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Spreading rock dust on fields could remove vast amounts of CO2 from air

Posted on 10 July 2020 by Guest Author

This is a re-post from The Guardian by Damian Carrington

Spreading rock dust on farmland could suck billions of tonnes of carbon dioxide from the air every year, according to the first detailed global analysis of the technique.

The chemical reactions that degrade the rock particles lock the greenhouse gas into carbonates within months, and some scientists say this approach may be the best near-term way of removing CO2 from the atmosphere.

The researchers are clear that cutting the fossil fuel burning that releases CO2 is the most important action needed to tackle the climate emergency. But climate scientists also agree that, in addition, massive amounts of CO2 need to be removed from the air to meet the Paris agreement goals of keeping global temperature rise below 2C.

The rock dust approach, called enhanced rock weathering (ERW), has several advantages, the researchers say. First, many farmers already add limestone dust to soils to reduce acidification, and adding other rock dust improves fertility and crop yields, meaning application could be routine and desirable.

Basalt is the best rock for capturing CO2, and many mines already produce dust as a byproduct, so stockpiles already exist. The researchers also found that the world’s biggest polluters, China, the US and India, have the greatest potential for ERW, as they have large areas of cropland and relatively warm weather, which speeds up the chemical reactions.

The analysis, published in the journal Nature, estimates that treating about half of farmland could capture 2bn tonnes of CO2 each year, equivalent to the combined emissions of Germany and Japan. The cost depends on local labour rates and varies from $80 per tonne in India to $160 in the US, and is in line with the $100-150 carbon price forecast by the World Bank for 2050, the date by which emissions must reach net zero to avoid catastrophic climate breakdown.

“CO2 drawdown strategies that can scale up and are compatible with existing land uses are urgently required to combat climate change, alongside deep emissions cuts,” said Prof David Beerling, of the University of Sheffield, a lead author of the study. “ERW is a straightforward, practical approach.”

Prof Jim Hansen, of Columbia University in the US and one of the research team, said: “Much of this carbonate will eventually [wash into] the ocean, ending up as limestone on the ocean floor. “Weathering provides a natural, permanent sink for the carbon.”

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Comments 1 to 18:

  1. Always felt that speeding up weathering is one of the more promising initiatives. Scalable, simple technology that simply speeds up the process that nature uses to draw down CO². There are other approaches than this farmland approach, but many of the others show the same mix of positive economies of use, scalable implementations, available to large swathes of the globe/population without gigantic capital investments, and well within present technical capabilities

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  2. JW Rebel @1, yes I wondered much the same. Came across another similar scheme here for spreading olivine on beaches, where the motion of tides helps tumble the material round and speed up the process of weathering.

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  3. The fail of this scheme, and quite frankly even in the comments, is in not realising 80% of weathering is biological. Sure you can do some good, but not nearly enough. A far better solution would be to restore ecosystem services over vast acreage currently degraded by agriculture.

    You don't do that by physically grinding rock dust or spreading olivine on some beaches.

    You do that by restoring biodiversity in the soil, where there are multiple species evolved over hundreds of millions of years all working in symbiosis with each other to a self regulating complex system that removes CO2 from the atmosphere.

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  4. NigelJ @2, one of the grand daddies of this approach was R.D. Schuiling, now 88, at the University of Utrecht (fairly close to the earth cone I occupy). He has been at it for a while, e.g., ENHANCED WEATHERING: AN EFFECTIVE AND CHEAP TOOL TO SEQUESTER CO2 (2004).

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  5. Red Baron,

    Pacala and Socolow at Princeton describe attempting to control AGW using climate "wedges."  Each wedge reduces the problem a little and together they amount to enough.  You have not provided enough data to support your claims that agriculture alone can provide enough to remove all the carbon released by the soil from poor agricultural practices and all the fossil carbon.

    While I am skeptical that enhanced weathering alone can control AGW, It seems to me that perhaps a wedge or two can be tackled with weathering.  Than there will be a little less of a  problem for the other approaches to solve.

    Considering the very long history world wide of farmers destroying the soil they farm, I doubt that you can even begin to get most farmers to utilize the strategies you espouse.  Even if you did I doubt agriculture alone can accompplish what you claim.  You do not need to provide another copy of your papers, I have read most of them and am not convinced.

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  6. No argument about the use of rock dust but combine this with so called regenerative Agriculture.  The best exposition of this way of farming that I have read is in a book by David R Montgomery, called Growing A Revolution.  Drawing down Carbon Dioxide from the atmosphere is just one amongst many benefits of this type of agriculture.  In a previous book, Dirt, he describes what previous civilizations did to their soil and the results of their mismanagement.  It sets the scene for Growing a Revolution

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  7. @Michael Sweet,

    I am aware that you are unconvince, as are many who do not understand the significant difference regenerative agriculture can make. It is why I tried to fund a peer reviewed experiment at

    Unfortunately the site closed all new launches indefinitly due to the corona virus outbreak just 3 days before mine was to launch.

