Reducing CO₂ emissions is crucial for mitigating climate change and its environmental impacts. A promising strategy for CO₂ reduction involves enhancing limestone dissolution in seawater by reacting it with industrial CO₂ waste gas to form dissolved bicarbonate, which prevents the CO₂ from being released into the atmosphere. This process of limestone dissolution and atmospheric CO₂ reduction occurs naturally over time-scales of 10⁵ – 10⁶ years and serves as “Earth's thermostat”. Enhancing this natural process could serve as an efficient way to remove man-made atmospheric CO₂. To adapt this process to perform at industrial scales and rates suitable for mitigating climate change it is essential to scrutinize limestone dissolution rates and assess the parameters governing this process under controlled laboratory conditions. To assess the potential of limestone dissolution rates and characterize the conditions required to maximize dissolution rates and CO₂ removal, we constructed a versatile benchtop reactor that mimics the natural limestone dissolution process and allows for experimenting with different materials and dissolution conditions. This experimental setup affords control over gas and recycled gas flow rates, as well as the mineralogy and grain size of the utilized limestones—parameters known to influence dissolution rates. The reactor is a 22 x 110 (cm) circular tube filled with a limestone medium. A continuous stream of seawater and CO₂ gas is introduced into the reactor where it reacts with the limestone. An air pump recycles CO₂ gas from the reactor head-space, in order to enhance the efficiency of CO₂ dissolution in seawater. Excess gas and seawater are removed continuously from the reactor, creating an open, through-flowing system. The system is monitored online using temperature, pCO₂ and pH meters. Total alkalinity (TA), dissolved inorganic carbon (DIC) and Calcium concentrations of the sea water in the reactor are sampled throughout the experiments and measured offline. To identify the parameters that achieve maximum limestone dissolution rates we performed experiments under different grain sizes, gas to seawater flows ratio, and recycled gas flow rate. Comparing our findings with previous studies reveals that a significant amount of limestone dissolution occurred in our system, leading to alkalinity enhancement in the sea water and removal of CO₂. In the presentation, we will discuss the effects of the different parameters on the final total dissolution rate and suggest the set of parameters that maximize the limestone dissolution rate.

How to cite: Moran, N., Goldsmith, Y., and Wurgaft, E.: Maximizing limestone dissolution rate and alkalinity enhancement in an open-system benchtop reactor , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5560, https://doi.org/10.5194/egusphere-egu24-5560, 2024.

A novel geoengineering technique aims to counteract global warming caused by anthropogenic CO₂ through artificially enhanced silicate weathering, achieved by the dissolution of olivine. Unlike other geoengineering concepts, CDR (carbon dioxide removal) techniques not only mitigate ocean acidification but also efficiently draw down atmospheric CO₂. Models predict that we can sufficiently enhance silicate weathering enough for it to be a useful CDR strategy. The models typically rely on kinetic rate constants derived from benchtop experiments conducted under conditions far from equilibrium. Hence, empirical field demonstrations are crucial to validate the effectiveness of enhanced silicate weathering. Here, we implement additional olivine (Mg₂SiO₄) fertilization in three plots with the same dimensions but various forest forms, grassland, Chinese fir, and mixed woodlands. The olivine doses were equivalent to 200 tons ha^-1 in this study. Combining monthly samplings of runoff chemistry with hourly runoff measurement, this study aims to delineate the chemical weathering flux. Preliminary findings reveal the concentration of Si⁴⁺,Mg²⁺, and Ca²⁺ within runoff at varying soil depths and forest forms. Specifically, in the Chinese fir plot, the concentration of Si⁴⁺ increased from 5.58 to 17.47 mg L^-1 within the initial three months, subsequently diminishing to 5.54 mg L^-1 after one year. Conversely, the grassland exhibited a decline from 4.20 to 2.46 mg L^-1 in the same period. For mixed woodlands, Si⁴⁺ concentration elevated from 4.16 to 10.87 mg L^-1 at three months, followed by a reduction to 5.54 mg/L after one year. The concentrations of Si⁴⁺ within the 30 to 85 cm depth exhibited minimal variation, fluctuating between 5–8 mg L^-1. The initial concentrations of Mg²⁺ for the Chinese fir, grassland and mixed woodlands were 2.70, 0.19, and 1.19 mg L^-1, escalating to 2.90, 1.76, and 2.14 mg L^-1, respectively. Correspondingly, initial Ca²⁺ concentrations were 42.87, 37.13, and 24.07 mg L^-1, increasing to 147.70, 49.40, and 45.58 mg L^-1, subsequently declining to 21.70, 7.04, and 11.78 mg L^-1. The observed trends suggest that nutrient deficiency in experimental plots prompts preferential Mg uptake by plants upon excess olivine addition, resulting in the release of Ca. These insights imply that olivine fertilization necessitates a minimum of three months and persists for at least 30 months in our case. Disparities in concentrations at different depths underscore the predominance of weathering in surface layers. While silicate weathering is more pronounced in forests compared to grasslands, excessive Mg addition may disrupt the equilibrium in plant nutrient uptake.

