Optimal grain size of powdered basalt/olivine for enhanced weathering?

[Jasper Sky]

Hi all. How many cubic kilometers of crushed basalt rock powder would be necessary to remove 1 trillion tons of CO2 from the atmosphere or ocean waters? What size should the powdered rock grains be milled down to?

And where should that rock powder be spread -- is it plausible to spread it on land, or must we turn to the ocean? Is it plausible that we could find locations sufficient to allow 50 GtCO2 CDR per annum via EW? Where? In the ocean? How?

I'm trying to figure out well-grounded numbers and a plausible narrative about this as part of my report to a development bank on CDR options.  

Enhanced weathering of powdered basalt or ultramafic rocks appears to be among the most scalable prospective CDR methods. Let's suppose we start with solid basalt (or serpentine, dunite, peridotite). We'll have to crush it into powder. In terms of EW reactivity, the finer the powder the better, since finer grains expose more surface area per kg of rock; however, crushing rock takes energy, and the amount of energy is a nonlinear function of the grain size. 

I'm imagining implementing large-scale EW in locations where the source basalt (or olivine, serpentine, dunite, peridotite) is found in almost limitless quantities in co-location with readily accessible stranded geothermal energy (e.g. Iceland, Hawai'i, or the Great Rift Valley in Kenya), so the geothermal energy can be used to drive the conversion of solid basalt into fine rock powder on a multi-Gigaton-per-annum scale. 

A subsidiary question is whether there's any way to get around having to first convert this geothermal energy to electricity so as to power rock crushing machinery, or whether direct heat could be used and converted directly to mechanical energy in a rock crusher, to skip the heat-to-power step. Any ideas on that?

Getting back to the question that may be the limiting factor in EW: WHERE would we dump the powder if we were looking to dump sufficient rock powder to soak up 50 GtCO2 per annum? That's going to be a lot of rock powder, nicht wahr! Spreading it on millions of hectares of fields (after first transporting it to those fields) will cost a lot of money and energy. It would be simpler and cheaper if we could just dump the powder off the back of a barge into the ocean, but that won't work very well, will it? The powder will sink to the bottom before it has the chance to encounter many CO2 molecules. As for dumping it in shallow water along coastlines, there's only so much plausibly available coastline for this purpose, right? How much?

It would be excellent if we could get the powdered basalt to float in upper ocean waters long enough to soak up a full load of CO2 before it sinks. 

One variable of interest is the grain size of the crushed rock. That (along with location and characteristics of EW rock powder dispersal sites) will determine the mass of basalt we'll have to crush to achieve CDR of each 10 GtCO2. 

Another important variable is the energy and financial cost of transporting a mass of powdered material to a field or shallow ocean waters where it is to be deposited for weathering. 

This suggests that there must be an optimal grain size beyond which it is not worth the additional energy input required to further reduce it. 

Has anyone seen some numbers on this - and the calculations underpinning them? 

I gather sub-mm grain size is desirable, maybe something between 0.1 and 0.5 mm, but has anyone done the math uniting the key variables into a single equation to allow estimation of an optimum?

This study is relevant, but it doesn't come to any conclusions about optimal grain size - it merely tested the EW effectiveness of crushed basalt as a function of grain size in laboratory conditions. The study's conclusions:

"5. Conclusions

Mg-rich silicates (chlorite, augite) were the main minerals affected by the experimental weathering design employed in this study, an observation that is consistent with field-based observations of mafic rocks in weathering environments. Weathering fluxes for chlorite and augite approximately double from sand-sized (∼250–500  m) to silt-sized (<45  m), and this has implications for forecasting potential for carbon dioxide reduction (CDR) by means of enhanced rock weathering (ERW) of basaltic powders applied to fields as a negative emission technology (NET). In particular, CDR rates vary by a factor of two, ranging from fine-medium sand of BR and PV basaltic powders (3–4 t/ha/yr), compared to a rate of 6–7 t/ha/yr for fine-medium silt."

[Andrew Lockley]

It depends on the carbon impact of milling vs spreading. Transport is carbon heavy and milling less so. You need to mill down finely or it takes too long to weather away your transport emissions, and you can't haul too far (with trucks) 

Reviewer 2 did a podcast on this. https://open.spotify.com/episode/5ZBTd1Fov5BWAy8Op5wUgx?si=Xxa9X1CeTTmLXWSfb0Xjhw

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[Brian Cady]

I believe surface area revealed by milling rock is linearly linked to energy consumed, with a coefficient relating the milling ease of the rock concerned. Since surface area revealed directly relates to CO2 fixed, CO2 fixed would be nearly linear to energy consumed, with only distribution being mass-related, thus varying with particle size inversely. 

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[Tom Goreau]

Small grain size is crucial for rapid dissolution, but there are tradeoffs as it is much more expensive to crush rocks to fine grain size!

 

Remineralize The Earth https://www.remineralize.org/ is the global NGO promoting use of rock powders, biochars, and sea salts as natural, slow-release, chemically balanced fertilizers that last decades, and is involved in developing applications for agriculture to promote rapid growth of healthy biomass, food, pastures, and forests around the world.

 

The carbon benefits naturally result, but a healthier, chemically-balanced, ecosystem with higher biomass, biodiversity, and ecosystem services is the goal, not simply dissolving chemicals where they serve no useful function, as seems to be the case with those only interested in peddling carbon credits to the fossil fuel producers who have driven coral reefs to imminent extinction. For this reason RTE promotes use of grain sizes that are not too small, as these clog the pores in soils and prevent water infiltration and CO2 and O2 exchange between soil air and the atmosphere.

 

Rock powders and biochar should always be used together because they  synergistically increase each other’s fertilization and water storage effects see:

 

https://www.remineralize.org/2020/08/rock-powder-with-biochar-synergies-co-benefits/#:~:text=Biochar%2Frock%20powder%20mixtures%20increase,Biochar%20does%20hold%20much%20bicarbonate).

