Knops (8:27): It was, three and a half years ago, three years ago, yes.

KG (8:30): Wow ok so 2018. And where has that struggle, perseverance, falling down, and getting back up. Where has that all led you to today?

Pol Knops (8:40): Yeah, our project is almost finished, so that is positive. We have some results, so let’s say something like some concrete substance. And I, learned quite a lot. I realized that, besides concrete, paper is an interesting market and you have to remember in paper, there’s quite some lime used to basically it’s the idea to replace the lime. Concrete is of course, a bigger market. Concrete is also, let’s say by its nature, a very slow process because you need to have certification and the validation. which will take you a very long time to have accepted. And paper is much easier for the acceptance, the market is also smaller, that makes things easier. So therefore we made paper.

JL (9:12): Okay. So let’s,… just to explain that. Cause I think that that’s very interesting. You would think that, you know, wow, big market concrete, let’s just go there, but the certification is really important because, can you just explain that for everyone?

Pol Knops (9:26): Yeah. Let’s say, if you’re making a new product in the paper industry, nobody minds, is the paper. If after one or two years gets bleached or something like that. Because most papers are used only for a couple of weeks, but of course, if you make concrete, you want to be bloody sure that your house stays there for 30 or 60 or 100 years. So you have all kinds of, let’s say aging process to know what is happening in due time. But you see, first of all, you see the market is slow to respond to new things because this is already at a very big scale. If you come there with a product where you can make, let’s say a thousand tons per year, they don’t take you seriously. And then you make thousand tons a year and a paper on the street you can already supply.

Also, in the paper market, you can sell this type of filler for 100 Euros per tonne, but in a concrete market, I know the prices are lower because let’s say typically cement is being currently sold for about 50 or 60 Euros per ton.  That means you cannot sell somebody. Who is just making cement for twice as much as he is at the end of the day getting for his product.

Pol Knops (10:35)

So that means that you need a big scale, but also you need more earning from CO2, but due time, I expect indeed that the CO2 prices will be higher, and then you can lower your import indeed, yes. So paper is a first step to the market. If it will be the complete market that will stick to 6 million tons of product in Europe. But I expect, that will be the first market. And then from there, there are other markets, which you never thought about.

KG: (11:04) And it is clear that, at this point, you’ve refined your technique and have this product that can be incorporated into end-user materials like paper and concrete. But I want to get into the business side of things. How can you actually make this happen?

Would these industries have to change how they make their products to incorporate the mineral powder that you produce? Or is it a one-to-one translation, where your mineral product can replace existing feedstocks for the concrete or the paper that these companies are making?

Pol Knops (11:33): The idea is one-to-one new placement because then it’s the easiest way to get into the market and it will be very hard to make a new market and make a new product. If you make paper in Europe there’s about 6 million tons of lime used in paper manufacturing, they add lime to that for a few reasons. First of all, for the color, making it more white, but more importantly to make it cheaper and to have better properties. And you see this 6 million tons is a very, yeah I would say, a big market. And also the prices are much higher than in concrete. So therefore, the idea is, just to, instead of use the traditional lime, use this material.

KG (12:15): So when we’re talking about these products, how long does the CO2 stay in it? Is it until you recycle it again or reuse it, or is it just always trapped, forever trapped, sequestered there?

Pol Knops (12:23): It is always trapped. Let’s say you are making that into a different chemical form. You’re making it into a carbonate. And therefore it is trapped. It only gets released. If you heat the paper to 630 degrees, let’s say if you burn the paper, but then, uh, otherwise you would have used other lime, which also releasing CO2.

JL (12:41): What does the business case look like? What are the costs?

Pol Knops (12:43): The CO2 let’s say, depending on the location, because it’s also a commodity, if you go in, if you are very close to fertilizer plant, you will pay something like 30 euros per ton.

JL: 30 Euros ok.

PK: But let’s say if you’re far away or need smaller amounts they can go much higher, indeed, yes.

(13:00) So let’s say you’re buying 2 tons of olivine, let’s say for 50 euros, so you‘re paying on the feedstock 100 euros, the CO2, let’s say at the beginning, you have to pay for that for 30 euros, but eventually you get paid because the ETS price is 50 euros per ton. And then on the other side, you make, let’s say three tons each for 100 euros per ton. So you have, let’s say a gap between the feed stocks you’re buying and the product you’re making, let’s say of uh, yeah let’s say 150 euros per 3 ton, indeed yes.

KG: (13:29) Well that is a pretty significant margin of profit, then, at least theoretically. So, I guess, the next question would be, how far can you scale this up? You mentioned that 6 million tons of lime are sold currently in Europe for the purpose of paper production. Is the idea to completely replace that market?

Pol Knops (13:47): Yeah, that means you need to have 2 million tons of CO2 and 4 million tons of olivine, if you want to replace all of this lime. But that’s feasible because CO2 in one coal fired power plant already has 1 million to 2 million tons of CO2, the global Olivine production at this moment, something like 8 million tons[3] of olivine.

JL (14:09):

It’s the global market. Is that annually?

Pol Knops (14:11):

Yeah. Indeed yes. But that’s as the olivine mines, they’re supplying for the steel industry for completely different purpose.

JL (14:18):

Okay. And CO2 production from a single coal plant, you said one coal plant will produce…

Pol Knops (14:26):

One or 2 million tons of CO2. That’s a typical value [4].

