Enhanced Rock Weathering (ERW) is emerging as a promising approach to carbon removal. At face value, it’s an elegant solution: simply spread finely ground rocks on a field and carbon is removed from the atmosphere. With low technology risk, massive scale potential, limited capital costs, and simple integration into land management practices, ERW has attracted interest from major buyers.

But as momentum builds, questions remain: can we reliably measure the carbon removal effect? At scale, can this pathway compete cost-effectively with other removal solutions? What challenges must still be addressed?

We took a deep dive into the mechanics and economics of ERW to identify what’s needed to unlock its full potential. While the focus of much of the discussion to date has been on monitoring, reporting, and verification (MRV) methods, we believe the pathway’s success depends on a great deal more.

ERW Fundamentals

Rocks weather as part of the natural carbon cycle. Silicate and carbonate rocks dissolve in the presence of CO₂ and water, release cations (Ca2+ and Mg2+) and form bicarbonate (HCO3-), which is transported via waterways to the ocean where it is durably stored for thousands of years.

Enhanced Rock Weathering companies accelerate this process by grinding silicate or carbonate rocks into fine dust, smaller than half the size of a grain of sand. This speeds up the natural reaction from millennia to years, helping us lock away carbon more quickly.

Rocky Mountain Institute estimates that terrestrial ERW could deliver around 500 Mt of CO₂ removal per year¹. Mining operations, which already produce large volumes of waste rock, present a low-cost feedstock opportunity, and there is plenty of farmland with infrastructure available to spread this material and remove carbon in a cost-effective way.

In addition to carbon sequestration, spreading rock dust on farmlands provides agricultural value. Rock powders can substitute agricultural lime to neutralise soil acidity, and in some instances offer fertilising properties. It’s important to note that the degree of beneficial effects is context-dependent and subject to the complex interactions of soil type, climate, weathering rates, application schedules, and specific mineral compositions - among many factors.

The ERW business model revolves around carbon removal sales and farming benefits. ERW companies aim to provide rock dust at low or no cost to farmers, which saves the farmers from buying more expensive agricultural lime. As this dust weathers and carbon is removed, ERW companies are able to “harvest” carbon removal certificates and sell them, which drives revenues.

On paper, it’s a win-win. But in practice, the economics of the pathway are quite a complex picture.

Cost-Competitive ERW Is Hard

In an effort to better understand how the project economics work, we built a project model of basalt rock powder deployments built from our research and input and feedback from industry players.

Our analysis suggests that while costs can be expected to fall in the short-to-medium term, in the long-run ERW companies may be fighting diseconomies of scale, leading to higher costs over time. This trajectory could lead to ERW being uncompetitive with other carbon dioxide removal (CDR) approaches that benefit from steep learning curves and economies of scale.

Current market price points for other CDR methods vary, but are generally lower than our projected ERW prices. For example, biochar ranges from $100 to $250 per ton, biomass burial from $50 to $170 per ton, and BECCS (which also generates energy) averages around $212 per ton². Furthermore, these costs will trend downward as technologies improve and supply chains mature.

ERW has the benefit of requiring little capital investment while using the Earth’s natural systems to passively remove CO₂, and so suggests that it should have a lower cost of removal than these aforementioned methods. However, our analysis suggests that rising costs will outweigh some of these benefits, especially as the pathway scales.

We’re not sure exactly when these cost dynamics will emerge and what the costs will specifically be. But directionally we expect the following dynamics:

• Input costs will increase. Rock dusts or fines, which today are sourced relatively cheaply and as byproducts of other grinding and milling operations, have a limited supply. At scale, we’ll need to start mining and processing materials specifically for ERW, requiring more energy and thus cost. Today these minerals have little value because they are a “waste”. Once there’s more value ascribed to them, it’s possible that suppliers will increase their prices to match.

• Transportation distances from the mine to the farm are likely to increase over time. Our research indicates that current trucking distances range from as little as 50 km to as much as 500 km in some regions. In the short term, companies may be able to optimize operations and minimize transport distances by partnering with nearby farms—provided a sufficient number are available. However, once these local sites become saturated, ERW companies will need to transport material over longer distances to reach new customers. This will increase costs and reduce net carbon removals.

• In the fullness of time and once competing ERW companies start vying for farmers’ attention, it seems reasonable to expect that landowners will look for a cut of the action and farmers may require some compensation for using their land and machinery for CDR, adding to deployment costs.

