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Launch HN: Heimdal (YC S21) – Carbon neutral cement
617 points by marcuslima 52 days ago | hide | past | favorite | 220 comments
Hi HN, I’m Marcus, I’m the co-founder of Heimdal together with Erik (https://www.heimdalccu.com/). We remove atmospheric carbon dioxide and trap it in materials that are used to make cement. More CO2 is trapped in our process than is re-emitted in cement production.

Concrete is responsible for 8% of global CO2 emissions. Cement is usually made from mined limestone, which is one of the largest natural stores of carbon dioxide. Using that to make cement is a bit like burning oil. The world is addicted to concrete, so this problem is not going away. We make synthetic limestone using atmospheric CO2, such that when it is used to make cement, the process is carbon neutral.

We were both master's students in engineering at Oxford University in the UK. I decided to write my dissertation on direct air capture of CO2. While looking through existing solutions it struck me that none were sufficient. They all operated a circular process that left them with gaseous CO2 that needed to be stored somewhere. A circular process is one that uses a sorbent to trap atmospheric CO2 but then re-releases the trapped CO2 as a pure gas stream to regenerate the sorbent for re-use. We don't have enough high-quality cheap stores of CO2 to justify such an approach. Storage must be permanent and safe. We realized that by taking a linear approach, we both make the process of capturing CO2 profitable and avoid the problem of where to store the CO2. We make sorbents for trapping CO2 in the form of mineral carbonates, these compounds are inert and trap CO2 for millions of years. They can also be commercialized as raw materials for making building materials including glass and concrete. In one step we solve three key problems of carbon capture: 1. How to trap CO2 energy efficiently 2. How to store the CO2 3. How to make money while doing all this.

Specifically, we use renewable electricity to extract dissolved oceanic CO2 as mineral carbonates of calcium and magnesium by contacting seawater with our proprietary alkaline sorbent. These mineral carbonates are important ingredients in cement as well as other building materials. The undersaturated ocean then re-absorbs an amount of atmospheric CO2 equivalent to the amount we removed when reacting with our sorbent. Effectively, the world’s oceans become our air contactor.

There are other companies addressing emissions from concrete production, but they don’t address the unavoidable process emission from the raw materials used in concrete. Start-ups in this space have so far focused on curing concrete with CO2 at the end of the production process. These are great solutions that can create low-carbon cement, however they’ll never get to carbon neutral cement that the world needs. The 70% of emissions from production are not being tackled by anyone on the market today. Until now concrete producers have favoured capturing emissions at the point where they’re released as their “2050-solution”, ie. in the distant future. Point source carbon capture can expensively capture 80-90% of emissions. This solution has the same problem as circular DAC solutions where a method of permanent CO2 storage is needed. There is a trial $3B (!) project in Norway to pump CO2 into empty gas fields at a cost of ~$1000/tCO2. This is expensive and complicated engineering. On the other hand, all we need is renewable electricity and seawater.

We make money from selling synthetic limestone to cement producers and commercializing parallel byproducts including green hydrogen and desalinated water. We also generate carbon credits from our process. We are currently negotiating with concrete producers to decarbonize their limestone supply. Response has so far been very positive with multiple LOIs signed with producers across Europe. We are also working with a construction company to build the world’s first carbon neutral houses this decade. We are currently building a demo plant just outside Oxford. It has the capacity to remove and store 1 tonne of CO2 per year. We will use this plant to make enough product that we can deliver to our commercial partners to confirm compatibility with their manufacturing set-up. Following successful testing, we will scale this up to replace all of global limestone mining; currently >2 billion tonnes of limestone per year.

We're excited to hear any thoughts, insights, questions, encouragement and concerns in the comments below! Erik and I will be monitoring the thread over the course of today to answer any questions. Also feel free to reach out to me by email at Marcus.lima@heimdalccu.com.

I did some lengthy analysis behind the chemistry / economics and wrote it up here.


TL;DR: ignoring all sources of overhead/inefficiency and purely on consideration of thermodynamic costs, $70 of electricity can generate $100 of lime, $300 of chlorine gas, and $75 of hydrogen gas.

Much more details on the chemistry and economics in the blog post...

Wow, that's the most in-depth response to a Launch HN I've ever seen.

This is probably the most substantive Launch HN thread (I mean of the official YC startup launches at https://news.ycombinator.com/launches) that we've yet seen. And it was very little work to put together.

The secret is apparently to be slightly cagey about your tech and nerd snipe half of HN into trying to figure out if your thing actually works or not...

The other secret is to not be using investor money to pay low wage gig workers while you build out a "platform" for the future when you take all the business from everyone because they are too dumb to possibly compete with you.


Impressive analysis! Missed out on a couple details, but I'll take that as a thoroughly researched/analyzed endorsement. Most importantly, we'll be scaling up a lot faster. Our current 1t/yr is just a demo. Our current roadmap is scaling up to a 300t/yr pilot in the next few months before setting up building a commercial plant (10kt+) in the second half of next year. Any chance we can poach you from Google? ;)

What's the status on your current 1t/yr demo? (i.e. is it fully operational?) What did you learn from it and what are the technical challenges to scale it up to bigger plants?

I love your approach but I think that you've made a mistake. $70.00 of electricity at $0.13/kWh is 538 kWh, or 1937 MJ. Hydrogen has a higher heating value of 142 MJ/kg. If you could actually get 36 kg of electrolytic hydrogen from 538 kWh of electricity, that's getting 5112 MJ of chemical energy from 1937 MJ of electrical energy. That can't be done. At first I thought maybe I was overlooking some consumable electrodes in the scheme, but it appears not.

Rule of thumb for electrolytic water splitting is 50 kWh per kg of hydrogen. That would mean about 0.29 as much H2 as estimated in the blog post. If you scale all salable products by 0.29 (not sure if that's sensible since I haven't identified the root error) it would still yield $142 of products from $70 of electricity. And good news there is that industrial scale electricity can be had for well under $0.13/kWh.

> More than just profitability, can they make a dent in our carbon problem? The scale of our carbon problem is on the order of 30 billion tons of CO2, of which maybe 1 billion tons are due to lime production. Heimdal is currently at the scale of 1 ton per year - nine orders of magnitude away from making a difference. Assuming continuous Silicon Valley ridiculous growth rates of 50% year over year, they will take 50 years to grow to a point where they are actually making a dent in our carbon problem. I wish them good luck.

They don't need to do it all alone. If this idea is solid, a lot of different companies and nations could be doing this.

I'm excited for China to have carbon-neutral cement. If they do, it will probably be of their own making and not tied to this company growth.

Interesting, thanks. The chemistry you discuss sounds a lot like this

Rau, G.H., Willauer, H.D. & Ren, Z.J. The global potential for converting renewable electricity to negative-CO2-emissions hydrogen. Nature Clim Change 8, 621–625 (2018).


Thanks for the analysis, interesting to read! What about the lime-burning for cement, does it imply "only" net-carbon neutral as all the captured carbon is released upon cement production? And what about iron smeltering? I suppose most carbon is also released in that process?

Same idea for iron!

Some comments and expansion on your analysis, which I enjoyed reading and provided a nice excuse to dust some mental cobwebs.

