Heirloom Carbon: Absorbing CO2 from the air using crushed rocks | Hacker News Reader

Heirloom Carbon: Absorbing CO2 from the air using crushed rocks

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97 pointstaylorbuley108 comments

Speaking as a geophysicist who worked in the research end of the Australian mining industry, just the fracturing of rock itself already consumes a LOT of energy.

Thermodynamically, think of all the fracture surface area being created. If you ever studied fracture mechanics, it's essentially the same as requiring that the elastic potential energy being released by creation of new fracture surface needs to come via work from somewhere (Griffith theory).

I think this approach needs significant "lifecycle analysis" before it can be declared to be a net positive.

Just my two cents.

(Edit: typo.)

Yeah, this strikes me as the kind of tech that becomes viable with unlimited free energy.

If/when fusion becomes harnessed I think we can expect to see a large variety of impractical tech like this suddenly becoming mainstream.

But if I'm understanding correctly, that's only a one-time cost.

Then the already-fractured rocks are used (forever?) to absorb CO2, heat to release, and repeat. (Do they somehow lose that capacity over time?)

But also this seems to be assuming that all the energy comes from renewables in the first place, including the energy for crushing the rocks...

We are also in need of sand for concrete. Can we not crush the rock until suitable for concrete and then entomb it in buildings and structures?

Olivine-supplemented cement actually absorbs CO2 in low-pH environments, healing cracks.

There's been quite a bit of work on enhanced weathering (google the phrase). Even powered by coal and diesel, it's entirely feasible at global scale, provided we are willing to blanket a fairly large area of sea with rock flour.

Heirloom's approach, turn limestone into quicklime and then let the quicklime turn itself back into limestone, is different, and I don't know how the energy economics work out for it.

> provided we are willing to blanket a fairly large area of sea with rock flour

That sounds like a different type of disaster.

The ocean is a very large place, and much of the floor is nearly barren of life (compared to coastal waters anyway, and certainly in terms of biomass). Furthermore benthic storms already cause a great deal of turbulence on the bottom; i don't think problems are obvious.

Granted, i have similar concerns about efficiency, but we need any wins we can find.

Water it. Freeze it? Sounds not very carbon intensive if done right?

Using energy to free up CO2, so that you can bind CO2 that was produced by using energy - do I have that right? Anybody see any trouble with that plan? If you're being charitable you can assume the whole thing is 100% efficient like in a physics textbook.

Don't worry about the CO2 we freed-up in the first step; we'll just use more energy to drill and pump it underground from where it'll escape, or inject it into one of the most energy-intensive building materials, concrete, which would of course continue to be produced in kilns and used. Speaking of kilns, this one is electric, meaning the fossil fuels are burned elsewhere, not on our premises! What an elaborate arbitrage.

There are no energy free ways to resequester atmospheric CO2. If you accept that we will have to do so to meet the world's climate change goals, then the question is really, how energy efficient can you make your process, and where can you get carbon-free energy. This company has a credible approach, although as soon as you look at any of the mechanisms being considered, the scaling problem is daunting.

Honestly, the low tech nature of grinding up rocks, baking them, and setting them out in a pile makes this seem pretty easy to scale, given any money

I'm really thinking of the energy scaling. Suppose you want to use such a technology to offset burning oil for some purpose. Even for highly efficient processes, you're going to get generate a ton of CO2 for a MWh of usable energy. You're then going to use 2 MWh of electrical energy to recapture the CO2. So, you've tripled the energy we need to produce for that process. That's really raising the bar on carbon neutral energy production.

energy production is orthogonal to CO2 production, neither requires the other to happen

so, imagine you want to absorb a ton of CO2 from the air to prevent the planet from further spiraling into uninhabitability: you could electrically bake the rock with renewable energy, then use it to absorb CO2

Isn't this just portland cement at that point?

The CO2 in the limestone was already sequestered by nature. They are freeing it, which is the opposite of what is needed. Leave the limestone alone and that CO2 remains sequestered, no additional energy needed. This sounds like a way to just capture CO2 on paper.

