CR2025_30 Crushed basalt addition to soil to enhance carbon sequestration: implications for soil physical and hydrological functioning
Lead Supervisor: Emilia Urbanek, Department of Geography, Swansea University
Email: e.urbanek@swansea.ac.uk
Co-supervisors: Anne Verhoef, Department of Geography and Environmental Science, University of Reading; Katie Preece, Department of Geography, Swansea University
Crushed basalt has recently received a lot of interest as a soil amendment that can facilitate atmospheric Carbon Dioxide (CO2) removal to mitigate climate change while improving soil fertility and reducing soil acidity (Beerling, et al., 2018; Beerling et al., 2020). Like any silicate-rich rock, basalt undergoes a process of chemical weathering initiated by rain, which reacts with atmospheric CO2 to form products that lock inorganic carbon in soil and water (Hartmann, et al., 2013). The speed of the slow process of rock weathering can be increased by crushing the rock into small particles, which increases the surface area, leading to ‘Enhanced Rock Weathering’ (ERW). Typically, the crushed basaltic rock used for soil amendment is a residual product of mining and rock crushing for the construction industry.
Most of the published research on ERW focuses on carbon sequestration potential and crop yield increase (Hartman et al., 2013; Beerling, et al., 2018; Beerling et al., 2020). However, there is a clear lack of understanding of the crushed basalt’s physical properties, and how the addition of crushed basalt to soil may affect soil hydrological functioning and overall soil health. Also, there is very little information available on the trade-offs between ERW’s beneficial and adverse effects, particularly in the context of its carbon sequestration potential.
Our preliminary research shows that adding crushed basalt to soil can affect soil water conditions due to changes in soil texture (i.e. the particle size distribution) and related pore size distribution, PoSD (Huyghebaert, 2024, UG Thesis). This can affect the flow and retention of water in the soil. The ability of soil to retain water, especially during dry events, will not only affect the weathering capability of crushed basalt and the rate of carbon sequestration, but also could change organic carbon dynamics and the rate of soil organic carbon release to the atmosphere via soil respiration (Urbanek and Doerr, 2015), as well as plants’ access to water.
Basic physical and hydrological parameters of the soil amended with crushed basalt need to be established to accurately estimate carbon sequestration and potential trade-offs in other soil parameters (and soil health) before ERW becomes a commonly used practice for carbon offsetting by land managers and farmers.
The proposed PhD project will focus on understanding how the crushed basalt application may affect soil physical and hydrological properties, overall soil health, and how to mitigate potential side effects of these amendments in the context of carbon sequestration by ERW.
This research would provide important parameters for measuring and modelling carbon sequestration using ERW and suggest standard tests of soil and crushed basalt before and after application on the fields.
The primary site for the project will be a large-scale forested site in Mid Wales coordinated by the Carbon Community (The Carbon Community), where crushed basalt has been applied for the last 3 years. Dr Urbanek from Swansea University has established links and ongoing projects at the Carbon Community site.
It is expected that the study will consist of field- and laboratory-based components followed by numerical modelling using the obtained model parameterisation and verification data.
Training opportunities:
The training opportunities will include access to a world-leading landmark carbon study site established by the Carbon Community (Carbon Community), where forestation and several nature-based climate solutions are tested on 11 hectares of land. This partnership will provide the opportunity to obtain field measurements and sample collection but will also offer access to datasets collected by other collaborating partners.
Other training opportunities will include soil physical in-situ monitoring and laboratory techniques, rock geochemical analysis as well as detailed soil modelling of changes in pore-size distribution and how this affects soil hydrological properties, basalt weathering rates and net soil carbon gain.
Student profile:
This project would be suitable for a student with a degree in physical geography, environmental science, soil science or a closely related environmental or physical science.