I'd also like to clarify up front that I'm limiting my analysis to the proposed electrochemical mechanism, and have no information on the specifics of Heimdal's proposed implementation - which may vary significantly and materially:

The theoretically minimum electrical energy input (often) winds up being set by one of the reaction intermediates, rather than the overall reaction enthalpy. Typically these analyses are done via determining the corresponding half cell potentials, then counting electrons and computing power via P = IV.[0] So we only need to consider H2O (and its dissociation -0.83[1]) and Cl- to Cl2 at 1.36). That sums to approx 2.19V for the cell, and 2 electrons to do 2H2O + 2Cl- -> H2 + 2OH- + Cl2. That the formed OH-'s pair with Ca2+, and/or CO2 is immaterial to the theoretical electrical efficiency of the cell. Accordingly, the cell energy requirement is on a molar basis identical to the chloralkali process. The only difference is the presence of 2Na+ vs. Ca2+.

Less concretely the lower reactant concentrations have two specific negative effects: Cell potential is adversely affected (per the Nernst equation) and Cell current can be adversely affected if/when depletion occurs. At 0.01M of Ca2+, vs. 6+M Na+[2], current densities could be 1-3 orders of magnitude lower. Cell count (CAPEX) is inversely proportional to current density.

Ultimately making CaCO3 this way (and CaO) winds up substituting a 400$/tonne product in NaOH for an approx 40$/tonne product in CaCO3. It is a very technically feasible approach for turning $$$ into sequestered carbon via non emission from natural limestone.

The analyzed approach reminds me a lot of Calera, who had an apparently similar electrochemical approach to CaCO3.

[0]Not that it can't be done from Gibb's energies, indeed the standard potentials for a reaction can be computed from the delta Gibbs, but the specific species the electrons are being pulled from/pushed into matters. Phrased a different way: electrical energy and overall reaction enthalpy are not necessarily fungible. e.g. (at a simple level) the reaction of CO2 with Ca(OH)2 doesn't affect the electrical energy requirement, nor does CaCO3 --> CaO because neither reaction involves electrons. Any exotherm just winds up 'wasted' as heat, instead of lowering the electrical demand.

[1]Per 2H2O + 2e- --> H2(g) + 2OH-(aq) #6.8.11 https://chem.libretexts.org/Courses/Mount_Royal_University/C...

[2] Saturated near room temp, don't have a better source handy.

Thanks for the comment, I also had to dust off some mental cobwebs for this analysis :)

You're pointing out the crux of the issue: "Ultimately making CaCO3 this way (and CaO) winds up substituting a 400$/tonne product in NaOH for an approx 40$/tonne product in CaCO3."

I calculated that Heimdal's process has 7x reality factor overhead, whereas chloralkali has 2x reality factor. This is seemingly in opposition to your statement. I think the diff comes from considering all the other energetics - precipitation of CaO from the hydroxide is thermodynamically quite favorable, reducing the overall theoretical cost by 65% relative to the chloralkali process. So to the extent that Heimdal can usefully harness that energy gradient, that's the difference.

>This is seemingly in opposition to your statement. I think the diff comes from considering all the other energetics - precipitation of CaO from the hydroxide is thermodynamically quite favorable, reducing the overall theoretical cost by 65% relative to the chloralkali process. So to the extent that Heimdal can usefully harness that energy gradient, that's the difference.

I guess the crux of my argument is that it is impossible[0] to capture the energy from CaO precipitation. E.g.[1] one has to spend 2J of electrical to create the hydroxide in Ca(OH)2, but the 1.5J get released on precipitation of CaO comes as heat[2], rather than a reduction in energy input.

So, in summary, Electrochemical CaCO3 would have [approximately] equal theoretical electrical demand to chloralkali and, to borrow your term, a higher reality factor overhead[3], to make a product an order of magnitude cheaper than NaOH.

[0]For a loose definition of impossible, to be fair reality's never quite so black and white.

[1]Made up numbers.

[2]And heat in sub-boiling water is not useful for doing work.

[3]I broadly agree with your position on reality factor overhead, just made less of an emphasis on it trying for 'equivalent but worse and creates less value'

According to their web site, one of their premises is that renewable electricity is now cheap and plentiful. If that's so, I'm led to wonder if there is a more direct way to reduce CO2 emissions in cement manufacture, namely, use resistive or carbon-arc heating to fire the ovens, thus replacing fossil fuels in the manufacturing process.

Sorry I don't have the chops to work out if that's economically feasible.

The thing you are firing in the oven (limestone) releases CO2. Fossil fuels aren't the only source of CO2.

We need zero CO2.

> The thing you are firing in the oven (limestone) releases CO2.

I'm aware of that. There are two main sources of CO2 in cement manufacture: the calcium carbonate raw material, and the fossil fuel required to cook the raw materials into clinker. Heimdal only deals with one. The questions I'm interested in are which source contributes more CO2 and which can be most economically eliminated.

> We need zero CO2.

Agree, but Heimdal won't get us there. We'll either have to find a replacement for cement, or devise a practical method to convert CO2 waste to something benign, like an improved Bosch process.

From my limited understanding this seems really impressive!

I immediately associated this to possible disruption in the cement supply chain that's about to hit Sweden. Cementa, which produces about 75% of Sweden's cement, will no longer be allow to mine limestone on Gotland. Their permit was due to be renewed but due to the low quality of their environmental impact study the court was unable to determine if the mining might impact the local residents groundwater. So just a week or so ago a Swedish court decided Cementa muts cease mining operations some time in October. And as I said this mine/factory produces 75% of Sweden's cement. So there are more problems with the current way of producing cement than just CO2.

Most probably there will be a limestone/cement void in Sweden that needs to be filled, and I'd rather have you doing it than some new limestone mine. Best of luck to you!

Yes! This is awesome, I saw this a couple weeks back. We're trying to get in touch with Cementa, but it seems Scandinavian holidays are getting in the way so far. Definitely an ideal place for us to start. That plant does 70% or so of Sweden's cement consumption

You know everybody will be working overtime up until then. Extra storage purchased, and possibly discounts to customers for accepting early delivery.

If this is as good as promised, you should apply for Elon Musk's XPRIZE [1]. Take the $50 million to scale this up faster. Plus, if you win you probably get to talk to Elon. I doubt there is anyone that has better tipps on how to scale and iterate a business than him.

[1]: https://www.xprize.org/prizes/elonmusk

Definitely one for us to get involved with. Unofrtunately it's a 5 year timeline, but that's still not a bad ROI

> Concrete is responsible for 8% of global CO2 emissions. Cement is usually made from mined limestone. [Snip] We make synthetic limestone using atmospheric CO2, [snip] when [snip] used to make cement, [snip] (it) is carbon neutral.

You should put that (slightly edited) paragraph on your home page. I looked at your home page first and didn't understand what you did until I came back here.

Best of luck!

(Btw: Try to avoid using the passive voice.)

If I understand correctly, you extract both Calcium and CO2 from ocean water, and use this as input for making cement. The ocean will absorb the CO2 from the air, and that's a win. Where does the Calcium in the oceans come from?

