Interview: Responsible MRV with Eion Cofounder & CTO Elliot Chang

Eion cofounder and CTO Elliot Chang sat down to discuss the importance of measurement, reporting, and verification (MRV) for enhanced rock weathering, and the multitude of ways that Eion is building trust in our direct measurement approach.


Q. What are the priorities of Eion’s science and innovation team?


Since 2019, we’ve focused substantial research resources into optimizing our practice of enhanced rock weathering (ERW) and generating bleeding-edge innovations that will unlock ERW at scale.

The main question we’ve honed in on pertaining to carbon dioxide removal is not if enhanced rock weathering works but rather when is CO2 removal occurring, which led us to our direct measurement approach of quantifying the extent of rock weathering as a function of time (within traditional agricultural harvest cycles).

Now, our work includes everything from honing in on soil sub-processes that impact the precision of CDR quantification, evaluating how fertilizers minimally interact with our CDR process, and how crop uptake of our weathering products needs to be accounted for in accurately reporting CDR.

We strive to be highly informed practitioners of the CDR approach and responsible stewards of the land and of the climate, and our numerous efforts on this front have yielded excellent results, allowing us to now publish white papers and peer-reviewed manuscripts.


Q. In the course of all of this research and numerous field trials on ERW, what have you learned?


First, carbon dioxide removal is difficult. The more we can do to unpack the mysteries of how to generate CDR, the better. That includes educating the public around fundamental ERW science and how we can innovate in the space to make the CDR practice easier to understand (and to verify!).

This is why Eion takes such a strong thought leadership initiative in the academic community. In July 2023, Eion researchers presented two oral presentations and one poster session pitch at the Goldschmidt Conference (the foremost annual international conference in geochemistry) in Lyon to disseminate our ERW science findings. We also co-authored a peer-reviewed publication on one of the longest running trials on ERW with researchers from the University of Illinois at Urbana-Champaign (UIUC) and the Leverhulme Center for Climate Change Mitigation.

Second, practice matters. How one executes an ERW project can impact the efficacy of the technology and the MRV results as well. For instance, choosing low potential minerals (tCO2/tOre) to amend alkaline soils will likely lead to slow weathering effects, including poor detectability using most traditional MRV schemes.


Q. How have these insights shaped Eion’s approach to MRV?


My background as a geochemical modeler has deeply informed our approach at Eion. I have spent much of my research career investigating the chemistry behind how rare trace elements, like lanthanides and actinides, move within deep layers of soil and sediment. However, despite the sophistication of current models, I couldn’t be convinced to rely on them exclusively to measure CDR for the purpose of validating carbon credits.

I wanted to truly “see” into the soil instead. In Eion’s early days, we explored inserting physical anion exchange columns directly into the soil. These would, theoretically, capture the sequestered CO2 in the form of bicarbonate aqueous species. However, the process proved too tedious and wouldn’t scale.

Then I realized: the physical device for measurement could be the soil itself.

Adding amendments like silicates to soil changes it. That’s precisely why farmers use agricultural lime—to change their soil from being acidic to being more alkaline. By identifying specific markers or “tracers” in the soil, we could observe the CDR process. We dove into researching soil’s cation exchange capacity (essentially, its ability to attract and retain positively-charged ions) and understanding how silicate rocks release immobile trace elements (ITEs) as they dissolve. These elements, which remain in the soil, became our signposts to confirm the application and weathering of the silicate rock.

Eion now uses this direct soil measurement process to detect exactly how much rock was spread on the field, and how much it weathered. This enables more accountability for the ERW process because it’s based on actual results rather than forecasts, and at the end of the day, it builds trust with buyers who want their purchases vetted by certified validation and verification bodies, such as DNV.


Q. Can you tell us more about how Eion’s direct soil measurement process works?


After our olivine material (known as CarbonLock) is applied to a field and dissolves, immobile trace elements remain in the top 15 cm of soil. By taking soil samples and measuring these ITEs, we can easily determine how much CarbonLock was added.

Using the same samples, we use what’s called an elemental mass balance equation of base cations. This is an equation focused on weathering product elements, magnesium and calcium to be specific, and the formulation is used to compute the soil’s marginal change in alkalinity.