 

RTE and the Geological Survey of India have recently published a major paper on how the world’s largest country by population, India, can use its own geological resources to feed itself, with the carbon benefits being ancillary. Please see:

 

I A. Mir, T J F. Goreau, J. Campe, J. Jerden, 2024, India's biogeochemical capacity to attain food security and remediate climate: a review, Environmental Geochemistry and Health, 46:17, https://rdcu.be/duxoV

 

https://link.springer.com/epdf/10.1007/s10653-023-01827-x?sharing_token=7iNhWegr_MBD9FIGl44-3Pe4RwlQNchNByi7wbcMAY6N0X9NbiM4gvLpG9CYvqXFBqf8EjTuSFpTLX07D9lW1aKnFjLI_BTH3JETaO23GLQFSnpo8TmZb3zhErcQaqYrHQW8_PhaN4-x_bNAWcatlOABWsIexVtqdiWiGDZwXHA=

 

RTE works with many groups around the world to develop these applications, especially in Brazil, which is the world’s largest user of rock powders to replace expensive, unbalanced, short-lasting, imported chemical fertilizers. Brazilian researchers are world leaders in this field. RTE is working with Tanzania Engineers Without Borders to produce natural material fertilizers from volcanic rocks near Mount Kilimanjaro, local biochar, and compost, and to increase the water holding capacity and fertility of soils in the Panama Canal watershed, among other projects. These applications are covered in a 600 page book:

 

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase

http://www.crcpress.com/product/isbn/9781466595392

 

Thomas J. F. Goreau, PhD

Scientific Advisor, Remineralize The Earth

 

--

[Michael Hayes]

Jasper, et al.,

There are basalt field(¹) that can be pulverized by road recycling machines(²). The bulk matterial transport and spreading costs would be eliminated with this approach. Such fields can likely be reworked each year as creating new fractured faces in the rock creates new CO2 reaction areas in the rock.  

1) https://digitalatlas.cose.isu.edu/geo/greatrft/greatrft.htm#:~:text=Recent%20Volcanism%20of&text=Very%20fresh%20basalt%20can%20be,from%20the%20great%20rift%20system.

2) https://en.m.wikipedia.org/wiki/Road_recycler#:~:text=A%20road%20recycler%20or%20road,a%20new%2C%20recycled%20road%20surface.

As to keeping rock dust at the surface of the Ocean, a slightly modified version of the below HDPE pipe tech can be a used today:

https://youtu.be/qXtVQWHgNig?si=c714Kj2ObKrl56BD

Such HDPE tanks can also function as floating freshwater/saltwater farms. Bio oil derived from the farms can create more HDPE floating grow tanks. Interestingly, due to the long service life of submerged HDPE, a largely self-replicating HDPE oceanic infrastructure would be a large C sink itself once at scale.

[Dennis Amoroso]

At Advanced Materials Processing Inc. we have shown that bacterial activity in the soil reduces the particle

size by 30% over a 48 hour period.  This research was done by Dr. Leonard Nanis who started SeaGate Computers

so it was done using all relative scientific protocols and his Scanning Electron Microscope.

Therefore, the use of rock powder based fertilizer products in agriculture passively removes CO2 from the air

as it brings primal nutrients to the plants.  We are presently delivering this fertilizer to farms by the hundreds of tons.

As a result the State of California is drafting legislation to remove chemical fertilizer from agriculture in the state.  This

then removes millions of tons of greenhouse gasses continuously.

Just so you know....

Dennis Amoroso President and Chairman

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[Jasper Sky]

The idea of running road-recycling machines across old or recent lava flow fields to pulverize basalt (and then simply leaving the powder in place) is interesting, thanks to whoever it is that contributed it. Seems like that would merit a field trial to see how much CO2 could be soaked up that way. But even lava flows have plants growing on them, and simply running road-recycling machines across old basalt flows would disturb an awful lot of land. I think it will be necessary to avoid that. The way forward for EW will be to find basalt sources (basalt mountains) that can be mined for billions of tons of low-toxicity basalt (basalt with low concentrations of heavy metals) for crushing and distribution over wide areas of land, presumably via EV trucks designed for that purpose. 

Also interesting: the idea of putting the crushed basalt powder into HDPE pipes floating on the ocean surface (or maybe into flat floating HDPE trays) with some kind of system for seawater to flow through without removing the powdered rock from the pipe/tray before the rock has had time to complete its enhanced weathering reaction. I wonder how much time T it would take for fresh powdered basalt to soak up about as much CO2 as it's capable of soaking up (at a given grain size)? The method would have to involve leaving the powdered rock in place until it is fully weathered, then discharging the CO2-saturated powdered rock from the floating HDPE trays at intervals of time T, and replacing it with fresh powdered rock. Does anyone have awareness of any research groups or companies working on developing such a system?

[Mike Williamson]

Jasper,

Basalt is very low in heavy metals and other toxic elements and is a favored source for aggregate used in construction. The rock powder is basically a waste material from the rock crushing process and is washed away or sold with the smaller screen sizes at a discount (1/4" minus, everything that passes a 1/4" screen). I have been experimenting with this material in landscaping applications and in one year the rock powder portion has weathered to calcium carbonate (annual precipitation of 112 cm, average temperature of 6.2 degrees C). 

It seems reasonable to expect that a larger scaled experiment could be could be conducted in partnership with an aggregate mining operator at low cost, but proposals to state and local government organizations have failed to attract interest. As a soil enhancement, ERW is scalable and could provide farmers with increased yields and lower fertilizer costs, but it may be that it is too simple technically to attract the interest of private investment (difficult to qualify for carbon credits, not patentable), and not flashy enough to advance political careers.

Mike Williamson

---

From: carbondiox...@googlegroups.com <carbondiox...@googlegroups.com> on behalf of Jasper Sky <jasp...@gmail.com>

Sent: Saturday, March 9, 2024 12:01 PM
To: Carbon Dioxide Removal <CarbonDiox...@googlegroups.com>
Subject: Re: [CDR] Optimal grain size of powdered basalt/olivine for enhanced weathering?

 

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[Brian Cady]

As I remember, crushing olivine (basalt type underlying oceans) fixes about 25 times the CO2 it takes to crush and distribute it, with typical basalt fixing about 8 times. 

[Tom Goreau]

I don’t think the dissolution rate of minerals in the alkaline ocean is nearly as fast as these proponents assume and require, and the trays would vanish in the first storm.

