Closer look at Enhanced Rock Weathering
“It’s not too unlike the first life-forms that covered the Terran [related to planet earth] continents, we think. We’ve just enhanced its speed of growth, and its root systems. The funny thing is that I think at first it’s going to cool the atmosphere, even though it’s warming things underground. Because it’ll really increase the chemical weathering of the rock, and all those reactions absorb CO2 from the air, so the air pressure is going to drop.”
This paragraph is from the science fiction book 1 Red Mars (published 1993) of the Mars Trilogy by Kim Stanley Robinson.
Lately enhanced chemical weathering of rocks has emerged as a promising tool to draw down carbon dioxide from the atmosphere. [1] But before we get to enhanced rock weathering, let us look at some well known practices for soil health (cover crops, no till), which are also sustainable from an environmental standpoint (in certain contexts) and their adoption in North America.
I. Carbon in agriculture is challenging
During peak pandemic in 2020 & 2021, carbon markets were all the rage. There was irrational exuberance around carbon markets, especially within agriculture.
I even wrote a tongue-in-cheek headline in the past calling Carbon Markets: The Substack of Agriculture
Some of the craziness has settled in the last 2 years as all of us have learnt more about what’s possible and what’s not.
Even though carbon and GHG often make all the headlines, I do want to emphasize it should be about a systemic approach which includes biodiversity, water, soil health, and carbon.
Carbon in agriculture has been challenging due to permanence, additionality, challenges to practice change, and the lack of scalable efficient ways to measure impact and attribute it to behavior change.
The upfront and ongoing investment required for adoption of conservation practices, the potentially slow time to ROI, the expertise and knowledge needed to transition, the suitability of practices for the context, familiarity with existing practices, and the lack of confidence in reliable and trustworthy ways to measure impact has made the adoption of conservation practices to be slow
II. Limited adoption
Anastasia Volkova, the CEO of Regrow.ag posted the following chart on LinkedIn. It shows very little growth for cover crop adoption (~3% to ~7%), reduced till (~44% to ~50%), and actual reduction in no-till adoption from ~42% to ~29% in a 7 year period from 2016 to 2022!
Are farmers giving up on certain practices after trying them for some time?
According to research published in the Choices Magazine, a publication of Agricultural and Applied Economics Association, “The Invisible Elephant: Disadoption of Conservation Practices in the United States” [2]
Dis-adoption played an even larger role in limiting the expansion of no-till than it did in limiting the expansion of cover crops. The dis-adoption ratio for no-till at the national level between 2012 and 2017 was 39.38% (Table 2), equivalent to about 2.5 times the dis-adoption ratio for cover crops over the same period. Dis-adoption of no-till was also more widespread than dis-adoption of cover crops, occurring in 35.49% versus 28.26% of all counties, respectively.
Panel A. No-Till Adoption Rate by County, 2017
Panel B. Percentage-Point Change in No-Till Adoption Rate by County, 2017 vs 2012
Source: Authors' calculations based on Census of Agriculture (USDA 2014, 2019).
If you look at Panel B above, the red counties with change in adoption rates of less than 0% had adopted no-till practices, but now (2017) have stopped their no-till practice.
Even if people go through the adoption of some of these practices, between a fourth and third of them are dis-adopting. More needs to be done to understand what drives behavior change in both ways, adoption and dis-adoption.
(Health Clubs famously run their business on signing up a bunch of New Year’s Resolution folks, and most of them don’t show up on February 1st - raising my hand here as well!)
Churn-no-till
Dis-adoption is called churn in the traditional subscription business. Companies spend a fortune to understand and lower churn as their existence, growth, and profitability is dependent on managing churn.
Taking a product management lens, one could think of farmers adopting new practices like cover crop and no-till as subscribing to these practices, as they can stop doing those practices anytime.
Based on the dis-adoption study, it looks like the churn rate for no-till and cover crop was pretty high.
So what could be potentially causing high churn for these conservation practices?
The adoption of conservation practices is a behavior change challenge, combined with an economic problem, a business model problem, a know-how problem, and a technology problem.
The MRV platforms (measure, record, verify) are critical to get incentives flowing based on carbon credits. The reliability and consistency of the MRV platform (the technology) has to go hand-in-hand with an attractive business model, and easy to make & sustain the behavior change.
In the case of adoption of conservation practices, what are the potential reasons for dis-adoption / adoption?
- Is the time to value (whichever way you define it - better soil health, higher yield, lesser inputs, incentive dollars) too long?
- Is it too difficult to make these practice changes?
