Lead supervisor: Ed Tipper, Earth Sciences
Co-supervisor: Oscar Branson, Earth Sciences
Brief summary:
Enhanced chemical weathering is proposed as a way to help remove CO2 from the atmosphere. The process needs to be optimised and verified.
Importance of the area of research concerned:
The pressing need for negative CO2 emissions to combat the rapid rise in atmospheric CO2 requires a myriad of approaches. A novel approach to combatting the anthropogenically forced increase in atmospheric CO2, and concomitant global warming, is to artificially increase the flux of solutes from chemical weathering processes, in particular alkalinity or the bicarbonate ion. This process of increasing alkalinity export is known as enhanced weathering. The majority of studies concerning enhanced weathering have evaluated the potential of mafic silicate rocks and minerals (e.g., basalt or olivine) as reactants and investigate spreading powders of these reactants on agricultural land. There are several major issues to address in determining whether enhanced weathering can be of use such as 1) the kinetics of dissolution of silicate minerals is realtively slow, meaning that other materials such as carbonates or industrial waste are being evaluated as reactants, 2) the monitoring, recording and verification to check that enhanced weathering is actually consuming CO2. This is a fast moving area of research using state of the art research tools.
Project summary :
Silicate weathering is a natural process whereby silicate minerals dissolve in carbonic acid (derived from CO2 in the atmosphere). On the timescales of mineral dissolution (10’s to 1000’s years) this converts carbon dioxide to alkalinity (aqueous). Over tens of thousands of years this alkalinity gets used to make biogenic carbonates in the oceans trapping carbon for millions of years. This process is one of the key natural climate feedbacks acting on geological time-scales. To be of use in mitigating anthropogenic CO2 emissions, the natural processes need to be accelerated and the carbon consumption fluxes quantified. Key to this is developing novel tracers of CO2 consumption associated with rock and mineral dissolution and finding natural and anthopogenic materials that can react much more rapidly than silicate minerals, yet still remove carbon dioxide from the atmosphere.
What will the student do?:
Experiments: The student will develop a series of laboratory experiments to quantify the consumption of CO2 associated with natural and anthropogenic materials. These carefully designed experiments will be an analogue for field trials, but with much greater control on external variables. The student will develop novel ways of tracing carbon consumption using well established isotopic tracers of mineral dissolution. Chemical analysis on fluids will be conducted by ICP-MS/OES.
Natural samples: The student will work on a series of analogue sites for CO2 consumption via the dissolution of anthropogenic materials. An archive of samples is already held in Cambridge, but there are opportunities for new field work either in the UK or beyond.
Data analysis and modelling: Combined literature data and the new elemental and isotopic data will form the basis for the development of models (using the R or Python programming languages for example) and exploiting simple equilibrium calculations using software packages such as PHREEQC.
References - references should provide further reading about the project:
Amann, T., Hartmann, J. (2022) Carbon Accounting for Enhanced Weathering. Frontiers in Climate Vol. 4, https://doi.org/10.3389/fclim.2022.849948
Knapp, W.J., Tipper E.T., (2022) The efficacy of enhancing carbonate weathering for carbon dioxide sequestration, Frontiers in Climate Vol. 4
Knapp, W.J., et al. (2023) Quantifying CO2 Removal at Enhanced Weathering Sites: a Multiproxy Approach, Environmental Science & Technology vol. 57, pp9854-9864., DOI: 10.1021/acs.est.3c03757
Applying
You can find out about applying for this project on the Department of Earth Sciences page.