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.
Launch HN: Heimdal (YC S21) – Carbon neutral cement
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Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#142I'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 proces…
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.
I'm probably missing something obvious.
> The world needs CaO for cement. We have a carbon neutral process for making it
vs
> 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?
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#143Could 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.
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#144Earlier 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? 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…
> 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?
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#145If 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)
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.
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#146Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#147Great 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?
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#148I 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 yo…
As far as I’m aware “aerated concrete” is the next step up in concrete tech:
https://www.buildinggreen.com/news-article/autoclaved-aerate...
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.
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#149Earlier quoted context omitted.
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. Unfortuna…
> 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.
Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement
#150> 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.)