If your process is scaled up massively, will the oceans run out of Calcium? Or will they absorb Calcium from somewhere? What would that Calcium source be?

Well understood! The ocean is supersaturated in the ocean (ie. there is about 20x more of it dissolved than you would expect). In fact it's the single largest deposit of calcium in the world. Risk of running out is zero. Calcium in the ocean comes from dissolved limestone (this does not emit CO2)

Could you elaborate on how dissolved limestone does not emit CO2? Limestone is CaCO3. The calcium gets dissolved, ready to be used by your process. The Oxygen, I don't care much whether it stays in the water or goes into the atmosphere. Where does the carbon go, if not into CO2?

That's part of the CO2 saturation of the ocean. So when we remove that dissolved CO2 that equivalent amount is removed from the atmosphere

I have the same question.

How will reducing the amount of dissolved calcium and CO2 in the ocean affect organisms like shellfish and crabs. Could there be local zones around your extraction points where these organisms can no longer produce shells?

The ocean is 20x supersaturated with calcium and is constantly being replenished by geological stores of the stuff coming in through rivers. As long as the ecosystem remains supersaturated this shouldn't be a problem for any marine life. Though a slight dislcaimer there is i'm not a marine scientist!

I think the diffusion rate of Ca and CO2 is also important. Even though the ocean is supersaturated *globally*, the local area around your plant might not have enough concentration. Hope you can get someone to check that.

Might have to spread your plants across multiple regions, or place it around somewhere with low impact to marine life I think.

They can reduce that risk by having very long tubes that can be re-positioned from the surface using ships to take water from different locations while the currents replenish the other locations. Or just have several tubes to draw from. Like rotating a pasture. No doubt they will need to actually monitor and plan for this or they will likely create a disaster.

What sort of waste water do you produce? What is the local ecosystem impact?

Edit: Also, it’s great that your de-carbonating the ocean as part of this project. Ecological damage to the ocean is out of sight, and usually out of mind.

All 'waste' we produce we either consume in our process or we're able to sell as a commercial product!

Not bad tackling ocean acidifcation to boot

I was just about to make this point: as I understood it, ocean acidification is a massive environmental problem.

Would your process reduce the local acidification significantly? Could there actually be a win-win situation here deploying around coral reefs? Especially given that such reefs are found in countries with massive solar potential (i.e Australia).

Coral reefs are having trouble with the ph of sea water. If you drop the calcium content then it’s probably more problems for them.

If you pull enough to dissolve more limestone, then they’re just mining limestone hydraulically, and they are mining it outside of the economic exclusion zone of their own country. This product plan is literally “I drink your milkshake.”

On the plus side Florida will fall into the ocean sooner.

I'm not sure I understand where the carbon savings comes from.

The cement industry specifically needs lime, CaO. Lime is most easily obtained by burning CO2 off of limestone, CaCO3. As you point out, this is effectively "burning off" captured carbon dioxide and is bad.

Where does the carbon savings come from when the ultimate destination is to just burn CO2 off and make the actual desired product, CaO? Is this process ultimately just a better way to make CaO?

Yep, exactly! The world needs CaO for cement. We have a carbon neutral process for making it. It's actually overall negative as not all carbonates we extract are usable in cement production. But as far as cement producers are concerned it's carbon neutral.

A way to help explain this to people is that it's the equivalent of rapidly growing trees and burning those for fuel instead of burning fossil fuels.

You do the same with limestone, rapidly creating it by capturing atmospheric CO2 (indirectly, via the ocean) so it can then be burned in cement production instead of the naturally occurring kind. In both cases, CO2 is released into the air at the end when the product is burned, but because the released CO2 had just now been sucked out of the air anyway (instead of having previously been sequestered in natural limestone) you're not adding to the total amount of CO2 in circulation in the system, making the process neutral.

Additionally governments could buy limestone and not use it. Carbon sequestration. The money could come from a CO2-tax.

I really hope this is scalable worldwide.

A followup question... how do you regenerate the alkaline sorbent? It gets acidified in the process of extracting CaO from the water and needs to be made alkaline again somehow.

He mentions producing hydrogen as another product, so I would guess they use electricity to turn protons into hydrogen gas, so removing acidity.

I'm probably missing something obvious.

> The world needs CaO for cement. We have a carbon neutral process for making it


> We make synthetic limestone using atmospheric CO2, such that when it is used to make cement, the process is carbon neutral.

Do you make CaO or CaCO3?

We make CaCO3, I mention CaO here because that's what cement producers ultimately need. They heat up limestone (CaCO3) to make CaO

Is there a reason not to make quicklime instead of limestone?

why does removing carbonates cause the ocean to absorb more CO2, though? Calcium and magnesium oxide aren't just floating around the ocean waiting to absorb more CO2. Removing salts does not lower oceanic acidity.

The ocean and the atmosphere exist in an equilibrium there is a 'balance' of relative concentration of CO2. Because CO2 can dissolve in water as CO3 and HCO3 the concentration is skewed to a higher concentration in oceans. When we take out CO2 from the oceans we lower the relative concentration, so we shift it out of balance. So the entire ocean becomes the surface area for re-absorbing CO2 from the atmosphere to re-establish that balance!

But the re-absorbed CO2 will come from new limestone dissolving into calcium bicarbonate, not from atmospheric CO2.

You'll be adding more CO2 to the air -increasing oceanic acidification- while increasing the ocean's ability to dissolve more CaCO3. Far from fighting global warming it sounds like this will put exactly as much CO2 into the atmosphere and double the leaching impact on shellfish and coral.

I am shit at chemistry and would really like cement to not release CO2, but I don't understand this.

Same question! As I understand it: CO2 pulled out of the ocean is replenished by atmospheric CO2, because limestone in the ocean dissolves too slowly to make up for the imbalance and it more readily comes in from the air. But if that's true, then the calcium will actually not be replenished quickly in the ocean (not sure what the significance of this is)! If it were true that the calcium is dissolved fast enough to replenish, then there must also be CO2 released from underwater limestone? Which means extracting Ca and CO2 will not remove any atmospheric CO2 really.

Alternatively, we do end up extracting Ca from the ocean that is not replenished (there's probably so much we don't care) and rely on the atmospheric CO2 to correct ph balance of the ocean?

Wait, no, why? As far as I understand the process of limestone dissolving into oceans is the long term (on the scale of millions of years) process and is based on rivers dissolving limestone so would not be affected by the ocean changes; in the short term (days/years/centuries) it would be balanced simply by CO2 exchange between the atmosphere and what's dissolved in the ocean.

Yeah absolutely, the CO2 balance comes from re-equilibration with the atmosphere. The rivers replenish calcium content on a longer time scale. But as you point out we're in no danger of running out of calcium in the oceans

so there is no more additional burning of limestone needed? instead your process directly produces the lime, CaO? and that then binds the CO2 when curing?

to my limited understanding cement production emits CO2 in two ways: by splitting limestone into lime and co2 and by burning carbon based fuels to split the limestone.

your method addresses both sources of co2 from cement production? or just one of them?

> so there is no more additional burning of limestone needed? instead your process directly produces the lime, CaO? and that then binds the CO2 when curing?