JL (14:28):

Okay. Okay. So is this sort of a niche solution then? I mean, cause if you’re basically able to take the CO2 from one coal plant, but obviously we have a much bigger problem than one coal plant.

Pol Knops (14:39):

Let’s say in respect to the problem, it is a niche, indeed yes. But I envision more that at the end you have a paper mill, which emits something, like 40,000 tons of CO2 for running their gas-powered boiler, and then use that CO2 to make their own filler. And then let’s say typically paper mill uses about hundred thousand of lime. So then you will need probably half the amount of CO2 they’re emitting already from their natural gas fired power plant. So you see, I don’t expect that you build one or two big installations for making this kind of material. I envision more that you ship your olivine to the paper mill and that you there make your own filler at the site of the paper mill with the CO2 they’re producing already from their own plant.

KG (15:28):

But that being said, even if it is sort of localized to the paper plant, it doesn’t change the total sequestration potential of the technology in Europe, right? I mean, we’re still talking about 6 million tons, which seems quite small compared to other proposed carbon dioxide removal technologies, like carbon capture and storage, or CCS.

Pol Knops (15:47):

So let’s say from a climate point of view, this is a small beer, but of course you have to remember, the paper’s only one market. The concrete is a much, much bigger market. And, in contrast with CCS, you can start at a small scale and learn and scale up. And CCS has got the disadvantage. First of all, you’re only dependent on the CO2 price. And secondly, your first step is already 1 million tonnes. You can’t do CCS for 50,000 tonnes. And of course the paper mills, they are typically orientated at historic locations, very close to cities inland, this kind of thing. So therefore, and yes, you’re right, the paper is a niche. On the other side, 2 million tons of CO2 sequestration is already, I think globally with CCS is about 6 million tons. So it is already quite a lot.

KG (16:38):

You make a good point. It is good to remember that all of these technologies are still quite nascent. And as you mentioned before, there are other markets besides paper and concrete.

James Lawler (16:47):

One more question on the economics of carbon capture and mineralization is, you know, you hear from industry that companies that are trying to go net zero, that they’re in desperate search of negative emissions, right where it’s clear that carbon is actually being sequestered, and your process provides that and, you know, they have funds to do that. So why not seek support from, from these corporations that are spending money, so that they can claim zero or have you done that?

Pol Knops (17:26):

I haven’t done that yet because I first need to make the paper.

James Lawler (17:30):

Right. But wouldn’t, they be interested even without the paper. Their interest is CO2 capture.

Pol Knops (17:34):

Indeed. Yes. Yes. I think you’re right. I think they would be interested, but then let’s say if you have one ton of CO2, we want to dispose, then you’re grinding up a mountain where you get two tonnes of olivine, and then you having 3 tonnes of end product where you need to dispose to a landfill. From climate change it makes sense indeed yes. But let’s say from environmental, you have all kinds of geoengineering discussions. So the grinding up a mountain, putting in the landfill. if you’re making paper, I can very simply say, okay, people are buying paper, they’re using lime for that. They already having a quarry for lime. Close the lime quarry, leave that as it is. And open an olivine quarry. And, so you see, you avoid all kinds of geoengineering discussions, economically it is more feasible.

KG (18:25): Building a new olivine quarry simply for the use of sequestering CO2 didn’t seem very environmentally friendly to Pol, unless it was replacing a lime quarry. But instead of digging out the olivine, some companies are trying what is called in situ mineralization in which the CO2 is captured and injected into suitable rock formations underground, where it then reacts with the rock in the same way, permanently changing its composition.

JL (18:51): This doesn’t result in a saleable commodity, but since companies are spending big money these days to offset their emissions – there is money in simply capturing and injecting the carbon under ground. And that’s exactly the type of project Carbfix and Climeworks launched in September 2021 – which is the world’s first direct air capture to mineralization facility. Although direct air capture is not very efficient – and extremely expensive – the project does save by being located in Iceland, directly over a huge reserve of basaltic rock that is perfect for mineralizing CO2.

JL (19:30): Also in the nascent stage is research on mineralization using mining tailings – or leftovers – to reduce environmental impact. While all of this is still in its elementary phase -including Pol’s work – one important thing to note is that the potential of mineralization is really unlimited, given the amount of available basaltic rocks in the earth’s crust. So perhaps, with enough funding, one or more of these processes might just take off in the coming years.

KG: Could be!

That’s it for this episode of the podcast. You can check out other interviews, watch our videos, and sign up for our newsletter at climatenow.com. And if you want to get in touch, email us at contact@climatenow.com or tweet us @weareclimatenow. We hope you’ll join us for our next conversation.

[1]  Ciais, P., et al (2013) Carbon and Other Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

[2] Hilton and West https://www.dropbox.com/s/qv9kxnu9gleyadk/Hilton%20and%20West%20-%202020.pdf?dl=0

[3] Kremer, D. et al. (2019) Geological mapping and characterization of possible primary input materials for the mineral sequestration of carbon dioxide in Europe. Minerals, 9, 485. https://doi.org/10.3390/min9080485

[4] United States Environmental Protection Agency: Greenhouse Gas Reporting Program (GHGRP) Power Plants. Accessed October 7, 2021. https://www.epa.gov/ghgreporting/ghgrp-power-plants


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