ZeroEx: Pioneering Enhanced Rock Weathering in Europe and Revolutionizing Carbon Dioxide Removal Verification Worldwide

Part of the ZeroEx team in the field during rock dust delivery (co-founder Tony Oehm, far right; co-founder Hannes Steinle, second from right) (photo from ZeroEx website).  

In the quiet agricultural landscapes of western Germany, a climate tech startup is revolutionizing the application of enhanced rock weathering (ERW) as a scalable carbon dioxide removal (CDR) solution. Founded in 2022 by Tony Oehm (CEO), Hannes Steinle (COO), and Marcel Kuhs (CTO), ZeroEx has quickly established itself as one of Europe’s leading enhanced rock weathering companies. The founders have brought together a dynamic team with complementary expertise in geoscience, software development, data science, business development, mathematics, economics, and communications. The company’s stated mission is to develop high-quality and regionally focused carbon removal projects to permanently remove greenhouse gases from the atmosphere.

Their early work has leveraged the team’s scientific expertise and German engineering precision to produce a truly innovative ERW monitoring and verification approach that is poised to revolutionize the field. However, the company is not solely focused on science and optimal engineering solutions; they also emphasize the importance of empowering farming communities by maximizing the agronomic benefits and minimizing the environmental impacts of their approach. 

“Our team is very practical in nature, so we realized that if we wanted to do something with carbon neutralization, we had to do it ourselves,” CEO Tony Oehm said in a recent interview with RTE, explaining the company’s early motivation. “Our first thought was that if we do it ourselves in some sort of pilot project, it has to be carbon removal. If it is carbon removal, it has to be permanent carbon removal. And if it’s permanent carbon removal, it should not only be targeted at carbon but also bring co-benefits and possibly something that we can scale up.”

“When we first discovered ERW, it sounded too good to be true. Because it’s a win, win, win using products from the mining industry that nobody uses economically,” Oehm went on to explain. “The farmers have a benefit from it, we can permanently lock away carbon in a very easy process, and we don’t have to invest hundreds of millions of dollars.”

However, the real synergistic spark that got ZeroEx involved in hands-on ERW work was a conversation between Oehm and a student working for the company. Oehm was researching the ERW scientific literature, and when the student understood the process, he realized it was something his family was already doing on their small agroecological farm. For over a decade, the family had been applying rock dust to the soil as a natural fertilizer. This chance interaction prompted the company’s first pilot studies.  

Enhanced Rock Weathering: Nature’s Carbon Capture System

Enhanced rock weathering accelerates a natural process that has been removing carbon from the atmosphere for billions of years. When raindrops form, they dissolve a small amount of carbon dioxide (CO₂) from air, making rainwater slightly acidic. When the rain falls and comes into contact with silicate rocks such as granite and basalt, this weak acid chemically reacts with the rock material, breaking it down and releasing mineral-bound elements such as calcium, magnesium, potassium, and phosphorus. During these reactions, the dissolved CO₂  is converted into geologically stable molecules called carbonates, the most common being bicarbonate. These molecules keep carbon in the oceans or as carbonate rocks for thousands to millions of years, thus keeping it out of the atmosphere.  

Enhanced rock weathering practitioners like ZeroEx accelerate this natural process by spreading finely crushed silicate rock onto agricultural fields. Finely crushed rock weathers much faster than pebbles and boulders, thus speeding up the CO₂-to-carbonate conversion in the soil. If the right rock types and amounts are applied, this process improves the physical and chemical properties of the soil and can have significant agronomic benefits. For instance, the weathering of common rock types like basalt releases essential macro- and micro-nutrients, including calcium, magnesium, phosphorus, zinc, and copper, into the soil. This process feeds beneficial microbial communities, enhances crop nutrient density, and boosts yields.  

One aspect of ZeroEx’s unique approach is their meticulous attention to feedstock selection and local implementation. The company has screened over 150 quarries in Germany to identify basaltic rock powders with above-average carbon removal potential (450-600 kg CO₂ per tonne of rock) while ensuring low concentrations of potentially toxic elements to comply with Germany’s strict environmental regulations. ZeroEx focuses on local deployments with field-to-quarry distances under 30 km. This minimizes transportation emissions and costs while supporting local, family-owned farms in adopting this sustainable agricultural practice.   

So, ZeroEx is not only focused on maximizing carbon removal rates. They prioritize practical, scientifically verifiable results that are environmentally and agronomically safe. They have deliberately chosen to operate within Germany’s stringent regulatory framework to create what Oehm has called “the perfect blueprint for ERW”. As Oehm explained in an interview with Quantum Commodity Intelligence, “If we can do it in this very strictly regulated setting first, then technically it’s possible to copy-paste this approach to anywhere.”