 

I was a student of the geochemistry pioneers who measured the dissolution rates of all the major silicate minerals. They used finely ground powders in heated flasks constantly spinning with magnetic stirrers in order to jack up the dissolution rate to be able to measure the silica and metals released to solution. Many added acid to speed it up. Then they extrapolated their results back to rates at surface temperature and acidity. If they had just dumped a rock in a flask without grinding, heating, and stirring, they would have had to have their great grandchildren make the measurements, and would not have gotten tenure!  

 

By far the best way to weather rock powders is not in the ocean but in soil penetrated by tree roots constantly releasing CO2 and organic acids and metal chelating agents at a far faster rate than the diffusion from the air that rock weathering proponents are counting on. In the 1970s I built soil probes to measure the vertical profile of CO2 and N2O in soil, and found it is much higher than in the atmosphere, sometimes thousands of ppm, depending on soil organic carbon content.

 

The best way to dissolve rock is growing plants in it! Dick Holland measured the rate of weathering of Iceland basalt, and found it weathered many times faster if the rock surface was vegetated. The Soil is not a sink of atmospheric CO2, it is a source, but largely recycled via fast root respiration, and slow decomposition.

 

The other reason dumping rock powder in the water won’t be very effective is that even if it all actually dissolves, ocean alkalinity has a 100,000 year residence time, so it takes impossible amounts of rock dissolution to make a significant difference, it’s pissing into the wind.

 

 

Thomas J. F. Goreau, PhD

President, Global Coral Reef Alliance

Chief Scientist, Blue Regeneration SL
President, Biorock Technology Inc.

Technical Advisor, Blue Guardians Programme, SIDS DOCK

37 Pleasant Street, Cambridge, MA 02139

gor...@globalcoral.org
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226 (leave message)

 

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase

http://www.crcpress.com/product/isbn/9781466595392

 

Innovative Methods of Marine Ecosystem Restoration

http://www.crcpress.com/product/isbn/9781466557734

 

Geotherapy: Regenerating ecosystem services to reverse climate change

 

No one can change the past, everybody can change the future

 

It’s much later than we think, especially if we don’t think

 

Those with their heads in the sand will see the light when global warming and sea level rise wash the beach away

 

“When you run to the rocks, the rocks will be melting, when you run to the sea, the sea will be boiling”, Peter Tosh, Jamaica’s greatest song writer

 

 

 

 

From: ishfaq ahmad <geoi...@gmail.com>
Date: Sunday, March 10, 2024 at 1:57 AM
To: Tom Goreau <gor...@globalcoral.org>
Cc: Joanna Campe <joanna...@gmail.com>, jje...@metamorphic1.org <jje...@metamorphic1.org>, Thomas Vanacore <ston...@gmavt.net>
Subject: Re: FYI: [CDR] Optimal grain size of powdered basalt/olivine for enhanced weathering?

How beneficial it would be to utilise buoyant fabric trays with fine rock dust disseminated and kept floating in tropical oceans for the best results of reacting with ocean water without sinking for the best outcomes of weathering, carbon capturing, and moving down the ocean.  

 

On Sun, Mar 10, 2024 at 2:54 AM Tom Goreau <gor...@globalcoral.org> wrote:

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/MW3PR18MB3481410FEDA62956C02E8CBFD2262%40MW3PR18MB3481.namprd18.prod.outlook.com.

[Dennis Amoroso]

Ladies and Gentlemen,

     After 32 years of research working with some of the greatest scientific minds of our time, I highly recommend taking

the word of Mr. Tom Goreau very seriously.  We have achieved a complete replacement of chemical fertilizers in agriculture

with outstanding results and 30% water reduction with NO loss in yield and an increase in the quality of produce, including

the nutrient density.

     We use the book GeoTherapy as our guide to achieve this success, which the State of California has offered to finance

and several business groups have entered into negotiations with us to have the rights to our technology in their countries.

We will literally save agriculture on a global scale and supply the world with nutrient dense healthy food, using rock powder blends.

Whether we sequester carbon in the process is for you to determine.  However, you must remember that, as Mr. Goreau has stated,

the activity in the soil is instrumental in the decomposition of the rock powder and the sequestration of CO2.

All the best to you and your families!

Cordially

Dennis Amoroso

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[Michael Hayes]

Tom, et al.,

Concerning in situ basalt field grinding:

[...] The coverage area for Columbia River flood basalts exceeds 60,000 square miles. At least 50,000 cubic miles of basalt can be found within that area, and some estimates go as high as 90,000 cubic miles.[...]

https://hugefloods.com/Basalt.html

MH] Accelerating the natural breakdown of the basalt fields with road reclamation equipment, thus increasing biotic activity, and likely increasing water retention/frost heave cracking etc is a project that Washington state would likely support simply for the economic boost in such a poor region of the state. Eventually, such surface treatment repeated over many years might result in largely barren areas being converted to excellent crop areas.

At the federal level, the DoD owned Yakima Training Center in E Washington sits on top of a huge fold of basalt, and field trials of in situ basalt grinding can likely be granted permission, if not funding support, if enough initial support is found within the CDR science community. 

https://en.m.wikipedia.org/wiki/Yakima_Training_Center

I went there many years ago, the natural flora and fauna are exceedingly sparse on the hill tops. The basalt gravel/sand in the valleys is where one finds prime farming grounds and robust natural growth. In situ grinding of either areas should offer an abundance of accelerated C capture and sequestration services.

Michael

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[Tom Goreau]

Bear in mind that rock crushing plants produce gravel to mix into Portland cement or asphalt, and the fine powders we use as a natural, slow-release, long-lasting, nutrient balanced fertilizers are the waste products of crushing, what they bulldoze to the side, and is therefore free. It would not be economically worthwhile to ground basalt to agricultural size as a primary product without a much higher price.

[Michael Hayes]

Tom, et al.,

I've studied road side runoff water quality here at my lake. I would not use the gravel for much beyond cement.

Economics is the problem with all C credit dependant options. The options that can make a profit in the market will likely be the options that will survive the inevitable shake out in the future of CDR work.

In situ basalt grinding would likely increase the value of the now largely barren land to some extent. The training center will likely be sold off in the near future, and improving the land, with C credit income help, might see lots of basalt get busted up. 

[Michael Hayes]

Apologies, Tom

I misread your post. 

In situ basalt grinding would not be meant to initially produce ag quality dust, although some dust would be created as a byproduct of the machine operations.

