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?
Launch HN: Heimdal (YC S21) – Carbon neutral cement
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Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#152Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#153Your post mentions desalinated water, how are you dealing with the desalination byproducts (very salty water I assume)?
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#154If 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)
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?
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#155Taking 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 counteri…
Seems the co2 binds the proprietary alkaline sorbent when released from the Ca/Mg.
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#156What'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
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#157I did some lengthy analysis behind the chemistry / economics and wrote it up here.
https://www.moderndescartes.com/essays/carbon_neutral_concre...
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...
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#158Aaaah 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.
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#159[deleted]
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#160Earlier quoted context omitted.
> 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…
> 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 energ…
> 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.).