Operations and Validation

By the end of 2024, ZeroEx had spread 12,472 tonnes of rock powder across 2193 hectares of agricultural land as part of their flagship project in the Eifel region of western Germany. The company works with 12 partner farmers and has secured exclusive contracts with 10 quarries that supply byproduct rock powder with no other economic use.

In a significant milestone for the company and the ERW industry as a whole, ZeroEx’s Eifel region project (ZX-24 Vulkaneifel) became the first ERW initiative in Europe to be validated under Isometric’s ERW protocol. Isometric is a UK-based carbon standard organization that provides rigorous third-party validation for carbon removal projects, ensuring they meet strict scientific criteria for monitoring, reporting and verification (MRV). This protocol represents a crucial step for the nascent ERW CDR industry as it provides buyers with confidence that the carbon credits they purchase represent genuine, permanent carbon removal. ZeroEx expects to receive 800-1,000 CDR credits from Isometric sometime after field measurements are completed between September and October 2025.

ZeroEx has also worked with Puro.earth, another leading carbon removal crediting platform, and received a preliminary assessment confirming their approach complies with Puro’s protocol. This multi-registry strategy demonstrates ZeroEx’s commitment to transparency and scientific rigor in an industry where credibility is paramount.

Farmer Partnerships and Agronomic Benefits

At the heart of ZeroEx’s business model is a deep commitment to supporting local farming communities. The company covers 100% of the costs associated with rock powder supply and compensates farmers on a per-hectare basis for participating in their trials. This approach creates a win-win scenario where farmers receive financial benefits and improved soil health without additional costs, all while helping to save the planet from climate change.

Many of the farmers partnering with ZeroEx have owned their land for generations. The oldest of these farmers recall a time when using rock dust as fertilizer was common. In fact, the agricultural use of rock dust or steinmehl (stonemeal) in Germany dates back to at least the late 1800s (e.g., Hensel, 1894). When ZeroEx contacted farmers about their initial on-farm trials, the team encountered considerable receptivity because of the historical familiarity with steinmehl. Oehm points out that many of the farmers still want to use rock dust, but there are economic hurdles, like finding the right material for their crop and soil and transporting it. ZeroEx helps the farmers overcome these hurdles. As Oehm told RTE, using rock dust as a natural soil amendment is “deeply rooted in Europe, especially Germany and I see ERW as an enabler to bring it back.”

However, some farmers expressed reservations about the relatively high application rates, uncertainties regarding soil effects, and project timelines. In response, the ZeroEx team optimized their project schedule and developed effective methods to explain the scientific justification for their approach and potential risks. The team continues to engage with farmers beyond formal stakeholder consultation sessions by organizing quarry visits for both partner and interested farmers.    

As mentioned above, the benefits of ERW extend beyond carbon sequestration. Well-chosen rock dust naturally enriches the soil ecosystem, providing essential macronutrients and trace elements that support microbial and plant health, improve nutrient density, and increase yields. Additionally, the uptake of silicon from silicate rock weathering has been shown to improve plant resistance to diseases and pests, thus reducing the need for potentially harmful chemicals like pesticides. Also, the alkaline nature of calcium and magnesium-rich rock dust (e.g., basalt) helps lower soil acidity, reducing the need for agricultural lime.

This focus on agricultural co-benefits distinguishes ZeroEx from many other CDR approaches. Rather than competing with food production for land use, carefully planned and well-implemented ERW projects can enhance existing agricultural practices while generating additional income for farmers. This distinguishes ERW from methods such as bioenergy plant production that may require dedicated land conversion for scale-up. The potential harmonious relationship between ERW, food production, and sustainable environmental practices (e.g., lowering synthetic fertilizer and pesticide use) allow companies like ZeroEx to contribute to multiple UN Sustainable Development goals. 

Ground Breaking ERW Monitoring Reporting and Verification

One of the groundbreaking scientific and engineering innovations that emerged from ZeroEx’s early experiments and field trials is a novel device for monitoring, reporting, and verifying (MRV) carbon removal by ERW. The new device, known as a Self-Integrating Accumulation (SIA), leverages well-tested, decades-old technology that the ZeroEx team has adapted and optimized in collaboration with the inventor for ERW applications. The primary motivation for the innovation was reducing major cost barriers to ERW scale-up. 

As Oehm explained to RTE, “We can’t change the prices of fuel and we can’t change the prices of rock but what we can change is the price of MRV…wanting to do everything as rock solid as possible we wanted to develop an approach that gives us better data at cheaper cost.”

Traditional MRV methods for ERW projects are complex and expensive, requiring frequent soil and water sampling to track rock dust weathering rates. According to Oehm, MRV represents the most expensive hurdle in ERW scale-up, keeping the method from cost-leadership in CDR. Accurate CDR measurements are possible but currently represent around 60% of ERW project costs due to highly repetitive sampling schedules with high manual labor involved. ZeroEx’s novel MRV devices streamline the process and have the potential to significantly reduce costs. 

