Field trial on Scottish pasture estimates CO2 removal from basalt using porewater
What was demonstrated
In a field trial of about 1.5 years on grassland pasture near Stirling, Scotland, crushed basalt applied at 78 and 126 tonnes per hectare gave direct potential CO2 removal of between 0.33 and 0.53 tCO2 per hectare at 5 cm depth, relative to unamended control plots. The estimates are calculated from porewater alkalinity, with porewater sampled from 20 September 2022 to 18 April 2024. After a 22% deduction for outgassing, the range for the significant treatments was 0.257 to 0.413 tCO2 per hectare. The abstract reports figures only for the 78 and 126 tonnes per hectare treatments. The Discussion states that direct removal was between 1.1% and 1.7% of the theoretical maximum.
Why it matters
Enhanced rock weathering is proposed as a route to carbon dioxide removal, but field measurements of the removal signal are scarce. This study gives a field estimate, calculated from porewater measurements, that is small and unreplicated. The authors say it most likely represents the minimum direct removal over the measurement period.
Caveats
- Each treatment had one plot, with no replication, so the authors say the differences should be evaluated with caution.
- Porewater was sampled about every two weeks, and only when soil saturation allowed extraction. Sampling covered under 14% of the total time integrated. The authors call the estimates potential CDR and do not assess durability.
- Plant uptake was not quantified, no full life-cycle analysis was carried out, and the 78 and 126 tonnes per hectare rates are above common agricultural spreading practice and are not operationally applied to agricultural land.
Technology profiles
Sources
- peer reviewed paper
Quantifying potential carbon dioxide removal via enhanced weathering using porewater from a field trial in Scotland
Amy L. McBride, Kirstine Skov, Peter Wade et al.. Frontiers in Climate, 5 Sept 2025. DOI: 10.3389/fclim.2025.1606574.
Last reviewed 21 Oct 2026.