New research from Cornell University modelled the global adoption potential of enhanced rock weathering and landed on a striking number: 1.1 billion tonnes of CO₂ removed per year by 2100. That’s roughly 3% of current annual fossil fuel emissions — meaningful at planetary scale.

The headline is exciting. The fine print is where the real story lives.

What the Study Actually Shows

The Cornell team did something most ERW projections skip: they modelled adoption rates rather than just theoretical capacity. Using historical data on how fast farmers adopt new practices (like irrigation), they estimated a range of 350 million to 750 million tonnes per year by 2050, scaling to 700M–1.1 Gt by 2100.

They also found that the Global South — Asia, Latin America, sub-Saharan Africa — would eventually surpass Europe and North America in ERW deployment. Higher temperatures and rainfall accelerate weathering. Farmers in tropical regions could earn more per tonne of rock spread, making it economically viable earlier.

Where CDI’s Research Adds Important Nuance

This is where we put on our CDI hat. The projection numbers assume weathering rates that may be too optimistic under real field conditions, and CDI’s own research — running the world’s largest greenhouse EW experiment with 400+ lysimeters — has shown critical complexities the models don’t yet capture:

Soil pH is a gatekeeper. In soils above pH 7, carbonate mineral saturation constrains dissolution. CDI’s data shows some high-pH treatments actually lost alkalinity compared to controls. The Cornell model doesn’t account for this.

Cation retention is the elephant in the room. CDI’s flagship experiment found that in year one, 10–50× more cations were retained in soil pools than exported as alkalinity in leachate. If you’re only measuring what leaves the field, you’re missing most of the story.

Dry conditions dramatically slow things down. The Thünen Institute’s Marcus Schiedung flagged this in Nature Reviews — without rainfall, CDR can be up to 25× slower than wet-condition estimates suggest.

Carbon-based MRV has fundamental limits in field systems. CDI and collaborators have argued in Biogeosciences that cation-based MRV — not carbon flux measurement — should be the standard for ERW verification.

The Bottom Line

ERW has genuine billion-tonne potential. That hasn’t changed. But getting from “potential” to “verified removal at scale” requires solving the MRV puzzle, understanding decade-scale cation dynamics, and being honest about where our data falls short.

The Cornell study asks the right question: how fast can adoption happen? CDI’s research asks the harder one: how much of that adoption actually removes CO₂?

Both questions need answers. At least we’re finally asking them at the same time.

Sources: New Scientist · CDI: Soil Processes Govern Alkalinity & Cation Retention · CDI: Carbon vs Cation-Based MRV · Nature Reviews — Schiedung et al.

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