Periodic Reporting for period 1 - CORES (CO-benefits and Risks of Enhanced Silicate weathering in agriculture)
Período documentado: 2023-09-01 hasta 2025-08-31
Agricultural systems are increasingly pressured by the combined challenges of ensuring food security, maintaining soil fertility, and reducing greenhouse gas (GHG) emissions, while contributing to climate change mitigation in line with the European Green Deal and the EU’s climate neutrality target by 2050. Enhanced Silicate Weathering (ESW) has been identified as a promising negative emissions technology that could capture atmospheric CO2 while simultaneously improving soil health and nutrient availability. However, uncertainties remain regarding its effectiveness, interactions with soil microbial communities, and potential environmental risks when implemented in agricultural contexts. These uncertainties have limited the scalability of ESW and hindered its integration into European climate and agricultural strategies.
In this project, the co-benefits and potential risks of ESW in agricultural settings are investigated through two complementary experimental approaches. A first controlled experiment is designed to assess the potential of the plant growth-promoting rhizobacterium Bacillus subtilis to accelerate basalt weathering rates. Basalt, chosen as the silicate mineral of interest due to its natural abundance and wide applicability as a soil amendment, is already used in agriculture as a fertilizer. Likewise, B. subtilis is widely applied as a biofertilizer, herbicide, and fungicide, with additional functions in mobilizing essential nutrients such as iron and phosphorus. When basalt weathers, nutrients such as calcium and magnesium are gradually released; however, phosphorus and iron often precipitate and accumulate around mineral surfaces, limiting reactivity and slowing down weathering rates. It is hypothesized that the phosphate- and iron-solubilizing capacities of B. subtilis could counteract this process, thereby enhancing basalt weathering while simultaneously supplying nutrients in depleted soils. The controlled experiment is established without plants to minimize complexity, with continuous monitoring of GHG emissions and weathering products.
A second experiment is implemented in field-based mesocosms to assess the combined effects of basalt and B. subtilis on plant growth and ESW under realistic environmental conditions. Maize is selected as a model crop due to its global importance and relevance for European agricultural systems. In addition to basalt and B. subtilis amendments, water availability is introduced as a variable, as both treatments are expected to provide resilience under conditions of water stress. Although extreme rainfall prevented the full implementation of the drought treatment, the experiment is generating valuable insights into treatment performance under variable water regimes that resemble increasingly frequent climate extremes in Europe.
By integrating controlled and field-based experiments, this project is expected to provide critical evidence on whether basalt and B. subtilis can be applied in synergy to enhance ESW and agricultural productivity, while mitigating risks such as soil nutrient imbalances or unintended GHG emissions. The work will contribute to a mechanistic understanding of ESW processes in agricultural soils, thereby addressing urgent knowledge gaps highlighted by the IPCC and EU climate policy frameworks.
At scale, positive interactions between basalt and B. subtilis could accelerate CO2 removal while improving crop yields and soil fertility, thus directly contributing to multiple EU priorities, including the Farm to Fork Strategy, the EU Soil Strategy for 2030, and the Climate Law. If confirmed, the approach would support the deployment of sustainable carbon dioxide removal methods in agriculture, offering co-benefits that go beyond climate mitigation by enhancing resilience in food production systems. The results are therefore expected to inform policy development, agricultural practice, and future large-scale ESW deployment in Europe and beyond.
In this project, the co-benefits and potential risks of ESW in agricultural settings are investigated through two complementary experimental approaches. A first controlled experiment is designed to assess the potential of the plant growth-promoting rhizobacterium Bacillus subtilis to accelerate basalt weathering rates. Basalt, chosen as the silicate mineral of interest due to its natural abundance and wide applicability as a soil amendment, is already used in agriculture as a fertilizer. Likewise, B. subtilis is widely applied as a biofertilizer, herbicide, and fungicide, with additional functions in mobilizing essential nutrients such as iron and phosphorus. When basalt weathers, nutrients such as calcium and magnesium are gradually released; however, phosphorus and iron often precipitate and accumulate around mineral surfaces, limiting reactivity and slowing down weathering rates. It is hypothesized that the phosphate- and iron-solubilizing capacities of B. subtilis could counteract this process, thereby enhancing basalt weathering while simultaneously supplying nutrients in depleted soils. The controlled experiment is established without plants to minimize complexity, with continuous monitoring of GHG emissions and weathering products.
A second experiment is implemented in field-based mesocosms to assess the combined effects of basalt and B. subtilis on plant growth and ESW under realistic environmental conditions. Maize is selected as a model crop due to its global importance and relevance for European agricultural systems. In addition to basalt and B. subtilis amendments, water availability is introduced as a variable, as both treatments are expected to provide resilience under conditions of water stress. Although extreme rainfall prevented the full implementation of the drought treatment, the experiment is generating valuable insights into treatment performance under variable water regimes that resemble increasingly frequent climate extremes in Europe.