Obviously, you didn't read how it is intended to work. Baking the rock gives them a stream of nearly pure CO2, which can be sequestered underground. The powdered rock then efficiently captures CO2 from the air (where it is of course, very low in concentration). That CO2 can then be baked off, sequestered, and the rock cycled to the air again. In an industrial plant, you'd have a continuous process of rock being baked, exposed, baked again, with a continous stream CO2 being sequestered geologically.

How can one sequester CO2 “geologically”?

There are two natural geologies I know of:

Oil fields often have dissolved CO2 and methane contaminants. Those gasses are captured and pressurized to force more oil out. Those empty caverns are the largest opportunity for capture.

At ocean depth, CO2 is trapped under hydrate caps. This is best-known around geothermal “smokers”, but the ocean floor is largely unknown. So, there is significant risk allowing the hydrate caps to melt.

>Those empty caverns are the largest opportunity for capture

How large?

We have 42,592 trillion cubic feet of CO2 in the atmosphere, and the projected total natural gas that can be extracted going forward in the US over the next 85 years is 2,973 trillion cubic feet.

First, will we even extract that much? I've heard that using that much will create more CO2 than we can handle.

And, taking the wild assumption that we do extract that much, how much of that natural gas will come from fracking, and how much from caverns?

Let's be generous and say that 50% comes from caverns. So now we have 2973 times 0.5 which gives 1486 trillion cubic feet of space we can eventually use for the plan you describe, if we use more natural gas than we safely can use.

And that's making again another overly generous assumption in favor of your plan which is that these caverns are somehow left in a state of vacuum before we start putting in CO2.

And let's be fair and assume we only want to sequester say 20% of the CO2, so we want to squeeze 8,518 trillion cubic feet of CO2 into this idealized generously estimated 1,486 trillion cubic feet.

Naturally the gas will be injected under pressure.

I imagine this gets incredibly complex, and there will be leakage, and it will be the province of huge contracting companies that historically have shown themselves to be mainly interested in getting to a finish line such that they can get paid by the taxpayers, with help from their bought-and-paid-for lawmakers, long term results and consequences be damned (see: oil and gas industry, nuclear industry).

I don't feel very good about this plan.

But I can envision the ear-to-ear grins at the contracting companies when they found out "the libs" are going to make tax dollars rain on them for continuing to extract oil and gas out of the ground using some paperwork and a variation of a process they were already doing, even though it probably won't achieve the ends those libs want.

You can inject it into coal beds and it should adsorb into the coal

You do realize that coal then gets dug up and burned, right?

Also, have you heard of fracking? It's a blend of the words "cracking" and "fracture" and why is that? Like virtually any geology, there are cracks, through which, for example, gasses, like methane or in this case CO2, can escape. Coal beds also happen to be riddled with fractures and cracks. So even if you don't dig up the coal, "should absorb" is pretty weak for something we would be betting our future on.

Presumably the concentrated stream of CO2 output from the kiln is easier to work with than pulling dilute CO2 out of the atmosphere, to the degree that it is worth doing that way.

I'd love to hear a more detailed explanation from experts about how the output stream is sequestered. It doesn't sound absurd though; getting gasses in the right place at the right time is not necessarily a trivial task.

Optimistically (and ostensibly), almost all the energy for the kilns would be free of direct emissions (e.g solar). In that case the plan sounds effective. Let's see if that actually works out.

> Using energy to free up CO2, so that you can bind CO2

...thereby concentrating CO2 which had previously been diffused throughout the atmosphere, so that it can be processed and stored.

> Speaking of kilns, this one is electric, meaning

...that fossil fuels need not be involved at all. Solar panels are cheap, and they can choose to build the factory in a sunny place.

> so that it can be processed and stored

it was already processed and stored.

In the limestone.

By nature. For free.

Just leave the CO2 stored in the limestone alone, and find some other way to capture the CO2 from the atmosphere.

I don't think you've properly understood the process. They free the carbon from the limestone, but capture it. They then use the resulting material to capture more carbon. Then they repeat the process. The first batch that was in the limestone originally is obviously of no benefit, but succeeding cycles are using carbon pulled from the air.

>but capture it

For certain values of “capture”

TFA says it could be pumped underground, etc. “could be” in theory if that gets proved out and doesn’t leak.

