the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 May 2026
Enhanced weathering of glacial rock flour drives coupled inorganic and organic carbon sequestration in a five-year field experiment
Abstract. Enhanced rock weathering (ERW) has been proposed as a scalable carbon dioxide removal strategy, yet long-term field-based constraints on weathering rates and associated carbon sequestration remain limited. Here, we present a five-year field assessment of Greenlandic glacial rock flour (GRF) applied at 50 t ha-1 to a sandy agricultural soil in Denmark. Using a soil mass balance approach, we estimate that approximately 56% of the applied GRF dissolved over five years. Initial uptake of CO2 via ERW is estimated at 3.2-4.9 t CO2 ha-1 when accounting for carbonate speciation in the acidic soil solution. If downstream transport of weathering products and subsequent re-equilibration with the more alkaline marine carbonate system is assumed, the estimated long-term atmospheric CO2 removal increases to 6.39 t CO2 ha-1. In addition to inorganic carbon removal, GRF-treated plots exhibited a significant increase in soil organic carbon stocks, equivalent to the storage of an additional 18.3 t CO2 ha-1, with gains primarily associated with the mineral-associated organic matter fraction. These results demonstrate substantial weathering and carbon sequestration over five years under field conditions in a temperate climate and suggest that both inorganic and organic carbon dynamics contribute meaningfully to the overall climate impact of ERW of GRF. The findings provide rare multi-year field constraints on ERW performance and underscore the importance of robust measurements for quantifying carbon removal in agricultural systems, representing the first implementation of mass balance methods within the framework of a randomized block design.
Competing interests: Minik Thorleif Rosing is Chairman of the Board for the Rock Flour Company, a Danish Start-up company aiming at developing glacial rock flour for climate change mitigation and global food security. Christiana Dietzen acts as a scientific advisor to the company. Neither receive financial compensation for these roles, but Rosing has invested personal equity for starting the company. The Rock Flour Company has not influenced the study and has no commercial interests in the research reported here. The remaining authors have no relevant financial or non-financial interests to disclose.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2026-2760', Anonymous Referee #1, 27 Jun 2026
- AC1: 'Reply on RC1', Christiana Dietzen, 04 Aug 2026
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RC2: 'Comment on egusphere-2026-2760', Anonymous Referee #2, 23 Jul 2026
General comments:
The paper contributes new, promising findings and methodological frameworks, specifically SOMBA, to account for Enhanced rock Weathering (ERW) rate estimates. I believe this to be an exciting and significant contribution to understanding effective carbon dioxide removal strategies (CDR), given that this was one of the few long-term field studies of five years duration. It also took into consideration both organic and inorganic carbon components. The improved and reevaluated methodology adds value and validity. This looks promising for scaling of new technologies for carbon mitigation in temperate climate agricultural settings.
The methods section is very detailed and long. Given many technical components of data analyses, some ideas could be elaborated, and other sections could be shortened to reduce the length of the methods. Some table captions in the results need re-evaluation. Results can be enhanced with more visual figures. The importance of temporal data assessment of cumulative responses of dissolution and weathering rates are mentioned in different parts of the manuscript, so a figure could be added as a visual graph to demonstrate this and add a clear message in the Results.
Specific comments:
- Line 143, Section 2.4: what is ICP-OES? It wasn’t mentioned before
- Line 200, Section 2.6 (or following related sections) could use more explanation on what the different linear mixed effects model designs were. For e.g. In Line 201, name or list the metrics/ parameters for the “measured parameters”. Additionally, could show the model equations too.
- Line 275: Briefly define and fully name “pCO2”
- Line 404: Section 3.5 Results can be expanded. What important implications are construed when the C assessment results are different for "bulk carbon concentrations" vs. "SOC stocks"?
- Line 457: The language here can be made more accessible for general and interdisciplinary audience by emphasizing how “robust constrains of dissolution” is meaningful, why the different cations matter and eventually connected to weathering. If such attempts were made to explain the concept in previous sections, it can be reiterated in this discussion section for immediacy and clarity.
Technical corrections:
- Line 347: Table 3 description mentions “Ti” but is not actually listed in the table.
- Line 390: Table 5 description could state or spell out what the three different variables pH, %C and C(t/ha) exactly are in brackets.
- Line 412: “Mean SOC stocks increased from 45.3 t C ha-1 in control plots to 50.3 t C ha-1 in treated plots,”
- Consider restructuring the sentence to say that treated plots had higher mean SOC stocks than control, not that SOC increased from… to …. This makes it sounds like the control and treated plots are compared to each other as before and after
- Line 457: “these” should be replaced with “the” as it is the first sentence of a new paragraph
Citation: https://doi.org/10.5194/egusphere-2026-2760-RC2 - AC2: 'Reply on RC2', Christiana Dietzen, 04 Aug 2026
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- 1
This study evaluates enhanced rock weathering using Greenlandic glacial rock flour applied to sandy agricultural soil in Denmark over five years. The research topic is timely and of interest to the EGUsphere reader community. The work is an extension and re-evaluation of work performed previously by the authors where they used an updated SOMBA framework to estimate ERW and CDR. While I agree that that the long-term 5-year evaluation is powerful, my impression is that this manuscript could be expanded and improved. Currently, its added benefit does not meet the expectations.
General comments:
Specific comments:
Lines 51-52 – I suggest adding here the actual particle size and surface area of the GRF.
Lines 52-53 – Is there literature or other reports confirming these claims?
Line 115 – Please add the exact texture as well.
Line 125 – It would be helpful to show the particle distribution and not only report the d50.
Line 143 – Please spell out ICP-OES and add details of the instrument that was used.
Table 2 title – What is the time of sampling for Ti and mobile cations? Perhaps specify directly?
Lines 352-355 – To be clear, maybe first spell our what SD and CI represent?
Figure 1 – Missing what panels (a) and (b) are?
Lines 372-375 – The authors suddenly mention BET analysis measured over the 5-year period. There is no mention of this in the Materials and Methods, and it is unclear to me which samples exactly were measured? How were the samples prepped? Which instrument was used? Where are the results presented? This raises uncertainty as to the calculated surface-area-normalized rate of total alkalinity release.
Table 5 – The title does not describe what the Table actually presents.
Line 425-426 – Looking at the cited papers, it seems that the surface-area-normalized weathering rates reported for acidic conditions are within a wider range, including faster rates similar to those reported in this work.
Lines 535-536 – Are there studies supporting this?