Harnessing the power of nature to remove the excess CO2 in the atmosphere piled up by humans is an area of focus in climate change mitigation. Silicate is a new carbon removal company, founded in 2022 that utilizes enhanced weathering to address the climate crisis.
We had a conversation with Maurice Bryson, Founder of Silicate who explained in detail the science behind enhanced weathering, the measurement approaches of CO2 removal associated with this method, and some exciting milestones achieved so far by Silicate.
Hi Mr Bryson, my first question to you is what does Silicate do?
Silicate is an enhanced weathering company leveraging the massive carbon removal potential of returned concrete. The point of differentiation between us and our competitors is that we primarily use surplus concrete as opposed to basalt or olivine.
We take this abundant material, process it to unlock its full sequestration capacity, and work with farmers to apply it to their fields. As the material breaks down in the soil, it removes carbon dioxide from the atmosphere, turning it into a stable bicarbonate ion, and in the process storing carbon for more than 80,000 years.
Concrete is pretty amazing for enhanced weathering because it breaks down very quickly in the soil so you can measure the weathering signal more easily in the fields compared to other materials. Basalt weathering, for example, is very slow and might take 20 years to break down while with concrete it happens in about 18 months.
It’s also very abundant around the world. One of the benefits of it being so readily available is that you don’t have to transport it too far to get to farmland.
Silicate is also based in Ireland and our lab is in Dublin. Our active sites are down in the South of Ireland, County Wexford. We have applied about 2,000 tons of material over the last two years, on about 200 hectares of land, with plans to apply material in the US later this year.
Why did you decide to start a carbon removal company in particular?
It’s a tough question to actually think about. I think you are either born green or you’re not and I think I’ve always been green. I studied marine biology for my undergrad at the University of St. Andrews in Scotland. I am a man of the sea – a lifelong surfer and sailor (I have sailed the famous Rolex Fastnet race) but I am also a tad obsessed with the land, too.
I grew up around my uncle’s farm in Donegal, Ireland. As soon as I finished my degree in St Andrews, I went off farming. For three years after my BSc, I farmed potatoes in Essex, wheat and cereals in Australia, and sheep in Scotland.
A few years ago, I was working in London in sustainable finance, and I read a paper about enhanced weathering. A way to permanently remove CO2 from the atmosphere while working with farmers seemed like a dream world for me. It all started from just reading this paper in the journal Nature by David Beerling and then another one by Phil Renforth.
Then I reached out to Professor Frank McDermott, who is a director of the National Centre for Isotope Geochemistry (NCIG) at University College Dublin (UCD) and a Principal Investigator in iCRAG (SFI Research Centre in Applied Geosciences), and who teaches at UCD’s School of Earth Sciences.
I suggested we do some enhanced weathering trials with returned concrete on a friend’s farm, and that was the beginning of our work. That was two years ago. The data we gathered from this trial was so compelling that we ended up pitching to Klarna to get a carbon removal credit prepurchase contract. The development of our work has been organic – trials, solid result, pitching, scaling and now honing our MRV process.
How exactly does concrete spread on agricultural land, draw down CO2 from the atmosphere and store it permanently?
Some people imagine it like a layer of concrete spread on the ground, but it is actually like a light touching of icing sugar on a cake. After application, the material is incorporated into the soil and then weathered by acids, so in a short period it disappears from view. We typically apply concrete after harvest or before seeds go in the ground in the spring, which means either August-September or February-April.
We would look to reapply material in a field every three or four years, based on the pH change the field requires – importantly, our application rates (8-10 tonnes of milled returned concrete per hectare) are based on the agronomic requirements of the field, not necessarily to maximize carbon drawdown.
Then, we measure what’s happening in the field – we measure the soil, the waters in the soil, and the greenhouse gases going from the soil to the atmosphere. Measuring across these three phases gives us a good understanding of how much carbon we are drawing down but this approach to measurement is not necessarily scalable.
The work we’re doing now is viewed as foundational work that is essential to build the knowledge to be able to scale this at a later date. We’re focused now on measuring this well, as opposed to growing the solution very quickly. But we see huge potential in turning enhanced weathering into a meaningful climate solution, especially if we can build this firm foundation through our work now.
When concrete is spread on the soil, does it connect with the CO2 from the atmosphere or the CO2 in soil?
