This session invites contributions that tackle these uncertainties through theoretical and observational approaches. We particularly encourage cross-disciplinary work that explores not only the carbon removal potential of EW, but also its environmental co-benefits, possible risks, and applications in under-studied regions. By bringing together diverse perspectives, the session seeks to advance a more comprehensive understanding of EW and its role in achieving scalable and safe climate mitigation.
Orals: Tue, 5 May, 08:30–12:30 | Room 0.11/12
Using crushed rock products as a soil amendment or for enhanced plant growth is an old method and literature on this topic goes back to the early 20th century and before. However, the systematic conceptualization of terrestrial mineral reactions as a carbon capture strategy was prominently outlined in an article by Schuiling and Krijgsman (2006). Their work might be seen as a pivotal starting point for systematically discussing the method of Enhanced Weathering in the scientific literature, which was now 20 years ago. Early studies evaluated underlying principles and tried to assess the carbon dioxide removal (CDR) potential. As the research field of Enhanced Weathering became more mature, additional aspects and processes were brought into the discussion. Considering the nearly unlimited possible combinations of the application of ground rock/alkaline products to the terrestrial system – across different soil systems, located in different climates and including diverse ecosystems or agricultural systems - makes the understanding of the underlying processes and rates of matter transfer highly relevant. This includes, liberating cations from rock/alkaline material, “parking” cations in soil pools, assessing the influence of organic acids, carbonate formation, changes in soil organic carbon, transport of alkalinity or co-benefits with other CDR-methods. I will reflect on this journey, which began in the specialized domain of geology and geochemistry and has since evolved into a highly interdisciplinary research field at the intersection of agronomy, climate policy, and economics. While many aspects remain to be fully elucidated, an Enhanced Weathering CDR industry is emerging, with carbon credits already issued. Therefore, ongoing, collaborative research remains critical to refining our understanding of geochemical uncertainties and environmental co-benefits.
How to cite: Hartmann, J.: About 20 years of science on terrestrial Enhanced Weathering , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8365, https://doi.org/10.5194/egusphere-egu26-8365, 2026.
Enhanced weathering (EW) is a promising, scalable approach to carbon dioxide removal (CDR). It involves accelerating the weathering of minerals in soils to convert atmospheric CO₂ into carbonate alkalinity. Despite numerous studies, it remains unclear which soil/feedstock combinations achieve the highest alkalinity export and greatest CDR. This uncertainty remains because results strongly depend on experimental design, environmental conditions and soil/feedstock types.
We systematically investigated alkalinity formation and the fate of released or retained cations in a large-scale greenhouse experiment. Over a period of two years, we operated 10 L lysimeter mesocosms that grew English ryegrass (Lolium perenne) under controlled accelerated weathering conditions (>19 °C and > 2,000 mm irrigation per year). We tested four soil types with thirteen feedstocks and recorded alkalinity and cation export in soil water leachates monthly. For a subset of the samples, we quantified soil cation pools using sequential extractions (exchangeable, carbonate-bound, oxides and clay/silicate fractions) to determine the potential temporary reservoirs and irreversible cation sinks.
Our results show that the amount of weathering products entering the leachate varied substantially: although several treatments showed increased cumulative leachate alkalinity relative to their controls, some soil/feedstock combinations showed no change or even reduced alkalinity export, including for the same feedstock applied to different soils. Alkalinity production generally followed expected dissolution kinetics (steel slag > limestone/carbonate-rich metabasalt > peridotite > basanite). Highest leachate alkalinity export relative to control was observed in acidic soils, whereas little to no relative change observed in more neutral ~pH 7 soils could reflect suppression of mineral dissolution and carbonate saturation and precipitation. Soil cation pool distribution shifted markedly within the first year, and collectively retained 10 to 50 times more cations than exported as alkalinity. This implies that short-term 'realised' CDR as exported carbonate alkalinity can be far lower than the potential unrealised CDR that could be unlocked when cations are released from temporary soil retention pools.
A follow-up greenhouse experiment on 23 soils and 22 feedstocks was commenced in early 2025, spanning more than 300 soil/feedstock combinations. This expanded dataset will enable more robust attribution of controls on EW performance, such as soil pH/buffering capacity, mineralogy and reactive Ca–Mg supply. This setup will also allow identification of soil/feedstock combinations that maximise alkalinity generation under minimal cation retention in non-exportable pools. We will for the first time share early results from this follow-up experiment.
Our results emphasise that robust CDR quantification for EW should consider cation binding dynamics and pool transfers, as well as mineral saturation effects. Leachate-based alkalinity measurements alone provide an incomplete picture of available weathering products, particularly when rapid soil retention dominates early stage dynamics.
How to cite: Hammes, J. S., Hartmann, J., Barth, J. A. C., Linke, T., Smet, I., Hagens, M., Pogge von Strandmann, P. A. E., Reershemius, T., Casimiro, B., Vienne, A., Stoeckel, A. A., Steffens, R., Murphy, M. J., and Paessler, D.: Rock/soil interactions governing alkalinity release and cation retention in greenhouse enhanced weathering experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8083, https://doi.org/10.5194/egusphere-egu26-8083, 2026.
Enhanced rock weathering (ERW) has the potential of being a comparatively cheap carbon dioxide removal method, as most infrastructure already exists. However, questions still remain on both dissolution rates of the feedstock added to agricultural fields, as well as processes that reduce the efficiency of the CO2 drawdown reaction.
Such significant process are the soil’s cation exchange capacity (CEC) and secondary mineral formation. These take up elements from the dissolving feedstock, and retain them on timescales varying from several years (CEC) to thousands of years (secondary minerals).
In this study we have sampled 10 fields in Germany 27 months years after they were amended with Eifelgold basalt by the Carbon Drawdown Initiative. These samples, combined with pre-amendment and control samples, allow us to examine feedstock dissolution and secondary mineral formation on fields that subsequently underwent standard agricultural use. Amendment amounts vary between 12 and 48 t/ha, and the fields also have a range in cation exchange capacity and soil pH.
We use a combination of SOMBA (soil mass balance approach – i.e. cation/Ti ratios determined by isotope dilution (Suhrhoff et al., 2025)), sequential leaching of the soils to separate different secondary phases, and lithium isotope ratios. The latter are fractionated by secondary mineral formation, and provide a highly sensitive method to estimate secondary mineral neoformation (Pogge von Strandmann et al., 2025).
Based on these methods, between 25 and 45% of the feedstock dissolved during the 27 months of reaction. Of this dissolved material, on average 40% was taken into the CEC, 15% into carbonates, 4% into oxides and <10% into clays.
Thus, between 3 and >20% of the total feedstock actually remained in solution after secondary mineral formation, with an additional 3 to 16% of the total feedstock temporarily retained by cation exchange. These values align with those predicted for German climate from weathering experiments and natural basalt samples.
Pogge von Strandmann P. A. E., He X., Zhou Y. and Wilson D. J. (2025) Comparing open versus closed system weathering experiments using lithium isotopes. Applied Geochemistry 189, 106458.
Suhrhoff T. J., Reershemius T., Jordan J. S., Li S., Zhang S., Milliken E., Kalderon-Asael B., Ebert Y., Nyateka R., Thompson J. T., Reinhard C. T. and Planavsky N. J. (2025) An Updated Framework and Signal-to-Noise Analysis of Soil Mass Balance Approaches for Quantifying Enhanced Weathering on Managed Lands. Environmental Science & Technology 59, 26440-26453.
How to cite: Pogge von Strandmann, P., Hammes, J., Steffens, R., Stöckel, A. A., Smet, I., and Paessler, D.: Assessing mineral dissolution and secondary mineral formation during enhanced weathering on agricultural sites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4047, https://doi.org/10.5194/egusphere-egu26-4047, 2026.
Theobroma cacao is a cash crop that is both economically important and environmentally intensive, presenting a major sustainability challenge. In Brazil, cacao production is largely carried out by smallholder farmers on highly weathered, nutrient-poor, acidic soils (Oxisols and Ultisols). These soils have low fertility due to acidic pH, phosphorus (P), and potassium (K) levels, but high aluminium (Al) content. Enhanced rock weathering (EW) could be a pathway to access carbon financing while potentially having a ‘liming’ effect, which increases nutrient availability by raising the soil pH. However, evidence-based empirical data demonstrating the utility of EW-cacao on carbon capture and the impact of rock-dust spreading on agronomic productivity and forest ecosystem health are currently lacking.