The method would be intended to break up the hard surface to allow natural weathering processes to accelerate. Periodically going over the same area with the machines would likely keep the C drawdown active, and thus over many years the area might become crop worthy or gain mature, not pioneer, natural growth.

Using the word 'grinding' is likely wrong on my part as it infers grinding down to dust. To 'Pulverize' the surface of a hard basalt field is more accurate. Below is a type of machine that can likely do the job.

https://west-cansealcoating.com/services/custom-pulverizing-milling-services/

[Tom Goreau]

Rock fragmentation speeds weathering up, but primary chemical weathering soils from even fairly small broken rocks typically takes thousands of years to form clay soils (such as rock scree fragments frost-cracked off mountain cliffs that fall into moraine lakes at their  base).

 

The faster you can get life to grow on it the faster it will dissolve.

 

This takes a long time by itself, but can be kickstarted by adding biochar, compost and inoculation with beneficial bacterial and fungal cultures to the cracks in the basalt. Biogeochemically enhanced soil formation in years to decades will greatly accelerate carbon sequestration.

 

Under such conditions the best carbon farmers can draw down up to 40 TC/Ha/yr. Unfortunately the average global farming is not enriching their soil carbon but systematically depleting it and putting it into the atmosphere.

 

If all farmers followed best carbon farming practices there would be globally significant drawdown!

 

The CDR time scales to reduce CO2 to safe Preindustrial levels (280 ppm) for the spectrum of soil carbon increase rates and for the proportion of long lived soil carbon (biochar) are shown graphically in my poster at the UN Food and Agriculture Organization Conference on Soil Organic Carbon attached.

 

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance

Chief Scientist, Blue Regeneration SL
President, Biorock Technology Inc.

Technical Advisor, Blue Guardians Programme, SIDS DOCK

37 Pleasant Street, Cambridge, MA 02139

gor...@globalcoral.org
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226 (leave message)

 

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase

http://www.crcpress.com/product/isbn/9781466595392

 

Innovative Methods of Marine Ecosystem Restoration

http://www.crcpress.com/product/isbn/9781466557734

 

Geotherapy: Regenerating ecosystem services to reverse climate change

 

No one can change the past, everybody can change the future

 

It’s much later than we think, especially if we don’t think

 

Those with their heads in the sand will see the light when global warming and sea level rise wash the beach away

 

“When you run to the rocks, the rocks will be melting, when you run to the sea, the sea will be boiling”, Peter Tosh, Jamaica’s greatest song writer

 

 

 

 

 

[Michael Hayes]

Thanks, Tom.

It looks like the mining, transport, reducion to dust, and speading costs will be what they are now. 

Best wishes

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[Jasper Sky]

Tom, what I'm wondering is what could be achieved with a brute-force method of applying rock crushing machinery to turn a cubic km of basalt rock into rock powder of a suitable average grain size (and I am wondering what that grain size would optimaly be: 0.1 mm? 0.3 mm? 0.5 mm?).

I have no idea how much CO2 could be soaked up and sequestered per ton of crushed basalt powder at a given grain size. I've been trying to find out via Google scholar searches, and so far not having much luck. Let me arbitrarily assume (pulling a number out of the ether) of 2 tons of crushed basalt powder of some grain size n, where n is perhaps more than 0.1 mm but less than 0.5 mm. I want those damn numbers, because I can then also find out what input of electricity will be necessary per ton of basalt and hence per ton of CO2, after combining the energy required to crush basalt down to the desired grain size, and also to mix the crushed basalt with biochar and transport it to suitable fields in EV trucks, and spread it on the land at suitable density.

I cannot work out these numbers on my own. I'll need input from people who have actual experience in doing this kind of thing in the field.

There are regions of the world where there is plentiful stranded geothermal energy co-located with plentiful basalt. Some of that energy could be harvested to run rock crushers and biochar ovens and biochar/rock powder mixing facilities. 

How big a mountain, in cubic km, would be required to draw down one trillion GtCO2? How many TWh of electricity would be required? And how much land would be required to draw down one trillion GtCO2 over (say) twenty years via basaltic rock powder EW?

The foregoing may not be the most efficient possible way to draw down CO2 (though it may actually be a reasonably efficient way, perhaps better than current-generation DAC, at any rate; to be determined via detailed models and field trials with MRV). But it could serve as an upper bound on the energy input that will be required. Having such an upper-bound estimate for a highly scalable CDR method (such as powdered-basalt EW) would be extremely valuable.  

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[Chris Van Arsdale]

On Sun, Mar 10, 2024, 5:39 PM Jasper Sky <jasp...@gmail.com> wrote:

Tom, what I'm wondering is what could be achieved with a brute-force method of applying rock crushing machinery to turn a cubic km of basalt rock into rock powder of a suitable average grain size (and I am wondering what that grain size would optimaly be: 0.1 mm? 0.3 mm? 0.5 mm?).

Sub 100um is generally the target. Above that and the kinetics are very slow. Below that and the grinding energy grows quadratically.

I have no idea how much CO2 could be soaked up and sequestered per ton of crushed basalt powder at a given grain size.

Say a few microns of surface dissolved per year (argument sake, very very dependent on ambient conditions ... Zero microns some soil types, faster in others), you can work out the volume change.

I've been trying to find out via Google scholar searches, and so far not having much luck.

That part is a bit simpler for a first order estimate. Just count the Mg++ (or whatever cation) per unit mass. You'll get that much buffer capacity in the soil/runoff.

For a rule of thumb, ~1ton of basalt per ~1 ton CO2 (assuming the cations eventually wash out into the ocean after dissolving).

Let me arbitrarily assume (pulling a number out of the ether) of 2 tons of crushed basalt powder of some grain size n, where n is perhaps more than 0.1 mm but less than 0.5 mm. I want those damn numbers, because I can then also find out what input of electricity will be necessary per ton of basalt and hence per ton of CO2, after combining the energy required to crush basalt down to the desired grain size, and also to mix the crushed basalt with biochar and transport it to suitable fields in EV trucks, and spread it on the land at suitable density.

There are papers on that, milled diameter vs energy input.

I vaguely remember ~$6/ton estimate for grinding (roughly comparable to the mining cost), though I don't have my notes (traveling). That would be for 50-100um.