How to cite: Yang, C.-J., Tseng, C.-W., Wang, C.-H., Shi, X., and Tsui, C.-W.: Olivine Fertilization for Carbon Dioxide Removal: Field Demonstrations and Insights in Diverse Forest Ecosystems in a Tropical Monsoon Climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7456, https://doi.org/10.5194/egusphere-egu24-7456, 2024.

Enhanced rock weathering (ERW) is a recognized carbon dioxide removal (CDR) strategy that uses crushed silicate rock (e.g., basalt) to capture atmospheric CO₂, offering co-benefits such as improved soil health and increased crop production [1]. One of the main disadvantages of ERW includes the production of energy needed to crush and transport rocks to their application site [2]. Basalt quarries might be capable of removing CO₂ on-site by optimizing the management of their quarry fines. This approach would reduce transport-related emissions while repurposing valuable and previously underutilized material. To test this possibility, basalt and dolerite fines from Breedon’s Orrock Quarry and Tarmac’s Cairneyhill Quarry in Scotland are used as potential feedstocks for on-site CDR, respectively. These samples show initial evidence of on-site weathering as secondary minerals are present in some areas of the fines at both the quarries. Thermogravimetric analysis (TGA) on these samples corroborates field observations as 0.75% and 1.76% CO₂ were detected at Orrock and Cairneyhill, respectively. It is estimated that 10 kg CO₂/ t Orrock fines and 23 kg CO₂/ t Cairneyhill fines have been sequestered passively. Based on the CaO and MgO content, the carbonation potential is 190 kg CO₂/ t Orrock fines and 160 kg CO₂/ t Cairneyhill fines. Due to the challenge of accessing this potential under ambient conditions, it's essential to evaluate various on-site basalt management practices. To test this, ex-situ, column-based experiments were performed in the following manner. Fines from both sites were placed into columns with varying thicknesses (1 cm and 5 cm) and grain sizes (bulk and <75 μm). These columns were then subjected to ambient UK conditions (10 °C, 0.04% CO₂) in an environmental chamber and intensified carbonation conditions (50 °C, 20% CO₂) in a CO₂ incubator. Both sets of experiments were in place for three months, with monthly water addition to facilitate natural wetting and drying. Secondary precipitates were visible on the surface of bulk fines from both sites regardless of thickness or chamber conditions with mass increases up to 0.5 g by the end of experiments. Sieved Orrock fines (<75 μm) in the CO₂ incubator exhibit secondary precipitation, irrespective of sample thickness, displaying white patches on the surface and mass increases up to 1.5 g. Energy dispersive spectroscopy reveals that calcite has begun to fill in the pore spaces. Under ambient conditions, the bulk fines generally have the most significant carbon increase at greater depths, while the sieved fines show the greatest carbonation on the surface. This research has important implications for how fines are managed at quarries in the context of CO₂ sequestration and may offer new opportunities for removing CO₂ on-site at quarries.

[1] Beerling, D.J. et al., 2020. Potential for large-scale CO₂ removal via enhanced rock weathering with croplands. Nature, 583(7815): 242-+. [2] Edwards, D.P. et al., 2017. Climate change mitigation: potential benefits and pitfalls of enhanced rock weathering in tropical agriculture. Biology Letters, 13(4).