Essentially, CO2 is taken from the atmosphere from plants respiring. CO2 in the soil or CO2 from the air is essentially the same thing.
Would you say concrete is the most efficient material to use for enhanced weathering? How does it compare to the rest of the available materials?
One of the key things to look out for in these materials that help capture CO2 is how fast they break down. The weathering kinetics of our material (mostly carbonate minerals, with some hydroxide and silicate minerals, too), mean that carbon removal can potentially be enabled on human-relevant timescales and at climate-relevant scales.
We think that is a big win to be able to evidence a carbon removal process happening over a quicker period of time. It builds trust in our solution, as we can demonstrate carbon removal more clearly than if it weathered over a longer time period.
Another important factor is keeping the carbon emissions from the entire process low. We found that the transportation of the material to our farms is our biggest source of emissions. Keeping the distance short is important; if that distance is too far, the emissions from the trucking can be significant.
We think this is where concrete wins again as it is everywhere. Around 20-30 billion tonnes of concrete are made each year in the world, and 1-4% is returned to the producer unused – meaning we have a hyper-abundant, extremely local material that just happens to be very carbon thirsty. Ideal for terrestrial enhanced weathering applications.
How long does it take for nature to sequester CO2 via weathering?
The natural weathering cycle of silicate and carbonate minerals leads to the drawdown of about 830 million tonnes of CO2 each year. The idea is taking this 830 million tonnes and increasing it much more to like 4 or 5 gigatonnes per year, for example.
What is the scalability potential of enhanced weathering that you envision?
I’d like to say in the gigatonnes, the potential is huge, there is no doubt about it. The theory is very strong. What is unknown right now are some basic things like how much carbon is being drawn down per tonne of material for basalt, olivine, or our material?
We have some preliminary data here, which we are excited to publish in the coming months, but there is more to do to improve the removal efficiency of it, which we are full-steam-ahead working on.
There are some key risks that exist for some ultramafic materials, such as potential heavy metal contamination, but the literature is showing that these risks might actually be minimal. Equally, understanding the downstream impacts of alkalinity enhancement are also increasingly well understood.
Thankfully, agriculture has been adding milled limestone to agricultural land for many years to counteract soil acidification from fertiliser application, so we already know how this can impact, or not, riverine systems. And the potential to counteract ocean acidification through terrestrial and coastal enhanced weathering applications is also immensely exciting. Lots of positives, and lots of good science going on!
Relevant: New Study Shows Enhanced Weathering Could Bring Half Of UK’s Carbon Removal Target
Our team is working hard on this to gain a lot more certainty. I think the work is very worthwhile because the potential to remove a lot of carbon dioxide from the atmosphere is so immense, as well as the benefits to apply the material on the soil or to the ocean, such as combatting ocean acidification, are so big.
They are such a big win for the environment that it requires a bit more work now to do it right before it scales.
How familiar are farmers with enhanced weathering and what is the current scale of application of this method?
Farmers need to change pH in the soil as it gets more acidic. They typically add milled limestone to bring pH up. Limestone also breaks down very quickly. This happens pretty much all over the world in the areas where it’s needed.
It’s very common in the UK and Ireland. In some places, adding basalt is more common like in Brazil. Brazil is very well known for adding basalt to fields to change pH, but more so to add minerals, because the soil that is farmed gets depleted over time. The whole idea of adding crushed mineral salts to fields is very accepted in farming.
But the idea of trying to do that to capture CO2 is the new thing I would say. From our experience, farmers are very keen to figure out how this works and are up for the challenge to work on it. The key thing for them is understanding how this compares to what they are currently doing. They want to know how enhanced weathering changes the pH as they really care about it.
Is there a lot of research done already on topics like risks of enhanced weathering, that you mentioned or are you starting from scratch?
There’s a lot of work done on understanding many of the unknowns but there’s more left to do. For example, sometimes we don’t know how much carbon is being drawn down per tonne of material. That has not been answered sufficiently and it’s an important question, and there are many teams in academia and in industry trying to do just that.
The second one is in tracking the dissolved bicarbonate (stable store of captured carbon) from the fields to the oceans. For the carbon removal process to work, i.e., for the captured carbon to be stored for a long period, it must eventually be exported to the ocean. Tracking how these molecules get to the ocean, which is primarily done through models, will be another key area for the space to address. There is already some detailed work done on it.