I cannot work out these numbers on my own. I'll need input from people who have actual experience in doing this kind of thing in the field.

There are regions of the world where there is plentiful stranded geothermal energy co-located with plentiful basalt. Some of that energy could be harvested to run rock crushers and biochar ovens and biochar/rock powder mixing facilities. 

Probably not that easy. Geothermal is not cheap for electricity generation (even if you move to Iceland), it is only really useful on this scale for low grade heat (and even then I'd bet on solar+heat pump in most cases).

Ultramafic rock is indeed plentiful. The problem is fundamentally one of surface area... Land uptake of CO2 is slow, and it is expensive to ship rock more than 50 miles.

How big a mountain, in cubic km, would be required to draw down one trillion GtCO2?

A 10km cube, ish. Hydrauloically mining such a mountain isn't terrible in the grand scheme of things... It's the grinding/distribution step.

How many TWh of electricity would be required?

And how much land would be required to draw down one trillion GtCO2 over (say) twenty years via basaltic rock powder EW?

Land kinetics would limit you globally to probably a few Gt/yr at best, though the error bars are wide and we might get lucky (however, this is why a lot of folks have looked more at OAE and electrochemical approaches despite the extra cost, or combining electrochemical and mining together to get the best of both worlds).

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[Michael Hayes]

It does appear that soil cations determine the timescale:

Soil cation storage as a key control on the timescales of carbon dioxide removal through enhanced weathering

https://www.authorea.com/users/749955/articles/721069-soil-cation-storage-as-a-key-control-on-the-timescales-of-carbon-dioxide-removal-through-enhanced-weathering

[Tom Goreau]

Cation release, like alkalinity, is a measure of CO2 consumption by weathering, but both are complicated by secondary reactions and formation of clay minerals.

 

Tom Vanacore knows much more about crushing costs and availability of fine rock powder “waste” material, and optimal sizes, which depend on the soil type and application.

[Chris Harding]

Hello, 

I am currently learning PHREEQC, and one could use this software to find the optimal particle size in my opinion. For example, 

PARM(1) = specific surface area (m^2/mil) #PARMS defined in KINETICS block. 

PARM(20 = Lab to field adjusted rate. 
SR = Saturation Ratio 

250 rate     = rate_H + rate_H2O + rate_OH + rate_CO2

260 area     = PARM(1) * M0 *(M/M0)^0.67

270 rate     = PARM(2) * area * rate * (1-SR("K-feldspar"))

280 moles = rate*TIME 

It is a steep learning curve, but not as steep as OpenFOAM. Great documentation and UsersGroup. 

As an example, I believe I solved the challenge problem. The below graph shows the effect of water advection through a column of 10 cells. The time frame was near 520,000 years for kinetics these specific feldspars. Note, there is a typo in the legend, but it is obvious.

I find this software could be very useful for enhanced weathering and how the chemistry in the soil is affected. As you can see here, with the setup[see attached file for code.]. The potassium feldspar dissolves, and albite dissolves along the column of cells. Since Na CL are apart of the solution, the extra Na and Ionic Strength as well as pH could be affecting the albite precipitation. It is not a graded problem but a "Challenge Problem" so I am awaiting Dr. McNab's remarks on my script, results, and analysis. I share it here as an example of what can be done. Much more capable than this. A good book to read that uses PHREEQC samples is[1]. 

References: 

[1]  Appelo, C., Postma, D. (2004). Geochemistry, Groundwater and Pollution. Netherlands: CRC Press.

 .  

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BS Chemical Engineering and BS in Biological Sciences

100% Total And Permanent Disabled US Veteran | Affiliate of MIT Alumni Association | Affiliate Member of MIT Alumni for Climate Action (MACA) | Past Member of The Economist Global Advisory Council (The Economist Group) | Affiliate of John Hopkins University Energy Policy and Climate Program Students and Alumni LinkedIn Network

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[Chris Harding]

Should be mol instead of "mil" in PARM(1). 

[Tom Goreau]

There’s no time frame on the graph?

 

Shouldn’t pH be going up if CO2 is being neutralized by weathering?

 

From: Chris Harding <littl...@gmail.com>
Date: Monday, March 11, 2024 at 11:35 

AM

To: Chris Van Arsdale <cvana...@google.com>

Cc: Jasper Sky <jasp...@gmail.com>, Tom Goreau <gor...@globalcoral.org>, Michael Hayes <electro...@gmail.com>, CarbonDiox...@googlegroups.com <carbondiox...@googlegroups.com>, ishfaq ahmad <geoi...@gmail.com>, Joanna Campe <joanna...@gmail.com>, jje...@metamorphic1.org <jje...@metamorphic1.org>, Thomas Vanacore <ston...@gmavt.net>
Subject: Re: [CDR] Optimal grain size of powdered basalt/olivine for enhanced weathering?

Should be mol instead of "mil" in PARM(1). 

 

On Mon, Mar 11, 2024 at 8:27 AM Chris Harding <littl...@gmail.com> wrote:

Hello, 

I am currently learning PHREEQC, and one could use this software to find the optimal particle size in my opinion. For example, 

PARM(1) = specific surface area (m^2/mil) #PARMS defined in KINETICS block. 

PARM(20 = Lab to field adjusted rate. 
SR = Saturation Ratio 

250 rate     = rate_H + rate_H2O + rate_OH + rate_CO2

260 area     = PARM(1) * M0 *(M/M0)^0.67

270 rate     = PARM(2) * area * rate * (1-SR("K-feldspar"))

280 moles = rate*TIME 

 

It is a steep learning curve, but not as steep as OpenFOAM. Great documentation and UsersGroup. 

As an example, I believe I solved the challenge problem. The below graph shows the effect of water advection through a column of 10 cells. The time frame was near 520,000 years for kinetics these specific feldspars. Note, there is a typo in the legend, but it is obvious.

I find this software could be very useful for enhanced weathering and how the chemistry in the soil is affected. As you can see here, with the setup[see attached file for code.]. The potassium feldspar dissolves, and albite dissolves along the column of cells. Since Na CL are apart of the solution, the extra Na and Ionic Strength as well as pH could be affecting the albite precipitation. It is not a graded problem but a "Challenge Problem" so I am awaiting Dr. McNab's remarks on my script, results, and analysis. I share it here as an example of what can be done. Much more capable than this. A good book to read that uses PHREEQC samples is[1]. 