The OP says they'll make money by selling synthetic limestone ("We make money from selling synthetic limestone to cement producers..."), so I think the CO2 still needs to be burned off of it before the cement is produced. However they say they already (indirectly) pulled that same CO2 out of the air, instead of the ground, so overall the process is carbon neutral.

> they say they already (indirectly) pulled that same CO2 out of the air, instead of the ground, so overall the process is carbon neutral.

I find that difficult to understand. If the output is CaCO3 that still needs to kilned to make CaO, then CO2 gets emitted. Even if that volume of CO2 was obtained from dissolved CO2 in the ocean, one would have had to expend energy to extract that CO2 from the ocean and that energy would have generated emissions as well.

If the output of this is just CaCO3 again, then I fail to see how this is a better solution than carbon capture using a clay geopolymer technique that goes directly to a concrete like structural material. What I mean is, wouldn't it be better to just skip all of this and go focus on rediscovering the technology for "creating" rock like what was possibly achieved at Cuzco (Hatun Rumiyoc) or Pumapunku? Or more realistically in the short term, using fly ash and silica flume or slag to make concrete without requiring CaO?

> one would have had to expend energy to extract that CO2 from the ocean and that energy would have generated emissions as well.

I suppose they could planning to use renewable energy?

> If the output of this is just CaCO3 again, then I fail to see how this is a better solution than carbon capture using a clay geopolymer technique that goes directly to a concrete like structural material.

I don't have a horse in this race, but one possibility is that concrete is a better understood material than some novel "concrete like structural material," so it's more acceptable in safety critical situations (e.g. people know how it fails, how to detect failures, how to remediate problems, etc.).

They'd also need a significant source of Calcium.

> one possibility is that concrete is a better understood material than some novel "concrete like structural material," so it's more acceptable in safety critical situations (e.g. people know how it fails, how to detect failures, how to remediate problems, etc.).

Your explanation and argument looks correct to me. However, I should point out that concrete structures fail regularly and frequently, and sadly with great loss of human life, most recently in Miami. I should also point out that I've seen this argument used as a tactical trick. I watched a Microsoft rep using this argument successfully convince a management team that they should use Embedded Windows instead of Linux because, just as you pointed out, "we know how it fails", "we know how to detect failures", "we know how to remediate problems".

I think the difference between materials and software through is that with materials, there's definitely a better understanding that comes with actual aging that you can't really get otherwise.

With some new material, they'd probably need to rely significantly on accelerated aging tests (at least for a few decades), and there's always the question with those of how accurately those actually model real aging under real conditions.

That's not to say they shouldn't try new materials, just that the rollout probably should be slower, and maybe not so good for tackling climate change. For that reason, I can see the benefit of a less carbon intensive way to produce an existing material, since that could be rolled out/scaled up immediately without some of the concerns of alternatives.

yes that kilning is what bothers me, not for the co2 that is captured at sea, released in the kiln. that is then recaptured when curing, isn't it?

what bothers me is the 1400°C needed in the kiln. to my understanding the ratio of limestone-to-lime co2 to fuel-for-the-process co2 is 2:3. you need lots of co2 intensive energy for that kiln.

they said the H2 produced can be used for kilning.

Our process produces calcium carbonate, CaCO3, which cement producers can then burn to make quicklime, CaO. This does release CO2 but that CO2 has been captured from the atmosphere in the process of making that calcium carbonate. We only address process emissions (ie. splitting CO2 from CaCO3), but we do also produce hydrogen on-site, which can be used to replace fossil fuels in generating the requisite heat

ok so your cement does not expose additional co2 from the lime-to-quicklime transformation, instead it takes co2 from the oceans. that is released to zhe athmosphere during cement production. and that co2 from the air is then recaptured by the ocean. so your process creates a ocean-co2 -> air -> ocean cycle.

and when and where the hydrogen is replacing some carbon based fuels, somehwere, that counterbalances the carbon based fuel used in the cement furnace.

now I get how it becomes carbon neutral overall.

do you guys have data points at hand how long it takes for an ocean to recapture the co2?

This is great to see and I hope it’s a very successful enterprise! Since this is a novel enterprise and I think there is some appeal among architects and consumers, it may be worth carving out some marketing moat with a registered trademark and perhaps an icon. While they aren’t your customer, the whole supply chain would be pleased to use your materials in their projects- so anything you can do to help them brag ultimately helps you.

Absolutely! We're in the early stages of developing an idea like this. We're working with a californian construction start-up to reduce embodied carbon in their building materials.

We've also thought about working with some big name companies like Apple, Amazon, big name hotels etc. to build a carbon neutral office/store/hotel. Haven't been able to reach the right people here yet though. Any intros/suggestions are appreciated!

I can see the appeal but would recommend against pursuing large name brand companies at this point. If your solution does what you say, that’s already incredibly novel and interesting to the right buyers; people are seeking these solutions out. The real question will be: what’s the cost? So scaling and cost reduction is where I’d focus. It’s likely non-trivial to go from 1 ton, to 1000, to 1 M.

If you’re looking for a novel way to generate excitement, how about the X-Prize?[0] You’re doing a demo of “1 tonne of CO2 per year“, that’s enough to enter, and entering is enough to tell investors. Doing well could provide dilution free capital, technical validation, in addition to free publicity.

[0]: https://www.xprize.org/prizes/elonmusk

Great thoughts! Our strategy so far has mainly been focused on targeting large producers of cement and glass. We're in the process of signing LOIs here. Agreed that getting scaling right will be the big challenge

X Prize is on our radar, only a shame we mised the cement specific one. Though the dollar value on this one is certainly better

Curious about the name, my immediate thought (and interest making me click in) was that it sounds Norwegian. Any connection?

I really like the idea. One thing I'm curious about is what's in it for the contractors (edit: cement producers) buying from you instead of others? I get the environmental impact, but my guess is they only care if touches their bottom line. Will it be cheaper, either in raw price or because of green incentives etc?

Nice catch! I'm orignally from Norway. Heimdal is the norse god of foresight. Something the world needs in buckets when it comes to climate change.

Our experience so far has been that the environmental angle has been sufficient to persuade. Cement companies are in a bit of a bind given the attention to their sustainability efforts. However we're pitching ourselves as a cost competitive solution. Depending on geography we'll be able to positively affect their bottom line through the carbon credits system. Under the European ETS for example, they reward companies that reduce emissions (https://carbonmarketwatch.org/wp/wp-content/uploads/2016/11/...)

Cool. Yeah, maybe the old way of making cement will be too expensive in the future compared to a greener way. Good luck with your first mover attempt!

Another curious question: Do you make an "actual" limestone, or what is the final output? A rock, chalk, mudlike or something?

Thanks! Yeah, we think it will be. But more importantly, the old way isn't a viable option. It's effectively off the table. Sweden has already banned mining of limestone (https://www.ribaj.com/products/cementa-limestone-mine-suspen...) The product comes out as a really finely ground powder

to be specific, an application was not approved and the reason the court gave was insufficient proof that continued mining wouldn't effect the local groundwater

Yes, thanks for clarifying

I think it's a bit late for foresight, maybe Cassandra (is there a Norse equivalent?) is a more apt description of the situation we are in ;-)

Good luck, great idea, hope it works out!

