Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Launch HN: Heimdal (YC S21) – Carbon neutral cement

news.ycombinator.com

Post reply on HN
Print view View original

191–200 of 227 posts

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#191

Post by m12k »

marcuslima wrote: post #53
brilee wrote: post #49

I'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.

A way to help explain this to people is that it's the equivalent of rapidly growing trees and burning those for fuel instead of burning fossil fuels.

You do the same with limestone, rapidly creating it by capturing atmospheric CO2 (indirectly, via the ocean) so it can then be burned in cement production instead of the naturally occurring kind. In both cases, CO2 is released into the air at the end when the product is burned, but because the released CO2 had just now been sucked out of the air anyway (instead of having previously been sequestered in natural limestone) you're not adding to the total amount of CO2 in circulation in the system, making the process neutral.

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#193

Post by m12k »

If your solution for generating limestone is carbon neutral, does that mean that if it were combined with other approaches that inject CO2 back into the cement while it is curing (e.g. CarbonCure or similar, see [1]) we could actually achieve net carbon capture from cement? Might make sense if that allows extra credits to be sold in the EU ETS, assuming the curing-injection process is also economically viable. I'm just thinking that some of your competitors in the space might turn out to be future partners, because your approaches complement each other.

[1] https://arstechnica.com/science/2021/07/quest-for-green-ceme...

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#195

Post by hippari »

marcuslima wrote: post #176
pabs3 wrote: post #154

Earlier quoted context omitted.

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.

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#197

Post by immmmmm »

quickthrower2 wrote: post #186
immmmmm wrote: post #184

(former) cement scientist here. you say we are "addicted" to cement/concrete which is correct, but then propose more cement? i get we might need cement here and there for energy transition and might need your tech. but isn't using less cement a better/complementary approach? im addicted to tobacco, not sure natural tobacco is my best bet. at a time where half of the world is burning, do we need more 10 ways bridges f…

One startup cannot solve all the problems right? Also I like solutions that don't rely on people changing their habits, because they are most likely to work. The alternative to tobacco is no cigars or cigarettes, the alternative to cement is not simply no buildings, no railways, no roads, no infrastructure.

we are building out of clay, stone and wood for a long time. we are only using concrete because it's cheap and convenient.

still not convinced of hydrogen for steel rebar production also.

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#198

Post by hippari »

froh wrote: post #179
robinsoh wrote: post #144

Earlier quoted context omitted.

> 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…

yes that kilning is what bothers me, not for the co2 that is captured at sea, released in the kiln. that is then recaptured when curing, isn't it? what bothers me is the 1400°C needed in the kiln. to my understanding the ratio of limestone-to-lime co2 to fuel-for-the-process co2 is 2:3. you need lots of co2 intensive energy for that kiln.

they said the H2 produced can be used for kilning.

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#199

Post by _nalply »

m12k wrote: post #191
marcuslima wrote: post #53

Earlier quoted context omitted.

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.

A way to help explain this to people is that it's the equivalent of rapidly growing trees and burning those for fuel instead of burning fossil fuels. You do the same with limestone, rapidly creating it by capturing atmospheric CO2 (indirectly, via the ocean) so it can then be burned in cement production instead of the naturally occurring kind. In both cases, CO2 is released into the air at the end when the product is…

Additionally governments could buy limestone and not use it. Carbon sequestration. The money could come from a CO2-tax.

I really hope this is scalable worldwide.

Re: Launch HN: Heimdal (YC S21) – Carbon neutral cement

#200

Post by marcuslima »

m12k wrote: post #193

If your solution for generating limestone is carbon neutral, does that mean that if it were combined with other approaches that inject CO2 back into the cement while it is curing (e.g. CarbonCure or similar, see [1]) we could actually achieve net carbon capture from cement? Might make sense if that allows extra credits to be sold in the EU ETS, assuming the curing-injection process is also economically viable. I'm ju…

Yep, absolutely right! Combining our product with something like the carbon curing tech of Solidia or CarbonCure would make a net-negative concrete. I don't consider us competitors at all!
Post reply on HN