By integrating controlled and field-based experiments, this project is expected to provide critical evidence on whether basalt and B. subtilis can be applied in synergy to enhance ESW and agricultural productivity, while mitigating risks such as soil nutrient imbalances or unintended GHG emissions. The work will contribute to a mechanistic understanding of ESW processes in agricultural soils, thereby addressing urgent knowledge gaps highlighted by the IPCC and EU climate policy frameworks.
At scale, positive interactions between basalt and B. subtilis could accelerate CO2 removal while improving crop yields and soil fertility, thus directly contributing to multiple EU priorities, including the Farm to Fork Strategy, the EU Soil Strategy for 2030, and the Climate Law. If confirmed, the approach would support the deployment of sustainable carbon dioxide removal methods in agriculture, offering co-benefits that go beyond climate mitigation by enhancing resilience in food production systems. The results are therefore expected to inform policy development, agricultural practice, and future large-scale ESW deployment in Europe and beyond.
During the fellowship, two major Enhanced Silicate Weathering (ESW) experiments were carried out, complemented by contributions to a long-term mesocosm study.
The first major experiment was a plant-free mesocosm study under controlled conditions, designed to assess the carbon sequestration potential of basalt weathering and the influence of the rhizobacterium Bacillus subtilis. Results showed that basalt weathering provided only limited potential for inorganic carbon sequestration, mainly due to restricted downward transfer of weathering products within the soil profile. Although B. subtilis accelerated basalt dissolution, this did not increase inorganic carbon removal. Instead, evidence was obtained for enhanced stabilization of organic carbon through organo-mineral interactions and clay formation.
The second major experiment was a plant-mesocosm study under natural field conditions, examining the combined effects of basalt, B. subtilis, and water availability on weathering and maize growth. Similar to the first study, findings highlighted greater potential for organic carbon stabilization than for inorganic carbon sequestration. Water availability strongly influenced basalt weathering rates and soil CO2 fluxes. Plant responses indicated that basalt ESW had only modest effects on aboveground biomass under the nutrient-rich soils and temperate climate of Northern Europe. However, improvements in plant nutrient status were observed, and root growth was markedly enhanced when basalt was combined with B. subtilis under reduced water availability.
In addition, contributions were made to a long-term plant-mesocosm experiment with multiple silicate types, focusing on organic and inorganic carbon dynamics in soils.
Overall, the fellowship objectives were achieved by evaluating the carbon sequestration potential of basalt-based ESW, its effects on plant growth and nutrient cycling, and the interactions between basalt and B. subtilis.
The first major experiment was a plant-free mesocosm study under controlled conditions, designed to assess the carbon sequestration potential of basalt weathering and the influence of the rhizobacterium Bacillus subtilis. Results showed that basalt weathering provided only limited potential for inorganic carbon sequestration, mainly due to restricted downward transfer of weathering products within the soil profile. Although B. subtilis accelerated basalt dissolution, this did not increase inorganic carbon removal. Instead, evidence was obtained for enhanced stabilization of organic carbon through organo-mineral interactions and clay formation.
The second major experiment was a plant-mesocosm study under natural field conditions, examining the combined effects of basalt, B. subtilis, and water availability on weathering and maize growth. Similar to the first study, findings highlighted greater potential for organic carbon stabilization than for inorganic carbon sequestration. Water availability strongly influenced basalt weathering rates and soil CO2 fluxes. Plant responses indicated that basalt ESW had only modest effects on aboveground biomass under the nutrient-rich soils and temperate climate of Northern Europe. However, improvements in plant nutrient status were observed, and root growth was markedly enhanced when basalt was combined with B. subtilis under reduced water availability.
In addition, contributions were made to a long-term plant-mesocosm experiment with multiple silicate types, focusing on organic and inorganic carbon dynamics in soils.
Overall, the fellowship objectives were achieved by evaluating the carbon sequestration potential of basalt-based ESW, its effects on plant growth and nutrient cycling, and the interactions between basalt and B. subtilis.
The fellowship advanced ESW research beyond the state of the art by showing that accelerated basalt weathering does not automatically lead to higher inorganic carbon sequestration. Instead, organic carbon stabilization was identified as a key mechanism by which ESW may contribute to long-term climate benefits. It was further demonstrated that basalt addition improves plant nutrient status without increasing heavy metal uptake, while the combination of basalt and B. subtilis enhances root growth under water-limited conditions. These findings highlight new pathways for maximizing the agricultural and climate co-benefits of ESW.