How to cite: Stubbs, A., Khudur, F., MacDonald, J., McDade, L., and Friel, M.: Potential for atmospheric carbon dioxide removal in mafic quarries via enhanced rock weathering of basalt fines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12257, https://doi.org/10.5194/egusphere-egu24-12257, 2024.

Carbon dioxide (CO₂) is the main greenhouse gas emitted by human activity, and reducing its presence in the atmosphere is one of the major challenges of the 21st century. The building and construction sector is responsible for a significant proportion of current anthropogenic CO₂ emissions. According to the “2022 Global Status Report for Building and Construction”, the sector accounted for approximately 37% of global CO₂ emissions in 2021.  Reducing the carbon footprint of building materials is a challenging task, as some process-related CO₂ emissions are unavoidable. The industry is currently developing methods to mitigate these emissions by capturing CO₂ from flue gas streams. In this study, we investigate an alternative approach to reducing the carbon footprint of building materials by incorporating olivine into building materials such as façade plaster.

In nature, CO₂ is removed from the atmosphere through silicate weathering and stored over geological time scales as carbonate minerals. Incorporating olivine powder into building materials exposes the mineral to increased weathering conditions, which is expected to accelerate the process of CO₂ sequestration. Façade plaster is advantageous because it covers large areas of building walls that are in direct contact with the atmosphere. The method is similar to the original idea of enhanced weathering, where crushed olivine is spread over large areas of land. However, the crucial distinction is that olivine-based façade plaster is a marketable product, making its implementation more appealing.

In collaboration with Knauf Gips KG, two test stands were constructed to expose olivine-containing façade plaster to natural and accelerated weathering conditions. Knauf Gips KG is a company that specialises in drywall and flooring systems, plaster, and facades, and produced the olivine-plaster used in the experiments. This plaster is exposed to ambient weathering conditions for 12 months at an outdoor test stand. Rainwater runoff is collected and analysed for dissolved species. The fluid analyses are used to identify potential ecological hazards resulting from olivine weathering, such as the release of heavy metals into the environment. In addition to the outdoor test stand, laboratory experiments are conducted to accelerate weathering by exposing the olivine-plaster to a constantly moist CO₂ atmosphere. The composition of the water and atmosphere is monitored throughout the experiment. Mineralogical and structural changes of the plaster samples are analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The extent of CO₂ mineralisation will be assessed based on mass balance calculations with the experimental reactants and their products. This contribution reports interim results from the outdoor test stand after a 6-month period and presents the results of laboratory experiments on olivine and plaster alteration.

How to cite: Irmai, A., Berndsen, M., Baese, R., and Alms, K.: Enhanced weathering in building materials: Capturing CO2 with olivine-based façade plaster, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15573, https://doi.org/10.5194/egusphere-egu24-15573, 2024.

Basalt Enhanced Weathering as a Carbon Dioxide Removal (CDR) technology accelerates natural weathering, enhancing the CO₂ removal from the atmosphere. The main objective of the ongoing field trials in Scotland and the UK is to combine geochemistry modelling with in-field measurement to most accurately quantify CO₂ sequestration. To measure the weathering signal in the field, we track changes in indicators such as soil inorganic carbon (SIC), soil organic carbon (SOC), exchangeable cations, trace/immobile elements, and soil biomass. Pore water analysis is critical for directly quantifying CO₂ sequestration. Bicarbonate in soil pore water is a  CO₂ removal indicator, as it forms through the reaction of silicate minerals with dissolved CO₂ during the initial weathering process. We analyze pore water for pH, alkalinity, Electrical Conductivity (EC), major cations, and anions. This task can be challenging due to sampling issues, the absence of rainfall, and the time-sensitive nature of alkalinity measurements. Analyses of pore water chemistry rely on the ability to separate water from solids with minimal modification of its chemistry. Rhizon samplers and ceramic lysimeters are commonly used for pore water extraction. They may not be ideal for parameters like pH and alkalinity due to certain limitations, such as degassing of dissolved gases, and biases in molecule diffusion through the membrane. In response, we are testing a centrifuge method for pore water sampling from basalt amended fields. In the initial trial, statistical significance tests were conducted to compare the pH and total alkalinity between control plot and Treatment 126 t/ha in both centrifuge and rhizon samples, revealing a statistically significant difference (p < 0.05) in values within the centrifuge samples. However, no significance was observed in the rhizon samples. We present the results of ongoing tests from different treatments and soil types conducted to investigate whether centrifuge would be a suitable method for pore water sampling and alkalinity measurement for the enhanced weathering field trials.