To put it simply, we’re gauging the soil’s shift from being acidic to alkaline by measuring weathering products of silicate mineral dissolution that buffer the soil pH. As these weathering product elements move through the soil, they provide us with evidence that soil alkalinity has in fact been generated—an important, measurable artifact of the carbon dioxide removal process. So, by understanding the levels of alkalinity-inducing base cations that dissolved and flushed through the soil—while precisely constraining how much was added in the first place—we can determine the amount of carbon dioxide removal that has taken place.

Our weathering field trial and deployment results demonstrate a monotonic trend, where the fraction of rock weathered increases from 0% to ~100% through direct measurement of weathering products in our CarbonLock-amended soils. All to say, our olivine material consistently weathers without interruption and has been measured to effectively generate carbon dioxide removal that is quantifiable with relatively strong precision metrics.

So, while I still can’t take a literal measurement of the missing carbon dioxide, I can confidently quantify how much was removed in the weathering process by understanding the elements that our CarbonLock left behind and observing changes in the soil.

(Watch Elliot explain Eion’s patented approach to measuring ERW in depth>>)


Q. How is Eion working with others in the space to promote and refine ERW and MRV practices?


Eion takes CDR MRV extremely seriously, and have worked diligently with validation and verification bodies such as DNV and registries such as CarbonFuture, Isometric, and Puro to ensure the CDR we generate can be monitored following an ISO-compliant methodology and within the confines of an ICROA standard. These established certifications matter, and it is up to us as responsible CDR practitioners to deliver science-backed, auditable evidence of CDR through a rigorous MRV framework.

At the end of 2022, I felt the disparity in how practitioners of ERW were verifying their CDR process and wanted to do something that would advance scientific collaboration broadly. After meeting with numerous other ERW founders, I created the International Science-In-Industry ERW Working Group and we now meet quarterly to advance ERW science in a more unified way, which includes things like designing common field trial concepts to gain learnings through real-world practice.

We recently evolved our format to increase diversity of thought and discussion, and now each company can lead the quarterly meetings. We also now invite guests to Working Group meetings, including organizations like CarbonFuture, Isometric, and Carbon180.

At the end of the day, MRV is about accountability for the practice of ERW. We need to remove gigatons of carbon dioxide, and CDR buyers need to know they’re directly putting their money towards things that are working.


Q. Aside from MRV, are there other ERW practices that Eion’s team is working on to ensure ERW can be scaled safely?


This is where direct measurement comes in again. A true MRV entails both monitoring/reporting and CDR verification. As a supplier committed to responsibly scaling ERW, we deliver on the dual-purpose of MRV, using direct soil measurement to monitor/report on health and safety and verify CDR.

Each and every soil sample we analyze accounts for total trace elements, including nickel and chromium which are naturally present in agricultural soils and in rocks. We rely on both nickel and chromium as immobile tracers, and use them to do a safety check and provide evidence of the rock that was applied (all within agricultural time scales which are ~9 month seasons). This unlocks the elemental mass balance approach to quantifying alkalinity generation from silicate weathering.

Eion is also conservative when it comes to olivine application and recommends rates of approximately 1-2 tons per acre which is 10-20 times less than what is typically published in the academic literature.

With our recommended rate, CarbonLock meets the total acid-neutralizing capacity required to directly replace ag lime in fertile, acidic agricultural soils. Additionally—the way our process works, growers are working with their trusted crop advisors to determine whether or not our olivine material is a fit, and they’re making the best choice for the farmland’s fertility first and foremost.

At the end of the day, Eion takes responsible land stewardship seriously. We only apply enough of the rock to gently elevate the soil’s pH and are consistently in the field working to understand the impact and benefits of our process.


Q. Okay, last question. What is it like to do science at Eion?


Eion approaches science as the foundational division within the company to generate credible results of CDR. We invest heavily into our team of diverse staff (ranging from field trial specialists to soil biogeochemists) to create an efficient and collaborative R&D process. At the end of the day, my personal hope is to facilitate the development of cutting-edge innovations that will unlock ERW practice at scale.

The Technology and Innovation team, as we call ourselves, loves challenges, ranging from high-level methods to improve the efficiency and effectiveness of our CDR quantification pipeline to in-depth topics around subsurface soil biogeochemical sub-processes. Through it all, we are a dedicated and passionate crew of scientists who share a deep common vision of developing safe and scalable ERW. We also find balance with fun and high regard for emotional care, valuing that just as much as intellectual engagement and thought integration.

Ultimately, I want to instill in our team and others working in climate that we, the next generation of scientists, can truly make our world a better place by owning up to our potential and unlocking the bleeding edge of technological innovation.