> Nice catch! I'm orignally from Norway. Heimdal is the norse god of foresight.

I figured you guys just like Marvel movies. :)

They're pretty good too ;)

I thought it was something Kerberos related initially, but that's only due to the fairly mundane circles I move in :)

It is norwegian! My SO lived in Heimdal, Trondheim.

I love Trondheim! Gorgeous city

Yeah, just got done with my degree at NTNU. Really enjoyed living there.

Very cool project!

A couple questions:

1. How does your synthetic limestone compare to natural limestone? Are there any important performance differences in terms of the material properties of the resulting concrete?

2. What are the biggest bottlenecks/obstacles in terms of scaling this to the point it could replace a significant portion of natural limestone used today?

Edit: do you have any blog posts/more information about what you're doing? I would love to share this around, but unless I'm missing it your site is very light on details.

Thanks! 1. We are entering the product testing stage with our cement producing parnters in the next few months, so I'll have a better answer for you then. But from a chemical composition point of view, our product is purer than mined limestone and so should perform better. 2. Biggest bottleneck from our perspective is nailing planning permission to build our plants quickly enough to supply cement producers.

Unfortunately no blog post or anything like that just yet. Website is very light on details for now, we haven't prioritised updating (+ some patent considerations).

> 2. Biggest bottleneck from our perspective is nailing planning permission to build our plants

How do you get permission to mine seawater? Its kinda of a weird question and I imagine its very country dependent.

Very intersting project.

I suppose it must be similar to permissions to use seawater as coolant, or for producing freshwater from it.

Yeah cool! If you have a twitter or any other way to follow you guys I would love to - I work at a sustainability-focused startup and I know a lot of people who would be interested in this, and not all of them would be in the HN audience.

Love the enthusiasm to share! This is a bit of a coming out party for us, so not much out there in the way of public information. We'll add to that as it comes higher on the list of priorities

Could you share more details about your startup?

If you wish to do it privately, check links at my bio.


Will DM you

Would love to learn more details too! Info in bio :)

Taking bicarbonate to carbonate releases about 0.8 moles of CO2. This has the opposite effect of what you are intending. See the below link for a discussion of the mechanism for how taking carbonate (i.e. limestone) to bicarbonate sequesters carbon. Please don't just run this reaction in reverse. That's almost as bad as our current process for making cement. If you're doing something different (e.g. adding a counterion to replace calcium), then where does this come from?

It seems what they do is Ocean Water + Sorbent -> Leaches Carbonates for use in Cement -> Heated in Kiln -> Releases C02 -> Captured and redissolved in Ocean water. This still has to be proved how to reabsorb such large amounts of c02 in ocean water.

Absorbing large amounts of CO2 happens every second since 2-3 centuries at this point, and is the main driver of ocean acidification and subsequent coral bleaching, loss of wildlife, etc. If the mentioned process could "recycle" the CO2 needed for lime production, then it could be a big win for a very hard to decarbonize sector.

What is still to be checked is how more expensive this lime will be, and how it will stack up compared with traditional limestone+carbon tax

Price can be justified, if the government puts carbon tax on cement companies who dump large quantities of CO2 in the atmosphere.

Seems the co2 binds the proprietary alkaline sorbent when released from the Ca/Mg.

How many orders of magnitude separate your current cost per ton of limestone from the popular status quo methods?

You're talking about ancillary products and regulatory credits, which is a fine business model; but I'm asking about the core industrial process. Trying to get a sense of how much more efficient your scale-up needs to be, before your process is in the black.

Our current cost per tonne is in the same order of magnitude when including the carbon value from the European ETS. The key success criteria for making large plants profitable will be connecting to cheap electricity at <$50/MWh we're in the black

How "flexible" is the production? I mean during peak-sunny hours the price of electricity is well below that mark in some regions of europe? And would it e.g. make sense to scale up in a very sunny region & produce your own power? Last question: Do you need electrical power or heat? If latter, would a more efficient thermo-solar power plant make sense? Best of Luck! :)

> And would it e.g. make sense to scale up in a very sunny region & produce your own power?

It’s an interesting point. The most sunny region might be not the target market. Then you need to factor in the CO2 emissions arising from the transport to consumers.

Cement has the advantage of being a small fraction of the weight and volume of the finished product. You source your water, sand and gravel closer to the work site but ship in your cement, I think you’re still in pretty good shape from an overall footprint standpoint.

Of course they are now electrolytically strip mining the entire ocean floor…

True and interesting point - but if you're able to produce as cheaply to "push out" dirty competitors and still have a net saving when including transport, it would still make sense I suppose. Also, there are always relatively close sun intensive regions near major customers: mongolia / tibet china, north africa europe & middle east, the US has its own deserts...

also, transport is a minor fraction compared to the net saving

Absolutely, CO2 emissions from transport isn't much of an issue compared with the saving. Hopefully someone like Remora will crack that problem anyhow. We'll most likely need to build our plants closer to where the market is though, to limit the financial cost of transportation

This kind of scale would require establishing factories all over the world. Every feasible region in every developed country.

Yep! It'll be quite a journey to get there

Thanks! ABsolutely, looking at optimizing time of day we operate will be important. As grids become more dominated by renewables a solution like ours will be able to help stabilize acting as a electricity sink when the wind is blowing too hard or the sun too strong, taking advantage of lower power prices at these times

What electricity sources have you identified as acceptable for this? Proximity of e.g. hydro to an ocean seems like a small set of sites. :) A naive glance suggests that solar capacity factor of 25% is going to put that particular source out of your budget.

One fortunate aspect of electricity is that it's easy and efficient - on the order of 2-6% losses due to transmission for hundreds of miles - to transport.

Whether your country has invested in renewable sources like hydro plants and associated high-voltage, long-distance transmission lines is what matters. The geography of whether hydro plant is near the coast or not is of less importance than whether it exists or not!

There's quite a lot of wind power available at sea.

Convenient that ;)


Can you handle intermittency in your power, or do you need to run continuously? What capacity factor do you assume in your cost model?

That's actually the trickiest part of the engineering, but we've managed to make it directly compatible with the an intermittent energy source like solar and wind

What is the current price of carbon credits in the ETS? I am from the USA / am dumb, so don’t know how to find it

Also good read for everyone: https://www.gatesnotes.com/Energy/Introducing-the-Green-Prem...

The World Bank has a great resource here which lists out pricing for emissions trading systems (ETS) and carbon tax by country.[0] (Map & Data > Price > Type of Instrument). Highest carbon taxes are $100+ / ton (Sweden, Switzerland, Lichenstein), high initial value for trade is about $50 (EU, Switzerland).

We are a bit behind in the US in credits or taxes, we are now treating the social cost at $51, but not using that for tax or trade policy.[1]

There's one more number that is useful to get a numerical sense of the costs: $258 / ton, an estimate of the actual cost to society. [2]

[0] https://carbonpricingdashboard.worldbank.org/map_data [1] https://www.scientificamerican.com/article/cost-of-carbon-po... [2] https://www.nature.com/articles/s41467-021-24487-w

That estimate of cost to society should tell us something when contrasted with the actual prices being levied right now. Hopefully we'll get closer to that number eventually!