How to cite: Radkova, A., Liu, X., Bierowiec, T., Chen, E., Edeh, I., Frew, A., Healy, M., Jones, L., Mc Bride, A., Murphy, M., Palmer, R., Skov, K., Solpuker, U., Turner, W., de Toro Sanchez, V., Wade, P., Wardman, J., and Mann, J.: Application of an Innovative Centrifuge-Based Soil Pore Water Sampling Method in Basalt Enhanced Weathering Field Trials., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20843, https://doi.org/10.5194/egusphere-egu24-20843, 2024.

In this study, we investigate the use of milled returned concrete as an enhanced weathering soil amendment, on two arable fields in County Wexford, Ireland. The applied concrete consists of portlandite (Ca(OH)₂) cement with limestone (CaCO₃) aggregate. The high cation concentration and rapid weathering kinetics of both components indicate good potential for carbonic acid neutralisation and atmospheric CO₂ removal as soil-water dissolved bicarbonate (HCO₃^-). In spring 2023, prior to crop planting (oats and barley), both trial fields were divided into two sections. Milled returned concrete was applied to a ‘treatment’ section while no concrete was applied to a ‘control’ section. All other farming practices (ploughing, tilling, sowing and fertilisation) were equivalent across control and treatment. Twelve suction-cup lysimeters were installed in each field (6 control and 6 treatment) to collect soil-water samples across the growing season and the concentrations of bicarbonate, major cations and anions were measured to assess carbon removal. Preliminary results indicate that where nitrate (NO3^-) levels are low in concrete amended sites, bicarbonate concentrations are elevated above control. However, where soil-nitrate levels are high, weathering liberated cations are balanced by nitrate, and bicarbonate production is suppressed. Our findings highlight the importance of fertiliser management for optimising CO₂ removal outcomes of enhanced weathering.

How to cite: Magee, R., Bryson, M., Hickey, L., Chondrogiannis, C., O'Dea, K., van Acken, D., and McDermott, F.: Concrete as a soil amendment for carbon capture: learnings from year one of an enhanced weathering field trial in County Wexford, Ireland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21707, https://doi.org/10.5194/egusphere-egu24-21707, 2024.

Enhanced Mineral Weathering (EMW), a Carbon Dioxide Removal approach, is of growing interest to scientists and practitioners due to its scalability, low technological demand, and co-benefits to farmers and soil health. Enhanced Silicate Weathering (ESW) is distinguished from EMW by grinding silicate rocks (e.g., basalt) into dust and applying it across a landscape, primarily agricultural land. After application, the silicate minerals react with carbonic acid (H₂CO₃) present in rainwater and soil pore water to generate weathering products such as base cations (Ca²⁺, Mg²⁺, Na⁺), alkalinity, trace elements (Al, Fe, Mn), and clays. These weathering products are used by plants or transported from the land to surface water. These weathering products influence streamwater chemistry by increasing in-stream pH, salinity, and alkalinity, which may worsen water quality and impair aquatic ecosystem function. Previous research has described the adverse water quality impacts of increased stream pH, salinity, and alkalinity at the continental scale across North America. The sources driving this change in freshwater quality have been identified as road salt, agricultural lime, and strong acids derived from anthropogenic activities (e.g., fertilizer and acid mine drainage). We are interested in understanding how ESW deployed at large scales may contribute to ongoing changes in freshwater quality. Here, in a small agricultural watershed in Northeastern Vermont, United States, we monitor water quality pre- and post-application of basalt at high-frequency intervals at two stream locations (measuring temperature, pH, specific conductance, dissolved oxygen, chlorophyll-a, and CDOM). In addition, we collected weekly baseflow water samples and stormwater samples across 19 rain events. All water samples were measured for a suite of chemical parameters, including DOC, alkalinity, major anions, cations, trace elements, and water isotopes. We analyze this data through multiple lenses, estimating changes to water quality, describing concentration-discharge dynamics, and analyzing aquatic ecosystem response via community respiration.