In a presentation given at the December 2024 American Geophysical Union meeting in Washington DC, ZeroEx MRV expert Dr. Gabriella Faria identified a critical gap in “affordable approaches to accurately quantify weathering rates and associated solute fluxes at the field scale.” To address this, ZeroEx researchers developed the Self-Integrating Accumulator device, which remains deployed for up to a year below the root zone in the field. This device uses a process that functions like a chemical sponge to capture and accumulate the chemical products produced by rock dust weathering. After retrieval and analysis, the SIA results enable researchers to directly calculate the amount of CO₂ removed by rock dust weathering over the deployment period.

The ongoing SIA development and verification work was the subject of a presentation at the April European Geosciences Union General Assembly 2025 in Vienna, Austria. ZeroEx MRV expert Dr. Tamara Michaelis presented results from controlled outdoor experiments (i.e., mesocosm tests) that further verify the effectiveness of the SIA devices. In the abstract, Dr. Michaelis reports that the SIAs demonstrated >90% adsorption efficiencies for the major weathering products needed to quantify carbon removal.

In addition to these controlled tests, ZeroEx has deployed over 700 SIAs in the field for their on-farm trials. For these trials, ZeroEx researchers are performing the traditional, well-established (but costly) MRV techniques alongside their novel SIA-based method. The extensive data sets will allow the research team to compare MRV methodologies and demonstrate the advantages of their novel approach. For the field testing, the devices are installed below the root zone and can remain in place during tillage, making them invisible to farmers while continuously collecting data. As Oehm confirms, “Farmers love it because farmers don’t see it.” 

The device reduces sampling efforts considerably because it accumulates key weathering products continuously and stores them internally. Thus, by retrieving a device after a year in the field, the researcher can determine the time-integrated CDR for a particular application. The SIAs can also be altered to capture the flux of potentially toxic metals such as chromium and nickel, which are present in varying levels in different types of rock dust. 

The SIA technology represents a potential breakthrough in field-scale monitoring, enabling more accurate and cost-effective quantification of CO₂ removal via ERW. Isometric has already approved the technology as a secondary measurement approach in their protocol, with the potential for it to become a primary measurement method once sufficient validation data is collected.

Global Expansion and Future Outlook

While ZeroEx is focused on perfecting their approach in Germany, they are also investigating potential international expansion into regions with wet, humid climates where ERW can achieve even higher carbon removal rates. The company has also established a pilot project on a 160-hectare plot in western Ukraine, working with the Agrarian University of Kyiv to validate ERW’s effectiveness in Europe’s most agriculturally expansive and fertile country. After finding a suitable local rock using ZeroEx best practices, Ukrainian partners initiated trials, and SIA devices were installed in November/December of 2024. Despite the desperate state of the country, Oehm notes how ZeroEx’s Ukrainian partners have shown immense resilience and dedication to testing the potential of ERW for carbon removal in their country.       

As for the longer-term future of the company, Oehm is most excited about ZeroEx’s role in the scientific and technical aspects of ERW.  As he shared with RTE: 

“We want to focus on doing–what we do best–is the scientific part…for the future we want to focus on building–I don’t know what to call it yet–MRV as a service. We want to help other people figure out the science who have the rock and the farmers.”

Conclusion

ZeroEx represents a new generation of climate tech companies, combining scientific rigor and engineering innovation with practical implementation to address the climate crisis. By accelerating a natural carbon removal process while supporting local farming communities, they have created a model that delivers multiple benefits: long-term carbon sequestration, improved soil health, increased crop yields, improved nutrient density, reductions in pesticide and synthetic fertilizer use, and economic support for rural regions.

As the world increasingly recognizes the need for gigatonne-scale carbon dioxide removal to meet climate targets, ZeroEx’s approach offers a scalable, cost-effective, and verifiable solution that works with nature rather than against it. Their commitment to transparency, scientific validation, and community engagement sets a high standard for the emerging CDR industry.

From their meticulous feedstock selection process to their innovative MRV technology, ZeroEx embodies the German engineering tradition of precision and reliability. As they expand globally, their blueprint for responsible, effective enhanced rock weathering has the potential to make a significant contribution to global carbon removal efforts while supporting sustainable agriculture worldwide.

James Jerden is an environmental scientist and science writer focused on researching and promoting sustainable solutions to urgent environmental problems. He holds a Ph.D. in geochemistry from Virginia Tech and a Master’s degree in geology from Boston College. Over the past 20 years, James has worked as a research geochemist and science educator. He joined Remineralize the Earth because of their effective advocacy, research, and partnership projects that support sustainable solutions to urgent environmental issues such as soil degradation (food security), water pollution from chemical fertilizers (water security), deforestation, and climate change. As a science writer for RTE, his goal is to bring the science and promise of soil remineralization to a broad, non-technical audience. When not writing, he can be found at his drum set.