For a period.

At least for long enough to collect the tax credit.

Meantime, it was already captured in the limestone.

If we reject the idea that captured carbon can remain captured, then no carbon capture mechanism works. I'm not sure your skepticism on that front is warranted, though.

What I’m rejecting is a kind of perpetual motion machine style setup where you need to redirect a bunch of already captured CO2 in order to capture an equivalent amount.

If however the resulting CO2 as they cycle this can be and is in practice truly captured (not just on paper), then sure, I can see the use, if it makes a more efficient way to glean and gather CO2 molecules out of the atmosphere.

Still the energy costs (solar, say) have to be weighed against the opportunity cost of using that solar to simply replace some CO2-generating combustion process directly, avoiding putting most of the differential amount of CO2 into the atmosphere to begin with.

In other words, it’s really hard to see a win here unless they’re going for some kind of tax or PR win.

To your first point, it's like wringing out a sponge to continue soaking up water. A sponge saturated with water still has the ability to soak up more water, just not the capacity. The issue isn't storing the water, we can do that in buckets (and in the earth in the case of CO2), the issue is collecting it in the first place.

To your second point, we need to find a way to sequester CO2, not simply stop generating anymore. It's also more complicated than 1 MWh generated by solar = 1 MWh generated by coal, there's a time dimension, among other complications, to it as well. If we produce more solar energy during the day than we use, we can turn that towards capturing CO2.

It's going to take work, but if we can sequester more CO2 than we generate, than we can ostensibly reverse climate change, or at least mitigate it.

Depending on how the organization is operated, some individuals are going to be in position to prosper financially in proportion to the size of the cash flow they preside over or participate in, rather than the net positive outcome to the entire whole. Often quite a net negative outcome, usually due to a hidden flaw which is not obvious to many.

On really big scales things can take a lot of work and this could be a lot of people.

Until there is truly not only an abundance of clean renewable energy, but an absolute surplus left over after everyone ends up with more than they ever thought possible, and almost all sources of atmospheric carbon have been addressed, the best use of renewable energy will continue to be the elimination of carbon at the source[0] rather than direct removal from the atmosphere no matter what you do.

Something about you can't fool mother nature.

During these uncertain times the renewable energy (like any form of energy) will also continue to have a greater financial value on the market directly, compared to the alternative return after involvement with inefficient processes.

So for the forseeable future there will always be incentive somewhere in the chain to sell the valuable energy outright, maybe even clandestinely, rather than "divert" some of it to an inefficient fate. Unless of course that is a subsidized fate.

Like wholesale release of any kind of CO2 from limestone ever. Give me a break. When limestone is already one of nature's best known forms of long-term solid carbon repository on the geological scale, and for best results the natural limestone needs to have its chemical composition stay undisturbed for additional eons.

Limestone is simply Calcium Carbonate. CaCO3.

If you're going to turn CO2 into limestone or some other solid, that would be great as long as you start with something that's not limestone to begin with. Almost anything else would be more sensible.

It's just that capturing CO2 using slaked lime or quicklime (carbon-free alkaline compounds of calcium) is a well-known laboratory process. For centuries. That's all most people are ever going to know. Which seems to work so great on the bench because you can merely open a jar of the raw lime and it spontaneously absorbs CO2 from the atmosphere, eventually turning into you guessed it, limestone. Deceivingly cheap enough at lab scale, the raw lime is one of the lab chemicals where the packaging and shipping cost more than the contents, because it was made industrially in bulk from abundant limestone and discounted energy. So the jars of raw lime in the chem lab are among the very lowest-cost lab chemicals[1] and that's still not good enough when you do the math at scale, "absorbing" the externalities.

>There are now hundreds of startups around the world racing to develop a variety of methods to do this. But many of them, including Heirloom, are still operating at a tiny scale, if they are even at the point of removing carbon at all. So this latest Microsoft deal stands out for signaling a high degree of confidence in Heirloom’s unique approach.

As unique an approach as you can get without any material advances in millennia.

What's needed instead to efficiently turn gaseous carbon to a stable solid is something that is not a known laboratory process. Yet.

Corollary to Murphy's Law says Mother Nature always sides with the hidden flaw. Mother Nature is a bitch.