    Without funding, my personal attempt to add to the evidence is just anecdotal evidence and not enough to convince a skeptic from another field of expertise.

    So I hesitantly agree with your criticisms.  Not that I believe you are correct, but that I agree for a skeptic it is not enough published evidence on most crops. (excepting possibly SRI rice and grazing management which have far more published evidence)

    I also agree with the statement "I doubt that you can even begin to get most farmers to utilize the strategies you espouse.", again tentively. Because it wont be from convincing that accomplishes this goal. Only economics can make this happen. This is why I am also working at putting together a "proof of concept" hub using “modular autarky” for a demonstration farm to fork. If it is profitable, people will change.

    Ultimately much like solar and wind, the changes will come from market forces when the economics beats the current antiquated systems. In this case it is doable even without subsidies. And with a properly designed carbon market adding to those profits, I believe it can change even faster.

    Unfortunately only about 2-3% of the money going to solving AGW is earmarked for these natural sorts of environmental solutions. So far I haven't been able to capture either the research or the business side of these funds to prove my synthesis to skeptics. But the evidense continues to roll in year by year as more and more people begin to seriously consider the evidence that is available. 

    At some point I am confident the scale will tip, with or without me. Too many others have begun to see it for it to be only in my head. Case in point, William's post above.

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  8. This research lifecycle assessment research located in the region of Sao Paulo gives a good base. As usual transport is a large element in the effect. Perfectly usable provided you have enough rock available close by. I wouldn't startmining to obtain the rock though.

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    Moderator Response:

    [DB] Activated link.

  9. Just to clarify things, I definitely don't advocate rock weathering as a stand alone answer to drawing down atmospheric CO2. There is definitely space for multiple approaches including rock weathering, regenerative agriculture, growing forests where feasible, and possibly carbon capture and storage. I dont think we know enough yet to put all our eggs in one basket, other than to say ideas like BECCS do not seem viable to me.

    That said, we know soils can sequester vast quantities of carbon from historical evidence in places like Asia. If all it takes is changing how we farm, and this can be done without big problems and has a range of other benefits, it seems a question of why wouldn't we? But those deep soils took a long time to build up, so soil carbon is unlikely to be a quick fix.

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  10. "Treating about half of farmland could capture 2bn tonnes of CO2 each year" — that's only about 5% of current anthropogenic emissions.

    Plus, strip-mining basalt, grinding it to dust, trucking it to the hinterlands, and spreading it on fields, all would require the use of fossil fuels, which would release CO2.

    Even if those additional CO2 releases would be less than the CO2 removed from the atmosphere (which is unclear), and even if rising CO2 levels were a problem (they aren't), this proposal would not be a solution.

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    Moderator Response:

    [PS] Blatant sloganeering. A reminder (again) of the comment policy operating on this site. If you want to make assertions, then you back them with creditable evidence, preferably peer-reviewed publication.

  11. Quite right, Daveburton.   Producing/distributing rock dust sounds a very inefficient method of reducing the CO2 problem, at least with present technology.

    Perhaps by 2100 the technology of renewable energy will be advanced enough to do it properly ~ but I'm figuring by then it would just be a part of a larger purpose of agricultural soil development.  Even so, it would be only one component of the overall effort to get CO2 down to a sensible 350ppm.

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  12. "...and even if rising CO2 levels were a problem (they aren't)..."

    What a broad, sweeping, unjustified and incorrect statement.

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  13. Bob Loblaw @12 ,

    your criticism is a bit harsh . . . but fair !   Daveburton's "No problem with CO2" was the sort of statement that belongs in the pseudo-science commentary found at WattsUpWithThat  blogsite.

    Don't get me wrong : as a semi-regular reader at WUWT , I do see occasional bits of real science in the comments columns there (most notably by the excellently-scientific Nick Stokes) ~ but most of the comments are crazy-extremist political stuff mixed with fruitcake anti-science.  Still, it's kind of entertaining : especially the utter nonsense there coming from Mr Monckton or the half-nonsense coming from Mr May et alia.

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  14. I said that rising CO2 levels aren't a problem, and Mod struck it out and wrote, "If you want to make assertions, then you back them with creditable evidence, preferably peer-reviewed publication."

    I'm surprised that you want me to do that, Mod, but I'm happy to oblige.

    Since you requested it, I hope you won't just delete it.