Here we report on a field trial spanning three years that has been designed to evaluate EW deployment on cacao under field conditions. Within Brazil, specifically Bahia, cacao is often grown in a multi-strata, forest-like environment, known locally as the ‘Cabruca’ system. This system has cultural and environmental significance, often cited for its preservation of endemic trees (Cassano et al., 2008). This field trial investigates EW on both traditional and commercial agroforestry systems to determine potential synergies and additive effects. Carbon removal rates (CDR), soil fertility and agronomic co-benefits have been assessed.
Here, we present the outcome of this trial after two years of EW (basalt) application and a parallel trial assessing the potential for a novel iron chelating biotechnology to accelerate EW and CDR rates in a field setting after 9 months. We show that carbon removal can be monitored through the magnetic extraction of weathered basalt grains and their subsequent analysis. We also discuss the implications of using an iron chelator to disrupt the rock surface passivating layer for cation loss, particularly calcium. In addition, we report on important agronomic indicators, including tree height, canopy size, pest and disease incidence rate, litterfall rates and yield after two years of basalt application.
How to cite: Steeley, I., Sousa, A., França, E., Freitas, L., Martin, D., Cobbold, V., Planavsky, N., Epihov, D., and Beerling, D.: Towards Sustainable Chocolate: Two Years of Enhanced Weathering in Tropical Cacao Agri-Ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19336, https://doi.org/10.5194/egusphere-egu26-19336, 2026.
The effectiveness of enhanced rock weathering (ERW) for carbon dioxide removal (CDR) in open systems, such as forests, remains poorly quantified. Although ERW has been deployed predominantly in agricultural systems, its performance in forestry contexts remains underexplored despite its substantial mitigation potential. Forests offer the potential for both inorganic and both above- and belowground organic CDR following silicate feedstock amendment, but field-scale evidence remains limited. We report findings from a four-year ERW-reforestation experiment in South Wales, UK (11.5 ha; N = 64 plots), designed to capture ecosystem-level responses. The experiment used a fully factorial design that manipulated forest type (native broadleaf versus coniferous), feedstock amendment (amended versus unamended), and incorporated measurements of feedstock dissolution, pore water chemistry, soil CO2 efflux, soil carbon pools, and aboveground tree biomass. Inorganic CDR was detectable but small: alkalinity export from upper soil layers corresponded to -0.19 ± 0.21 t CO2eq ha-1 yr-1, with most weathering products remaining in the soil column. Organic pathways dominated cumulative system responses. Tree growth accelerated following metabasalt amendment, yielding an estimated -0.34 ± 0.07 t CO2eq ha-1 yr-1 of additional aboveground CDR. By contrast, soil CO2 efflux increased by 2.54 ± 4.04 t CO2eq ha-1 yr-1, but with substantial variability across time and space. When integrated, these fluxes produced a net ecosystem carbon emission of 2.01 ± 4.05 t CO2eq ha-1 yr-1 over the study period. Although belowground plant biomass was not directly quantified, plausible upper‑bound estimates (≈0.3–0.4 t CO₂eq ha⁻¹ yr⁻¹) do not alter the magnitude or direction of this net flux. Overall, ERW influenced CDR primarily through organic pathways, underscoring the need to better constrain plant-soil feedbacks before large-scale deployment.
How to cite: Jones, G., Lancastle, L., Clayton, K., Epihov, D. Z., Zhang, Z., Averill, C., Smith, P., Beerling, D. J., Allen, H., Nicholls, C., Paschalis, A., and Waring, B.: Ecosystem responses determine the effectiveness of enhanced rock weathering for climate mitigation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5623, https://doi.org/10.5194/egusphere-egu26-5623, 2026.
Despite growing interest in enhanced weathering (EW)—the application of silicate rock powders to croplands—substantial uncertainty remains regarding its actual CO₂ removal potential. From a data perspective, small-scale laboratory experiments often indicate limited carbon uptake, but their representativeness of field conditions remains unclear. By contrast, field experiments yield highly variable results, but they face the challenge of quantifying percolation fluxes in open, heterogeneous, dynamic systems.
Here, we present a novel hybrid approach: a large-scale yet controlled laboratory experiment designed to quantify all soil percolation fluxes and EW-driven CO₂ removal. The experiment is conducted in an approximately 200 m² garden at the Politecnico di Torino (Italy), subdivided into three hydraulically isolated plots with different basalt applications: a control plot (no basalt), 3 kg m⁻², and 6 kg m⁻². Beneath the 50 cm soil profile, all percolating fluxes are collected, enabling direct measurement of drainage outflows and dissolved-ion fluxes. Combined with soil measurements, this setup can constrain the mass balance of the weathering products and their associated CO₂ removal potential.
Preliminary results from the first year of experiment show a small but statistically significant increase (≈ 50 µS/cm) in the electrical conductivity of percolating water in both high and intermediate application plots. This is accompanied by moderate increases in major cation and dissolved inorganic carbon concentrations. Changes in hydrological response and percolating dissolved nitrogen are also observed. Overall, this study aims to provide process-based evidence of EW performance at the plot scale, thereby improving the assessment and modelling of soil-based carbon dioxide removal strategies.
How to cite: Cannizzaro, F., Bertagni, M. B., Cagninei, A., Bosio, R., Fiorucci, A., and Boano, F.: A large-scale enhanced weathering experiment to quantify soil percolation fluxes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13246, https://doi.org/10.5194/egusphere-egu26-13246, 2026.
Large-scale carbon dioxide removal (CO2) could be achieved through enhanced weathering (EW) deployment onto agricultural land and forests. Whilst the effects of EW treatment on soil and plant properties have been studied, impacts on soil gas fluxes remain poorly characterised. Soils both emit and uptake a wide range of gases, including greenhouse gases, such as nitrous oxide (N2O), methane (CH4) and CO2, as well as reactive trace gases, such as nitric oxides (NO and NO2), ammonia (NH3), hydrogen (H2) and volatile organic compounds (VOCs) which together influence climate and air quality either directly or indirectly through atmospheric reactions. EW can modify soil properties such as pH, organic carbon and structure, which can affect soil gas fluxes both directly, through physical and chemical processes, and indirectly via impacts on the soil microbiome. Therefore, characterising these responses is critical for determining potential co-benefits and trade-offs associated with large-scale EW deployment and informing monitoring, reporting and verification (MRV) frameworks.
In this laboratory study, fluxes of an extensive range of gases were measured from EW-treated soils collected from existing field trials across the UK on different land uses. Treated and control soils were sampled from arable land, grassland and newly planted mixed-broadleaf and monoculture-Sitka spruce forests. Soil fluxes of N2O, NO, NO2, NH3, carbon monoxide (CO), ozone (O3) and VOCs were measured online during controlled-temperature incubation experiments (5 to 25 °C with a step of 5 °C) using an advanced dynamic air-through chambers system equipped with high-resolution gas analysers and a proton-transfer-reaction mass spectrometer. CO2 and CH4 fluxes were measured online at room temperature using a separate gas analyser, whereas H2 fluxes were measured offline from chamber headspace samples using gas chromatography.
Overall, we found no consistent pattern of EW effects across gases and land uses. Greenhouse gas fluxes had a land-use dependence, with arable soil showing increased N2O uptake under EW treatment, CO2 emissions decreasing in both forest soils, and CH4 fluxes responding differently across sites, with increased emissions in arable soils but decreased emissions in grassland and increased uptake in broadleaf forest soils. Trace gases generally showed fewer and less systematic responses to EW, with no consistent patterns across land uses. These results suggest that land use and soil properties are important factors in determining soil gas responses to EW and highlight the need for land-use-specific monitoring strategies. Future in situ studies with in-depth soil characterisation will be essential to support robust MRV of EW and to assess potential co-benefits and risks of its large-scale implementation.
How to cite: Rees, K., Val Martin, M., Beerling, D., Bezanger, A., Cowan, N., Devlin, R., Hanlon, M., Langford, B., Medinets, S., and Drewer, J.: Effects of enhanced weathering on soil gas fluxes across UK land uses , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12483, https://doi.org/10.5194/egusphere-egu26-12483, 2026.
