Setting the Bar for Model-based Enhanced Weathering Quantification

In December 2024, Isometric issued the world's first independently certified Enhanced Weathering (EW) credits to InPlanet. Since then, we've certified EW credits for four more suppliers across six projects, marking the steady growth of the pathway from initial pilots through to commercial-scale deployments.

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EW has the potential to remove billions of tonnes of carbon dioxide from the atmosphere every year and to play a key role in reducing the impact of climate change. But as the pathway scales, one question increasingly determines whether that potential is realized. Can Monitoring, Reporting and Verification (MRV) scale alongside it?

Today's EW projects quantify removals primarily through direct measurement. Soil samples are taken across project fields, analyzed in the lab for shifts in cation chemistry, and the weathering signal is statistically separated from natural soil variability. This process works. It is also a major reason EW credits cost what they do today. 

However, the underlying problem goes deeper than cost. Soils are naturally heterogeneous, and the weathering signal a project is trying to detect is often smaller than the background variation. Detecting it reliably requires sampling densities that are feasible for pilots but become unworkable across the hundreds of thousands of hectares across which EW needs to be deployed to deliver on the pathway's gigatonne-scale removal potential.

This is why model-based approaches have been the subject of so much discussion in the EW community in recent years. Done properly, models enable projects to concentrate intensive measurement at representative monitoring sites and extrapolate across the wider deployment area. They are one of the most actively explored approaches for enabling EW to operate at a climate-relevant scale.

The phrase "done properly" matters here. Models can be opaque, and without adequate validation there is a risk that they may systematically overestimate removals in ways direct measurements would catch. Some existing EW methodologies already permit the use of models, with limited guidance on what good looks like in practice. If model-based MRV is going to be part of EW at scale, the first step is setting out clearly what rigor requires. Otherwise, deploying models without sufficient safeguards and grounding in field data could erode trust and damage the credibility of EW as a pathway.

Zeke Hausfather, Climate Research Lead at Frontier, an advance market commitment to purchase over $1 billion in permanent carbon removal by 2030, said: “Creating a path toward more model-enhanced crediting will be a key part of scaling enhanced rock weathering. But we need to ensure that path starts with the use of modeling side-by-side with current measurement-intensive approaches, and only reduce – but never eliminate – the need for representative sampling as models are proven out by real-world data. Credible models must also be transparent and open to the broader scientific community to assess and improve.”

Over the past year, Isometric's Science Team has been working through what scientifically rigorous model-based EW quantification would look like in practice. What does a model need to show before it can be used to issue credits? How should direct measurements be used to anchor the model? How do you handle the uncertainty that comes with extrapolating from monitored to unmonitored ground?

Today, we are releasing the result of this process, the Model and Measurement Based Quantification of Enhanced Weathering Module, for public consultation. The module reflects careful thinking from the Isometric Science Team and was developed with input from data scientists, geochemists, and stakeholders from across the EW ecosystem, as well as participants in our workshop at ERW 2025.

This module is being developed as an alternative quantification module under Isometric's Enhanced Weathering in Agriculture Protocol. It does not replace the existing measurement-based quantification approach, which remains available to projects. All other Protocol requirements continue to apply, including feedstock characterization, environmental safeguards, life cycle assessment, and independent verification.

A few things to be explicit about up front:

• This is a measurements and models approach. Direct field measurements remain the foundation, and models extend their reach. Projects qualify under this module by demonstrating that their model performs against real-world measurements, at project validation, and again at every reporting period. There is no route to credits that bypasses field data.
• The bar is high. The module sets requirements on training data, cross-validation, uncertainty propagation, area-of-applicability checks, and ongoing re-validation. We have yet to certify a project that meets this bar, and that is deliberate. We see this as a roadmap for where EW needs to get to.
• Proprietary models must meet the same standard. Proprietary models must pass review by an independent expert panel, covering everything from scientific basis to model code, to assess compliance with the module's requirements. The findings of each review will be made publicly available.
• Model-based quantification of EW is a nascent field. Open questions remain, and the scientific community is still building consensus on best practice. This module is a starting point that reflects current scientific understanding. We expect it to motivate further research. Isometric will update the module as the science advances.

We expect a range of responses. The 30-day public consultation exists so the ecosystem can challenge what we have drafted, share learnings, and stress-test our assumptions. The consultation is open until July 8, 2026. 

Feedback from EW suppliers, buyers, and the wider scientific community will shape the version of the module we take through to certification. As with all Isometric protocols and modules, we will publish a summary of the feedback received, and the changes made in response.

Contribute to the public consultation. For a walkthrough of its key requirements, read our companion explainer.