- Is the knowhow not readily available?
- Is the ROI not there for the level of investment required?
- Are the MRV needs cumbersome and unreliable to capture value?
- Any other reasons?
It is critical to understand the reasons for first time adoption, for continued adoption, and for dis-adoption. This is true for any new practice, or technology, or a product which will be introduced new to existing operations.
Without understanding these reasons, it will be very difficult to get any product or practice adopted.
Let us talk about another such new practice called enhanced rock weathering for better yield outcomes, and permanent carbon capture within the context of agriculture.
III. Enhanced Rock Weathering
All rocks naturally absorb carbon dioxide from the air and break down (or weather) over time. Enhanced rock weathering is simply kickstarting the natural process of weathering by applying minerals to soil to speed up the natural carbon absorption, removal, and sequestration process.
What is ERW?
Enhanced rock weathering (ERW) is a process that aims to accelerate natural rock weathering during which carbon dioxide reacts with rocks. CO2 is removed from the atmosphere and converted to bicarbonates and/or carbonates. As a carbon removal method, ERW involves finely grinding down silicate rocks to increase their surface area and spreading them over soil. Utilizing natural rainfall and rock chemical reactions, it results in the long-term storage of large amounts of carbon dioxide, for thousands of years. (Remember the dialogue from “Red Mars” at the beginning of this week’s edition)
Image source: “Can Enhanced Rock Weathering help combat climate change?”
There are many companies playing in the ERW space, with Eion Carbon and Lithos Carbon being the most prominent ones, and each of them follow a slightly different approach.
The chart below from puro.earth lays out the whole process (not just how it works in the field).
As you can see, the right kind of rock needs to be mined, processed, transported, and applied to the right field in the right quantity, for the enhanced rock weathering process to work.
Image source: Puro.earth’s Enhanced Rock Weathering in Soil Methodology
Eion Carbon has laid out this process in great detail. Eion uses olivine, a silicate based rock found mainly in Scandinavia, which needs to be shipped to the farm.
Enhanced rock weathering (hence the “enhanced”) speeds the process of weathering from thousands of years to be a much faster process, to permanently capture carbon dioxide from air.
According to Lithos Carbon, the enhanced weathering process is faster but still takes 15-50 years, instead of thousands of years. Lithos Carbon captures ~70% of the carbon in year 1, and the rest in a couple of growing seasons.
Lithos Carbon leads with improvements in yield, which are projected in the 5-40% range at partner farms. I don’t believe we will see similar results on average and at scale.
Both Eion and Lithos rely on verifiable carbon credits. The ERW process is relatively new and so it will take some time for buyers and providers of carbon credits to trust the process, though certain voluntary markets have started accepting them.
In theory, the process of ERW sounds simple as farmers are used to applying lime especially in acidic soils every couple of years.
The enhanced rock weathering process cannot be used for any type of soil [3], and is most effective in acidic soils in a particular pH range (see diagram below - look at the red line)
Image source: Eion’s methodology white paper [4]
ERW’s MRV
It is very important to have a consistent, reliable, and trustworthy process to measure, record, and verify the carbon removal process. This is especially true, given many of the “verified” carbon credits have been deemed worthless.
There is growing research showing that silicate rock application to farmland significantly increased the amount of carbon captured in soybeans, corn, and miscanthus. This research is important, and the relevant MRV tools need to be incorporated in the process to establish trust, create liquidity, and provide incentives for behavior change.
At the moment the standard method is to measure how much basalt has been mixed into the soil, and then regularly measure soil samples to see how much has dissolved. The gray area is “the leakage” and amount of carbonate that is lost on the journey to the sea.
Eion has developed a patented measurement technology, which looks for trace elements to know the amount of carbon dioxide pulled down from air, and converted to carbonates through a chemical reaction between the rock and rainwater.
Image source: Eion’s Life cycle assessment
Eion’s life cycle assessment shows the losses or leakage during the entire life cycle of rock weathering, with most of the losses coming in transportation and natural system loss. Even though Eion is currently using olivine for farmers, their approach can be used with any silicate rock.
Image source: Eion’s Life cycle assessment
Lithos offers “cradle to grave” measurement. According to Mary Yap, CEO of Lithos, In certain conditions, such as a particularly acidic water environment, the bicarbonate can be re-released as a gas. To counter this, Lithos is working with the U.S. Geological Survey, which uses 2 million data points across the United States river network, to monitor water chemistry.