How to cite: Rioux, R., Sun, F., Tatge, W., Zacharias, Q. C., Miller-Brown, W., Shanley, J. B., Planavsky, N., Raymond, P. A., and Saiers, J.: Influence of Enhanced Silicate Weathering on Streamwater Quality: A Watershed Experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-756, https://doi.org/10.5194/egusphere-egu24-756, 2024.

Applied regionally to cropland soils, enhanced silicate weathering (ESW) is advocated as a viable technology for enhancing the consumption of atmospheric CO₂, while also providing ancillary benefits to soil fertility and crop growth. However, important uncertainties remain regarding the short- and long-term effects of silicate addition on weathering rate and soil properties. To address this issue, we adapted and used the reactive transport model WITCH¹ to simulate weathering in a tropical soil (Oxisol) amended annually with 50 t ha^-1 of crushed basalt over five years. We monitored the changes in the soil chemical properties, primary and secondary mineralogy and CO₂ consumption rate over a 10-year period. The modelling results confirm that the instantaneous CO₂ consumption rate increases with basalt application. Basalt weathering increases the pH of the soil solution, from acidic to alkaline values, and releases Ca, Mg and K in solution, thus serving as a plant nutrient source. We also found that allophanes may form in the Oxisol in response to dissolution of the basalt’s glass and plagioclases. As evidenced in volcanic soils, allophanes typically exhibit a significant potential for organic carbon stabilisation. The formation of allophanes in the Oxisol treated with basalt may improve aggregation processes, water retention and hydraulic conductivity, but may decrease phosphate availability further. Our modelling study highlights that the intentional application of basalt to a tropical soil affects various soil properties significantly. The short and long-term impacts of these changes on soil functioning will need to be assessed.

¹Goddéris et al., 2006. GCA 70:1128-1147

How to cite: Glorieux, J., Goddéris, Y., Kuppel, S., and Delmelle, P.: Reactive transport modelling reveals changes in properties of tropical soils subjected to enhanced silicate weathering, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-928, https://doi.org/10.5194/egusphere-egu24-928, 2024.

Enhanced Rock Weathering (ERW) is a method for capturing carbon dioxide from the atmosphere and turning it into inorganic carbon, which is then stored in soil or oceans. While ERW is typically acclaimed for its influence on inorganic carbon cycling, its interactions with soil organic carbon (SOC) - mainly formed through biological processes like plant and microbial activity - are less explored. This study aims to investigate the impact of ERW application on SOC dynamics, particularly through modifications in microbial activity. We tested two hypotheses: (1) The change in soil pH and micro-nutrient levels by ERW amendments could boost soil microbial activity, which then accelerate breakdown of easily decomposable SOC, and 2) Higher labile SOC content could increase SOC stabilization within soil aggregates or bound to minerals, which further contribute to an increase in long lasting SOC stock by ERW. In this study, to analyze SOC dynamics under the influence of ERW, we applied olivine, a common ERW material, to soil and conducted a four-month pot experiment with alfalfa. After experiment, soil samples from each pot were analyzed using size and density fractionation to distinguish SOC into four forms: light fraction carbon (LFC), particulate organic carbon in macroaggregates (Macro_oPOC), particulate organic carbon in microaggregates (Micro_oPOC), and mineral-associated organic carbon (MAOC). Additionally, to assess microbial activity, we measured microbial biomass carbon (MBC), extracellular enzyme activities (three hydrolases and two oxidases) associated with C decomposition, and glomalin-related soil protein (GRSP), thus providing insights into microbial processes influenced by ERW. As a result, the increased soil pH and supply of minerals from ERW are expected to boost microbial activities, potentially leading to a higher rate of labile SOC decomposition. This could result in decreases in LFC and Macro_oPOC and increases in both Micro_oPOC and MAOC. This research underscores the multifaceted role of ERW in carbon management strategies, demonstrating its potential not only in mitigating climate change through inorganic carbon sequestration but also in influencing SOC sequestration.

How to cite: Park, Y. L., Hyun, J., Ok, Y., and Yoo, G.: Impact of Enhanced Rock Weathering on Soil Organic Carbon Dynamics through Microbial Activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2598, https://doi.org/10.5194/egusphere-egu24-2598, 2024.