[0] such as by direct substitution for fossil fuels

[1] the kind that any lab budget can afford if there are chemicals at all. So any lab can start out opening new jars of lime, removing CO2 from their closed systems, then dumping the resulting CaCO3 as harmless solid waste. This scales only so far before financial reality can not be overcome. So the creativity has been focused more so on financial approaches with nothing unprecedented about the engineering or chemical research. Maybe enough to make Microsoft look good but not making a real dent in the overall picture. And what percent of people other than Microsoft have the level of profitability where they can afford to sequester any significant amount of their respective carbon emissions whatsoever?

Great post, thank you.

As you acknowledge in your wording, we don't know for sure, but for me this part states it very clearly what might unfortunately be a key driver at least at this stage of that company:

>Depending on how the organization is operated, some individuals are going to be in position to prosper financially in proportion to the size of the cash flow they preside over or participate in, rather than the net positive outcome to the entire whole.

Wait so the argument is: "There exists the possibility of corruption, so we should discount the opportunity to research further??"

I understand the trepidation for fear of greenwashing. But it's just that, a fear. Until you have evidence of wrong doing why trample on possible world saving research?

As for the above posters second rebuttal, is the argument: "This proccess has been done in the lab before, so this company couldn't have possibly found a more efficient process for doing the same thing?" Isn't this how every incremental step in efficiency is gained? Isn't it a good sign that the process is already known and proven, and so all this company has to do is make it more efficient?

Every new battery chemistry is given front page service, all the while everyone knows there's a slim chance in hell they'll ever be market viable. Shouldn't we be investing in tech that is already proven? Not wild moon shot ideas?

There exists an incentive for corruption, is more like it. Therefore we should be skeptical.

Then, with a skeptical eye, we examine the scheme and we see that in order to capture carbon, they are first freeing equivalent carbon that was already captured. And then they are proposing to repeat that process whilst sending the carbon to an unproven magical place that might not work (no concern of theirs) and then claiming credit for it.

>Solar panels are cheap

Not cheap enough for this.

That's OK, Microsoft can afford it.

Most important is to show on paper that your company is green. Other things don't matter

You’d hope the kiln is powered by nukes or renewables.

This sounds really interesting, but I'm a little nervous about the "baking produces pure CO2 that can be pumped underground" part. Is that really happening, or is that CO2 just going to get used for industrial processes and then dumped back into the atmosphere?

They have "transparent methods for verification".

"Developing and adopting scientifically rigorous and transparent methods for monitoring, reporting, and verification is essential for permanent carbon removal."

See: https://www.heirloomcarbon.com/news/heirloom-joins-carbon-re...

You wouldn't want to not recycle the quicklime otherwise you would have to release the CO2 from it first, then absorb the same amount of CO2 and then throw it away so you'd only be emitting CO2 in that case.

Does it really matter if the CO2 in your SodaStream or your favorite beer comes from this or an industrial process that generates CO2 (such as from ammonia)?

I mean, even if this all went to industry, if it was removing new CO2 that would have been generated otherwise, then it would still reducing atmospheric CO2 by the same amount from what it would have been otherwise -- right?

(Assuming this doesn't magically provide so much CO2 that it depresses prices and leads to new/increased CO2 uses, but that seems unlikely since this seems to be a much more expensive method than existing ones.)

You’d need a full lifecycle analysis to determine that. Sorta like how ethanol fuel is more polluting than just gasoline https://cleantechnica.com/2022/09/13/ethanol-burns-clean-but...

It is argued that ethanol is more polluting than gasoline based on the entire lifecycle but that article only shows how complicated it is to calculate - and ended with only an opinion that biofuel is worse than gasoline.

Providing cheap CO2 to industry (at any price!) is almost certainly going to be incentivized vs. pumping it underground, since the former provides revenue and the latter is pure expense. At small scales that probably won't matter, and will just offset dirtier sources. But at small scales this technology is just a novelty: it's only interesting to think about it at very large scale. And once it exists at large scale you really have to think very hard about how you're going to (artificially) counter the natural incentives that might produce perverse effects.

Not if you can sell carbon credits for pumping underground?