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    Moderator Response:


    (Off-topic Gish Gallop deleted)

    You are not new to Skeptical Science, although you have not posted here for a while.

    Challenging you to provide references for a claim is not an invitation to ignore the Comments policy, which states that comments need to be on-topic. Should you wish to post your comments on appropriate threads, please use the Search tool to find one (or more).

  15. Correction:

    I wrote:
    "So, the 0.4 to 0.9 °C of warming (associated with six decades of CO2 level increase) caused, on average, only about a 20 to 68 km growing zone shift (12 - 42 miles)."

    That's wrong. It should have been:
    "So, the 0.4 to 0.9 °C of warming (associated with six decades of CO2 level increase) caused, on average, only about a 40 to 135 km growing zone shift (24 - 84 miles)."


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  16. Very entertaining, Daveburton @14.   It's exactly why I enjoy viewing the Motivated Reasoning gymnastics by the regulars at WUWT.   

    Especially your bit where: "we've raised atmospheric CO2 levels for 61 consecutive years".   Reminds me of the old joke about the optimist who fell off the top of the Empire State Building . . . "61 floors and okay so far".   (I am sure you've heard something like it.)

    Such cherry-picking.  (I note cherries are always in season at WUWT.) Though you haven't yet played your ultimate argument ~ the Conspiracy of all the world's scientists, and their faked data.  And all that faked paleo data, too.

    But you will probably get around to your penultimate argument :-  "Forest . . . what forest?"

    Still, Dave, this is all a tad off-topic for this particular thread.  Find one of the old threads for this old stuff.  (And why are you coming out with such old stuff . . . right now?  Is it a sign that a seed of genuine skeptical doubt is starting to germinate in your brain?   Beware !! )

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  17. Eclectic, I agree that it's drifting from the core topic, into a discussion of the key assumption behind the core topic, but the Mod asked me for it, so I obliged.

    What do you imagine resembles "cherry-picking" in my response to him? I tried to avoid anything which could be considered cherry-picking.

    I showed him the highest and  lowest temperature indexes.  I showed him the effects of eCO2 on the most important C3 and  C4 crops.  I showed him the best sea-level measurement record in the biggest ocean, which has a very typical  trend.  I showed him both hurricanes and  tornadoes. Etc, etc.  What do you think I omitted?

    He asked a very broad question. He asked me to provide "creditable evidence, preferably peer-reviewed publication" in support of my contention that rising CO2 levels aren't a problem.

    To thoroughly answer that would require a full cost-benefit analysis!

    That's obviously not doable here. But even to quantitatively address the question of whether or not rising CO2 levels are a problem requires an examination of both costs and benefits. So I touched on all the major supposed costs, and also on the major benefits. I tried to answer his question, as best I could, without writing a whole book, and while providing credible references for every claim, as he requested.

    I relied on measured evidence, rather than speculative studies based on models, because, in science, measurements are much, much stronger evidence than modeling. Computer model outputs are just calculations: at their best representing the consequences of robust hypothesis, at their worst representing bugs — and usually, actually, somewhere in-between.

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    Moderator Response:

    [DB]  Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts, Gish Gallops or intentionally misleading comments and graphics or simply make things up. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter, as no further warnings shall be given.

    Off-topic snipped; the Gish Gallop comment was removed.

  18. Daveburton @17 , the Moderators at SkS  are typically rather sparing in "striking out or striking through" plain nonsense (such as your CO2 comment in #10 ).

    Alas, the Moderators at WUWT  are even more sparing : have a look at the comments columns at WUWT  ~ where 80 or 90% of comments would get the chop, if moderation were applied by the criterion of common sense.

    Dave, you have misunderstood the Moderator's response at #10 .   He was not asking for a Gish Gallop.   Implicit was the request (in accordance with the Modus Operandi here at SkS ) that you select the individual topics where you think the mainstream science is faulty or tied to poorly-pragmatic conclusions.   (And contrary to your "models" comment, the pragmatic conclusions are based on ordinary physics & common sense ~ reinforced by the paleo evidence.  None of this "61 floors and okay so far" business.   The "models" projections/estimations may or may not give further insights into the climate processes & possibilities . . . but the models are definitely not the foundation of climate science. )

    So, please select one individual topic which you believe is "wronged" ~ and discuss that one in the most appropriate thread here at SkS.   And when that topic has been suitably discussed/resolved . . . then select your No. 2 choice, and find the right thread for that.   And so on.

    Good luck.  (But it seems you are unaware of the sensitivity of maize yield, to heat waves.)   And you may be in danger of becoming a skeptic (and thus with little chance of "life" on the WUWT  blogsite.)

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