References: 

[1]  Appelo, C., Postma, D. (2004). Geochemistry, Groundwater and Pollution. Netherlands: CRC Press.

 .  

[Chris Harding]

The text file shows the time in seconds. Sorry. 

Follow the advice of: PHREEQC Users | Resource for geochemists | Forum  (Topic: Computation time for advection with kinetics  ) to find "age" of water. 

I used: 

I came close to 520, 000 years for K-Feldspar in KINETICS blocks. The seconds are listed in the same block. 

I am awaiting the verification, as I mentioned, from Dr. McNab of my results. With that said, precipitation of albite would, according to the PHASES block, produce H+ while dissolution of K-Feldspar will consume H+. 

With the above being said, PHREEQC can be used to model enhanced weathering. I am just getting started and learning. 

Cheers, Chris Harding.   

[Tom Goreau]

Tony Lasaga was a graduate student with me. His numbers come from many papers.

 

For the pH to fall like that implies that albite formation releases many more protons than orthoclase dissolution releases. In any event, it won’t be converted to albite at surface conditions but to clays.

 

Once again, the slowest way to dissolve minerals, regardless of grain size, is to dump them in the ocean! The second slowest is to expose them to rain on land! The fastest way is to grow tree roots in it!

From: Chris Harding <littl...@gmail.com>
Date: Monday, March 11, 2024 at 12:12 PM
To: Tom Goreau <gor...@globalcoral.org>
Cc: Chris Van Arsdale <cvana...@google.com>, Jasper Sky <jasp...@gmail.com>, Michael Hayes <electro...@gmail.com>, CarbonDiox...@googlegroups.com <carbondiox...@googlegroups.com>, ishfaq ahmad <geoi...@gmail.com>, Joanna Campe <joanna...@gmail.com>, jje...@metamorphic1.org <jje...@metamorphic1.org>, Thomas Vanacore <ston...@gmavt.net>
Subject: Re: [CDR] Optimal grain size of powdered basalt/olivine for enhanced weathering?

The text file shows the time in seconds. Sorry. 

Follow the advice of: PHREEQC Users | Resource for geochemists | Forum  (Topic: Computation time for advection with kinetics  ) to find "age" of water. 

I used: 

[Dennis Amoroso]

What Tom said....

This is the reason that UC Davis has published 4 reports on the use of rock powder in agriculture, stating that it is

the very best way to do 'carbon farming'.  These are based on a 5 year study initiated by our meeting with the

USDA from which the university received a $4.7M grant to study rock powder in agriculture.

UC Davis now has a School of Rock Powder and the lead professor in this study is now the Dean of the School

of Agriculture at Cornell University.  Both universities are conducting extensive studies on the results of putting

rock powder in farmland.......where the roots are!

Dennis Amoroso

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[Jasper Sky]

Tom, Dennis, we defer to your expertise. No one disputes that spreading basalt rock powder mixed with mature biochar is the best way to achieve enhanced weathering of a ton of rock powder. 

The problem is that there isn't enough plausibly available land to make much of a dent in the CDR challenge. If we assume a 1:1 mass ratio of basalt powder to tons of CO2 sequestered via EW, i.e. if spreading 1 billion tons of basalt powder of (say) 0.1 mm average grain size will sequester 1 billion tons of CO2, and if one hectare of suitable land can benefit from a mixture of basalt powder and mature biochar that contains (say) 4 tons of basalt powder, then it will take 250 million hectares of suitable land to absorb 1 billion tons of CO2 via enhanced weathering. 

It is not clear to me whether application of such amounts of mixed rock powder and biochar is something that the land can handle once a year, once every two years, or every five, or every ten years...? Anyone know? It matters a great deal, because that will determine how much CO2 sequestration can be achieved via enhanced weathering of basalt rock powder over several decades. 

The actual amount of CDR that we will require in order to get atmospheric CO2 concentrations back down to 350 ppm by 2100 (as Jim Hansen and many other climate scientists have proposed) is on the order of 55 billion tons per year. Assuming that 1:1 mass ratio of basalt powder to CO2 mineralization via land-based EW, and 4 tons of basalt powder per hectare, we would therefore need 55/4 = 13.75 billion hectares of land. The Russian Federation is 1.71 billion hectares in size. So we'd need a land area 8x the size of Russia to achieve 55 GtCO2 sequestration... and that's just one year's worth. Again, it is not clear to me how frequently the treatment can usefully be applied to a given hectare of land. Once a year? Once every two years, five years, ten years? If anyone knows, please tell us. 

The net assessment here is that although mixing basalt rock powder with mature biochar and spreading it onto farm fields is doubtless very good for soil structure and for increasing the nutrient density of the soil, and worth doing for agricultural productivity reasons, enhanced weathering of rock dust via land-based distribution of that rock dust CANNOT be a solution to the CDR challenge. At a land requirement of 250 million hectares per 1 GtCO2 sequestration, EW is quantitatively never going to be more than a rounding error on the overall challenge, because it isn't plausible that we will treat billions of hectares of land every year with this treatment.

This is why I'm desperate to learn whether there is some way we could suspend basalt rock dust in the upper ocean for long enough for it to fully weather. Maybe put floating burlap sacks full of basalt rock powder (tied to buoys), or something like that. This would overcome the problem of EW requiring implausible amounts of land to achieve multiple-Gt-scale CO2 sequestration. 

[Jeff Suchon]

How much does the biochar in the mix lower albedo?

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[Chris Harding]

Hello, 

From Chapter 7[1] who is an Oxford researcher. 

There is also superficial enhanced rock weathering where powdered silicate rocks and/or minerals are distributed over the land, coast or ocean. If 1 mm layer of basalt powder was spread over 2/3 of the global cropland, ~ 0.5-4 Gt CO2 per year by 2100 could be sequestered. 

References: 

[1] Greenhouse Gas Removal Technologies. (2022). United Kingdom: Royal Society of Chemistry.

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[Dennis Amoroso]

When we continue to say that something is NOT possible then it automatically becomes NOT possible.