*claiming to pump underground.

ftfy

If pumping underground even works beyond the timeline needed to claim the tax credit.

That isn't quiet true. One of the major pushes for carbon capture is CCUS which is a fancy word for greenwashing. You install carbon capture facilities and pump that carbon deep underground. But you do it not to store the carbon, but to get even more oil out of the ground [0].

[0]: https://en.wikipedia.org/wiki/Enhanced_oil_recovery

I would support this, assuming ratio is ~1:1.

It’s much bette than the alternative today where people pump oil and don’t put anything back.

Quote from your link > “The project is expected to inject a net 18 million ton CO2“

Industrial and food service CO2 is mostly captured from power plants right now, as I understand it. Besides that, most of that CO2 is only very temporarily stored - it's going right back into the atmosphere as soon as possible.

Yeah this is dubious, they get all the Co2 out of these rocks, and then the rocks will asorb Co2.

The rocks aren't the carbon sink in this process. They're a concentrating mechanism. They sit there and absorb CO2 from the air, then the kiln process is used to pull the CO2 from the rock to whatever sink they're using.

The bar for answering that is ambiguous.

What evidence would provide proof that it is really happening, as opposed to it being just words in an article?

Do we need to go to a plant?

Will following only _some_ of the carbon through it's lifecycle be sufficient?

Is burying _some_ of it sufficient?

Or are we looking for a full audit framework?

Is it okay if that's enforced by force of law?

200million is the estimated cost to capture just "75%" of Microsoft's carbon footprint in 2022. A footprint that is going to increase by more than 7.5% of the 2022 carbon footprint year over year("Bing" chat).

How about disabling all the spyware and garbageware. Then get to fixing the monstrosity that is Win11. Some Googling and math suggests about 100,000,000 tonnes of CO2 is coming from the bloat on Windows(per year). Microsoft claims there are 1.4billion devices using Windows.

*Napkin math

It always amazes me how we can sweat bullets trying to get page load times down and then someone slaps google’s and someone else’s tracking shit onto it and everything grinds to a halt, but that’s okay.

It sounds to me like the problem there is that Google is the gatekeeper, in that your ranking depends on their page speed metric, and also inserting their own tracking code which they get to decide to exclude from the metric

SEO matters, but so does customer experience and they’ve begun to diverge.

With SaaS, which we are, I occasionally catch customers who have managed to get two or three copies of analytics in their pages, with different ids. It’s just… Exasperating. I think I need to switch disciplines. Nobody who has tried to fix this one has made large inroads.

Are all Windows PCs are getting charged to Microsoft's carbon footprint? $200M/year quite a steal if so

The math from the article suggests a hard no.

Microsoft's officially reported carbon numbers don't include the impact of their software on devices sold by other OEMs.

This is a gray area of the GHG protocol on how to account for SW carbon emissions; some companies count it some don't.

[https://query.prod.cms.rt.microsoft.com/cms/api/am/binary/RW... pp 11.]

Maybe there's a good reason to have articles on this but the title just makes it sound like pure PR.

200 million isn't remarkably big for a trillion dollar company.

It's also a speculative investment in a tech company. This does not sound viable, but if it is I'm sure Microsoft has first dibs at the table.

it'll take roughly 1.5 million mature trees to sequester 315,000 metric tons of CO2 over 10 years. The "Billion Tree Tsunami" in Pakistan aimed to plant a billion trees from 2014-2017 and surpassed its goal. Similarly, India set a record in 2016 by planting more than 66 million trees in a single day.

How many will survive and make it to maturity? Planting saplings is easy. Having them mature is more difficult.

There's also a question of how good these plans are for the ecosystem as they tend to plant all the same tree in tight spaces so they wind up competing for resources and driving out other parts of the system.

I think surveys for five years survival are still being done, but an earlier survey by WWF found 70-85% survival rates for earlier stages in the life of the trees [1].

Regarding your point, yes, there is a lot of problems in the project with monocultures being planted, especially comprising non-local ones. This is a complex political problem because you want to incentivize planting, but cost of planting "multi"-cultures is much higher.

[1] https://d2ouvy59p0dg6k.cloudfront.net/downloads/btap_monitor...