Hopefully the US does this: https://news.climate.columbia.edu/2021/05/06/proposed-45q-ta...

Haha gotcha, European ETS is on a bit of a tear at the minute. Has risen to ~$70/tonne CO2

You should come to Quebec (Canada). The electricity is cheap and 99% from renewables. https://www.hydroquebec.com/business/customer-space/rates/

Make crypto mining illegal. Boom! Do something useful with the energy instead, like cut carbon dioxide.

Cheap green electricity at less than 50 $/MWh should not be a problem, most PPAs are already getting signed at costs substantially lower than that.

Will you be able to complete on cost without carbon credits, at scale?

We're competitive at scale. This does require us to hit our CAPEX targets and to capitalize on cheap renewable sources of electricity that are becoming prevalent

Did I correctly understand the idea if I summarise the product as similar to Climeworks, capturing atmospheric CO2 (indirectly through the ocean, same thing in the end), but with the difference that you can sell the resulting product as cement ingredients (plus some byproducts) rather than it being just stored away like Climeworks does?

If this is (roughly) correct, what price point per ton of removed CO2 are you at today, assuming the cement ingredients can be sold at an optimistic price point? I'm currently with Climeworks but it's prohibitively expensive to remove all unavoidable emissions that I cause by living a normal life today, so my subscription doesn't cover all emissions yet and I would love to.

Finally, I don't see a way to buy anything on your site, or even a waiting list. Is there some call to action, like if I were a cement producer could I buy your product today? Any plans to offer CO2 removal to consumers? Or anything else people or businesses can buy at the moment?

Yeah, that's the core of it. Climeworks absorbs CO2 on their amine solid sorbent surface before releasing it by heating up the sorbent to prepare it for a new round of CO2. That CO2 then needs to be stored somewhere. I'm not familiar with the inner workings of Climeworks, but if I were there that would be what concerned me the most. I know they're testing a mineralization solutipn with Carbfix in Iceland that could be promising, but expensive. We're not at sufficient scale to offer credits to consumers. but this could be on the agenda in a few months. As for cost per tonne this depends a lot on the commercial arrangements we have in place. More meaningful is the energy consumption per tonne which is <4 MWh/ tonne. This will be reduced to 3MWh/tonne. Based on current commercial conversations we're expecting a CO2 price below $50/t for our first plant

$50/t sounds amazing! That would be a price point where I could offset 100% of unavoidable CO2e emissions quite easily. Too bad it won't initially be available for consumers, but I'm very much looking forward to seeing where this goes :)

If your solution for generating limestone is carbon neutral, does that mean that if it were combined with other approaches that inject CO2 back into the cement while it is curing (e.g. CarbonCure or similar, see [1]) we could actually achieve net carbon capture from cement? Might make sense if that allows extra credits to be sold in the EU ETS, assuming the curing-injection process is also economically viable. I'm just thinking that some of your competitors in the space might turn out to be future partners, because your approaches complement each other.

[1] https://arstechnica.com/science/2021/07/quest-for-green-ceme...

Yep, absolutely right! Combining our product with something like the carbon curing tech of Solidia or CarbonCure would make a net-negative concrete. I don't consider us competitors at all!

This is great to hear. Most people don't know how bad concrete is terms of Co2. If you tell people that it's several times worse than aviation in terms of carbon, few people will believe you until they look it up.

We tend to focus on obvious sources of carbon: fuel and electricity, probably because it's something we all have some familiarity with. Agriculture and industry are hidden from our day-to-day lives, so few people are aware of their massive impacts on climate.

So true, it's a surprising statistic to most that 8% of global emissions is actually from concrete

I wish you the very best of luck. The kind of company that I'd like to be involved with and I'mm sure the same goes for others here.

Just one thing.

https://www.heimdalccu.com/our-story linked from your front page gives 'Page Not found'

Thanks a lot! Stay posted for open roles - we'll be needing to add to our team in the next few months.

Thanks for pointing out - will sort this out!

Sounds promising! I have noticed companies with environmental impact have disproportionately more success in crowd-funding. Many non-institutional investors (like myself) put their money in ideas that are good for the world - almost like charity. Perhaps you will consider raising funds and spreading the word using a crowd-funding site such as https://www.startengine.com/explore

I love the idea of crowdfunding! Definitely something we'll look into down the line.

I've been recently thinking about desalinization and what people could do with the excess salt rather than re-releasing it. It makes me wonder if you couldn't bake the salt into cement thereby killing two birds with one stone, so to speak.

We actually use concentrated brine in our solution!

What are the inputs and byproducts of the manufacturing process for your proprietary sorbent, and what are their environmental impacts, if any?

Good luck!

Sustainable cement and concrete production is needed now more than ever. Many people do not realize that the [1] cement industry is one of the main producers of carbon dioxide greenhouse gas emissions.

[1] https://en.m.wikipedia.org/wiki/Environmental_impact_of_conc...

Thanks! Yes it's pretty wild - fully 8% of global emissions!

Congratulations. Curious whether the process remains carbon-neutral after counting the carbon footprint of the renewable sources themselves

Yes! It's true wind, and solar especially, have a small carbon footprint associated with production, but our process is carbon negative enough to more than compensate for it

Very cool! It sounds like your sorbent requires calcium to precipitate calcium carbonate from sea water. What would be the source of this calcium? Hopefully it won't come from reducing lime!

The calcium all comes from dissolved calcium bicarbonate - we trigger precipitation by shifting bicarbonate to carbonate ions, which are insoluble. Essentially we acceelrate the oceanic carbonate cycle

I understand that calcium salts and bicarbonate ions are common in the ocean, and are increasingly common as the oceans become more acidic, but have no idea how common that is.

How much seawater do you need to get one kg of CaCO3 precipitate?

We're actually working on figuring this out. Our current calculations assume we need to process a huge amount of seawater (11,000 tonnes per tonne of CO2), if the CO2 is the limiting factor (2000 umol). However our R&D suggests undersaturated seawater re-absorbs CO2 from the air surprisingly quickly. Might be able to get this 10x lower

Wow .. 11,000 tonnes of seawater per tonne of CO2 is indeed huge.

Assuming that the new process stochiometrically generates CaO according to the amount of CO2 taken up from the ocean you'd produce 1.27 tonnes of CaO per tonne of CO2. (molar masses of CO2 and CaO: 44 g/Mol and 56 g/Mol)

Cementa website states [1] an annual output of 2.7 million tonnes of cement.

So in order to produce what is only a portion of Sweden's (a comparatively small country) annual demand for cement, Heimdal's process would require processing of ~ 23 billion tonnes of seawater.

That's 23 billion cubic metres or 23 cubic kilometres per year or ~ 730 litres of seawater per second.

[1]: https://www.cementa.se/en/about-cementa

.73 m^3/s of seawater is only a pipe of 1m diameter with water traveling at 1 m/s. Not that big a pipe in the grand scheme of things!

True. Not that big.

