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

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

#211

Post by blacksqr »

coryrc wrote: post #207
blacksqr wrote: post #205

Earlier quoted context omitted.

According to their web site, one of their premises is that renewable electricity is now cheap and plentiful. If that's so, I'm led to wonder if there is a more direct way to reduce CO2 emissions in cement manufacture, namely, use resistive or carbon-arc heating to fire the ovens, thus replacing fossil fuels in the manufacturing process. Sorry I don't have the chops to work out if that's economically feasible.

The thing you are firing in the oven (limestone) releases CO2. Fossil fuels aren't the only source of CO2. We need zero CO2.

> The thing you are firing in the oven (limestone) releases CO2.

I'm aware of that. There are two main sources of CO2 in cement manufacture: the calcium carbonate raw material, and the fossil fuel required to cook the raw materials into clinker. Heimdal only deals with one. The questions I'm interested in are which source contributes more CO2 and which can be most economically eliminated.

> We need zero CO2.

Agree, but Heimdal won't get us there. We'll either have to find a replacement for cement, or devise a practical method to convert CO2 waste to something benign, like an improved Bosch process.

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

#212

Post by thinkcontext »

brilee wrote: post #157

I 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...

Interesting, thanks. The chemistry you discuss sounds a lot like this

Rau, G.H., Willauer, H.D. & Ren, Z.J. The global potential for converting renewable electricity to negative-CO2-emissions hydrogen. Nature Clim Change 8, 621–625 (2018).

https://www.nature.com/articles/s41558-018-0203-0?WT.feed_na...

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

#215

Post by philipkglass »

brilee wrote: post #157

I 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...

I love your approach but I think that you've made a mistake. $70.00 of electricity at $0.13/kWh is 538 kWh, or 1937 MJ. Hydrogen has a higher heating value of 142 MJ/kg. If you could actually get 36 kg of electrolytic hydrogen from 538 kWh of electricity, that's getting 5112 MJ of chemical energy from 1937 MJ of electrical energy. That can't be done. At first I thought maybe I was overlooking some consumable electrodes in the scheme, but it appears not.

Rule of thumb for electrolytic water splitting is 50 kWh per kg of hydrogen. That would mean about 0.29 as much H2 as estimated in the blog post. If you scale all salable products by 0.29 (not sure if that's sensible since I haven't identified the root error) it would still yield $142 of products from $70 of electricity. And good news there is that industrial scale electricity can be had for well under $0.13/kWh.

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

#216

Post by hinkley »

danieka wrote: post #98

From my limited understanding this seems really impressive! I immediately associated this to possible disruption in the cement supply chain that's about to hit Sweden. Cementa, which produces about 75% of Sweden's cement, will no longer be allow to mine limestone on Gotland. Their permit was due to be renewed but due to the low quality of their environmental impact study the court was unable to determine if the minin…

You know everybody will be working overtime up until then. Extra storage purchased, and possibly discounts to customers for accepting early delivery.

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

#217

Post by hinkley »

frederikvs wrote: post #63

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?

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.

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

#218

Post by hinkley »

f6v wrote: post #50
go_elmo wrote: post #28

Earlier quoted context omitted.

How "flexible" is the production? I mean during peak-sunny hours the price of electricity is well below that mark in some regions of europe? And would it e.g. make sense to scale up in a very sunny region & produce your own power? Last question: Do you need electrical power or heat? If latter, would a more efficient thermo-solar power plant make sense? Best of Luck! :)

> And would it e.g. make sense to scale up in a very sunny region & produce your own power? It’s an interesting point. The most sunny region might be not the target market. Then you need to factor in the CO2 emissions arising from the transport to consumers.

Cement has the advantage of being a small fraction of the weight and volume of the finished product. You source your water, sand and gravel closer to the work site but ship in your cement, I think you’re still in pretty good shape from an overall footprint standpoint.

Of course they are now electrolytically strip mining the entire ocean floor…

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

#220

Post by nextaccountic »

brilee wrote: post #157

I 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...

> More than just profitability, can they make a dent in our carbon problem? The scale of our carbon problem is on the order of 30 billion tons of CO2, of which maybe 1 billion tons are due to lime production. Heimdal is currently at the scale of 1 ton per year - nine orders of magnitude away from making a difference. Assuming continuous Silicon Valley ridiculous growth rates of 50% year over year, they will take 50 years to grow to a point where they are actually making a dent in our carbon problem. I wish them good luck.

They don't need to do it all alone. If this idea is solid, a lot of different companies and nations could be doing this.

I'm excited for China to have carbon-neutral cement. If they do, it will probably be of their own making and not tied to this company growth.

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