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Comment by frederikvs | Hacker News Reader

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?

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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.

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).

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.

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.

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