Rivers transport and transform products of chemical weathering, yet the processes governing carbonate precipitation, biotic transformation and fixation of enhanced rock weathering products remain poorly constrained. We conducted a controlled stream flume experiment manipulating simulated basalt-amended runoff across six ERW levels (0–100 t ha⁻¹) in groundwater- and river-fed systems to investigate calcite saturation state (Ω) dynamics and ecosystem responses to alkalinity enhancement. Water chemistry and ecosystem responses were monitored for four weeks following alkalinity addition. Across all treatments and water types, flumes were generally calcite-supersaturated (Ω > 1), indicating baseline conditions favourable for carbonate precipitation. ERW treatments substantially increased supersaturation, and high temperatures combined with low flows led to Ω frequently exceeding 10 (a proposed precipitation threshold) and reaching > 50 under high-input scenarios. Relationships between Ca, CO₃²⁻ and Ω differed between groundwater- and river-fed systems, indicating that ERW effects on saturation state were mediated not only by cation supply but also by buffering capacity and carbonate speciation. Effects on benthic communities were weak, with invertebrate richness, abundance, and biomass being largely unaffected, though community composition contracted at the highest ERW level. Microbial respiration and primary production were generally only higher in groundwater-fed systems, while leaf litter and cellulose degradation were unchanged. Overall, these results indicate minimal ecological risk and demonstrate that thermokinetic conditions in small streams can support highly supersaturated calcite states during warm, low-flow periods without immediate carbonate precipitation. However, elevated supersaturation states may reduce carbonate solubility and increase the potential for secondary precipitation under changing hydrological or thermal conditions, representing a potential constraint on ERW-derived alkalinity transport efficiency within river networks.
How to cite: Macaulay, S., Khamis, K., Mignanelli, L., and Cavan, E.: Experimental insights into the role of running waters in Enhanced Rock Weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21447, https://doi.org/10.5194/egusphere-egu26-21447, 2026.
Enhanced Weathering (EW) is increasingly discussed as a scalable carbon dioxide removal (CDR) approach, yet its real-world feasibility remains poorly constrained and is still largely inferred from modeling studies. Here we present results from an international systematic review and database effort that compiles reported CDR estimates alongside geochemical measurements and qualitative meta-data from the rapidly expanding EW literature, as well as from agronomic studies investigating silicate rock flour use as a fertilizer. Focusing on this agronomy-oriented rock flour literature, we leverage reported geochemical observations—including soil and porewater chemistry, changes in soil inorganic carbon stocks, cation exchange capacity and base saturation, and cation release from applied rock powders—to derive novel, observation-constrained estimates of EW-driven CDR. These geochemically derived estimates are integrated with reported CDR values from the broader literature to assess how deployment choices and quantification approaches influence inferred CDR rates. In addition, we systematically analyze reported agronomic responses to silicate rock flour applications, including crop yield and soil pH, to examine how agronomic performance co-varies with geochemical weathering signals and inferred CDR. Across both agronomic responses and CDR estimates, we find evidence for non-linear dose–response behavior with increasing rock application, indicating diminishing marginal benefits at higher rates in many contexts. This pattern suggests that a substantial fraction of agronomic utility and CDR may be achievable at relatively low application rates. The underlying database will be released open access to support transparent synthesis, scenario analysis, and measurement, reporting, and verification (MRV) development for EW research and applications.
How to cite: Suhrhoff, T. J. and the Enhanced Weathering Database and Meta-Analysis Team: Inferring Enhanced Weathering Carbon Dioxide Removal and agronomic impacts from agronomic studies using silicate rock flour: a systematic synthesis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8280, https://doi.org/10.5194/egusphere-egu26-8280, 2026.
Terrestrial enhanced rock weathering (ERW) is a geoengineering technique that amends soils with crushed magnesium (Mg) and calcium (Ca) rich silicate rock to accelerate carbon dioxide removal (CDR) with the production of dissolved and solid carbonates. Although ERW is projected to store large amounts of inorganic carbon, up to 2 Pg carbon (C) per year (Beerling et al., 2020), significant uncertainty surrounds ERW research, with a critical question remaining as to how ERW affects soil organic carbon (SOC), the largest terrestrial C reservoir with 1550 Pg C globally. While increases to SOC after crushed rock additions could increase the carbon removal capacity of ERW, reductions in SOC could negate its benefits. Field-scale ERW studies examining SOC dynamics, remain few. Sokol et al. (2023), found that ERW can destabilize organic carbon, making a seemingly stable pool vulnerable to decomposition. Conversely, Xu et al. (2024) reported SOC increases four to eight times higher than soil inorganic carbon (SIC) growth in oxisols after CaSiO₃ amendments. These studies highlight that the effect of ERW on SOC is influenced by soil properties. I will address this gap in knowledge by gaining a comprehensive understanding of ERW’s impact on SIC and SOC pools across ten agriculturally relevant soils in the US with unique soil properties that have been previously taken from all major US ecosystems and climate zones (Davenport, 2024). My study involves a one year incubation assessment that leverages exploration of outcomes across a broad soil gradient under a controlled environment. My findings will elucidate what conditions (i.e., soil properties, climate) will lead to the greatest mitigation impact for targeting ERW deployments.
How to cite: Rivera, M., Viatkin, K., Oldfield, E., and Lehmann, J.: The impact of enhanced rock weathering on soil organic carbon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15391, https://doi.org/10.5194/egusphere-egu26-15391, 2026.
Pyrogenic carbon capture and storage, enhanced weathering (EW), soil organic carbon (SOC) enhancement and biomass carbon capture are terrestrial carbon dioxide removal (CDR) methods that could be implemented on a short timescale. To maximize the CDR potential per area, these methods could be co-deployed and provide complementary co-benefits. This requires a substantial understanding of the ongoing reactions and interactions in the system at different scales, backed up by field data and dynamic models to estimate applicability and scalability of the method combination. Biochar and weathering of silicate rock powder have the potential to provide besides CDR also nutrients, change soil properties and affect plant growth, directly impacting soil organic carbon storage and biomass carbon capture. Nevertheless, the interactions between the amendments and their combined effects in the soil system are sparsely researched.
PyMiCCS as part of CDRterra addresses these knowledge gaps and estimates the potential of the proposed combination of the different methods. The co-application of various biochars with rock powder as well as the co-pyrolysis of both amendments was realized and products characterized. The co-pyrolysis of biochar and rock powder can modify biochar properties, such as weight, porosity, nutrient content and stability. Furthermore, the application of materials to different soil types with and without crops was tested at various spatio-temporal scales. Biochar additions improved water circulation in clayey soils, while rock powders released nutrients. Furthermore, amendments increased SOC contents, with differences between combinations and single applications. While soil nutrient levels were elevated, no significant plant growth increases were observed in comparison to single applications. In the long-term, simulations for temperate climate and sandy soil suggest that the solo-biochar applications can increase non-biochar SOC by up to 300 kg ha-1 yr-1 per ton biochar and result in net ecosystem carbon uptake over 1000 years. Complementing experimental results and process-based modeling, an integrated economic assessment was conducted using a global land-use modelling framework. The analysis shows that the environmental and mitigation outcomes of biochar-based CDR depend on interactions between costs, agronomic yield responses, biochar persistence, application rates, and assumptions about carbon pricing or crediting.
Overall, the results demonstrate that co-application of biochar and enhanced weathering can enhance soil carbon storage and nutrient dynamics, but side-specific assessments are needed, and amendments do not necessarily translate into increased crop yields. Our results highlight the substantial CDR potential and the importance of tailored evaluations, management strategies, and policy frameworks for their scalable and effective implementation.
How to cite: Linke, T., Amann, T., Ansari, M., Becker, J. N., Beer, C., Busch, F., Eschenbach, A., Hagemann, N., Hamburger, S., Kammann, C., Karstens, K., Maslouski, M., Meyer zu Drewer, J., Popp, A., Porada, P., Schmidt, H.-P., Vorrath, M.-E., Weindl, I., and Hartmann, J.: Potential of combining biochar and enhanced weathering and impacts on soil organic carbon and biomass: PyMiCCS project results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19725, https://doi.org/10.5194/egusphere-egu26-19725, 2026.
Terrestrial enhanced weathering (EW) involves the application of crushed silicate-rich rock on soil which can then sequester inorganic CO2 by forming bicarbonates and carbonates. However, more recently, the effects of EW on soil organic matter (SOM) cycling have been gaining increasingly more attention. An increase in soil pH and the release of nutrients from silicate minerals might activate microbes to decompose more SOM, thereby possibly offsetting CO2 removed via the inorganic pathway. On the other hand, EW might promote SOM stabilization mechanisms that could increase the lifetime of carbon bound in SOM and strongly boost CO2 removal by EW. There are two major pathways of SOM stabilization in soils. Firstly, EW can increase formation of mineral-associated organic matter (MAOM) by forming highly reactive secondary minerals such as (hydr)oxides and other clay-sized minerals that can chemically bind SOM. Secondly, the formation of stable aggregates can physically protect SOM from microbial decomposition. While these stabilization mechanisms could greatly elevate the potential of EW, they have received little attention compared to the inorganic CO2 removal pathway of EW. Studies that focused on SOM stabilization mechanisms by EW have been showing contrasting, possibly context-depending effects. Therefore, more experimental data is needed to unravel the complex network of interactions between EW and SOM stabilization.
