The Weekend Wonk: Enhanced Weathering – Rock Dust, Soils, and Climate

March 3, 2018

James Hansen – Columbia University:

Today’s governments are wittingly leaving young people with a grinding, growing climate mess.

Delayed response of climate to human-caused rising atmospheric CO2 threatens to leave young people a situation out of their control. The primary action required to avoid that outcome is rapid reduction of fossil fuel emissions. However, our “Young People’s Burden” paper1 shows that more is required: it is also necessary to extract CO2 from the air.

A study led by David Beerling and his group in Sheffield, UK, proposes a change to agricultural practices that could increase the rate of the natural weathering process that removes CO2 from the air. Logistical infrastructure to apply appropriate (basaltic) rock dust to managed croplands already exists due to the common need to apply crushed limestone to reverse acidification.

Rock dust has potential to improve soil fertility and provide protection against pests and diseases so there is hope that costs could be offset by financial benefits. If it proves feasible to employ such practices on a large scale an important benefit could be reduction of ocean acidification, which threatens marine biocalcifiers such as corals and shellfish. Further study and field assessments are needed to verify benefits and address potential obstacles to large-scale adoption.

Farming crops with rocks to reduce CO2 and improve global food security

  • Enhanced rock weathering involves adding minute rock grains to cropland soils which dissolve chemically taking up carbon dioxide and releasing plant essential nutrients.
  • Unlike other carbon removal strategies enhanced rock weathering doesn’t compete for land used to grow food or increase the demand for freshwater.
  • Other potential benefits include reducing the use of agricultural fertilizers and pesticides, lowering the cost of food production and increasing farm profitability.Farming crops with crushed rocks could help to improve global food security and capture CO2 from the atmosphere, a new study has found.

    The pioneering research by scientists at the University of Sheffield together with international colleagues suggests that adding fast-reacting silicate rocks to croplands could capture CO2 and give increased protection from pests and diseases while restoring soil structure and fertility.

Professor David Beerling, Director of the Leverhulme Centre for Climate Change Mitigation at the University of Sheffield and lead author of the research, said: “Human societies have long known that volcanic plains are fertile, ideal places for growing crops without adverse human health effects, but until now there has been little consideration for how adding further rocks to soils might capture carbon.

“This study could transform how we think about managing our croplands for climate, food and soil security. It helps move the debate forward for an under-researched strategy of CO2 removal from the atmosphere – enhanced rock weathering – and highlights supplementary benefits for food and soils.

“The magnitude of future climate change could be moderated by immediately reducing the amount of CO2 entering the atmosphere as a result of burning fossil fuels for energy generation. Adopting strategies like this new research that actively remove CO2 from the atmosphere would contribute this effort and could be adopted rapidly.”

The research, published in Nature Plants, examined the approach which involves amending soils with abundant crushed silicate rocks, like basalt, left over from ancient volcanic eruptions. As these minute rock grains dissolve chemically in soils, they take up carbon dioxide and release plant-essential nutrients.

Critically, enhanced rock weathering works together with existing managed croplands. Unlike other carbon removal strategies being considered, it doesn’t compete for land used to grow food or increase the demand for freshwater. Other benefits include reducing the usage of agricultural fertilizers and pesticides, lowering the cost of food production, increasing the profitability of farms and reducing the barriers to uptake by the agricultural sector.

Crushed silicate rocks could be applied to any soils, but arable land is the most obvious because it is worked and planted annually. It covers some 12 million square kilometres or 11 per cent of the global land area.

Arable farms already apply crushed rock in the form of limestone to reverse acidification of soils caused by farming practices, including the use of fertilizers. Managed croplands, therefore, have the logistical infrastructure, such as the road networks and machinery, needed to undertake this approach at scale. These considerations could make it straight forward to adopt.

Professor Stephen Long at the University of Illinois Champaign-Urbana, and co-author of the study added: “Our proposal is that changing the type of rock, and increasing the application rate, would do the same job as applying crushed limestone but help capture CO2 from the atmosphere, storing it in soils and eventually the oceans.

“Global warming is a problem that affects everyone on the planet. Scientists generally have done a poor job of getting across the point that the world must reduce emissions of greenhouse gases from fossil fuels and combine this with strategies for extracting carbon dioxide from the atmosphere to avoid a climate catastrophe.