America has 980M acres of farmland with another 500M in grazing lands.  At 2 tons per acre that is a LOT

of rock powder...Your math is incorrect to the sequestration of carbon because you do not take into account

the amount of carbon that bacteria uses when growing plants.

Canada has just a bit less farmland than America.  Australia has more than half of America's land.  Then we have

Latin America, Africa, India, China...

Let us agree that putting rock powder on farmland is an excellent means of achieving food production as we

passively remove CO2.

NOW, consider the fact that we also remove Methane and Nitrous Oxide because we repurpose millions of tons of

food waste out of landfills and we completely remove Nitrogen from use in farmland.  NOW, we have NO nitrous

oxide, NO potassium and phosphates in our water and in our oceans.  The temperature of the ocean decreases

by 1.3 degrees F and the marine ecosystem is restored, which then begins to restore the kelp forests and coral

reeves.  This, then affects the greenhouse gasses and the global warming...Tom can explain far better than I.

The use of Rock Powder based fertilizer impacts a great many problems in our environment in a positive way!

Dennis Amoroso

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[Tom Goreau]

Nor does their bogus mathematics take into account the vastly larger increased soil and biomass carbon storage, which multiplies the weathering sink many, many times over!

 

As my FAO abstract shows, good farmers add up to 40m TC/Ha/yr.

[Tom Goreau]

Sorry, typo 40 TC/Ha/yr, no m for millions unfortunately.

 

But that’s good enough to make a huge difference if farmers regenerated their own soil carbon instead of degenerating it!

 

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[Jasper Sky]

I read your FAO abstract carefully yesterday, Tom, and while I think it's a good start and intriguing -- as you know, it will take a lot of additional work to persuade the scientific and policy communities that 40 tons per hectare of carbon (is that carbon, or carbon dioxide, by the way?) is a realistic number. I'm not dismissing your claim about this, just pointing out that it will take multiple field trials reproduced by independent teams of researchers to verify the numbers, preferably independent teams with no carbon credit axe to grind (double blind experiments should be feasible by getting teams with no knowledge of the treatments that have been applied or not applied to a give plot of land to take soil measurements). 

40 tons of carbon per hectare is 10x as much as 4 tons of carbon, which is roughly the amount that would be taken up per hectare of land based application of 4 tons of basalt powder per hectare and a ratio of 1 ton basalt powder : 1 ton CO2 sequestration, a number that has been suggested by someone else in this group. 

So even within this group, there is no consensus. 

Everyone in this google group will be absolutely delighted if it turns out that 40 tons (of C? or of CO2?) per hectare per year can be routinely achieved in real-world conditions on a billion hectares of agricultural soils worldwide. 

[Tom Goreau]

I said, UP TO 40 TC/Ha/yr as a best case scenario, but many farmers who regenerate their soil health are getting over 10 TC/Ha/yr, see the graph. These are real results based on soil carbon measurements, not guess calculations made by people who don’t understand soil carbon.

[Tom Goreau]

Also this is up to 40 TC/Ha/yr measured soil carbon increases!

 

4 tons of basalt per hectare will not dissolve and provide four tons of carbon alkalinity in one year as your calculation assumes.

 

It will take decades, to centuries, to millenia, to millions of years, depending on the setting.

 

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[Dennis Amoroso]

Here we go again!!!!!!

WE are delivering rock powder to farmland right now and we are sequestering 500 pounds of carbon per acre.  That is

an absolute number.  When we deliver to ALL of farmland in America alone we will sequester 120M tons of carbon per YEAR in a single country.  That does not take into account the millions of tons of CO2 that will be drawn from the atmosphere as the bacteria decompose the rock powder and continue to do so deep into the soil.    AT NO COST TO THE GLOBAL ECONOMY!!!!!!!!!!

[Jeff Suchon]

For the global scaling of enhanced mineralization, is there a chart of potential minerals and the resulting change in albedo. This, of course, includes natural mixing with the soils and overtime reflectivity change to the soils. Am trying to find out which mineral(s) might also help boost albedo. Basically, enhanced mineralization as also an SRM tool.

[Tom Goreau]

Biochar is not spread as a pure black surface layer except by the laziest.

 

Only a few percent are normally added, and to get the best effects it is mixed down into the soil, so that the albedo effect is minor.

[Tom Goreau]

The whitest soils, like quartz clays and kaolinite are practically barren of nutrients and are the slowest minerals to weather, almost nothing grows on them, so very little CDR benefit.

 

Limestone soils can hurt your eyes with reflection, but are severely deficient in all nutrients except calcium, and sometimes magnesium (if on dolomite). They are especially poor in nitrogen, because ammonium oxidizing bacteria just love high pH, and the nitrate is flushed into the groundwater and out to sea. In Jamaica marine groundwater springs have a dissolved nitrogen to phosphorus molar ratio of up to 600! The phosphorus retained in the soil is useless, immobilized as insoluble surface phases by calcite and by iron and aluminium oxides in soils. That’s why we have so many nitrogen fixing trees in Jamaica.

 

Mirrors may be a better bet than white powders for albedo for cooling, but no CDR benefit.

 

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[Dennis Amoroso]

That is why we combine 5 different kinds of rock powder and achieve a full spectrum of nutrients.  Even the clay has value in a blend as does silica and silicon.  Bacteria will decompose anything and will use carbon in the process.  

Dennis Amoroso President 

On Mar 11, 2024, at 1:07 PM, Tom Goreau <gor...@globalcoral.org> wrote:



<LIfetimeOfMinerals.Laboratory.png>

<Module 6.Rates.Kinestics.Advection.jpg>

 .  

[Jasper Sky]

Dennis, yes, your technology is wonderful, I fully support and endorse it, and I am sure everyone here does.

The point I am making is that 120 million tons of carbon (do you mean carbon, or carbon dioxide? there's a 3.7x mass difference there) is an almost negligible amount in the teeth of the global net negative emissions challenge we're facing - several tens of billions of tons per year.

And while I like the thought that 100% of all farmland everywhere will be treated with the method and product you offer (combined mature biochar and rock dust at 2 tons per acre), I am a bit skeptical that such a comprehensive coverage will ever be attained. Nevertheless, let's try to promote it as a contribution to soil health and farm productivity, and figure out its co-benefits in terms of total annual CO2 drawdown. 