But let's not forget that it's not about merely pumping the water around. All this water must be processed. And I figure the process is a little more involved than simple reverse osmosis for seawater desalination.

In the desalination business 1 m diameter pipes with water traveling at 1 m/s and the resulting volumetric flow rate isn't a big thing .. but I'd guess for more complex processes it indicates huge/expensive apparatuses.

Is it surprising? Carbon dioxide equilibrates between salty water and air fast enough to keep every single terrestrial animal on the planet alive, after all.

(former) cement scientist here.

you say we are "addicted" to cement/concrete which is correct, but then propose more cement? i get we might need cement here and there for energy transition and might need your tech. but isn't using less cement a better/complementary approach?

im addicted to tobacco, not sure natural tobacco is my best bet.

at a time where half of the world is burning, do we need more 10 ways bridges for huge cars?

how do you tackle the worldwide sand shortage problem?

does your tech solves the issue that comminution (grinding) of clinker is one of the biggest electricity consumers worldwide?

how does that scales up, how long to deploy? what are the consequences (please be honest) to marine life, knowing that most kelp forests/corals are now gone/bleached?

how does your tech tackles the massive corruption problems that come with concrete?

thanks in advance

edit: don't take it badly, your tech looks promising on paper.

One startup cannot solve all the problems right?

Also I like solutions that don't rely on people changing their habits, because they are most likely to work.

The alternative to tobacco is no cigars or cigarettes, the alternative to cement is not simply no buildings, no railways, no roads, no infrastructure.

we are building out of clay, stone and wood for a long time. we are only using concrete because it's cheap and convenient.

still not convinced of hydrogen for steel rebar production also.

Cool initiative!

Can we talk turkey? What's your cost of capture per ton, and how do you scale from one ton to two billion tons?

The average emissions per capita per person in the US is 15 to 20 tons per year. You're building a plant that can capture 1 ton per year.. so 1/15th of a single person. How does this make a dent?

Thanks! You're right the current version is pretty small. The demo we're building is just about making enough product for our commercial partners to test in their facilities. That way they can confidently sign binding purchase agreements that we'll leverage to build commercial scale facilities. We're aiming to build our first commercial scale plant next year. Since our product is chemically identical to mined limestone, only much more pure we're confident we have a compatible product!

Yeah, I was wondering about that too. Is the 1 tonne a typo? Even for a demo product it doesn't seem all that much.

We're building it out to ~300 tonnes/year in the next few months. Our commercial partners don't need more than 20-30kg of product for initial testing and then just a few tonnes to run industrial testing.

I was just talking to a friend a week ago who is pretty deeply interested in concrete. A Civil engineer who had been considering physics research before eventually ending up taking the civil route. A few years of “designing” bridges (they tend to be all about the same, for good reason) and he remains pretty fascinated by the materials and how much room remains (he thinks) for innovation in a very old material, but you know, is a little sick of the day to day.

Any tips for what exists out there in the world of “exciting” concrete? Talking to him he didn’t have too much idea what even existed for research, or if civil/physics was an appropriate background for working at least close to research in concrete.

As far as I’m aware “aerated concrete” is the next step up in concrete tech:


It’s lighter, less energy intensive, better insulator, basically just by inserting bubbles into the structure. Widely used in Europe but not adopted by the US because lumber is cheap and we don’t have any established manufacturers.

That and lumber is stored carbon while concrete releases CO2 (at least for now).

Really inspiring to see some progress in this area. Capturing in cement is indeed pretty clever! I wish you the best of luck to scale up production.

Thanks so much!

What do you find to be your greatest challenges when marketing to existing partners in this space? From an engineering perspective, it seems to be a "no brainer", but I'm curious to hear the push back or objections (if any) you've received.

Existing players have all been overwhelmingly positive! From their perspective we're not competing with their core business and they don't have to change any of their existing plants to use our product. All they have to do is buy from us rather than a mining company to get carbon neutral cement. The main push-back is the need to perform testing on the product to make sure they udnerstand performanc before integrating in production at scale. The biggest problem on our side is sorting out planning approval to build facilities on the coast that use seawater

Tremendous news, thanks for sharing. Best of luck with your product.


Excited to see new implantations in concrete! Given the low lifespans (and thus higher environmental costs) of reinforced concrete, what are you thoughts on basalt rebar? Are sustainable reinforcement methods on your radar?

All intiatives worth doing. Can't tackle this problem from too many angles at this stage. Alternative reinforcement would be compatibel with our solution in any case

Aaaah so cool. More and more I'm thinking the largest impacts seem to be happening "in the real world." As a software engineer lately I've been feeling kinda.. pointless. Like we've made some cool apps out here for identifying and tracking illegal factories here in Taiwan, but now we have a backlog of thousands, and the "real work" is happening in the bureaucracy and paperwork that eventually results with cops being sent to the factory to deliver court paperwork and shutdown / modification orders, and that feels real-world and unfixable by me.

Kinda a ramble as my friends and I are actively talking about this right now in regards to this thread, but I'm curious how other HNers feel about this. Like when I was at Electric Imp, the real magic seemed to happen when the soldering irons got busted out. Here in Taipei I asked my buddy who's driving all the lamborghinis, and he said "just regular entrepreneurs, import/export types." I'm not money-motivated but I have been feeling I guess "left out?" I'm thinking about all those engineering projects I hear about out in Africa where they make super efficient mini stream turbines, or float wifi balloons. Feels like the good shit happens IRL.

Really cool! Looking forward to follow your journey.

I understand that you might not be ready to share numbers, but you mention both hydrogen and desalinated water as byproducts, which both are quite energy intensive to produce. Any chance to give a hint along the lines of:

    X kWh of power + sea water + sorbent (consumable?) => Y% CaCO3 + Z% H2 + W% H2O
When at scale, will your synthetic limestone be much more expensive than mined limestone or roughly the same?

Our synthetic limestone will be on par with mined limestone. At scale when accounting for the higher calcium content per tonne and value of carbon we expect to be cheaper even than mined limestone.

You hit the nail on the head there. The most important cost factor is energy. We're looking at <3MWh/tonne of CO2 removed. Somewhat higher than some competing DAC companies that claim 1.5-2.5MWh. But these guys have the added cost of finding permanent storage of their gaseous CO2. Cost estimates for this, at scale, are as high as $100/tonne

Is it that expensive to pump the c02 back down an old oil or gas well so that it is stored underground again?

Sounds similar to seacrete.


Very interesting. I'd definitely like to hear more about your business plan and your plans moving forward. I work for a Japanese bank and help connect startups with the bank's Japanese corporate clients in the US, and Asia (and soon Europe). Many of the bank's clients are looking for solutions like this. Happy to connect if you're interested.

Could it be profitable to take advantage of the overabundance of renewable energy during certain periods of the day? Or does profitability require running the process 24/7?

I'm thinking, for example, whether this could sink some of the overabundance of solar energy in places like California.

Absolutely! This is a big part of our thinking for how this integrates with future energy systems based on renewables. We'd offtake cheap electricity when oversupplied, like in California right now

I am curious what is your take on Davidovits geopolymer based carbon capture. I believe he was using kaolinite as the starting point with alkali activation. A second approach was using fly ash and silica flume/slag, byproducts of power plants and steel production.

