Equatic OAE process (Gaurav Sant, UCLA spinoff): does it work well?

[Jasper Sky]

Does anyone have an opinion about Equatic, a spinoff from UCLA"s Institute for Carbon Management? 
Their approach is to run an electrical current through seawater, which generates hydrogen gas that can be collected and increases alkalinity, with calcium and magnesium carbonates precipitating out. They claim 2 MWh per ton of CO2 sequestered in the solid carbonates, and about 1 MWh can be recouped in the energy content of the hydrogen gas (a significant co-benefit). If powered from RE, e.g. stranded geothermal energy, maybe this is plausible. 
Has anyone taken a close look at the technology?
And does anyone take the view that more energy-efficient approaches to OAE are available?

[Josh Perfetto]

Hi Jasper,

Their approach is described by the paper La Plante et al., 2023.

I think what the process basically does is use renewable energy and access to seawater to turn silicate rocks into carbonate rocks. I think the main disadvantage of the approach is you need to have renewable energy, seawater, and silicate rocks all at the same place, and then transport carbonate rocks out of that place. But I see the advantage in that you are transporting safe, concentrated rocks/minerals, rather than acid, or even worse dilute acid, which would be expensive.

I spent a while looking at electrochem OAE approaches and came to the conclusion that these may play a bigger role in later years after more available sources of alkalinity are exhausted, but I'm glad people are pursuing it now to progress the technology.

-Josh

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[Chris Van Arsdale]

As far as I can tell, without an external source of alkalinity (e.g. mined/crushed rock), their setup actually has a net outgassing of CO2. This statement in the abstract is incorrect:
"This results in the trapping and, hence, durable and permanent (at least ∼10 000–100 000 years) immobilization of CO2 that was originally dissolved in water, and that is additionally drawn down from the atmosphere within: (a) mineral carbonates, and/or (b) as solvated bicarbonate (HCO3–) and carbonate (CO32–) ions (i.e., due to the absorption of atmospheric CO2 into seawater having enhanced alkalinity)."

... since while CO2 is trapped in CaCO3, removing Ca++ from the water results in the water losing 2 CO2s (well, 1.6), one to CaCO3 (good) and the other outgassed back to the atmosphere (bad). So, the net effect is to add more CO2 back to the atmosphere, the worst possible outcome.

Of course, with an external source of crushed rock that changes. But, at that point, it's basically House et al with an extra step backwards.

- Chris

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[Achim Hoffmann]

I did have a quick look at this as my immediate gut fee reaction was that this does not make much sense to me, and it looks more like a theoretical exercise without taking into consideration real hardware relevant technical and economic considerations.

 

That cannot be the case as they seem to have already quite a team on this incl Chemical Engineers. They also state that they have 2 plants, one in California and one in Asia, i.e. I have to assume I am missing a lot of information which makes sense given as a start-up, you don’t want to put all your cards on the table for everybody else to see.

 

I have not found any numbers that would indicate the size of plants, only intentions on how much they want to remove in the future.

 

Putting on my former hard tech VC hat combined with my Chem.Eng water Science hat there are a number of questions that I would have want to be answered before backing this idea.

 

1. Number one would be about real experimental data and how that backs their assumption I the many models they present. The linked paper contains a lot of exsiting knowledge, some hypothetical modelling but without any experimental proof for assumptions.
2. Those numbers have to include basic Electrolysis data anybody else would quote, such as current efficiencies and current densities for their process as that then links you to the critical economic modelling parameters.
3. More information on plant design. I go the impression that this is an asymmetric electrode design, a smaller Anode in the Centre and then a bigger cylindric mesh around it as a cathode. I am probably wrong on this, but with my time limited search I could not find anything other than that no membrane is used and they were using pH numbers of 10-12 for the Cathode and then 1-2 for the Anode. Given the input water should be around 8 (Ocean pH) this indicates asymmetry. That then immediately leads to the next question about future plant footprint. There is a reason for the geometry of exsiting electrochemistry stacks: it ensures hi current efficiency but also a small plant footprint. The footprint might not be an issue going forward if you are out in the Ocean but the current efficiency of the electrode design is connected the green input electron costs.
4. The Acidic pH is quite aggressive and is likely to kill most biological content in the water (something to keep in mind for future ‘negative consequences’/risk considerations).
5. It would be good to see a summarised mass balance on this. It seems that this is supposed to be a rock logistics company: They need rock material that needs to be ground up to counter the acidic pH before putting that liquid stream back into the Ocean and then they are collecting the Carbonate solid output from the cathode as they cannot just put it back into the Ocean where – while it is not soluble at pH 12, it will redissolve in the pH8 Ocean environment ,i.e. not an option, even though suggested in one of their graphs.
6. A closer look at what is happening at both Electrodes is however what interests me most.
1. Anode: The standard way electrochemical CDR works is the CO2 capture form the Anodic reaction. At pH of 1-2, you will have lost >99% of all the C in the water, CO2 gas will have evolved ,which can then be collected and used/sequestered. I could not find any comments on that so far, but that must be down to me not looking hard enough as that is such a basic key question.
2. Cathode: What about precipitation/scaling? The solid carbonate salts will preferably form where the pH is highest, i.e. right at the Cathode, or more likely on the electrode and by that clogging up active electrode area, killing off the process over time. How do you prevent that from happening? There migt be some clever IP stuff in this area as they mention the supersaturation levels on Ocean water and you might be able to play with this, but it is not clear from what I have seen. They seem to indicate that the particles are formed in the liquid phase and that they can filter it out. This by itself is not a trivial step as if the seed crystal is indeed formed in the bulk water it will be small and the filtration requirements to capture those seed crystals are demanding.
3. Once all the challenges have been resolved, it would be good to understand how that all would look like in a scaled up real world version and given then solid material logistics considerations and the green electrons needs, what an ideal location would like.