Co-deployment of EW with biochar (biomass stabilized via pyrolysis) could promote the CO2 removal efficiency even further. To date, studies that combined EW with biochar application remain scarce, limiting our understanding on how the two technologies interact. Biochar application can stimulate, slow down or exhibit neutral effects on SOM decomposition. Given the potential for co-deployment of EW and biochar in agricultural soils, there is a need for understanding interactions between EW, biochar and SOM.
In a mesocosm experiment we mixed basalt and poplar wood biochar with a sandy loam soil in a full factorial design. We quantified SOM stabilized in aggregates and via mineral association after 9 and 21 months. Aggregates were separated by size via wet sieving and their carbon content was quantified via loss on ignition (4h at 550 °C). Subsequently, the smallest size fraction (<50 µm) was used to target different organo-mineral associations via sequential extractions to determine MAOM formation. Results will be shown at the conference.
How to cite: Roussard, J., Cosgrove, M., Vandecasteele, B., and Vicca, S.: Does co-deployment of enhanced weathering and biochar affect soil organic matter stabilization?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18456, https://doi.org/10.5194/egusphere-egu26-18456, 2026.
Enhanced rock weathering (ERW) is an emerging carbon dioxide removal (CDR) strategy that can support net-zero emission targets. However, current ERW modelling efforts rely on assumptions that introduce substantial variation in CDR estimates across varying ecosystems and hydroclimatic conditions. They typically ignore or oversimplify plant–soil interactions and high-frequency hydrological dynamics, obscuring short-term weathering responses and biotic feedbacks to soil moisture dynamics. Here, we introduce an integrated, process-based modelling framework, T&C-SMEW, which represents ecohydrological and ERW dynamics, along with microbially explicit biogeochemical processes. We compared framework simulations against a controlled mesocosm experiment and long-term field observations, demonstrating its ability to reproduce feedstock cation release, soil pH dynamics, gross primary production, and CO2 fluxes. T&C-SMEW reveals hydrological constraints and vegetation effects on ERW-mediated CDR by quantifying impacts on ecosystem respiration, net ecosystem exchange, and alkalinity export, emphasising the importance of ecohydrological modelling for ecosystem-level CDR estimation. These advances provide a modelling framework for identifying optimal deployment scenarios to establish ERW as a viable and operationally feasible CDR approach.
How to cite: Zhang, Z., Jones, G., Calabrese, S., Bertagni, M., Fatichi, S., Waring, B., and Paschalis, A.: An Integrated Modelling Framework to Determine Terrestrial Carbon Dioxide Removal via Enhanced Rock Weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11419, https://doi.org/10.5194/egusphere-egu26-11419, 2026.
Although enhanced weathering is a promising CDR technology, experimental evidence from the past years have tempered expectations and call for caution. These experiments show two major things: first the impact on soil organic matter (SOM) can be large and, particularly in the short term, can lead to enhanced carbon dioxide emissions rather than the hoped for carbon dioxide removal. Second, very limited (or no) leaching of alkalinity to deeper ground water is observed, and instead the cations released from weathering end up locally in different soil pools.
Advancing our understanding of this inorganic-organic (IC-OC) coupling requires the development of numerical models that couple inorganic and organic carbon cycles. Here we present the implementation of several established SOM models in the geochemical software platform PhreeqC. This well established platform has a strong track record in simulating soil water chemistry and allows for a flexible selection of a broad range of geochemical processes. We show how different models and different ways of coupling affect simulated behavior of CO2 exchange with the atmosphere and alkalinity fluxes towards ground-water, how they compare to observed data from selected experiments and elaborate on the challenges involved.
How to cite: Cox, T., Vandenhove, C., Vienne, A., Janssens, I., and Vicc, S.: Inorganic-Organic Carbon coupling in models for enhanced weathering., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22127, https://doi.org/10.5194/egusphere-egu26-22127, 2026.
Quantifying carbon dynamics during enhanced weathering has been challenging, given spatial and temporal soil heterogeneity, complex biogeochemical interactions, and limitations in measurement resolution. For example, intensive and repeated sampling campaigns over the duration of several years are required to detect changes in soil organic carbon (SOC) stocks given that a comparatively small shift needs to be detected in a large pool with high spatial heterogeneity. Thus, low signal-to-noise ratios often prevent the detection of shifts, as EW induced changes in SOC stocks are often below the natural variability of SOC. Given the high uncertainty associated with both, SOC sequestration estimates but also CO2 removal estimates, the integration of Bayesian approaches into modelling efforts could be particularly valuable. Bayesian modelling frameworks offer a powerful tool, explicitly integrating experimental observations with mechanistic understanding and prior knowledge, while quantifying uncertainty across all model components, thereby also accounting for soil heterogeneity.
In our presentation we will illustrate the advantages of Bayesian analyses via a model developed for soil CO₂ efflux partitioning (in rhizosphere respiration and SOM decomposition). Soil CO2 flux partitioning is an important tool to inform EW effects on organic C dynamics that requires a sequence of calculations and the combination of different data sources. Several sources of uncertainty arise which often remain unaccounted for in conventional partitioning approaches (e.g. the regression used during the determination of the isotopic signature of the soil CO2 efflux extrapolates far beyond measured data, isotopic fractionation due to physical and/or biological processes, CO2 originating from soil carbonates, CO2 removal due to enhanced weathering, etc.). A Bayesian model allows the integration of such diverse datasets with different structures flexibly while explicitly accounting for variability in the data and for sources of uncertainty. Given its probabilistic framework, outputs are expressed as probability distribution rather than point estimates, therefore yielding far more informative results.
Further developing this model, potential applications could include the joint assessment of organic C sequestration and inorganic CO2 removal. Thus, building on this example, we will discuss how Bayesian approaches could be further developed to support monitoring, reporting and verification (MRV) efforts for enhanced weathering.
How to cite: Steinwidder, L., Ogle, K., Boito, L., and Vicca, S.: Accounting for uncertainty in carbon fluxes: Towards the integration of Bayesian approaches in enhanced weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18487, https://doi.org/10.5194/egusphere-egu26-18487, 2026.
Carbon dioxide removal (CDR) is an essential and integral part of the European Climate Law, while the Intergovernmental Panel on Climate Change (IPCC) recognizes CDR as a “necessary element” to keep global warming well below 2°C, let alone 1.5°C. There is extensive debate in expert and policy circles about the role of CDR for achieving ambitious climate objectives. Engaging with publics around CDR technologies is crucial, however, given their broad unfamiliarity and the potential for backlash once technologies are deployed more widely (if not earlier).
Though there is an increasingly rich literature on public perceptions of CDR, several key gaps remain. First, there is a tendency to neglect those in the global South. Second, though there has been an understandable focus on climate beliefs and beliefs about science and technology, there is little consideration of the individual differences to take risks, delay outcomes, and act pro-socially (i.e. “economic preferences”). The broad importance of economic preferences has been established across various domains. As CDR becomes a more commercially viable (and less hypothetical) proposition, such economic preferences are also more likely to have meaning.
Using cross-country, nationally representative surveys in five countries (China, Germany, US, Brazil, Kenya; 4000 participants), we examine perceptions and support of CDR technologies and climate policies. Following our pre-registered hypotheses, we employ regression analysis to establish whether six types of economic preferences (risk-taking, patience, altruism, positive reciprocity, negative reciprocity, trust) predict support for three CDR technologies: direct air capture; afforestation and reforestation; enhanced rock weathering. We employ validated measures from Falk et al. (2018) as the key determinants, along with variables for climate beliefs, environmental identity, science and technology beliefs; and trust in responsible institutions. These additional variables will be examined as potential moderating factors of the relationship between economic preferences and CDR support.
How to cite: Baum, C. M., Lades, L., Fritz, L., and Sovacool, B.: Do economic preferences predict public support for different carbon dioxide removal technologies?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2563, https://doi.org/10.5194/egusphere-egu26-2563, 2026.