Professor James Hansen from the Earth Institute at Columbia University and co-author of the work, added: “Strategies for taking CO2 out of the atmosphere are now on the research agenda and we need realistic assessment of these strategies, what they might be able to deliver, and what the challenges are.”

UPDATE – Thanks to reader SirCharles – Nature:

Decarbonization of the world’s economy would bring colossal disruption of the status quo. It’s a desire to avoid that change — political, financial and otherwise — that drives many of the climate sceptics. Still, as this journal has noted numerous times, it’s clear that many policymakers who argue that emissions must be curbed, and fast, don’t seem to appreciate the scale of what’s required.

According to the Intergovernmental Panel on Climate Change (IPCC), carbon emissions must peak in the next couple of decades and then fall steeply for the world to avoid a 2 °C rise. A peak in emissions seems possible given that the annual rise in carbon pollution stalled between 2014 and 2016, but it’s the projected decline that gives climate scientists nightmares.

The 2015 Paris agreement gave politicians an answer: negative emissions. Technology to reduce the amount of carbon already in the atmosphere will buy society valuable time. The agreement went as far as arguing that incorporating one such technology — bioenergy with carbon capture and storage (BECCS) — could even see the global temperature increase kept to 1.5 °C.

What would negative emissions look like? A Perspective this week in Nature Plants offers another glimpse, and it’s not pretty (D. J. Beerling et al. Nature Plants; 2018). The review focuses on the idea of enhanced weathering, which aims to exploit how many rocks react with carbon dioxide and water to form alkaline solutions that, over time, find their way into the sea. It’s one of a number of proposed negative-emissions technologies.

In theory, enhanced weathering could lock up significant amounts of atmospheric carbon in the deep ocean. But the effort required is astounding. The article estimates that grinding up 10–50 tonnes of basalt rock and applying it to each of some 70 million hectares — an area about the size of Texas — of US agricultural land every year would soak up 13% of the annual global emissions from agriculture. That still leaves an awful lot of carbon up there, even after all the quarrying, grinding, transporting and spreading.

It’s not hard to see why many climate scientists have dismissed the near-impossible scale of required negative emissions as “magical thinking”. Or why the European Academies’ Science Advisory Council said in a report this month: “Negative emission technologies may have a useful role to play but, on the basis of current information, not at the levels required to compensate for inadequate mitigation measures.”

The IPCC is now working on a report on strategies to keep warming to under 1.5 °C, which is due to be published later this year. By necessity, those strategies will lean heavily on negative emissions. Scientists must continue to spell out to policymakers the harsh reality of what this would involve, and in the strongest possible terms.


32 Responses to “The Weekend Wonk: Enhanced Weathering – Rock Dust, Soils, and Climate”

  1. Sir Charles Says:

    Nature has an editorial on this “magic wand”:
    Why current negative-emissions strategies remain ‘magical thinking’
    Work on how rocks draw carbon from the air shows the scale of the challenge.

    • Gingerbaker Says:

      Yup. Basalt plan used on U.S. grain belt acreage would be large undertaking and would remove 13% of world-wide agricultural emissions per year, which are themselves only 13% of total global emissions.

      So, if emissions went to zero tomorrow and stayed there, this is a about a 3500 year strategy to get back to pre-industrial levels.

      There is also a proposal to spread crushed olivine around Pacific rim waterfronts. A trillion dollars a year would remove an amount equal to the emissions from year ~ 2015. That is a lot faster, seems to be scientifically rational, but is totally theoretical:

  2. Sir Charles Says:

    Survivable IPCC projections based on science fiction – reality is far worse

  3. Alan Thorpe Says:

    The worldwide brainwashing of the masses by all governments moves money from the poorest to these fraudsters. The earth’s climate is essentially unstable and unpredictable. It has been in an ice age for thousands of years and if the pattern of glacial and interglacials continues then we are heading for more cooling. There is no evidence from proxy temperatures and CO2 than CO2 has any influence on climate. Warming is good for us, higher CO2 is good for food production. It is why the human race has been so successful over the last 3000 years. Cooling will be a disaster. This is the problem that the useless climate scientists like Hanson should be studying.