• On the other hand, MRV costs and losses from uncertainties and inefficiencies will likely come down. Cheaper sensors are already in development, reducing hardware costs. Projects will optimise based on their learnings about optimal weathering conditions, rates and timings of applications, and many other practical factors, which should improve removal efficiencies. And as our understanding and models of bicarbonate transport improve from more data, it’s likely that how we account for storage uncertainties will sharpen, too.

ERW can scale, and there’s opportunities abound

If ERW companies want to be competitive in the CDR market, we think that they would have to sell credits in the range of $100-150 per tonne of carbon removed in the long term. Getting to this price point could be done a few different ways. For example, one way to achieve a price of $125 per tonne would be to:

1. Limit trucking distances to 100km or less - this unfortunately restricts the number of viable mineral sources and fields for application, but this would manage the key cost and source of process emissions of the pathway.

2. Reduce uncertainty and inefficiencies³ while keeping MRV costs low (less than $10 per tonne removed). This probably means that the losses need to be less than 20% of total removals expected from a deployment. Isometric and InPlanet incorporated soil and water system losses of around 45% in their issuance earlier this year⁴.

3. Acquire basalt rock dust costs at around $10 per tonne (or using other rock or rock blends that allow for costs less than $40 per tonne of carbon dioxide removed).

4. Reduce the weathering period, minimizing financial discounting of future revenues, enabling lower pricing while maintaining the same project IRR.

In reality, the order, nature, and magnitude of these improvements will vary, but together they give us a sense of what it takes to achieve low-cost ERW.

There are plenty of opportunities and tactics companies can use within each of these buckets. Some ideas we’ve been thinking about within each of these categories are:

Limiting trucking distances

It is difficult to move rock dust very far by truck because it’s not that valuable relative to its cost, and the emissions associated with transport are not helpful to net removals.

Keeping trucking distances short could imply that companies who scale to millions of tonnes of CDR will need many distributed rock sources each with a small radius of deployment, rather than a few large central “mines” servicing vast areas. It’s likely that there are areas where rail or ocean transport (both cheaper and less carbon intensive than trucking) can help move materials further. We can expect that deploying in regions with fewer viable sources of feedstock, low carbon transport infrastructure will be vital.

The limited transportation radius could constrain an ERW company’s ability to scale beyond a local region. However, this constraint can also become a strategic advantage: within that area, companies can build strong operations based on established logistics, local partnerships, and in-depth knowledge of regional farming practices and rock-soil interactions. At the same time, these geographic constraints open the door for other players to succeed in different regions, hinting that this may be a fragmented market in the short term. Over the mid to long term, perhaps larger companies follow a growth-by-acquisition strategy, capitalising on the established science and customer bases of smaller firms while applying refined logistics expertise to drive down costs at scale.

Reducing losses from uncertainties and inefficiencies in ERW

Overcoming the MRV challenge is fundamental to building confidence in the ERW pathway and delivering on the promise of high volume at low cost. If we can’t, premiums due to losses may be too high, no matter how cheap the inputs are.

The reality is that this is going to need a lot of data, demonstrating weathering dynamics in different climates, soil types and agronomic systems. And there are still many questions to be ironed out (Robert Hoglund's latest blog highlights a few). Luckily, there’s a lot of focus on this area. Organisations like Cascade Climate, a non profit, are building models and MRV databases to empower operators in the pathway - and developers can help by sharing their data to build better models of removal. The teams at Aquatic Labs and Everest Carbon are challenging themselves to build cheap, higher confidence field sensors for mass deployment, it's early days but innovations here will certainly help manage costs.

One way the uncertainty and inefficiency losses can be reduced is by avoiding the mechanisms that cause them in the first place. Some companies we are big fans of (though these are not terrestrial enhanced rock weathering companies) are CREW Carbon and CarbonRun. CREW Carbon leverages wastewater systems, while CarbonRun adds minerals directly to rivers, both avoiding some of the upstream inefficiencies caused by soil interactions and uncertainties in bicarbonate transport through waterways. They are fundamentally different processes and opportunities, but illustrate that there are ways of leveraging weathering and using carbonate rocks in novel applications with compelling economics and value propositions.

Rock dust costs less than $10 per tonne of basalt – or less than $40 per tonne of CDR if using other rocks.

The cost of raw feedstock is critical to achieving low cost ERW. It's possible that bespoke partnerships with mining companies may be the best way to secure the low cost and high volumes necessary, and could very well be a strategic moat for many companies. But to what extent can this be replicated across regions and geographies, and can enough rock be spread quickly enough to make it worthwhile for established mining companies? Grinding energy and costs is the second part of this equation; this is a great breakdown on grinding costs and technologies, getting into the details of how to make small particles at low costs.