Enhanced Rock Weathering (ERW) is emerging as a promising Carbon Dioxide Removal (CDR) strategy. While existing research predominantly measures dissolved inorganic carbon (DIC) and soil inorganic carbon (SIC) to evaluate CDR effects, the significance of plants and their influence on soil organic carbon (SOC) within the ERW process remains underexplored. Our study aims to investigate the impact of ERW amendments on SOC sequestration when applied to soils with planted vegetation. The variation in SOC sequestration due to ERW depends on factors such as the composition of ERW materials, soil conditions, and the presence of plants and microorganisms. Under these interactions, stable SOC storage for at least several decades needs to be considered a CDR effect, although the increase in plant growth may not be considered a CDR effect due to the short carbon storage time. Additionally, we propose the inclusion of non-CO₂ greenhouse gas emissions, particularly N₂O emissions resulting from microbial activity changes, in our comprehensive CDR Index. Here, we suggest a comprehensive CDR Index for ERW, encompassing direct effects on SIC and DIC, indirect impacts on SOC, and N₂O fluxes. To thoroughly investigate the CDR impact of ERW materials, we assessed the CDR Index for two distinct ERW materials: natural rock and industrial by-product silicate. Our four-month pot experiment involved control and two ERW amendments(olivine and blast furnace slag) alongside two planting scenarios(with alfalfa and without plants). We hypothesize that the CDR effect calculated using our comprehensive CDR Index will differ from that calculated using only DIC or SIC measurements. We anticipate significant increases in SIC and DIC for treatments, particularly with blast furnace slag due to its composition. In the plant-involved treatments, we anticipate both higher SIC, as plants accelerate weathering with their acidic exudates, and increased SOC, indicating improved plant growth and subsequent carbon sequestration. Variations in N₂O fluxes are also anticipated with different ERW amendments. Initial data from three weeks shows significant DIC increases with blast furnace slag and modest increases with olivine. Greater plant biomass was observed in treatments compared to control, suggesting varied biological impacts. Throughout the remaining four-month experiment, we aim to document changes in SIC, DIC, SOC, and differences in N₂O fluxes. These results are anticipated to vary based on the type of amendment and the planting options. This research is expected to underscore the significance of the biological effect in a comprehensive CDR assessment and contribute to identifying the most effective conditions for CDR with ERW when considering biological impacts. The findings are expected to guide future research and the implementation of ERW strategies, contributing to global climate change mitigation efforts.

How to cite: Ok, Y., Hyun, J., Park, Y. L., and Yoo, G.: Assessing the Impact of Enhanced Rock Weathering on Soil Biological Interactions with Comprehensive Carbon Dioxide Removal Index, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2602, https://doi.org/10.5194/egusphere-egu24-2602, 2024.

Enhanced Weathering (EW) is a promising negative emissions technology for atmospheric CO₂ removal, particularly in agricultural setups. Spreading silicate rock powder, such as basalt, over extensive agricultural lands not only sequesters CO₂ but also provides essential nutrients like K, Mg, and Fe to crops. However, the efficiency of carbon sequestration in this system varies strongly, posing a challenge to widespread adoption, particularly among stakeholders like farmers.

Climate change intensifies weather extremes, exacerbating crop drought and heat stress, with detrimental effects on production. To address these challenges, the use of Plant Growth-Promoting Rhizobacteria (PGPR), such as Bacillus subtilis, emerges as a nature-based strategy. In addition to inducing stress resistance, B. subtilis possesses Fe and P solubilizing features, potentially enhancing EW rates. Indeed, our previous study demonstrated B. subtilis efficacy in accelerating basalt weathering by increasing Ca, Mg, and Fe dissolution in bare soil.

In a maize mesocosm experiment combining B. subtilis, basalt, and water content as variables, we observed a significant impact of B. subtilis on plant biomass in treatments, while basalt showed no major effect. In treatments with reduced irrigation, plants that were amended with basalt and B. subtilis displayed elevated leaf chlorophyll levels and improved nitrogen balance compared to plants that were not amended with B. subtilis. Across both high and low watering conditions, plants amended with basalt and B. subtilis exhibited enhanced photosynthetic activity and improved stomatal regulation. These findings suggest a promising added effect of PGPR B. subtilis to basalt-based EW for efficient crop health management under varying environmental conditions. This synergy has the potential to address the challenge of variable carbon sequestration efficiency and can provide a robust basis for improving crop health under diverse settings.