    • dumboldguy Says:

      warming is good for us….should be studying….should be studying….should be studying….should be studying… should be studying…. should be studying

      Would someone please get up and go over to lift the needle off the record? It often happens with old broken records that they just keep repeating, especially at the end.

      BTW—-doubt that this is from the real Alan Thorpe, the British scientist who DOES believe in climate change and would likely NEVER make this comment.

      IMO, staling a climate scientist’s identity to spout denier bullshit is a serious sim and should result in INSTANT banning from Crock for whoever this fool is (likely one of the Russian trolls).

      • dumboldguy Says:

        stealing is a sin

      • Lizard Breath Says:

        Sorry dumboldguy – I accidentally down rated your comment and then couldn’t figure out how to undo it (no, I’m not very bright….). But, since I have your attention, I wanted you to know that I always misread your handle as dum bold guy. Hope you find that mildly amusing.

        • dumboldguy Says:

          I came up with that handle for many reasons that made me smile, and one was the way dum(b) and (b)old overlap, so you’re right on track. You can call me DOG.

          (And speaking of dogs, I do like the pic you’re using—-resembles a Border Collie I know who will chase frisbees for hours—-when she gets tired, she takes the frisbee to the far end of the yard and rests—-when she’s not tired, it keeps getting dropped in your lap or on your foot)

          PS Undoing thumbs is easy—-just wait a while and click on the other one and they’ll switch

        • Sir Charles Says:

          Just hit the other button (thumbs up) and it will swap. Easy as that.

    • grindupbaker Says:

      +Alan Thorpe You have a mind-bogglingly stupid mix of incorrect basic facts and faulty logic there. Quite staggering in its scope. How about you study the topic for 90 minutes some time over the next couple of years and try again.

    • Sir Charles Says:

      CCDDr may be effecting your parents, grandparents, or congressperson…

  4. Keith McClary Says:

    For comparison, it is “estimated that on a worldwide basis, humans move more of the planet around, about 45 gigatons (billion tons) annually, than do rivers, glaciers, oceans or wind.”

    • dumboldguy Says:

      Also from the link: “Hooke estimated that over the last 5,000 years of human history, the total amount of soil and rock moved by people would be enough to build a mountain range about 13,000 feet high, 25 miles wide and 62 miles long”.

      Ever been to the Sierra Nevada? “Extending more than 250 miles (400 kilometres) northward from the Mojave Desert to the Cascade Range of northern California and Oregon, the Sierra Nevada varies from about 80 miles wide at Lake Tahoe to about 50 miles wide in the south”. That’s about ten times bigger than the “man-made””one above.

      That 45 gigatons annually is highly localized, also. Mother Nature has her “shovels” working everywhere on the planet.

      • Keith McClary Says:

        My point was, the “grinding up 10–50 tonnes of basalt rock and applying it to each of some 70 million hectares — an area about the size of Texas … every year” works out to 0.7 to 3.5 gigatons annually. Applying this globally would be in the neighbourhood of 45 gigatons.

        And, as you point out, the 45 gigatons annually is highly localized (using monster haul trucks on the mining or construction sites), whereas the spreading of basalt rock would involve long distance transport (not to mention crushing beyond what is done in mining or construction).

        Even if we were to devote all our current earth moving capacity to this, I think it would cancel only a small % of FF emissions.

        • pendantry Says:

          Another aspect to this is whether those who propose this rock-scattering technique have factored in the carbon cost of extracting, crushing and transporting the rock. I bet: not.

          • dumboldguy Says:

            Nor have they determined who is going to come up with the $$$ to pay for any of it—-we are paying little attention to the health of our soil now, and unless many governments get involved, this is just more pie-in-the-sky.

  5. grindupbaker Says:

    One of the various clowns I’ve heard about geoengineering is the “great heretical free thinker” hand-waving Freeman Dyson. He said a few degrees warmer Earth ecosphere is likely no problem but if humans in 500 years find it a problem then they’ll just genetically modify Earth biosphere to take up more (3x or 10x, he never did say what) CO2 than the present Earth biosphere DNA is programmed for. That’s all. He’s fully protected by a powerful SEP force field, as are we all.

    • dumboldguy Says:

      What we’re going to do when SHTF time arrives is not grind up rock but instead launch a panicky geo-engineering aerosol program, since it’s quick and cheap. After all, look at what Pinatubo did!