Posters on site: Tue, 5 May, 16:15–18:00 | Hall X3
Enhanced silicate weathering (ESW) can contribute to carbon dioxide removal (CDR) while improving acidic soils, but the interplay with fertilization remains poorly understood. We performed pot experiments with water spinach (Ipomoea aquatica) to examine how fertilizer, KNO₃ and K₂SO₄, interact with powdered olivine to affect CO₂ removal and plant growth. We estimated CO₂ uptake via extractable Mg and measured the Mg budget in our pot experiments, including: accumulated Mg in leachate, extractable Mg in soils, and Mg stored in plant tissues. Results showed that both fertilizers, KNO₃ and K₂SO₄, can accelerate Mg dissolution. The addition of 1.0 g KNO₃ with 20 g olivine could remove 1.97 t CO₂ ha⁻¹, nearly twice the amount removed by olivine alone (0.92 t CO₂ ha⁻¹) and more than K₂SO₄ (0.69 t CO₂ ha⁻¹). Compared with the control, KNO₃ increased dry biomass by 217% and Mg uptake in plants by 3.8–4.2 times, indicating that EW can also enhance vegetation uptake and lower soil acidity (pH increased from around 4.1 to 4.5). The Mg mass balance revealed that less than 2% of dissolved Mg was found in leachate, while roughly 40–54% remained in soil, about 7–13% in plant biomass, 3–5% in extractable pools, and 26–60% in residual pools that could not be explained. Our study suggests that combining powdered olivine with nitrate fertilization offers a synergistic approach to boost crop productivity, enhance CO₂ removal, and mitigate soil acidity. It is noted that the leachate measurements of Mg would not represent the short-term CO₂ removal and closure of Mg budget is not easy due to the uncertainties in soil extraction.
How to cite: Tsui, C.-W., Yang, C.-J., Huang, J.-C., and Hsu, Z.-Y.: Nitrate fertilization doubles chemical weathering and boosts crop yield in olivine-amended acidic soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-916, https://doi.org/10.5194/egusphere-egu26-916, 2026.
Enhanced Silicate Weathering (ESW) using olivine is a promising Carbon Dioxide Removal (CDR) technology, yet the influence of forest type on its efficiency remains poorly understood. This study presents results from a 897-day field experiment comparing olivine (194 t ha -1 ) dissolution across grassland, coniferous, and broadleaf forest. By coupling high-resolution runoff chemistry with vertical hydrologic monitoring, we demonstrate that vegetation type dictates carbon sequestration efficiency. Our field trial reveals that the broadleaf forest achieves the highest CDR rate of 377.24 kg ha -1 y -1, which is 2.2 times higher than the 168.10 kg ha -1 y -1 of the coniferous forest and over 10 times that of 35.29 kg ha -1 y -1 of the grassland. Owing to the broadleaf forest has 1.74 times higher belowground biomass than a coniferous forest, root-derived organic acids may contribute to mineral dissolution. Scaling these findings via a 0.05° global model, we identify tropical broadleaf forests as primeESW hotspots, capable of removing up to 3.77 t ha -1 y -1, higher than 1.16 t ha -1 y -1 of cropland.
How to cite: Shi, X., Yang, C.-J., Tseng, C.-W., and Wang, C.-H.: Forest modulation in enhanced olivine weathering: Insights fromMulti-Year Forest Trials and Global Scalability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2931, https://doi.org/10.5194/egusphere-egu26-2931, 2026.
The optimization of enhanced mineral weathering as a carbon dioxide removal technology is a topic of recent research, also for agricultural land in Europe. The combination of organic amendments with silicates is one strategy to optimize the carbon dioxide removal potential of enhanced weathering. In the C-Farms project the focus is on the added value of combining enhanced weathering through basalt or metal slags with the application of C-rich materials in agricultural soils. Co-application of inorganic (silicate rocks or metal slags) with organic (biochar, digestates or compost) amendments revealed synergistic effects whereby organic amendments may increase the rates of silicate weathering. These interaction effects are studied in soil mesocosms studies and controlled soil leaching trials.
In one of the experiments without using soil as a matrix, the direct interaction between weathering and organic C in mixtures of metal slags from stainless steel production and different carbon-rich materials was studied. Mixtures of 80% v/v carbon-rich materials and 20 % v/v metal slags were amended with mineral fertilizer, moistened and incubated for 8 weeks at 20°C. Different types of biochar were compared with other organic amendments like hydrochar, compost, manure-based hydrochar, and dried digestate. CO2 flux was measured three times per week. After the incubation period, the mixtures were analysed for chemical composition, including pH, mineral N and both organic and inorganic C content.
Negative CO2 fluxes were observed in most of the mixtures during incubation, confirming the reactivity of the stainless steel slags and their potential for carbon dioxide removal. Some organic materials had a lower biological stability, resulting in higher CO2 fluxes than for organic amendments with a higher biological stability. Although some types of manure-based organic matter had high positive CO2 fluxes due to the lower biological stability when incubated as a pure material, the combination of the unstable organic matter with metal slags resulted in negative CO2 fluxes, indicating that metal slags counteracted the CO2 emissions from the organic amendment. This may be related to the high pH and acid-buffering capacity of the metal slags, resulting in a pH of the mixture beyond the optimal pH range for biological activity.
By mixing metal slags and manure-based products with a lower biological stability and thus a higher CO2 release, the C capture as inorganic C by the metal slags may be increased. This may indicate a higher potential for enhanced weathering than when only metal slags are applied in the soil, but this should be confirmed in ongoing soil-based experiments. The added value for enhanced weathering of testing the direct interaction between pure metal slags and organic amendments will be discussed.
How to cite: Vandecasteele, B., Roussard, J., Cosgrove, M., and Vicca, S.: Interaction between enhanced weathering and sources of organic carbon: effects on reactivity of metal slags and inorganic carbon dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5913, https://doi.org/10.5194/egusphere-egu26-5913, 2026.
Enhanced Rock Weathering (ERW) holds significant potential to achieve substantial, durable carbon storage at a global scale. As ERW continues to grow as a commercially deployed carbon dioxide removal technology, there is a critical need to identify and quantitatively assess its effects on ecosystem processes beyond measures of carbon storage. Previous studies have examined the effects of ERW on soil, plants, and animals; however, few studies have explored potential effects on the water cycle. In particular, observations that the application of crushed rocks may increase plant biomass raise important questions as to whether there is a concomitant increase in plant water use, which would alter ecosystem water balance.
We compared primary productivity and evapotranspiration between control and treatment plots in two independent trials where crushed rock (basalt) was applied for enhanced rock weathering. The trials comprise 4 different crop combinations (miscanthus, maize, soybean/corn, and hay) totaling 59 plots with an average size of ~2 ha. Basalt was applied at a rate of 44.8 t ha-1in one trial and 50 t ha-1in the second trial. We used the Normalized Difference Vegetation Index (NDVI) from Sentinel-2 as one measure of productivity and estimates of gross primary productivity and evapotranspiration were obtained from NASA’s ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS).
Both trials found evidence for significant increases in grain yield in plots where crushed rock was applied, although we found no significant differences in NDVI or GPP between control and treatment plots over the course of the time series. Notably, we found no significant differences in evapotranspiration between control and treatment plots, even when specifically comparing times where peak biomass would be expected to lead to peak water use. Crops followed typical seasonal patterns of productivity and water use, indicating the utility of high-resolution satellite remote sensing for monitoring ERW.
A change in evapotranspiration associated with ERW deployment would have important implications for ecosystem water balance in these commercial agricultural systems, as well as for the water available for exporting dissolved inorganic carbon from the system. We find no evidence for a change in evapotranspiration. Our results serve as the foundation for studying how ERW may affect different parts of the terrestrial water cycle.
How to cite: Goldsmith, G. R., Chang, E., Patterson, M., Fisher, J., Jones, R., Kantola, I., Martens, J., and Shirkey, G.: Effects of Enhanced Rock Weathering (ERW) on primary productivity and evapotranspiration rates estimated via satellite remote sensing , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6619, https://doi.org/10.5194/egusphere-egu26-6619, 2026.
Silicate weathering is assumed to serve as a long-term climate stabilizing process by drawing down CO2 from the atmosphere. Weathering also has the potential to act as a negative emissions technology (enhanced weathering). A particular aspect of weathering that affects CO2 drawdown is clay formation, which hinders the sequestration of carbon. The Lithium (Li) isotope system is considered to trace silicate weathering processes and secondary mineral formation, but the exact mechanisms that control fractionation are still not fully understood, especially aspects like adsorption vs. incorporation, and the controls by secondary mineralogy. A further aspect that is currently unknown is the effect of the water-rock ratio, given that in principle, more water relative to rock should result in less supersaturation (and hence precipitation) of secondary minerals.
In this project, we present data from a series of closed batch silicate weathering experiments, conducted at different temperatures, and with different rock types and different water-rock ratios. We let basalt, granite and sandstone react with a characterized water for ~70 days under different conditions to simulate weathering of powdered silicate rocks in different climatic settings.