Wow 315,000 metric tons. That’s the yearly CO2 output of 21,000 Americans!

Yeah, tree planting is mostly feel good unsustainable crap. People keep trying to get around this problem without taking a hit to lifestyle, but I don't see how that happens.

It's also the goal of Microsoft in this project

Pakistan actually went for Ten Billion trees [1] next. This one is going slower, because of a variety of political and scientific reasons but there is still quite a lot of progress.

[1] https://www.unep.org/news-and-stories/story/pakistans-ten-bi...

1 billion trees over 3 years is not much for such a big country. Much smaller Poland has managed forests and plants 500 million trees a year.

It's interesting that discussions of this process don't mention the potential to combine the carbon sequestration with, say, nuclear power generation. This process basically requires a lot of heat. So, maybe build high temperature gas cooled reactors to provide process heat for this process (which is inherently highly interruptible), used to offset continued use of petroleum in applications where electricity just doesn't work (commercial aviation, e.g.), with the option to switch to electrical generation when renewables fall short.

How this compare cost wise to other solutions for carbon capture like planting trees? Looking at its cost per ton of CO2 it seems quite expensive for a normal consumer trying to go net-zero.

Mineral weathering is reasonably predictable in terms of what it will be capable of capturing.

Planting trees is anywhere from very good (cutting the trees down and burying it so deep it doesn't rot back to the atmosphere) to very bad (the tree doesn't grow or burns in a fire, effectively adding CO2 equal to the cost of planting).

Maybe we can plant fields of new coal to be found in a million years ;-)

Apparently we can’t. That worked because there were no bacteria that’d consume the biomass and release CO2 back then.

If its deep enough underground, the conditions favorable to that bacteria may not exist.

I'd disagree with "very bad" being the bottom end of the scale. The cost to plant a tree is not very resource intensive and many trees lost would be made up for a single successful tree. It's almost all upside.

The problem is you haven't actually offset anything, and by the time you find out that you have offset nothing, the carbon you were hoping to sequester is back again.

There's other not good (carbon-wise) uses of trees, like harvesting for firewood, or culling to prevent the spread of diseases like oak wilt or bugs like the emerald ash borer.

Compared to chemically weathering minerals, trees are at best a gamble. Most people aren't stuffing dead ones in really deep holes; the best we can hope for now is they get cut up into quality furniture or building materials that will last decades or more.

There's really very little long-term upside to randomly planting trees and hoping for the best, aside from the fact that trees are really nice things and intrinsically good to have. Just not a super effective carbon sequestration scheme by comparison.

Planting trees isn't a method of carbon capture. Trees die, decay, and release the CO2.

Famously, they also burn.

Famously they also make houses and many other products like paper.

If you plant a forest where there was no forest before, then while individual trees will die, the entire forest will capture carbon dioxide proportional to its biomass.

Forests will typically grow for years-decades, and absorb carbon dioxide throughout, till their biomass (per km^2) reaches an equilibrium point. At that point the forest will go from a carbon sink to carbon neutral (averaged over several years to account for forest fires and subsequent regrowth).

Yes, they emit some carbon when they decay, but not all of vegetation goes back into CO2, so even mature forest is an overall carbon sink. New forest is an even larger carbon sink.

Estimates of the carbon sink per km2 are about ~200-400 Ton/km2/yr or ~2-4 Ton/ha/yr (Slope of curves in Fig 7 in https://www.nature.com/articles/s41598-021-99395-6) To absorb our current 10 GTon C (~30 GTon CO2) we would need ~30-50 M km2 of area; Arable (crop) land area is ~15 M km2 (~10% of Earth's total land area) and grassland is ~30 M km2. Clearly we aren't going to turn nearly all of arable/grass land area to forests, but vegetation management could be a significant part of carbon management.

$200 million, only paid upon delivery, is not a "remarkably big bet" for a company with $73 billion in net income.

Nah dude. It’s totally fair to not pay for snake oil. Microsoft is doing a good thing here and you’re just shitting on it. It’s easy to sit on your high horse here, but how much have you paid into carbon sequestering? And would you pay some unproven company a huge stack of money up front on a pinky swear?

