Enhancing the soil carbon sink: Towards characterising and quantifying new stabilisation methods.

Amy Lewis

Email: allewis2@sheffield.ac.uk

Start Year: 2018, 5th cohort

Host University: The University of Sheffield

Department: Animal and Plant Sciences, Simon Kemp

Supervisors:  Prof David Beerling, Dr Binoy Sarkar (University of Sheffield); Prof Mark Hodson (University of York);

CASE partner collaborator: British Geological Survey

Twitter: @amy_lewis143

Academic profile


MESci Geology, 1st Class Honours, Cardiff University, 2013-2017)


Skills and relevant qualifications

Basics of PHREEQC and PHREEQPY (geochemical modelling); Geochemical analysis including XRD, XRF and SEM-EDX; Experience designing experiments to determine kinetic rates.

ACCE PhD Research topic


Enhancing the soil carbon sink: Towards characterising and quantifying new stabilisation methods.

Reducing overall global CO2 emissions is crucial to preventing the global climate rising 1.5°C above preindustrial temperatures: the threshold before irreversible impacts of climate change. Governments have responded with individual pledges to try to reduce CO2 emissions in wake of the Paris Agreement (UNFCCC, 2015). While government pledges are crucial in the fight against climate change, reports suggest these targets account for just one-third of the total CO2 emission reduction and that at least 19 GtCO2 equivalents yr-1 will need to be removed by 2030.

Coupling slow integration of renewable technologies and increases in energy demand, the partial removal of atmospheric CO2 has been proposed as a short-term solution to regulate CO2 emissions.

The Earth has natural feedback to regulate atmospheric CO2. Naturally, the weathering of silicate minerals takes CO2 from the atmosphere and through a series of weathering reactions converts it to bicarbonate and deposits it in the oceans as bicarbonate. Scientists have proposed applying fast-weathering rocks, crushed to increase the surface area rainwater and fluids can react with, to soils to accelerate this natural cycle to capture more CO2 in a process coined enhanced weathering.

Basalt is an example of a fast weathering rock, and its application as a rock amendment to capture CO2 has been the subject of several recent studies.

This inorganic pathway has been the subject of numerous studies. However, in the soil environment, however, the basalt and its weathering products will interact with the wide variety of organic molecules present in the soils. Organic acids could enhance the dissolution of basalt. The weathering products, a series of short range order minerals and clays, can then bind with organic matter to increase the organic carbon concentration in soils. Not only could this provide a new carbon storage pathway as a consequence of enhanced weathering, but also help to restore poor-quality soils around the world.
This project will focus on quantifying different mechanisms that soil organic carbon can be stabilised in cropland soils amended with basalt through experiments and a suite of geochemical analyses. Experiments will be conducted to derive kinetic parameters of important basalt/weathering product-organic matter interactions and samples from the LC3M field sites in Illinois and Australia will be analysed to assess different stabilisation mechanisms in croplands.

The partnership with the British Geological Survey provides invaluable access to a suite of advanced geochemical analyses including: X-Ray Diffraction, Scanning Electron Microscopy, Thermo-gravitational Analysis and Fourier Transform Infra-Red. These techniques can be used to determine changes in mineralogy, grain chemistry and morphology, quantification of Organic Carbon and characterisation of different organic phases. Together, these analyses will help build the soil organic carbon storage picture.

The rates of these various interactions can then be incorporated into enhanced weathering models coded by members of the LC3M to help determine (1) how much OC can be captured through basalt amendment and (2) where can basalt amendment make the most difference in terms of both Carbon-offset and soil quality improvement.

I would welcome any comments or questions about the project.