How to cite: Niron, H., Steinwidder, L., Rijnders, J., Boito, L., and Vicca, S.: Exploring the Synergy of Enhanced Weathering and Rhizobacteria in Sustainable Agriculture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16303, https://doi.org/10.5194/egusphere-egu24-16303, 2024.

Weathering, the breakdown of rock into its elements, is a carbon sequestering process and a significant component of the Earth’s long-term carbon cycle. As rock is weathered, atmospheric CO₂ reacts with elements released, forming bicarbonates. These compounds are transported to the ocean where they are stored for thousands of years.

The above mechanism has garnered much attention in recent years for its use as a potential negative emissions technology to advance efforts in climate change mitigation. Enhanced weathering (EW) aims to accelerate carbon sequestering reactions of rock weathering by applying crushed rock onto vegetated surfaces. It’s also believed this practice could provide secondary benefits of improving crop yields and soil conditions. A variety of rocks, such as basalt and olivine, have been applied to different crops all over the world in an attempt to test their potential as a CO₂ removal technique and natural fertilizer.

This study aims to build upon previous attempts by employing a novel material, crushed concrete. Concrete is abundant in fast-weathering minerals such as portlandite and amorphous calcium silicates, making it an ideal candidate for EW. By harnessing the same bicarbonate forming and carbon sequestering reactions but using a waste by-product of the construction industry, the sustainability and circularity of EW technology could be further increased.

In this study, crushed concrete was applied to fields of oat (Avena sativa) and barley (Hordeum vulgare) in Co. Wexford, Ireland, during the spring growing season. Physiological (chlorophyll fluorescence and stomatal conductance) and morphological (dry mass and plant height) parameters were measured through multiple stages of the plant growth to assess the impact of concrete application on crop health and yield. Our results showed an increase in the dry mass (specifically seed dry mass) of barley, suggesting that barley may benefit from concrete application. No significant changes were observed in oat. Our results suggest that concrete does not negatively impact crop yields and could even improve yields in certain crop species.

How to cite: Chondrogiannis, C., O’Dea, K., Bryson, M., Magee, R., and McDermott, F.: Concrete application in enhanced weathering: Investigating the effect of concrete on barley and oat under field conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11274, https://doi.org/10.5194/egusphere-egu24-11274, 2024.

As part of a study of enhanced rock weathering in tropical lowland soils in an agricultural setting we are embarking on an assessment of the role of ERW in urban farming scenarios. Here, we present an evaluation of key agricultural settings in which quantification may be best achieved. In the context of Singapore, which has an ambition of domestic production of 30% of its nutritional needs by 2030, this must include urban farming. We assess development of methods for geochemical analysis of cation mobility due to weathering in urban farming substrates. We have developed a matrix of key factors in enhancing soil and likely carbon drawdown; validation and testing of existing models. Finally, we conduct assessment of implications for agricultural productivity and economic viability.

How to cite: Redfern, S., Ma, S., Zhang, Y., Ouyang, Z., and Cheng, C.-H.: Enhanced Rock Weathering and Climate Mitigation: Prospects in Urban Farming , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20871, https://doi.org/10.5194/egusphere-egu24-20871, 2024.

Terrestrial enhanced rock weathering (ERW) is a promising carbon dioxide removal technology that consists in applying ground silicate rock on agricultural soils. ERW efficiency is based on the carbon dioxide sequestration associated with the chemical weathering of silicate minerals. On top of carbon sequestration, this chemical weathering can most notably raise the soil pH and release nutrients, thereby potentially improving soil fertility. Despite these possible cobenefits, potential drawbacks such as heavy metal pollution or soil structure damage have also been raised. Yet to our knowledge, these potential effects of ERW on soil fertility have not been simultaneously investigated.