Using other rocks with higher removal potential could be another way to achieve better economics. Wollastonite, for example, has more than double the removal potential of basalt⁵ and so less material and energy is needed to remove the same amount of CO2, helping improve unit economics. There are likely other rocks like Wollastonite out there with good characteristics for ERW, but depending on their ubiquity, they may have limitations on scale and may really only be representative of the “short term” scenario (which is still good!).

Shortening the weathering period

Another factor to consider is the rate of weathering and the impact that has on the rate of return of a project. In our financial model we optimistically assume that basalt rock dust weathers relatively quickly and takes only 10 years, but we know that this is realistically as long or longer than 20 years⁶, which has a major impact on cost. In our model, if we increase the weathering rate from 10 to 20 years, the “long term” price must increase from ~$320 to ~$540 to maintain a 10% IRR. Going the other way, shortening the weathering period to 2-5 years instead of 10 years can reduce the price by a further 10-20%.

Faster weathering also unlocks nutrients more quickly, which could help drive farmer adoption (though it may not impact the costs of ERW deployment directly). We know that weathering happens faster in warmer climates with more rainfall. Companies like Mati, InPlanet, and Tropicarbon are leading efforts in the tropics, focusing on building farmer-first businesses where volatile prices on scarce fertilisers leave the door open for more local, affordable, and abundant options^7,8.

Shortening the weathering period could offer a couple of other benefits: 1) it would boost bicarbonate concentration, which increases the weathering signal and “MRV-ability”⁹ and 2) it may open doors to markets where slow weathering has previously been a limiting factor.

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These are just a few opportunities in ERW that we’re excited about, and we are eager to hear about other innovative approaches in the works - or something we’ve missed that you think could be helpful in growing ERW’s potential. If you’re working in this space, shoot us a note here.

Going forward with grounded optimism

At a glance, ERW appears elegant, leveraging abundant materials and limitless lands for deployment with value-add to agriculture. In reality, scaling ERW means navigating complex chemistry, challenging logistics and environmental nuances, all of which influence cost effectiveness and scale. Many of the early catalytic buyers like Milkywire and Frontier are helping advance our scientific understanding of ERW, while other large scale purchases are derisking commercial deployments. As the pathway scales, we will be keeping an eye on how the cost curve is evolving, how and where removal certainty improves, and how business models evolve to unlock more ERW.

Many thanks to Brad Rochlin and Arielle Lok (Cascade Climate), Jake Jordan (Mati Carbon) and Cara Maesano (RMI) for their thoughts and feedback for this piece.

Some important notes:

1. There are dozens of variables we could have incorporated into this analysis and which would have added considerably more complexity - e.g. removal efficiencies of different types of rocks, different grinding sizes, etc. - but generally, we felt all of those considerations could broadly be rolled into the cost buckets we’ve identified. For example, “Rock dust” is intended to allow for any combination of raw feedstock & grinding energy that gets to that price point on a per-tonne basis. We do incorporate other elements like spreading costs, but these are relatively minor in our model compared to the other variables we mention and so are not worth highlighting here.

2. We chose not to include olivine and other ultramafic rocks in the analysis. While they have higher CDR potential and can improve project economics, their heavy metal content could have negative impacts on lands and waterways when deployed at scale, and so out of an abundance of caution, we have omitted them - for now.

Key resources:

1. https://rmi.org/insight/the-applied-innovation-roadmap-for-cdr

2. https://www.cdr.fyi/blog/cdr-pricing-survey-jan-2025

3. Inefficiencies stem from bicarbonate losses in soils. Some bicarbonate produced may never make it to the ocean because a) The cations could be taken up by plants: calcium and magnesium released from rock dusts are useful nutrients for plants, and if absorbed, reduce how much bicarbonate is formed in soils. b) Other acids could inhibit CO2 uptake: if strong acids (nitric or sulphuric) are present in the soil, the calcium and magnesium. Cations may react and neutralise them, rather than CO₂, and reduce total bicarbonate formation. https://carbonplan.org/research/ew-quantification

4. Isometric

5. https://carbonherald.com/canadian-wollastonite-and-undo-partner-on-enhanced-rock-weathering/

6. Rinder and Hagke 2021

7. IFPRI Fertiliser Markets

8. Food security portal Who's afraid of high fertiliser prices?

9. https://www.silicatecarbon.com/blog-posts/research-makes-the-world-go-round