Our results show that the pH of the solution decreases by 0.1-0.2 for sandstone and granite, and 0.4-0.5 for basalt. At room temperature, Li concentrations in the sandstone solution linearly decrease from ~40µg/l to ~37µg/l while granite solution Li concentrations decrease from 275µg/l to 247µg/l, suggesting varying amounts of clay formation in the different experiments. At 6°C Li concentrations in the sandstone solution stay constant between 33µg/l and 36µg/l. At the same temperature the granite solution shows an increase in Li concentration from 234µg/l to 280µg/l. Different water/rock ratios provided no systematic change in pH, but element concentrations were clearly affected after ~70 days of reaction time. Lithium isotope ratios increase as secondary minerals form, with variations according to water-rock ratio and lithology. Overall, the data shows that the water-rock ratio has a significant effect on both rock dissolution and secondary mineral formation, with implications for both natural and enhanced weathering.
How to cite: Borucki, P., Weinert, A., and Pogge von Strandmann, P.: Enhanced Weathering: The effect of water-rock ratio on secondary mineral formation – evidence from lithium isotopes , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7857, https://doi.org/10.5194/egusphere-egu26-7857, 2026.
The agronomic potential of crushed silicate rock amendments has long been suggested for highly weathered, nutrient-depleted soils of the tropics. Brazil has emerged as a global leader in the use of silicate agrominerals (ASi); silicate-rich rock powders that supply plant nutrients and improve soil properties. However, despite decades of research and a unique regulatory framework for soil remineralizers, the research landscape remains fragmented, and there is currently no synthesis of tropical ASi experiments.
We synthesized results from 54 peer-reviewed Brazilian field and pot experiments using a novel classification system for ASi based on lithochemistry and practical agricultural considerations. It evaluates the effects of ASi on soils, plant growth, and nutrient uptake. Our results demonstrate that ASi can significantly improve soil pH, cation exchange capacity, and base saturation, while enhancing yield and nutrient availability. Notably, a consistent trend emerged indicating that ASi can indirectly increase soil phosphorus availability, despite low intrinsic P contents of the applied ASi.
We recommend minimum requirements for standardized methodologies and suggest real-world research designs to support broader ASi adoption. Brazil's pioneering role offers valuable insights for scaling the usage of ASi across tropical agricultural systems worldwide, contributing to sustainable food production and climate resilience.
How to cite: Swoboda, P., de Souza Martins, E., Freitas Vilela, G., Marchi, G., Ferreira, L., Augusto Posser Silveira, C., Chiapini, M., Daubermann, M., Maniero Rodrigues, M., O. Clarkson, M., Kang, J., Furey, V., A.C. Manning, D., and Larkin, C.: An assessment of the agronomic benefits of silicate rock powders in Brazil in the context of a novel classification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9606, https://doi.org/10.5194/egusphere-egu26-9606, 2026.
Harnessing the prodigious power of the Greenlandic ice sheet, glacial rock flour (GRF) is a naturally occurring ultra-fine material with a median grain size <5μm, produced by subglacial abrasion of underlying bedrock. At least 3Gt of this mineralogically uniform resource lie around Greenland’s coasts, lending it massive potential as a scalable climate solution for European agriculture. Although unreactive in Arctic conditions due to temperature and seawater chemistry, GRF’s unique particle size enables it to achieve fast weathering kinetics once transported and deployed to more temperate croplands, all without the need for energy-intensive processing. High potassium (K), moderate phosphorus (P) content and positive effects on nitrogen soil retention also place GRF as a promising low-input alternative to conventional fertilizers, easing farmer acceptance by creating a co-revenue stream to subsidise carbon dioxide removal (CDR) revenues. To unlock this potential however requires validation along the entire supply chain of GRF, from collection in Greenland to field application. This presentation summarizes nearly two years of data on GRF’s dual CDR and agronomic impacts in a Danish context. Firstly, we provide strong evidence of negligible in-situ weathering in Greenland, and explore how operational decisions, guided by robust life cycle analysis (LCA), can ensure that GRF is net-negative when applied on fields. Further downstream, we synthesize lab results and initial field trials that capture yield productivity gains and nitrogen loss reductions—while addressing the challenges of detecting statistically robust enhanced weathering signals in temperate settings. We finally highlight how insights from farmers and related service providers can be mobilized to best integrate application of GRF and similar ERW feedstocks in practical agricultural routines.
How to cite: Oldcorn, D. and Eley, C.: Greenlandic rock flour: a unique material for Europe’s agricultural transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10074, https://doi.org/10.5194/egusphere-egu26-10074, 2026.
Enhanced weathering (EW), the application of fine silicate rock powder in croplands, has emerged as a promising nature-based strategy to remove atmospheric CO2. Nonetheless, further efforts are needed to provide reliable estimates of carbon removal and to identify key locations, while accounting for the diverse factors that influence the efficiency of enhanced weathering.
In this work, we assess which European farmlands are most suitable for carbon removal via EW by combining model simulations with spatially and temporally explicit geospatial datasets. The underlying EW model is the Soil Model for Enhanced Weathering (SMEW), a biogeochemical and ecohydrological model that simulates physicochemical processes in the upper soil layers. SMEW is combined with hydroclimatic and environmental parameters from ERA5, soil characteristics from the Harmonized World Soil Database v2.0 (HWSD v2.0), and an agro-hydrological model (WaterCROP) to account for specific crop characteristics and irrigation regimes. Simulations are then run at high time resolution over decades. The results reveal which European regions may serve as hotspots for carbon removal via EW, potentially guiding future mitigation efforts across Europe.
How to cite: Thomas, R., Tuninetti, M., and Bertagni, M.: Analysis of enhanced weathering potential on European agricultural land, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12448, https://doi.org/10.5194/egusphere-egu26-12448, 2026.
The commercial scaling potential of enhanced rock weathering (ERW) as a carbon dioxide removal (CDR) strategy remains limited due to the need for reliable and cost-effective monitoring, reporting, and verification (MRV). Soil- and porewater-based MRV approaches present several challenges: soil-based mass balance methods require extensive measurements to account for loss pathways, increasing uncertainty, while water sampling relies on frequent and expensive analyses that require significant operational effort. To overcome these limitations, we evaluated the field performance of self-integrating accumulators (SIAs) – ion exchange resin-based passive samplers – as an ERW MRV tool that has the potential to increase accuracy while reducing analysis and operating costs.
For this field study SIAs were installed in summer 2024 across three agricultural fields in southern Germany and captured time-integrated fluxes of major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and anions (NO₃⁻) over one year. In total, 216 SIAs were deployed below topsoil (20 cm on grassland and 30 cm on cropland). Each field was divided into untreated control and basanite-amended plots. SIAs were deployed in sets of 12 replicates per treatment and field for two installation methods and were paired with suction lysimeters. Annual SIA-derived ion fluxes were compared against soil and porewater datasets to assess consistency and performance.
This study represents the first field-scale evaluation of SIAs as an MRV approach for ERW. On well-drained cultivated land, SIA-derived ion fluxes corresponded closely with porewater-based measurements, demonstrating their potential as scalable, time-integrative, and cost-effective tools for quantifying both cation and anion fluxes. In contrast, SIAs installed in soils that remained waterlogged for extended periods consistently overestimated fluxes. The measurement principle of the SIAs assumes vertical drainage flux, but lateral flow is possible in waterlogged soils. Under continually saturated conditions, the resins’ high adsorption efficiency (>90%) could also induce concentration gradients that enhance ion transport toward the device.
These findings highlight the importance of careful site selection for ERW and the need to assess which MRV method is most appropriate for each project location. Nevertheless, broader adoption of SIA-based MRV could significantly accelerate ERW deployment by reducing logistical and analytical requirements, lowering operational costs, and increasing the likelihood of full credit issuance without losses due to insufficient aqueous-phase sampling. Additionally, SIAs have negligible impact on farming operations, making them well-suited for large-scale agricultural deployment.
How to cite: Michaelis, T., Bell, D., Faria, G., Orenstein, P., Bisping, C., Bischoff, W.-A., Schwarz, A., McBride, A., Kelland, M., and Oehm, T.: Using Self-Integrating Accumulators (SIAs) to Monitor Enhanced Rock Weathering (ERW) in German Agricultural Fields, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13003, https://doi.org/10.5194/egusphere-egu26-13003, 2026.