The key standard in the market is the Puro.earth enhanced rock weathering methodology, which was launched in 2022, to be used in the voluntary carbon market and allows the issuance of what Puro calls C02 removal certificates (CORCs). Verra is working on a verification methodology for enhanced rock weathering.
Even the US DOE has announced it would spend $35 million on carbon dioxide removal credits from firms using technologies such as ERW or direct carbon capture.
“The fact that the government is now stepping in and saying it will purchase carbon dioxide removal credits is also an indication of the rapid maturation of the market. And what’s exciting is that enhanced rock weathering and Eion’s technology is lower cost and readily scalable, unlike some carbon capture technologies.”
IV. Behavior changes required for ERW
If there is anything we know about humans, we know behavior change is very challenging, especially when you are asking someone to change something they have been doing for a long time. So let us look at the behavior change a farmer will have to make to adopt enhanced rock weathering as a solution.
As we saw earlier, enhanced rock weathering primarily works in acidic soils, and can be used as a replacement for lime treatment, though it often requires much more rock application than lime (UNL extension data on lime application rates in acidic soils). [5]
More research needs to be conducted on any side effects of enhanced rock weathering, to make sure there are no major negative externalities. For example, a research report (Biogeosciences Discuss Manuscript under review for journal Biogeosciences) recommended not to use olivine, due to Ni (Nickel) concentrations exceeding the limits of drinking water quality. [6]
“The release of potentially harmful trace elements is an acknowledged side effect of Enhanced Weathering. Primarily Ni and Cr are elevated in soil solution, while Ni concentrations exceed the limits of drinking water quality. The use of olivine, rich in Ni and Cr, is not recommended and alternative rock sources are suggested for the application.”
Based on the table above, if companies (and governments) want farmers to adopt enhanced rock weathering, they will need to convince them about the added friction of different applications rates, provide evidence and confidence on yield impact and no major side effects, provide a trustworthy and rock solid MRV platform, and some of the incentives have to flow to farmers to help them balance out any risks.
V. Value creation, value capture, and scaling
So what is the potential of enhanced rock weathering on carbon dioxide sequestration? For reference, the annual estimated total GHG emissions in 2022 were 50 Gigatons of CO2 equivalent.
Potential of ERW at a global scale
According to some estimates published in the August 2023 edition of the journal “Earth’s Future” (a publication of Advancing Earth and Space Sciences), [7]
Applying a fixed rate of 10 tons of basalt dust per hectare on these sites sequesters 64 gigatons of CO2 over a 75-year period; when extrapolated to all agricultural land, ERW sequesters 217 gigatons of CO2 over the same time interval. However, we find that a significant fraction of applied basalt does not weather even on a multidecadal timescale, indicating the need to optimize application strategies for cost effectiveness. We find that ERW becomes modestly more effective with global warming and predict that the payback period for a given ERW deployment is significantly shorter in hot and humid environments currently coinciding with relatively low per-capita incomes.
If we convert the 64 Gigaton of CO2 as an annual number, it comes to about 64/75 = 0.85 Gigaton per year (about 1.7% of total annual GHG emissions). This number is important as we look at some expert views on carbon dioxide removal vs. reduction in emissions of fossil fuels.
Will ERW work at a global scale?
So will an approach like enhanced rock weathering scale in the future? It does look promising, though it is too early to tell. Some of the foremost experts in the field of carbon dioxide removal (CDR) are still divided about the value of CDR, in the broader context of emissions reduction vs. carbon dioxide removal. [8]
“Climate experts are divided over whether CDR is a necessary requirement or a dangerous distraction from limiting emissions.”
Holly Jean Buck, assistant professor at the University of Buffalo, and one of the foremost experts in the space, had to say the following.
“There are a number of methods that deserve more research, including ocean alkalinity enhancement, enhanced rock weathering and agrigenomic ideas such as engineering plants for enhanced carbon sequestration or microbe-based carbon capture soil amendments. It is early to assess the scalability of all these approaches, and much of the scalability depends on culture and policy.”
Glen Peters, research director for the The Climate Mitigation group had to say the following,
Although many advocate CDR for the right reasons, it is important to acknowledge that CDR deters emission reduction efforts. The level of deterrence is difficult to define and quantify. The mitigation levels reported by the IPCC, and used by countries to support their emission pledges, assume that large-scale CDR will be deployed.
Main components to make ERW work
As we look at the value chain for delivering enhanced rock weathering solutions, which players are best positioned to create value, and actually capture value. Farmers are obviously a key player, as they will have to adopt this slightly different practice.
There are five main components required to make ERW work
- The logistics necessary to extract, process, transport, deliver and apply powdered rock on fields and farms.