Tom, I don't know if the realistic number is 40 tons per hectare (again: do you mean tons of CARBON or of CARBON DIOXIDE? There's a 3.7x mass difference!) or 10 tons per hectare or 4 tons per hectare, and I'm trying to understand what the realistically achievable numbers might be and what will be required to attain them. I don't understand why you and Dennis get angry with the rest of us about this as we try to learn more. You're proselytizing a particular technology. Generally it's best not to get angry at the people you're trying to sell your idea to. As a marketing strategy, anger doesn't work well. People won't, and shouldn't, simply take your word (or mine, or anyone's) as Gospel truth just on your say-so. People will ask questions to learn more and patience will be required in answering them.

It's useful to keep in mind that while everyone here is very smart, not everyone here has your deep background in the particulars of soil geochemistry. Impatiently dismissing people who lack knowledge in your area of specialist expertise as boneheads isn't a useful perspective. We're as smart as you are. We just have different specialisms. 

[Jeff Suchon]

Dennis, Do you have reflectivity measurements, before and after? Over a period of time? It would be nice to kill 2 birds with one stone ( CDR and SRM ).

[Tom Goreau]

Measured CARBON increase in soil. NOT CO2!

[Renaud de RICHTER]

Jeff,

The increased biomass cover will be darker. The change in albedo will theoretically induce some level of warming, but aerosol emissions may be CCN and increase cloud cover at low altitudes, inducing cooling. The reflectivity of the rock powder and biochar mixture introduced into the soil will not make a big difference.

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[Jeff Suchon]

Hi Renaud,

Thanks for the update. You mentioned possible cloud nucleation from the crops in the long run that might increase albedo. Are there at least certain rotated crops that are known for transpiring the aerosols that can be used globally? Am trying to get a clearer idea of methods of CDR that SRM can be done as well.

[Renaud de RICHTER]

Jasper,

If your aim is to demonstrate that rock dust is not a silver bullet, you are right and everybody agrees, neither biochar, nor other NETs.

What is needed is a full portfolio of different NETs.

Although quite "old" the 2015 report of the NASEM provided useful estimates.

Carbon Dioxide Removal and Reliable Sequestration

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[Renaud de RICHTER]

I was tinking to forests

https://engineering.princeton.edu/news/2021/08/09/planting-forests-may-cool-planet-more-thought

https://www.scientificamerican.com/article/tropical-forests-cool-earth/

https://www.science.org/doi/10.1126/sciadv.aax8859

https://link.springer.com/article/10.1007/s10584-017-1962-8

[Dan Miller]

As part of my on-going Climate Chat interview series, today I interviewed climate scientist Kevin Anderson for the second time (the first time was nearly 3 years ago).

As always, Kevin tells it like it is… and that is unlike what everyone else says and does about climate change.  On one hand his message is depressing because he makes it clear that we are all deluding ourselves about our climate “actions”. On the other hand, I find his words inspiring and, when I first heard him in 2010, he drove me to work harder on engaging people on climate.

I think this is one of the most important discussions on climate change because it shakes you into understanding the fantasy we are living with. And, while Kevin thinks CDR is mostly an excuse for inaction, I believe it highlights the need for CDR (coupled with rapid emissions reduction) and SRM because, well, we’re not doing anything to address climate change right now so future aggressive steps will be needed.

Best,

Dan

[Josh Perfetto]

On Mon, Mar 11, 2024 at 9:48 AM Jasper Sky <jasp...@gmail.com> wrote:

This is why I'm desperate to learn whether there is some way we could suspend basalt rock dust in the upper ocean for long enough for it to fully weather. Maybe put floating burlap sacks full of basalt rock powder (tied to buoys), or something like that. This would overcome the problem of EW requiring implausible amounts of land to achieve multiple-Gt-scale CO2 sequestration. 

Hi Jasper,

This question was examined by Köhler et al. 2013. To do what you're trying to do you don't need the particles to float but rather to sink through the mixed layer slowly enough so that they dissolve there. Specifics will vary (for example with mixed layer depth), but that paper finds that for 80% of olivine to dissolve in the mixed layer, the particles would need to be ground to 1 um. At 10 um, dissolution is only 5%.

I agree with you that it's a good question as there are limitations to the amount of terrestrial ERW that can be achieved along and the riverine systems' ability to transport DIC and alkalinity without precipitating it. The obvious challenge with this approach is the energy needed to grind olivine/basalt to this tiny size.

-Josh

 

[Jasper Sky]

Thanks, Josh, very helpful!

Is there any chance you could work out the energy needed to grind olivine/basalt to 0.01 mm grain size? 

Or find someone who has already done so and written it up?

I suspect the energy cost would be prohibitive, but who knows. 

Also... if the energy cost would be prohibitive, what's the next best alternative? Go back to 0.1 mm grain size and float the rock powder in bags hanging off buoys? Give up on EW as a scalable CDR method altogether (while respecting and supporting its value as a soil improvement method)? 

What are your thoughts?

Jasper 

[Josh Perfetto]

Hi Jasper,

Well the paper I linked to references Renforth 2012 as saying it would take 300 - 350 kWh to grind a ton of olivine to 1 um. If you wanted to use olivine and didn't want to spend this energy grinding them, then I think the best thing to do is Coastal Enhanced Weathering where you grind them to much larger sizes and then place them in shallow environments where you don't need to worry about them sinking.

I think the idea of floating rocks in bags or some sort of structure will be difficult because you will need to ensure robust exchange of water while preventing small particles from escaping, and prevent this solution from fouling. If there are ideas on how to do this I'd be interested to hear them.

BTW I wasn't saying that terrestrial ERW wasn't scalable. I think terrestrial ERW is highly scalable and a great solution. I was just saying that like everything else it's not infinitely scalable - we need many solutions and I think it makes sense to consider creative ways of how to use olivine for OAE in addition to terrestrial ERW.

-Josh

[Brian Cady]

Here is a link to folks working on milling (comminuration) energy efficiency: https://www.ceecthefuture.org/

Because of both accelerating mineral use, hence more and more mining, and because of increasing use of lower grade ores as the bes tores re used up, global energy costs of ore comminuration are accelerating very rapidly.

Perhaps one might find comparisons of various mill designs' efficiency here.

Brian

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