Finally, we need to be cognizant of the downstream impacts of adding lots of alkalinity to riverine and ocean systems. Thankfully, the outlook is positive here, and as agriculture has been adding milled limestone to fields for years to amend soil pH decrease (caused by fertilizing fields), we already have seen that the impacts here are on the whole positive.
How do you measure the exact amount of CO2 being removed? What tools or technologies do you use?
We are measuring across the three phases – solid, aqueous and gas, to enable carbon sequestration assessments on a mass-balance basis. We undertake a three-part measurement approach incorporating data from liquid, gaseous, and solid states relevant to the weathering reactions through soil water sampling, soil-to-air gas flux measurement, and soil sampling.
- Soil water samples are the foundation of this approach as they measure dissolved bicarbonate, the inorganic store of carbon that EW seeks to produce. This measurement is a direct measure of carbon removal; however, as with soil samples, there are uncertainties regarding the temporal and spatial representativeness of such samples.
- To increase the robustness of removal quantification, soil water sampling is complemented with soil-to-air gas flux measurements, as an independent measure of removal.
- Finally, soil sampling provides information about the rate of weathering reactions and soil pH change. However, unlike in other approaches, soil sampling is not used to determine how much carbon dioxide has been removed, only to track the weathering progress, monitor any heavy metals and characterize changes in bioavailable nutrients and silica.
| Type of measurement | Information provided | Inference supported | Gaps present |
|---|---|---|---|
| Soil water sampling | – Dissolved bicarbonate concentrations- Stoichiometric ratios of bicarbonate to balancing dissolved cations | – Extent to which atmospheric carbon dioxide is removed, as bicarbonate is product of removal- Which acids are weathering applied material, as molar ratios differ depending on acids present | – Removal estimates reliant on assumptions about site hydrology- Uncertainties regarding temporal and spatial representativeness of samples |
| Soil-to-air gas fluxing | – Quantity of carbon dioxide fluxing between soil and air | – Extent to which carbon dioxide is being removed, as reduced fluxes indicate removal- Extent to which applied material might be releasing carbon dioxide, as increased fluxes indicate release of carbon dioxide | – Differences in carbon dioxide fluxes between control and experimental sites close to limit of resolution of measurements unless removal rates are large |
| Soil major element chemistry | – Cation (e.g., calcium or magnesium) loss from applied material | – Weathering rate over time | – No indication of fate of cations post-weathering- Unclear what acids have weathered material and thus whether or not carbon dioxide is being removed |
We spread about 1300 tons of material on about 120 hectares this spring in Ireland. We are sampling about 10% of that or 12 hectares very well. We have samplers, we have the gas flux devices, we have soil samples. For the rest of it, though, it’s just extrapolation as we can’t measure all that well.
I’m pretty confident in saying that our measurement approach really is industry-leading. Nobody is measuring at this level as we are. I hope other companies will be encouraged to do so because for this industry to scale it needs more foundational data which really comes from measuring the three things – the soils, the soil waters and the gases.
From that, we learn what’s happening to carbon and we also hope it will lead to learning other things as it’s a very comprehensive data set.
Are you currently selling carbon credits and where? How are they verified?
We sold credits to Klarna – our first paying customer – Carbonfuture and Milkywire. We just did a second deal with Klarna in May. However, we are not selling credits anymore. We are stepping back from that and focusing on working on the sites to deliver the credits. Klarna has given us money to help us do our work.
The carbon credits are not verified yet. We are developing a methodology with key market participants that we hope will enable enhanced weathering to become a robust carbon removal solution. The methodology and the verification will come in a couple of years time, I hope.
What is your company’s climate target? What scale of growth do you want to achieve?
We used to say a gigatons of carbon removal by some year but it actually does not convey the right message, we feel. We interrogated our language because what’s better to say is we want to achieve climate-relevant levels of carbon removal at human timescales.
The theoretical maximum of removing carbon dioxide using concrete is around 0.3 or 0.4 tonnes of CO2 removed per tonne of material applied to soil but that will never be achieved in real life. Basalt is similar but it’s not achievable because of the complexity of the environment. We don’t focus on what is in theory but on measuring what’s actually happening.