 

 

 

 

 

 

From: carbondiox...@googlegroups.com <carbondiox...@googlegroups.com> On Behalf Of Josh Perfetto
Sent: Monday, January 15, 2024 12:07 AM
To: Jasper Sky <jasp...@gmail.com>
Cc: Carbon Dioxide Removal <CarbonDiox...@googlegroups.com>
Subject: Re: [CDR] Equatic OAE process (Gaurav Sant, UCLA spinoff): does it work well?

 

Hi Jasper,

Their approach is described by the paper La Plante et al., 2023.

I think what the process basically does is use renewable energy and access to seawater to turn silicate rocks into carbonate rocks. I think the main disadvantage of the approach is you need to have renewable energy, seawater, and silicate rocks all at the same place, and then transport carbonate rocks out of that place. But I see the advantage in that you are transporting safe, concentrated rocks/minerals, rather than acid, or even worse dilute acid, which would be expensive.

I spent a while looking at electrochem OAE approaches and came to the conclusion that these may play a bigger role in later years after more available sources of alkalinity are exhausted, but I'm glad people are pursuing it now to progress the technology.

-Josh

 

On Sat, Jan 13, 2024 at 4:49 PM Jasper Sky <jasp...@gmail.com> wrote:

Does anyone have an opinion about Equatic, a spinoff from UCLA"s Institute for Carbon Management? 
Their approach is to run an electrical current through seawater, which generates hydrogen gas that can be collected and increases alkalinity, with calcium and magnesium carbonates precipitating out. They claim 2 MWh per ton of CO2 sequestered in the solid carbonates, and about 1 MWh can be recouped in the energy content of the hydrogen gas (a significant co-benefit). If powered from RE, e.g. stranded geothermal energy, maybe this is plausible. 
Has anyone taken a close look at the technology?
And does anyone take the view that more energy-efficient approaches to OAE are available?

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[Michael Hayes]

The use of minerals to deal with the produced chlorine is expensive and has a long upstream supply chain. However, using the Cl to disrupt microalgae for oil extraction is cheap and can be used out on the Ocean without shore resources being used. Mutually supportive mCDR methods add value to each method. Combining electrolysis-based OAE and agricultural CDR methods might lead to rather cheap fuels, Biochar, food, feed, fertilizer etc:

https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-018-1614-9

Coupling OAE methods, electrolysis-based and ag-based, and Biochar will 'stack' CDR benefits and bridge the marine and terrestrial divide. Converting marine C, which we have too much of, into soil C, which we have too little of, does seem to be offer a rather strong CDR path with few technical questions.

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/030101da479f%24a0123190%24e03694b0%24%40woxon.com.

[Chris Vivian]

All,

 

There was some discussion about this technique on the CDR Group back in December 2021 – see:

https://groups.google.com/g/CarbonDioxideRemoval/c/TCWLLEC1xsY/m/naVvqr3zCgAJ?utm_medium=email&utm_source=footer – see teve Rackley’s comments in particular.

 

Chris.

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/030101da479f%24a0123190%24e03694b0%24%40woxon.com.

[Chris Vivian]

There is also, an Open Air, This is CDR webinar by Equatic that took place on 8th August 2023 - https://www.youtube.com/watch?v=b8SPjrnHxY0&list=PL1je2pACUAbKdS4529vLLHgZR2MGk9KLm&index=4

 

Chris.

 

From: Chris Vivian <chris....@btinternet.com>

Sent: Tuesday, January 16, 2024 11:36 AM
To: 'Achim Hoffmann' <ac...@woxon.com>; 'Josh Perfetto' <jo...@ephemeralcarbon.com>; 'Jasper Sky' <jasp...@gmail.com>
Cc: 'Carbon Dioxide Removal' <CarbonDiox...@googlegroups.com>

Subject: RE: [CDR] Equatic OAE process (Gaurav Sant, UCLA spinoff): does it work well?

 

All,

 

There was some discussion about this technique on the CDR Group back in December 2021 – see:

https://groups.google.com/g/CarbonDioxideRemoval/c/TCWLLEC1xsY/m/naVvqr3zCgAJ?utm_medium=email&utm_source=footer – see teve Rackley’s comments in particular.

 

Chris.

 

From: carbondiox...@googlegroups.com <carbondiox...@googlegroups.com> On Behalf Of Achim Hoffmann

Sent: Monday, January 15, 2024 10:43 AM

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/030101da479f%24a0123190%24e03694b0%24%40woxon.com.