I'm not saying it's bad, I agree that it's a good thing! It's just nothing even close to a "remarkably big bet."

315,000 tons of CO2 over 10 years, so 31,500 tons per year.

40 billion tons of CO2 per year will be created globally by 2030.

So Microsoft's deal will remove 0.00007875 percent of globally emitted CO2 on an annual basis.

This process would have to be scaled up by 1,269,841 times to capture all emitted CO2, neglecting the increased CO2 emissions associated with the scaling itself.

That seems like a lot of work just to enable humans to increase our numbers and consumption on a finite planet.

Can someone please remind me why more people consuming more resources is a given?

Even if we stopped all emissions tomorrow, we would probably need to do stuff like this because the CO2 level is already too high.

Because nature existing in a vaguely pre-human state is only a means to an end. Climate change is only a problem so far as the problems it creates get in the way of humans and their actual goals. Humanity first.

About $25T, about a third of global GDP to scale up to full offset. Even more to offset the last century. We need massive innovation in this space. Even if we make reliable and scalable fusion we are still far away because we need enough batteries to offset all other carbon emissions in planes, cars, and other vehicles.

How does this compare to olivine weathering, a much cheaper technology that seems rather similar, and is already being used in many projects? Is it more effective, longer term, what?

It sounds like the advantage is that can repeat the process storing CO2 underground. It sounds like a weird way to store CO2, like they are trying to do the same thing as direct capture. When storing underground was one of the big flaws with direct capture.

But I would think it would be an advantage to dump the crushed olivine in the ocean where it would be sequestered for a long time. It isn't like trees where have to worry about the CO2 being released from fire or decay.

Another post and some more discussion yesterday:

https://news.ycombinator.com/item?id=37430323

This is nonsense.

Start with limestone. Cool, there's lots of that. Cook it - using energy - which you'd otherwise have to do other stuff. That drives off CO2. Put it somewhere. You get something nastier that would indeed absorb CO2 from the air.

The sketchy parts are the "put it somewhere" and the energy going into the process. Thermodynamics is a harsher mistress than lifecycle analysis. Not a chance this is a net decrease in atmospheric CO2.

I wish these articles would publish an energetic tally.

It's pretty tough to remove CO2 from the atmosphere (an inert and pretty stable molecule at trace quantities), but that becomes easy with infinite energy.

Does the energy for mining and crushing the rock come from oil, and coal for example.

In short: what does it look like when you close the system loop?

there's a good podcast here talking about one of their partnerships for storing the carbon in concrete

https://www.volts.wtf/p/taking-carbon-out-of-the-air-and#det...

I'm not sure why you're getting downvoted. David Roberts's Volts podcast is one of the best resources around for really weedsy discussions on clean energy and decarbonization.

I trust the chemistry but it's the source of the energy to power the furnaces and where to pump away the co2 that are the critical limiting factors. Also, are they going to just grind it into a nanometer powder and mix it with air in a hyperboloid flue?

Don't we want to leave those calcium compounds in the ocean to counteract the acidification of the ocean from CO2?

Reverse Fracking.....baking soda pumps...

i want a small scale version of this to scrub CO2 out of my office (not too different than what they do on submarines).

i already dump out a dehumidifier every day, could imagine swapping the "carbon brick" along with it

(yes yes -- fresh air exchanger on the HVAC system would also do this, but i want gadgets)

Well, you could grow algae as a CO2 sink!

https://youtu.be/64cEmjtwRgw?si=QmRd716sgFmjaM-0

I realize your suggestion is surely not practical, but at the same time it's got my curiosity now.

How big would such a brick have to be to absorb all of somebody's CO2 for a day?

I just have no intuition whatsoever around it.

(Also you'd need a carbon filter for all of the VOC's as well.)

Hmmm...I would just spend the money planting trees and lobbying for legislation that makes people get permits to cut them down.

Just plant trees. Not in monocultures

Most tree planting projects fail to capture the CO2 spent on planting them. There maybe ways to use trees to capture carbon efficiently and at scale, but it's still an unsolved problem.

I was thinking bamboo. But you need like 900 pounds of bamboo to offset one passenger flying from SF to NYC.

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