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Research Questions/Objectives: The objective of this project is to experimentally determine the effects of soil acidity-related variables and how they may impact carbon dioxide removal through the enhanced weathering of alkaline minerals within the soil. These variables include a) the pH of the soil, b) the stored acidity within the soil, and c) soil processes that produce or consume acidity.
Brief Description of the Project: The enhanced weathering (EW) of alkaline silicate minerals within the soil environment presents an opportunity to use a common geological process to facilitate the removal of carbon dioxide from the atmosphere at a higher rate than is achieved naturally. Tropical agricultural soils are a suitable medium for enhanced weathering deployment as weathering of added minerals will be fast due to high temperature and humidity. The strongly acidic nature of tropical agricultural soils also contributes strongly to fast weathering rates found in these soils. However, recent models have found that the efficacy of carbon capture within acidic environments (pH<4.5) is low, which presents the need to investigate how soil acidity and the components that contribute to it, impact carbon dioxide removal effectiveness.
Background and Significance of the Research Question to drought risk, vulnerability, preparedness, or resilience: The risk of drought has been exacerbated by rising temperatures caused by global warming. Continued warming up to 1.5-2°C above pre-industrial levels increases the likelihood of more intense and more frequent droughts to impact the tropical North Queensland region. According to the IPCC report released in 2018, successfully limiting global warming to 1.5°C is expected to significantly reduce the probability of extreme drought and the risks associated with reduced water availability (Hoegh-Guldberg, 2018). However, the combined deployment of carbon dioxide removal strategies and reduced emissions is a necessity to restrict warming to 1.5°C above pre-industrial levels with limited overshoot.
Enhanced weathering presents an opportunity for farmers to contribute to the removal of carbon dioxide from the atmosphere whilst simultaneously improving the quality of their soil. Traditionally, liming agents are used to treat soil acidity which contributes to carbon dioxide emissions from the agricultural sector (West & McBride, 2005). However, incubation experiments testing the effectiveness of olivine as an alternative liming agent found that while the mineral had an overall weaker impact on increasing soil pH compared to traditional lime, it was able to decrease aluminium availability to a level suitable for plant growth in a relatively short time (Dietzen et al., 2018).
As a result, large scale deployment of enhanced weathering as a carbon dioxide removal strategy may leave farmers in tropical regions with the most to gain. Before such deployments are possible, there is a need to better quantify how soil acidity-related variables may impact carbon dioxide removal rates. Such information will aid future programs in determining the best land management practices to use when amending soils in order to derive the largest benefits for the farmers and the soil.
Hoegh-Guldberg, O., D. Jacob, M. Taylor, M. Bindi, S. Brown, I. Camilloni, A. Diedhiou, R. Djalante, K.L. Ebi, F. Engelbrecht, J. Guiot, Y. Hijioka, S. Mehrotra, A. Payne, S.I. Seneviratne, A. Thomas, R. Warren, and G. Zhou, 2018: Impacts of 1.5ºC Global Warming on Natural and Human Systems. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 175-312, doi:10.1017/9781009157940.005.
West, T. O., & McBride, A. C. (2005). The contribution of agricultural lime to carbon dioxide emissions in the United States: Dissolution, transport, and net emissions. Agriculture, Ecosystems and Environment, 108(2), 145–154. https://doi.org/10.1016/j.agee.2005.01.002
Dietzen, C., Harrison, R., & Michelsen-Correa, S. (2018). Effectiveness of enhanced mineral weathering as a carbon sequestration tool and alternative to agricultural lime: An incubation experiment. International Journal of Greenhouse Gas Control, 74, 251–258. https://doi.org/10.1016/j.ijggc.2018.05.007
Academic and research experience relevant to the honours project: I completed my Bachelor of Science at James Cook University in 2023, majoring in chemistry and achieving an overall GPA of 6.40. During my studies, I enrolled in several classes that deepened my knowledge and understanding about the environment within the context of chemistry. EA3207: Soil Properties and Processes was a class responsible for introducing soil science as a niche yet critical area of study and helped me to better understand how the conditions of soils critically impact all other environmental systems. EA2404 From Icehouse to Greenhouse outlined the history of the Earth’s climate and the drivers behind the changes from formation to today, helping to better understand the processes that may impact the current climate. While this is my first research project I possess experience within the field of soil analysis. For Work Integrated Learning during my degree, I partnered with a local company in Townsville, during their experiment in treating high conductivity dredge soil with organic matter. My role in this project was to analyse the samples collected from the site over the course of the experiment and provide accurate data that mapped the changes in soil pH and salinity that occurred.
Principal Supervisor’s skills and experience in relation to this project topic: Paul Nelson is a soil scientist with a 25-year record of research project leadership, often in collaboration with industry. He has led projects on carbon cycling in soils and catchments, nutrient cycling and management, GHG emissions, and soil chemistry in tropical agriculture in Queensland, Papua New Guinea and Indonesia, including the project in collaboration with the Leverhulme centre for Climate Change Mitigation that led to this proposal. Since joining academia in 2004 he has supervised 10 PhD (4 as Primary Advisor), 7 MPhil (3 as Primary Advisor) and 11 Honours candidates to completion. He is currently leading a large research project on enhanced weathering, including field trials on 3 farms, and is supervising 2 PhD projects on the topic.
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