One thing also worth pointing out is that CO2 is emitted when farmers apply fertilizers or limestone. It’s a huge win if you can avoid emissions from liming.
Relevant: New Startup Lithos Carbon Improves Enhanced Rock Weathering To Store More CO2
The third big win for the environment is nitrous oxide. When farmers fertilize their fields, greenhouse gases such as nitrous oxide are released to the atmosphere which is a very warming greenhouse gas.
With the pH increase of our material in the soil, you can reduce the N2O fluxes from the soil. There is a lot of big wins from our process like N2O avoided besides just CO2 drawdown, which is all very encouraging. We’re measuring CO2 and shortly N2O in our fields and we hope to see visible changes in N2O.
Can you reveal how many carbon credits you have sold so far? Also, what is your future project pipeline?
We have sold around 2,000 carbon credits. Currently, we’re operating in the hundreds of hectares scale. We spread concrete twice a year – post-harvest and pre-planting. We are actually doing our first trials in the US starting September, in Illinois.
We will be spreading material on probably tens of hectares in Illinois and Chicago. We are working with a big landowner down there, and a concrete company in Chicago. Those trials start in September and will run until this time next year.
Apart from these field trials, we have smaller trials happening in our labs. We are also going to rent our own lands to run trials which will be more controlled. We have lots of research plans for next year, I would say.
How do you plan to scale your solution?
We work with big farmers and concrete companies. Concrete companies, especially in America, have a lot of returned amounts that don’t know what to do with it. That is a waste for them and yet it has massive carbon removal potential.
If they could sell it to us for a small price, they solve this problem. As far as farmers are concerned, they love it because it changes pH of their fields really well. We are working with two industries that have a problem – agriculture needs to reduce emissions and concrete producers need to reduce waste. We tap into these problems at the same time and we have allotted very willing partners to work with us.
We purchase the material from concrete companies, mill it to fine dust and transport it to our farms. We cover the cost of the material and spreading it. Then we sample the fields for about a year afterwards. Farmers get pH amendment for free and concrete companies get a small price for their waste material.
You took part recently in the Thrive Shell Climate Smart Agriculture challenge and you were one of the winners. How did that competition help Silicate?
It was good to go to South by Southwest (SXSW), it’s a very well-known meeting. Shell is giving us $100,000 as a grant and access to a lot of fancy and expensive greenhouse gas measurement devices. Shell also has a lot of geochemistry expertise. They’re going to help us with our trials in Illinois.
We have no obligation to give them any data, carbon credits or anything. We are very much an independent party, we just want advice.
We are certainly very conscious of how we work with Shell. We don’t want to be an encouragement for more gas and oil drilling. We are aware of who we are working with but also, it’s been a good working relationship so far. We are looking forward to how it progresses.
Are you looking to partner with other large corporations?
Absolutely, Silicate is working with huge global concrete players and large farmers already. We are on an accelerator called the 2050 Accelerator. The largest landowner in Ireland, Coillte, is part of it, as is Kerry Group, the ESG, The Grantham Foundation and the Irish Department of the Environment, Climate and Communications.
We are up for making the right partnerships across concrete, agriculture, and regarding the science work. Silicate is partnering with the University College Dublin. Our Advisory Board has scientists from different research institutions from all over the world. We’re all about collaborating, I would say.
You were also announced as a participant in the Carbonfutures’ Catalyst Program and the 2050 Accelerator program that you mentioned. Could you please tell us about these two programs?
The 2050 accelerator is amazing, it’s funded by The Grantham Foundation and has The Irish Department of the Environment, Climate and Communications and ESB as part of it. It’s an opportunity to really speak to people who can make things happen on a bigger scale which is very encouraging.
The Catalyst program also brings together leading companies so it’s a way for us to communicate and work together. For example, we aim to come together on policy or how we measure in the fields. Carbonfuture (running Catalyst) is very focused on the science and doing this part right so we love working with them. It’s been a real pleasure.
What are you hoping to achieve next?
Silicate is growing the team. We are also growing our science team tremendously and hiring senior academics to work on some of the core problems we want to address. We are also traveling to America to do some trials starting in September. These are the next big steps for Silicate which we are very excited about.