      Inevitably, like nearly all the other grand technology experiments modern humans have conducted, we will likely screw it up. I highly recommend the book TAMBORA for a look at what major injections of material into the atmosphere can do to weather patterns. 1816-1818 was a time of global suffering as well as global cooling, and that, unfortunately, will happen again when we push the panic button.

      • Sir Charles Says:

        Yeah. And Tambran is a Mickey Mouse company telling the Irish that they could frack for shale gas without the use of chemicals. After having been exposed for that nonsense their CEO resigned. Fortunately enough, after years of massive public protest, the Irish government imposed a ban on onshore fracking last year.

        Obviation is way better than any cure.

        • Sir Charles Says:

          Sorry. Typo. It should read ‘Tamboran’.

          • dumboldguy Says:

            Your thought processes are nothing but one huge “typo”. It’s the weekend—-are you drinking?

            TAMBORA refers to a volcano, not some energy company in that flyspeck of a country you call home.

          • Sir Charles Says:

            Sure, dumbo, and now you think I wouldn’t have known that. I was getting Google news alerts for several years. The keyword was ‘Tamboran’. Guess what news articles I mostly got forwarded by Google. Do I hear envy because you live in a country where it is 7.6 times as likely to get murdered than in my country? Or is it just because we could succeed to get fracking banned here? Stop crying into your armchair, dumbo (or should I say DBOG?). Spring into action.

          • dumboldguy Says:

            Yes, Chucky, I DO think you didn’t know that the Tambora I referred to was a volcano. Otherwise you wouldn’t have come out of left field with bullshit about a gas-fracking company that has NOTHING to do with the topic at hand.

            What I don’t understand is why you just can’t say OOPS when you screw up, but instead have to make personal attacks and spew even more BS. Oh, wait, it’s your narcissism that keeps you from doing so. You are turning into Ireland’s little version of Donald Trump, and I thought you didn’t even like him—-if that’s true , why are you becoming a Trump Mini Me?

          • Sir Charles Says:

            You constantly remind me on this guy, dumbo:

            A day in the life of the HB manikin

            This “HB manikin” only got relief when the man with the HB cigarettes came (missing here) and gave him a puff. Old German TV ads from the 1960s, but still funny 😉

  6. nickreality65 Says:

    More of that pesky science.

    RGHE theory could not exist without the concept of “back” radiation, energy/heat moving from a cold tropospheric “surface” to a hot ground “surface.”

    Consider a small heated rod of 0.5 m^2 inside a larger outer tube of 2.0 m^2.
    The heated rod is fed 25 watts of electricity for a radiative flux of 50 W/m^2.
    The outer tube absorbs that radiation for a radiative flux of 12.5 W/m^2.

    RGHE theory says that 50 W/m^2 radiate outwards while 12.5 W/m^2 “back” radiates for a net of 37.5 W/m^2 warming the earth.

    A watt is not energy, but power, energy over time: 3.412 Btu per English hour or 3.6 kJ per metric hour.

    25 watts is 85.3 Btu/h.
    25 W spread over area 1 is 50 W/m^2 moving 85.3 Btu/h.
    25 W spread over area 2 is 12.5 W/m^2 also moving 85.3 Btu/h.

    Conservation of energy demands that input and output must be equal.

    The 25 W, 85.3 Btu/h, that entered as electricity must radiate to the world from surface 2, 25 W or 85.3 Btu/h.

    There is exactly ZERO left over to “back” radiate.

    • dumboldguy Says:


      (roll over, go back to sleep)

      • nickreality65 Says:

        The 396 W/m^2 upwelling and net 333 W/m^2 GHG energy loop as shown on the K-T power flux balance diagram (Figure 10 Trenberth et al 2011jcli24) is calculated using the S-B equation with an assumed emissivity of 1.0 and an average surface temperature of 16 C, 289 K. Because of the conductive/convective/advective/latent heat participating processes of the atmospheric molecules the actual and correct radiative emissivity is about 0.16, i.e. 63/396.

        This GHG energy loop is an inappropriate calculation with zero physical reality.

        Without this energy loop the radiative greenhouse effect theory fails.

        Without RGHE man-caused climate change does not exist.

        It’s called “science.”

        Don’t be frightened, spit out the Kool-Aid and give it a try.

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