- Grower connections and distribution capabilities.
- The data, analysis, and technology required to know how much rock to apply where, and when. The data required will include soil tests, topography, weather, etc.
- A trusted and certified measure, record, and verify (MRV) tech platform & infrastructure.
- Connection with carbon credit buyers to provide liquidity.
I believe numbers 2, 3, and 5 above are relatively easy to solve or already solved problems.
The logistics and supply chains do exist for lime, and other bulk inputs like fertilizers. The logistics problem is the key problem to solve to scale enhanced rock weathering, especially if some of the rocks are specific like olivine, which is only available in some parts of Scandinavia.
A trusted MRV platform is key to help farmers adopt, and buyers able to buy the credits. I don’t understand the science in detail, but the measurement using trace elements (Eion has a patent on it), and understanding leakage can be solved, and the technology can be licensed.
Due to this, when it comes to splitting the captured value from carbon capture, a majority will go to the farmer in terms of agronomic value and share of the carbon credit price, with the logistics provider taking the second big chunk of value, and the MRV provider capturing a smaller percentage of the value.
Based on this analysis, an existing player like Nutrien is in a great position to provide this capability to their network of growers within North America. Nutrien has experience in mining, and logistics of large bulk products, has a large network of growers, and also has the technology backbone needed to target the right set of growers for scaling this technology. Given their brand name, they can also bring to the table a good mix of carbon credit buyers. They need to license the MRV technology to provide confidence to buyers, and farmers.
It makes sense for companies like Lithos or Eion to license their technology out to players like Nutrien, though they need to prove the validity of their models and methods through real science, collaboration, and trials. For example,
Eion is the first enhanced rock weathering solution to successfully deliver carbon removal to Stripe. Stripe’s acceptance–and corresponding $1 million carbon repurchase—affirms the scientific rigor underpinning our approach to ERW, and this achievement is a testament to the dedication of our partners and collaborators.
Other potential players who could help with adoption and scaling of ERW are players like Land O’Lakes and Truterra.
So will enhanced rock weathering adoption and scaling be as simple as the rock, paper, scissors game?
Spread enhanced rock, measure, record, and verify the impact on paper, and cut (scissors) the carbon dioxide in the atmosphere.
Will what the characters in Red Mars thought will work on Mars, work on earth?
References
[1] Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering Kantola, I. B., Blanc-Betes, E., Masters, M. D., Chang, E., Marklein, A., Moore, C. E., von Haden, A., Bernacchi, C. J., Wolf, A., Epihov, D. Z., Beerling, D. J., & DeLucia, E. H. (2023). Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering. Global Change Biology, 00, 1–17. https://doi.org/10.1111/gcb.16903
[2] Sawadgo, W. and A. Plastina. 2022. "The Invisible Elephant: Disadoption of Conservation Practices in the United States" Choices. Quarter 1. Available online: https://www.choicesmagazine.org/choices-magazine/submitted-articles/the-invisible-elephant-disadoption-of-conservation-practices-in-the-united-states
[3] von Uexküll, H.R., Mutert, E. Global extent, development and economic impact of acid soils. Plant Soil 171, 1–15 (1995). https://doi.org/10.1007/BF00009558
[4] Methodology for Carbon Dioxide Removal by Enhanced Mineralization on Farmland in the United States by Adam Wolf, Alison Marklein, Maria Mooshammer, Elliot Chang. June 15, 2023 /content/files/wp-content/uploads/2023/08/eion-methodology.pdf
[5] “Lime Use for Soil Acidity Management” University of Nebraska Extension Publication
[6] Constraints on Enhanced Weathering and related carbon sequestration – a cropland mesocosm approach by Thorben Amann, Jens Hartmann, Eric Struyf, Wagner de Oliveira Garcia, Elke K. Fischer, Ivan Janssens, Patrick Meire, Jonas Schoelynck (2018). /content/files/preprints/bg-2018-398/bg-2018-398.pdf
[7] Baek, S. H., Kanzaki, Y., Lora, J. M., Planavsky, N., Reinhard, C. T., & Zhang, S. (2023). Impact of climate on the global capacity for enhanced rock weathering on croplands. Earth's Future, 11, e2023EF003698. https://doi.org/10.1029/2023EF003698
[8] Anderson, K., Buck, H.J., Fuhr, L. et al. Controversies of carbon dioxide removal. Nat Rev Earth Environ (2023). https://doi.org/10.1038/s43017-023-00493-y
[9] Mary Yap and Adam Wolff on the My Climate Journey podcast