Is enhanced rock weathering more useful for adaptation than mitigation?

Does enhanced rock weathering mainly remove carbon or help adapt to climate change?

The core purpose of enhanced rock weathering is carbon dioxide removal (mitigation), and the numbers are large. A UK-wide modeling study found ERW on arable croplands could deliver net CO2 removal of 6–30 MtCO2 per year by 2050, which is up to 45% of the atmospheric carbon removal the UK needs to hit net-zero [1]. Globally, applying 10 tons of basalt dust per hectare on croplands could sequester 64 GtCO2 over 75 years, and when extrapolated to all agricultural land, that rises to 217 GtCO2 [2]. These are mitigation numbers, not adaptation numbers.

Adaptation co-benefits do exist but are smaller and less certain. The same UK study found ERW can reverse soil acidification and reduce fertilizer costs by cutting nitrous oxide emissions [1]. A separate field experiment in a Welsh forest found that ERW accelerated tree growth, yielding an additional -0.34 t CO2eq ha-1 yr-1 of aboveground carbon storage, but this was more than offset by increased soil CO2 efflux, leading to a net carbon emission over four years [5]. So the adaptation benefits are real but context-dependent and often outweighed by other effects.

What are the risks that limit ERW's usefulness for adaptation?

A major concern is toxic trace element accumulation. One study found that at the suggested application rate of 40 tonnes of basalt per hectare per year, regulatory limits for copper and nickel would be exceeded after just 6 and 10 years, respectively [4]. This directly threatens long-term soil health and agricultural productivity, which are central to adaptation. The authors argue that site-specific rock selection is essential to avoid harming soil uses [4].

Another limit is that ERW's effectiveness depends heavily on climate conditions. In hot and humid environments, weathering is faster and payback periods shorter, but in cooler or drier regions, a significant fraction of applied basalt may not weather even on multidecadal timescales [2]. This means ERW is less useful as a reliable adaptation tool in many agricultural regions that are already vulnerable to climate change. Additionally, the energy penalty of grinding rocks to fine particle sizes can be justified only when CO2 supply is non-limiting, which is not always the case [3].

Does ERW work better through chemical or biological pathways for mitigation?

The mitigation potential of ERW comes from two pathways: geochemical (direct CO2 capture via mineral weathering) and biotic (enhanced plant growth from phosphorus release). A modeling study found that applying basalt to forests could triple the total carbon sequestration compared to applying it only to croplands, because forests benefit from both pathways [6]. The biotic pathway alone added significant carbon storage through increased tree growth [6].

However, field evidence shows the picture is more complicated. In a four-year reforestation experiment, the geochemical pathway removed only -0.19 t CO2eq ha-1 yr-1, while the biotic pathway (tree growth) added -0.34 t CO2eq ha-1 yr-1, but increased soil CO2 efflux released 2.54 t CO2eq ha-1 yr-1, resulting in a net carbon emission [5]. This suggests that in real ecosystems, biological responses can either amplify or undermine the mitigation benefit, and we need better understanding of plant-soil feedbacks before large-scale deployment [5].

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This answer is built on 6 peer-reviewed studies — published from 2022 to 2026, 2 from 2024 or later, 4 in Q1 journals, collectively cited 275 times — selected as the most relevant from 9 studies that passed quality screening, drawn from 36 papers retrieved from a database of over 500 million.

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