This field trial assessed the impact of ERW on biological, physical, and geochemical dimensions of soil fertility. Overall, basalt addition had a predominantly positive to neutral effect on soil fertility. The majority of soil properties showed no significant change either 1 month or 1 year post basalt application. Nevertheless, our study highlighted a significant increase in earthworm biomass, soil respiration and sodium concentration as early as 1 month post application. These changes, suggestive of rapid initial weathering processes, require further investigation before enhanced rock weathering can be considered a viable and secure carbon dioxide removal technology.

How to cite: Dupla, X., Claustre, R., Bonvin, E., Graf, I., Le Bayon, C., and Grand, S.: Assessing the biogeochemical impacts of terrestrial enhanced rock weathering on soil fertility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20481, https://doi.org/10.5194/egusphere-egu24-20481, 2024.

The emergence of land plants and their expansion across the Earth's surface has helped shape the climate of the Phanerozoic. Land plants are a major contributor to global photosynthetic biomass which in turn influences atmospheric CO₂ and O₂ levels. They also amplify continental weathering processes, which are a critical component of many global biogeochemical cycles. The inclusion of spatially-resolved vegetation within climate-biogeochemical models that predict paleo-CO₂ and O₂ levels can create a more accurate picture of the paleo-Earth [Gurung et al., in revision], however these applications have been limited by the availability of climate model simulations at high time resolution, which makes continuous spatial modelling difficult. Here, we use a new machine learning approach [Zheng et al., in revision] to build a 1-Myr climate emulator for the SCION climate-biogeochemcial model, and couple this to a deep-time vegetation model [FLORA; Gurung et al., 2022]. This allows us to re-run the plant colonisation of the land over the Paleozoic in detail and to view the global impact of changes in land occupation and productivity between early and more complex plants. By integrating simplified evolutionary and competition dynamics into the model, we can compare the effects on weathering, carbon burial and climate to help us better understand the dynamics that influence the expansion of plants and the resulting long-term Earth system changes.

Gurung et al., Climate windows of opportunity for plant expansion during the Phanerozoic Nat Comms 13 (2022)

How to cite: Gurung, K., Mills, B., and Zheng, D.: Assessing the spatial expansion of plants in an Earth System model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15291, https://doi.org/10.5194/egusphere-egu24-15291, 2024.

Using industrial solid waste to capture CO₂ by mineral carbonation is considered one of the promising technologies to prevent waste disposal while combating global anthropogenic CO₂ emissions. Especially, the carbonation reaction is spontaneous and the carbonated products are relatively stable; thus, mineral carbonation is an effective means of stabilizing CO₂ and valorizing industrial solid waste. Previous estimations report that a 4.02 Gt per year mitigation potential can be facilitated through CO₂ mineralization of industrial solid waste. However, existing estimates do not take into account the impacts of unfavorable impurities, which have broad uncertainty and variability due to different industrial processes and ore sources. The existence of certain impurities might influence the rate of the carbonation reaction and therefore, the amount of CO₂ captured and carbonates formed. For instance, some elements (e.g., Pb, Cd, and Mn in mine tailings) can enhance the CO₂ capture capacity due to the precipitation of heavy metal carbonates. While some organics (e.g., organic matter in sludge) and anions (e.g., phosphates in phosphogypsum) can influence the carbonation reactions negatively. Especially, the questionable releasing behavior of these potentially toxic elements can bring about new environmental issues when the deposited body reaches groundwater or aquifer resources. Therefore, in this work, we have attempted to clarify the roles of impurities in the mineralization process and the afterward usage period, including the accelerating or retarding effects of impurities in carbonation and the leaching behavior of potentially toxic elements. Industrial solid wastes from different sectors, such as typical mine tailings (e.g., copper mine tailings and nickel mine tailings), industrial by-products (e.g., phosphogypsum, fly ash, red mud, and coal gasification slag), and construction and demolition waste, are used for accelerated and atmospheric carbonation at ambient temperatures. Our study reveals that although mineralization and in-stu storage could turn industrial solid wastes into a global carbon mitigation sink, unfavorable impurities may curb abatement potential.

How to cite: Liu, Y., Chen, Q., Dalconi, M. C., Valentini, L., Yuan, X., Molinari, S., Wang, Y., and Artioli, G.: Role of unfavorable impurities in CO2 mineralization process of industrial solid waste: Uncertainties in decarbonization potential , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-972, https://doi.org/10.5194/egusphere-egu24-972, 2024.