Enhanced rock weathering (ERW) and algal biochar have emerged as promising carbon dioxide removal (CDR) strategies in the past decades, with ERW gaining substantial attention in recent years. However, significant knowledge gaps persist regarding the mechanisms and carbon flux pathways that determine effective CDR in terrestrial ecosystems.
To systematically trace carbon (C) fluxes and deepen the mechanistic understanding of organic-inorganic carbon (OC-IC) interactions in soils, we initiated a multi-year lysimeter experiment in very large model systems/macrocosms (5 m², 1.5 m depth) within an advanced controlled environment facility for ecosystem research (Ecotron). This setup enables quantification and verification of effective carbon sequestration by ERW and algal biochar in Mediterranean agroecosystems.
This controlled experimental framework enables continuous, high-frequency, and precise monitoring of C and nitrogen (N) fluxes comparable to natural agroecosystems, complemented by corresponding field reference sites (INRAE UE DiaScope) in Southern France. Integration of biogeochemical C and N cycling data allows assessment of ecosystem functions (e.g., microbial diversity and abundance, soil invertebrate fauna) critical for evaluating these CDR strategies prior to large-scale deployment. In addition, by coupling ecosystem-level C and N budgets with micro-scale analysis using soil fractionation and advanced spectrometry techniques, we expect to further disentangle potential mechanistic interactions between IC and OC in these Mediterranean alkaline soils.
This presentation will report preliminary results on ecosystem-scale C and N fluxes (e.g., CO2 and N2O emissions, soil physicochemical properties, and leachate at multiple depths), with implications for understanding the effectiveness and environmental impacts of ERW and algal biochar deployment in Mediterranean alkaline soils.
How to cite: Lei, K., Olanipon, D., Landais, D., Grau, A., Meunier, F., Tiouchichine, M.-L., Sauze, J., Piel, C., Abiven, S., and Milcu, A.: Quantitative and mechanistic assessment of carbon cycling of enhanced weathering and algal biochar in Mediterranean agroecosystems: An Ecotron study , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11168, https://doi.org/10.5194/egusphere-egu26-11168, 2026.
Accurate quantification of alkalinity export from the near-field zone remains a key bottleneck for monitoring, reporting, and verification (MRV) of carbon dioxide removal (CDR) through Enhanced Weathering (EW). Here we validate the Everest Pulsar, a field-deployable alkalinity sensor that accumulates total alkalinity (TA) using a weak acid ion-exchange resin and transduces resin saturation into a digital, in situ measurement. In a 7-day continuous-flow soil column experiment (10 no-soil, 5 soil units), the sensor quantitatively retained incoming alkalinity, with capture efficiencies of 98.9% (SD=0.3%) without soil and > 97.7% (SD=0.2%) with soil. Combined capture-and-recovery efficiencies were 98.8% (SD=4.1%) and at least 93.9% (SD=1.3%) for no-soil and soil units respectively. Effluent alkalinity remained well below 2% across all loading states, and mass-balance residuals averaged 0.1% (SD=4.3%) without soil and 4.0% (SD=1.3%) with soil. The digital readout closely matched chemically recovered TA with an average deviation of -0.3% (SD=6.0%). These results provide the first quantitative validation of an in situ sensor capable of measuring cumulative alkalinity export and demonstrate a practical path toward accurate, cost-effective, real-time MRV of EW carbon removal.
How to cite: Michel, P., Boysen, J., and Muth, A.: Direct In Situ Measurement of Alkalinity Export for Real-Time Enhanced Weathering MRV, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12267, https://doi.org/10.5194/egusphere-egu26-12267, 2026.
The efficacy of Carbon Dioxide Removal (CDR) methods that enhance alkalinity in natural waters is dependent on the successful transport of that alkalinity through river networks to the ocean for long-term storage. However, as alkalinity-rich water traverses these flow channels, reduction of net carbon dioxide removal can occur through several natural processes such as: abiotic or biotic carbonate mineral precipitation, CO2 outgassing from re-speciation of the carbonate system, and suppression of natural alkalinity fluxes. Existing Measurement, Reporting, and Verification (MRV) protocols recognize these losses, but lack a rigorous, standardized quantification framework across different CDR methods.
In this work, we present a unified framework for quantifying riverine and marine carbonate system losses across diverse CDR pathways, including enhanced weathering, river alkalinity enhancement (RAE), and ocean alkalinity enhancement (OAE). This framework includes applicability criteria for eligible rivers, such as the maximum transit time of the river reach and hydraulic residence time for surface-water storage. We introduce the use of a total retention factor, calculated as the product of specific retention factors from relevant riverine and marine loss processes.We outline guidance for evaluating relevance, risk and quantification for each loss term. For implementation, we provide a simple PHREEQC-based geochemical model to calculate losses from carbonate precipitation and DIC re-speciation. We also discuss standardized requirements for alternative acceptable models. .
Using scalable and standardized loss quantification calculations, we provide a transparent methodology to ensure that alkalinity-based CDR projects yield accurate quantification of durable carbon storage. It gives project developers clear direction for accounting for complex biogeochemical interactions between terrestrial discharge and the marine environment. This framework also provides the academic community with a shared, reproducible foundation for cross-study comparison and targeted research prioritization.
How to cite: Lu, X., He, J., Yin, J., and Gill, S.: From source to sink: Quantification of Riverine and Marine Carbonate System Losses for Alkalinity-Based Carbon Dioxide Removal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14755, https://doi.org/10.5194/egusphere-egu26-14755, 2026.
Enhanced rock weathering (ERW) is a carbon dioxide removal (CDR) technology that accelerates natural silicate weathering through the application of crushed silicate rocks to soils, commonly in agricultural settings. Identifying optimal feedstock application rates is essential for balancing operational feasibility with the rock densities necessary for robust monitoring, reporting, and verification (MRV). We investigated these dynamics in a mesocosm-scale trial, quantifying the weathering efficiency of crushed wollastonite skarn applied to a circumneutral (pH 7.2) sandy UK agricultural soil across a doubling application gradient: 0 (control), 5, 10, 20, 40, and 80 t/ha. The soil was selected for its sandy texture and relatively low cation exchange capacity (CEC) to maximize the potential for cation leaching. To isolate the vertical reactive transport of weathering products and characterize the progression of the alkalinity front, feedstock was incorporated solely into the uppermost (0–5 cm) soil horizon.
Mesocosms (30 cm soil depth) were sown with perennial ryegrass (Lolium perenne), maintained under a diurnal climatic cycle (25/17 °C, 60/80% RH day/night), and irrigated twice daily for three months. Our results reveal a clear, non-linear dose-response relationship; while soil pH and exchangeable Ca2+ increased significantly with application rate, we observed diminishing returns with successive doublings, particularly above 20 t/ha. This suggests that at higher application densities, weathering efficiency may be constrained by self-inhibiting geochemical feedback, including the inhibitory effect of increasing pH on proton-promoted mineral dissolution or localized pore-water saturation during the trial.
High-resolution depth profiling demonstrated considerable vertical translocation of weathering products. Although the feedstock was applied only to the top 5 cm, pH and exchangeable Ca2+ peaked in the 5–10 cm layer (immediately below the mixed zone) suggesting a strong downward alkalinity flux. However, despite the soil’s low CEC, the soil matrix acted as an effective sink, retaining the majority of the Ca2+ weathering signal within the upper 15 cm and preventing a breakthrough in leachate chemistry for any treatment. The absence of an aqueous signal was likely obscured by high leachate variability driven by heterogeneous plant uptake of water and nutrients.
We propose that cation exchange dynamics were largely governed by competitive adsorption and mineralogical signatures. The large influx of Ca2+ from feedstock mineral dissolution (e.g. calcite, wollastonite) displaced more mobile native cations, driving a dose-dependent depletion of exchangeable Mg2+ in the 0–15 cm root zone. Conversely, exchangeable Na+ increased strongly (across all depths) with application rate, suggesting that the dissolution of Na-bearing minerals (e.g. readily-soluble salts) from the skarn outweighed competitive displacement effects for this highly-mobile low-background cation. Exchangeable K+ exhibited localized depletion in the 5–15 cm horizons, possibly due to Ca2+ competition for exchange sites and increased biomass-driven nutrient demand.
These findings demonstrate that wollastonite applications can trigger a complex, non-linear reconfiguration of soil geochemistry and nutrient pools. The observed weathering signals provide essential empirical constraints for calibrating reactive transport models and refining CDR accounting frameworks for scalable ERW deployment.