A really cool project. Good luck to you.

One question: why can't the electricity be from nuclear power as well as renewables? The UN IPCC says nuclear is as low in carbon emissions as wind, and around 1/4 that of solar.

This is a really interesting project/opportunity. Does the trapped CO2 become permanently trapped? And how do you guys envision “integrating” into the existing processes to offer them the solution? Is it a fairly heavy lift?

When you need a senior/lead level software engineer, contact me (info in profile.) It'd be nice to work on something that could really, actually, literally make the world a better place.

Thanks, will keep you in mind! Watch out for posts on Work at a Start-up for when we expand our team in the next few months

Do you have a patent or publication that describes this process. In particular I'm interested to know the thermodynamic efficiency and also the timescales involved in adsorption of CO2.

Haha, definitely. Got any links to Elon Musk? ;)

I guess you can get in touch by participating in https://www.xprize.org/prizes/elonmusk :)

Haha, fair point ;)

Seems to me you're also solving a 4th key problem : what to do with renewable electricity when it's being produced but there is no demand at that moment.

Have you done any research into alternatives to concrete? My limited understanding is that besides the actual production process of concrete releasing CO2, the increasing surface area of the Earth covered in concrete is amplifying the effects of global warming. So maybe this process is carbon neutral in the production sense, but remains a net negative? I'm curious about your thoughts there.

Take a look at Stripe Climate if you're looking for customers -- https://go.stripe.global/climate-projects

This looks exciting! You mentioned building a demo plant that has 1 tCO2/year of capacity, which you plan to scale up to 300 tCO2/year. What is your estimated cost for building a plant, per tCO2/year of capturing capacity? (As opposed to the ongoing cost per tCO2 captured, which sounds like it will be somewhere around $100/tCO2?)

I would love to see you success!

Do you have more technical details on your process? Did you publish anything? I try to dig more on your website but the content is rather thin (I learn more about what you are doing by reading your post here).

What are the by product? You mention cement and drinkable water, but there should be other byproduct to handle such as brime?

Thanks a lot for that! We have very little published at the minute for patent reasons. It's actually pretty neat as we consume the waste brine in the process, so nothing to disturb local marine life as you have issues with at reverse osmosis desalination plants

Very cool.

What would the net effect on carbon be (presumably the carbon not emitted + the carbon captured) per ton of concrete?

Thanks! Actually the process is carbon negative as not all is stored as carbonates that can be used in cement production. But for the materials we sell it's 1:1. One molecule of CO2 is captured for every molecule that's emitted in production

Great project, congrats!

Regarding this statement:

> The undersaturated ocean then re-absorbs an amount of atmospheric CO2 equivalent to the amount we removed when reacting with our sorbent

How can it be effectively measured/confirmed? Were you able to produce data to prove it, or is it a theoretical assumption?

Congrats on the launch!

Just curious if you're interested in an incubator? We went through the Oxford Foundry[1] last year and would highly recommend it.


> Until now concrete producers have favoured capturing emissions at the point where they’re released as their “2050-solution”

Just curious: at what point does concrete release C02? In a particular part of the manufacturing process? Or throughout the process?

Thanks that answered my question.

What's your primary source of calcium? Can you write your process as a chemical reaction equation? Would that compromise some kind of trade secret? E.g.

CaSiO3 + NaCO3 >> Na2SiO3 + CaCO3

Interesting, the entire website - other than a content free holding page has now disappeared,

Missed this thread till now. Very intriguing product!

Is there a use for your synthetic limestone in the agricultural sector? E.g., for soil treatment?

What’s the greatest challenge or limitation, technology- or business-wise, that your startup faces? If it fails, why will it fail?

Honestly, our biggest problem right now is moving quickly. In the next 6 months our biggest problem will be getting planning permission to stick large pipes into the sea to process large amounts of seawater ;) We don't discharge anything but seawater undersatured with CO2 so we're not negtaively impacting the surroundings. But government is slow with these things

I guess that all depends on which government you're talking to, and where.

Here's my random question. Assume your process works perfectly, and truly represents a solution to the CO2 problem.

Some very wealthy person shows up at your door, and offers you and your partners serious money to put the entire idea and process into the public domain, and release all IP rights worldwide, immediately.

How much?

Looks great, good luck! Question about the seawater aspect, are ecological impacts similar to conventional desalination processes?

It's actually better, we consumer concetrated brine in our process, so we don't create a high local salinity that disturbs marine life. In fact we're a pretty good fit for a bolt-on to existing RO desalination plants. Let me know if anyone's connected to someone at a plant like that!

wow, long and interesting thread! I'm sure people have already pointed out but your website needs a content overhale to actually say what your doing and roughly how... also, tangent question, can concrete be made from concrete? just thinking what happens when we cover the earth in the stuff we could use something else or reuse?

Your post mentions desalinated water, how are you dealing with the desalination byproducts (very salty water I assume)?

When I saw this the article title being about cement and carbon, I got excited that someone invented a way for cement to better absorb heat and solar radiation.

I have to imagine global temperatures are affected by the reflection of cement quite a bit. Blacktop certainly returns heat into the air, as do roofs, but I would guess so does most cement -- why does no one talk about it? Soil aborbs, plants absorb, solid cement reflects, no?

I’m confused; wouldn’t you want it to reflect the solar radiation, not absorb it? The energy has to go somewhere! Unless the energy is going into something else, like increasing some chemical potential energy, or producing electrical power, or something, if it is absorbed, it is as heat. While, if it is reflected, (some proportion of) it may leave the earth as light.

I guess something which might help is if you could change the wavelengths that went out from it to be ones that would be more likely to leave earth rather than being absorbed/reflected by the atmosphere? But I don’t know if that can be done efficiently enough to not produce more heat in the process of changing the wavelengths than just reflecting it would, if it is even possible.

Some exciting innovations in this field in terms of using white paints to reflect away light and reduce surface temperatures!

This sounds really cool, and I hope it goes well. We need to work every angle we can to address climate change, and test as many ideas as necessary to get there.

My issue with this post is the claim that you will be making the world's first carbon-neutral houses. I understand the need for strong exciting marketing language, but, surely you mean something like, first modern Western-style carbon-neutral houses.

Thanks! Yes that's absolutely true, that could've been more specific. In the modern world almost every house needs concrete for something, at a minimum for the foundations.

Good luck but the laws of physics, chemistry and economics are against you... just saying!

"Making money" is the biggest Co2 unleashing endeavour by far. Trapping science in hic-ups bursts in a linear narrative is not explanatory. Be well, the World is dumbed down enough to take your desires for solutive. You might reach for local fame and hoaxy glory. The Co2 in your case is released by your approach.

> We are currently building a demo plant just outside Oxford.

Where are you going to get the seawater?

We're currently driving it up in a van from Southampton!

What's the long term plan?

Bigger van.

Is the price per kg competitive to the conventional cements?


are you capturing Carbon or CO2? It seems we've released Carbon from prehistoric oil, but not O2. what is the consequence of capturing O2 as well?

Is the capture a chemical or biological process?

Very cool! Wish you best of luck!

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