Crush rocks, spread them on farmland, remove CO₂. On paper, Enhanced Rock Weathering (ERW) is elegantly simple. Silicate minerals react with carbon dioxide in the soil, locking it away as stable carbonates that can persist for thousands of years. As a bonus, the rock dust adds nutrients like calcium and magnesium, potentially reducing the need for synthetic fertilizers.

But a new review paper in Nature Reviews Earth & Environment just mapped all the things that could complicate this story — and the list is longer than most headlines suggest.

The Promise

The numbers are genuinely exciting. A recent analysis by Carbon Credits estimates ERW could remove up to 350 million tonnes of CO₂ annually by 2050. A Cornell University study published this month modeled adoption trajectories and found that under strong uptake — particularly in the Global South — ERW could reach about a gigaton of removal per year by 2100.

That’s roughly comparable to the yearly emissions of a major industrial economy. And unlike Direct Air Capture, ERW doesn’t need massive energy inputs. The chemistry happens naturally once you spread the rock.

The Uncertainties

The Nature paper identifies several categories of concern that the CDR community needs to take seriously:

Toxic trace elements. Not all silicate rocks are clean. Some contain heavy metals like nickel, chromium, and cadmium that could accumulate in soils and enter the food chain. The composition varies enormously depending on the rock source, which means quality control at scale becomes a real challenge.

Carbon tracking from soil to ocean. ERW’s carbon accounting depends on dissolved bicarbonate eventually reaching the ocean. But the pathway from field to stream to river to sea is long and uncertain. Some of that carbon may be released back to the atmosphere along the way. Current MRV (measurement, reporting, and verification) methods struggle to track this journey with confidence.

Soil impacts. Changing soil chemistry at scale could affect microbial communities, nutrient cycling, and crop performance in ways we don’t fully understand yet. The interactions are complex and site-specific.

Scaling logistics. Mining, grinding, and distributing millions of tonnes of rock powder requires significant infrastructure. The energy and emissions from this supply chain need to be subtracted from the gross removal.

The Honest Take

None of this means ERW doesn’t work or isn’t worth pursuing. It means we’re in the messy middle — past the theoretical promise, before the scaled reality. The companies working on ERW (and there are now over $121 million invested in ERW projects globally) need to solve these problems in parallel with scaling.

The Cornell study makes another crucial point: adoption patterns matter enormously. ERW works best in warm, wet climates where weathering rates are highest. That means the Global South — particularly India and Brazil — could eventually contribute more removal than high-income early adopters. Tech transfer and carbon markets will be essential to making this happen equitably.

ERW is promising. But honest science means naming the hard parts too. That’s how we build a CDR industry that actually delivers on its promises.

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Sources

  1. Nature Reviews Earth & Environment — [Uncertainties of enhanced rock weathering for climate-change mitigation](https://www.nature.com/articles/s43017-026-00761-7) (Feb 2026)
  2. Carbon Credits — ERW Could Cut 350 Million Tonnes of CO₂ Annually by 2050 (Feb 2026)
  3. Earth.com / Cornell University — Farms covered in crushed rock could remove gigatons of carbon (Feb 2026)
  4. Beerling, D. J. et al. — Potential for large-scale CO₂ removal via enhanced rock weathering with croplands. Nature 583, 242–248 (2020)

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