How to cite: Stubbs, A., Kelland, M., Albahri, T., Cazzagon, G., Dobson, M., Healey, M., Skov, K., Tostevin, R., Turner, W., and Liu, X.: Assessing carbon dioxide removal across wollastonite application gradients in mesocosm enhanced rock weathering experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15266, https://doi.org/10.5194/egusphere-egu26-15266, 2026.
Soil degradation severely limits agricultural productivity, particularly in regions where farming is the primary source of livelihood. Enhanced weathering offers a promising and underexplored approach to restoring these degraded soils while improving their capacity to support plant growth. To evaluate this potential, we conducted a one-year mesocosm experiment in 2025 where we assessed the capacity of a newly engineered soil to support plant growth under controlled conditions. This newly engineered soil consisted of basalt combined with biochar and compost and was applied as a top layer onto a sandy soil mimicking degraded, nutrient-depleted soil. Alfalfa (Medicago sativa) successfully grew on this newly formed soil in contrast with the mesocosms where no new topsoil was added. Furthermore, the experiment investigated how key parameters, like silicate grain size (fine = 0.01-0.09mm, coarse = 1/3mm), mixing regime (mixed vs. layered) and application rate influenced plant performance. Plant performance was quantified through biomass harvests and analysis of macro- and micronutrient uptake, alongside heavy metal concentrations in plant tissue to ensure crop safety.
How to cite: Janse, S., Niron, H., and Vicca, S.: Soil restoration via enhanced weathering: insights from a mesocosm experiment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18060, https://doi.org/10.5194/egusphere-egu26-18060, 2026.
Enhanced rock weathering (ERW) has emerged as a promising strategy to remove CO₂ from the atmosphere through the application of silicate rock dust to agricultural soils. To realize its full carbon sequestration potential, however, it is crucial to understand how mineral weathering interacts with soil organic carbon dynamics. Recent experimental work indicates that these interactions can substantially influence carbon cycling and cannot be neglected.
In this study, we couple the soil organic carbon model Millennial with the geochemical model PHREEQC, which is widely used in ERW research, to explicitly represent organic–inorganic interactions during weathering. We evaluate the integrated model against data from a mesocosm experiment and use this comparison to address three key questions: (i) which organic–inorganic interactions exert the strongest control on predicted carbon sequestration, (ii) which model components require further optimization to improve simulation accuracy, and (iii) which metrics are most informative for data-model integration in ERW experiments.
Our results highlight the importance of representing coupled organic and geochemical processes when quantifying carbon sequestration by enhanced weathering and provide guidance for both future model development and experimental design.
How to cite: Vandenhove, C., Cox, T., Vienne, A., Steinwidder, L., Boita, L., and Vicca, S.: Towards Coupled Organic–Inorganic Modeling of Carbon Cycling In Enhanced Rock Weathering Soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18210, https://doi.org/10.5194/egusphere-egu26-18210, 2026.
Enhanced rock weathering (ERW) using silicate rock amendments represents a promising carbon dioxide removal (CDR) strategy, yet its viability in smallholder agriculture hinges on demonstrable agronomic co-benefits. Here we report findings from a farmer-participatory field trial conducted across smallholder cropping systems in central India, designed to quantify productivity responses and changes in input requirements following basalt application.
Basalt rock powder (particle size <2 mm) was applied at a mean application rate of 25 metric tons ha⁻¹. The study included 42 smallholder farmers managing over 200 ha of agricultural land. All plots were monitored over a full annual cycle encompassing multiple cropping seasons (Kharif and Rabi). Yield, fertiliser application rates, crop health indicators, irrigation frequency, and farmer-reported observations were recorded. Treatment effects were assessed as within-plot changes relative to farmers' baseline practices from the previous year under identical crop rotations.
Basalt-amended farms showed significantly higher crop yield relative to baseline and compared to controls (mean difference: 9%, p < 0.05). Yield gains exceeding 5% were observed in 70% of the treatment plots, with 45% showing increases > 10%. Fertiliser application rates showed a decreasing trend in 82% of basalt-treated plots, with 60% reporting reductions of ≥10%; absolute fertiliser inputs were lower in treatment plots compared to control plots. Improved crop health was reported by 63% of participating farmers, while 29% noted reduced irrigation requirements. Farmer acceptance was high, with 60.5% indicating willingness to recommend ERW adoption within their communities.
These field-scale observations suggest that ERW deployment in smallholder systems can yield agronomic benefits, alongside carbon sequestration, potentially facilitating adoption through reduced input costs and enhanced productivity, rather than relying solely on carbon finance.
Keywords: Enhanced Rock Weathering, Carbon dioxide removal, Smallholder agriculture, agronomic co-benefits.
How to cite: Kumar, S., Thorat, T., Sharma, A., and Jain, M.: Agronomic co-benefits of enhanced rock weathering in smallholder farming systems of central India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20855, https://doi.org/10.5194/egusphere-egu26-20855, 2026.
Enhanced Weathering (EW) is gaining traction as a carbon dioxide removal (CDR)
technology, yet its viable large-scale deployment requires balancing carbon sequestration
efficiency with agronomic, environmental, and economic costs and benefits. In this
study, we present the setup and preliminary insights from a mesocosm experiment
carried out at the University of Palermo (Italy), designed to compare the performance of
regional volcanic by-products against a commercial olivine benchmark. We utilized 32
outdoor mesocosms (0.27 square meters each) arranged in a randomized block design,
applying silicate amendments at a rate of 50 t/ha.
The experiment compares three silicate materials with distinct physical and mineralogical
properties: (i) basaltic mine waste from local quarrying (Dv50 of 38.7 microns), (ii) volcanic
ash from Mt. Etna—a sandy, highly porous material rich in amorphous silica with a low bulk
density—and (iii) commercial olivine (Dv50 of 30.2 microns). These materials are applied to
both bare soil and soil vegetated with a mix of local forage legumes, allowing us to assess
the role of plant roots in driving the dynamics of weathering rates and the fate of weathering
products.
We quantify the CDR potential by monitoring alkalinity, Dissolved Inorganic Carbon (DIC),
and major cations (Mg2+, Ca2+, K+, Na+) in drainage waters. Crucially, we also analyze
the soil profile to monitor the precipitation of pedogenic carbonates and changes in
exchangeable major cation pools to assess the long-term effects of the silicate
amendments.
Simultaneously, we monitor the biomass growth to identify potential fertilization benefits.
We also assess the potential trade-offs of trace element release, specifically focusing on
the high Nickel (Ni) content inherent in olivine compared to the volcanic waste streams.
Data collected will be used to calibrate the Soil Model for Enhanced Weathering (SMEW),
bridging the gap between mesocosm-scale observations and numerical simulation to
refine dissolution factors for the seasonally dry, alkaline soil conditions typical of the
Mediterranean.
Using regional volcanic waste streams can provide a cost-effective and agronomically
viable alternative to commercial minerals, delivering competitive CDR rates while
supporting a circular economy and reducing the carbon footprint of mineral sourcing,
grinding, and transport.
How to cite: Gianni, L., Ciriminna, D., Pettignano, A., Giambalvo, D., Calabrese, S., and Noto, L. V.: Comparative Assessment of Regional Volcanic By-products and Olivine for Enhanced Weathering in Mediterranean Alkaline Soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21374, https://doi.org/10.5194/egusphere-egu26-21374, 2026.
Enhanced weathering is under active consideration as a permanent carbon dioxide removal pathway, but its agronomic and biogeochemical outcomes remain insufficiently constrained under field conditions. We report a two-year field trial with four treatments: (i) basalt, (ii) control, (iii) manure, and (iv) basalt + manure, conducted on grassland in the Austrian Alps.
Soil water was sampled continuously at 40 cm depth using suction plates to capture high‑resolution dynamics in pH, alkalinity, and dissolved ion composition. Soil measurements were conducted at the start and end of the experiment. Nutritional quality of forage was analyzed after each cut. The aim of the experiment was to quantify CO2 drawdown from weathering and potential agronomic benefits in the context of typical regional farming practice.
Basalt addition did not lead to a detectable increase in alkalinity in soil water over the study period, highlighting the slow dissolution rates under temperate field conditions. However, basalt application resulted in a measurable increase in biomass production compared to the control, suggesting potential agronomic co-benefits.
We present further observed geochemical and biological responses and discuss implications for monitoring, verification, and the design of future trials.
How to cite: Rinder, T., Inselsbacher, E., Schrempf, F., Schink, M., and Bohner, A.: Insights from a Two-Year Field Trial of Enhanced Weathering with basalt on alpine grassland: Soil, Water, and Biomass Responses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21820, https://doi.org/10.5194/egusphere-egu26-21820, 2026.
