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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 9:

  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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