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Comment by chris_va | Hacker News Reader

(disclaimer that I manage a climate research group)

There has been quite a lot of interest in Ocean Alkalinity Enhancement (OAE) in the last few years.

This is kind of an unfortunate title, as "geoengineering" (while not wrong) has a very negative connotation in non-scientific publications. Presenting OAE as ocean acidification remediation would have been a much nicer way to drive adoption.

As a side note, lime can be very problematic under some conditions (parasitic CaCO3 precipitation can cause a net release of CO2). But ultramafic rock is alkaline and everywhere. It tuns out you need approximately one large mountain dissolved into the ocean to reverse climate change (neutralize ocean acidification and causes the ocean to take up any extra CO2 in the atmosphere). Or you can just remove acidity from the ocean using solar power, and pour it on rocks somewhere.

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Are you kidding me? One large mountain? That can’t be true. Why are we collectively losing our shit over climate change when we should just blow up some coastal mountains?

This seems eminently doable and a lot cheaper than just moving every city away from the coast, among other things.

I feel like there’s some fineprint I’m missing.

I don’t know the details of this concept but even if it’s true we have to decarbonize our economy or we’ll just have to keep blowing up mountains. Also I presume the parent meant “one mountains worth of lime” and I presume most mountains aren’t pure lime.

We will decarbonize. The only fossil fuel we have in massive abundance is coal, and it’s already not economical for electricity generation. Natural market forces could get us there alone. The problem has always been that it doesn’t get us there fast enough.

If we can just mine a mountain worth of lime and dump it in the ocean, that seems simpler and cheaper than trying to move all our coastal cities. Even if we decarbonize at the maximum possible speed, we’ll still have to do that.

What timeframe do you think every coastal city will have to be moved? Is there a reputable hedging market for that outcome?

A few centuries. The biggest sea level rise will be at the end, the effect will be non linear. Long after we decarbonize, sea level will keep rising.

some are a lot earlier than others. New Orleans and Most of Florida are already having problems (especially when a hurricane creates a big storm surge).

1) You can't just blow them up. You have to crush the rocks into something resembling sand to get the alkalinity released in human time scales.

2) Large means quite large. I ran a back-of-the-envelope estimate some years ago and found that the Hawaiian island [1] of Kauai could reduce atmospheric CO2 roughly back to pre-industrial levels if it were completely pulverized and weathered away down to the seafloor. That's trillions of tons of rock.

3) The benefits of curbing CO2 are shared globally, but the costs are concentrated locally. It's the same kind of prisoner's dilemma that results in e.g. people still burning billions of tons of coal each year.

I think that accelerated silicate weathering is the best geoengineering option and one that's likely to be deployed at scale later this century, but it's not really going to be easy.

[1] AKA "underwater mountain, with the top poking above water"

I’m sold, where do I sign up? Seriously, this sounds so amazing, I’m blown away* that I’m only learning about it now!

* pun intended

For #3, I wonder if the way out of the prisoner’s dilemma would be to use this method specifically for local ocean acidity reduction. Over time it helps globally but it doesn’t do so quickly enough that other countries become disincentivized from doing the same.

I think that 'large mountain estimate' depends heavily on atmosphere-ocean mixing rates, doesn't it? IIRC, ocean circulation takes about ~2000 years to mix the oceans.

Ocean acidification is a local near-surface phenomenon caused by the oceans absorbing the higher levels of CO2 and pulling the carbonate equilibrium to the left, so to speak. CO2(atm) <-> (H2CO3) <-> (HCO3)- <-> (CO3)-2 -> CaCO3 precipitate ?

I don't know a whole lot about this, but it seems you'd have to keep doing this steadily and gradually for > 100 years (maybe 1000 years) at global scale to get that effect? ...and that's assuming no more fossil fuel combustion was taking place?

As a mitigation for coral reefs, oyster beds etc. it seems to have more immediate value.

No, we'd need to dissolve that amount into the mix layer (call it the top 50m, for argument's sake), which takes a few months to equilibriate with the atmosphere through that carbonate chemistry. But, if one managed to do it all at once (not sure how), it would only take a few months.

One would want to avoid downwelling regions that get sucked into deep ocean circulation before reaching equilibrium (e.g. the north atlantic), that alkalinity would take a long time to come back up and be useful.

Um....is anyone working on the two methods you mentioned?

If you have any links I'd love to learn more. (And if your climate research group is involved in stuff like this, I'd love to check that out.)

Vesta, Ebb Carbon, Planetary Technologies, Heimdal (YC), some stealth companies, and some academics are looking at OAE directly.

(may be missing a few)

There are a lot of terrestrial enhanced weathering folks too, where the alkalinity eventually washes into the ocean after being spread on land.

thank you for posting!

> a very negative connotation in non-scientific publications.

yes, after decades in higher ed, I too find a very negative connotation in the field of "geoengineering"

I’m really interested in learning more about ocean modifications to enhance its ability to store carbon (not via seaweed farms) or protect life that is fragile to increase acidity levels. Do you have any recommendations for further reading? Feels like everything I real on this topic is either carbon removal or solar geoengineering

This sort of thing?

https://iopscience.iop.org/article/10.1088/1748-9326/ac002d/...

... Oceans equilibriate with the atmosphere after a few months (they absorbs more co2 in response to pH/carbonate shift), so one has to keep injecting alkalinity to keep a local ecological effect. The CDR effect is persistent, though.

drill spiral tunnels in some mountains and pump water though them.

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