Seasonal dynamics of carbon dioxide removal through enhanced basalt weathering in temperate croplands: insights from reactive transport modelling

Details

Supervisors

Delmelle, Pierre ; Glorieux, Juliette

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

enEnhanced silicate weathering (ESW) is considered a promising method to reduce atmospheric carbon dioxide (CO2) and help to fight climate change. However, the literature on this method presents a large variability in carbon dioxide removal (CDR) potentials, rendering these predictions highly unreliable and highlighting the need for more precise understanding of the dynamics behind the process. This study evaluated the seasonal dynamics of ESW with basalt on a temperate agricultural land via a geochemical modelling approach. The temporal dynamic of four parameters influencing the weathering rates (WRs) of minerals, i.e. soil temperature, water content, drainage and CO2 partial pressure (pCO2), was assessed. The soil solution pH was found to increase after basalt addition. Four minerals were found to drive basalt WR: apatite, labradorite, olivine and nepheline. Apatite, labradorite and nepheline WR present a pH-dependence while olivine WR is found to follow the temperature evolution. Besides its pH-dependence, apatite WR is found to be transport-limited in summer when the drainage is zero. Moreover, labradorite WR is lower when basalt is added than in the bare soil, contributing negatively to basalt WR. Given these temporal evolutions, the bare soil is considered to have, 15 % of the time, a greater CDR potential than with basalt addition. The CDR potential found in this study is 0.088 tCO2 ha-1 yr-1. This value is lower than the rates commonly reported in the literature, confirming the recent questioning of the literature values. CO2 consumption was found to be zero in June and July, when there is no drainage. Overall, this modelling study has highlighted the importance of considering the temporal influence of extrinsic (soil) factors in controlling weathering reactions and, thus, CDR potential from crushed basalt applied to temperate agricultural lands. It contributes to better understanding ESW via four new insights concerning ESW when considering temperate pedo-climatic conditions. Finally, this study presents some limitations and calls for further research to address process gaps and environmental impacts before large-scale deployment.