Sequestration of CO2 in Agricultural Soils Via Application of Carbon Capturing Soil Amendment
The global mean temperature has increased due to anthropogenic activities, and there is a pressing need to curb the annually increasing atmospheric concentration of CO2. To lock atmospheric CO2 at anthropogenic timescale, fast weathering silicates, wollastonite used in this study, can be applied to soil to accelerate CO2 sequestration via enhanced weathering. When finely crushed wollastonite are applied to the soil, the alkaline earth metal cations released during mineral weathering gradually react with carbonate anions and results in the formation of pedogenic carbonates, which, over time, and under the right conditions, can accumulate in soil. The aim of this doctoral research is to assess the application of wollastonite for large-scale carbon sequestration in Ontario agricultural soil and its suitability with the agricultural crops. To investigate the role of plants, a pot experiment was conducted by growing leguminous beans and non-leguminous corn in wollastonite ore-amended soil. Secondly, pilot-scale trials were conducted to determine the effect of different dosage of wollastonite ore on three types of legumes. Field-trials were carried out to study the changes incurred to the soil as a result of long-term applications of wollastonite ore. To test this, the soil sampled from agricultural fields which have been using wollastonite ore as a soil amendment continuously were analyzed. Additionally, our research team worked together with the producer to plan a field study to better understand the effects of wollastonite ore application on soybean crop within a single growing season. Lastly, wollastonite ore amended soil were fractionated using sieving to enhance the precision of identification and quantification of the weathering products. The inorganic carbonate content of the soil was analyzed using a calcimeter, CHNS, and thermogravimetric analysis (TGA), and the soil mineralogical assessment was performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results obtained from this study are of significance for climate change mitigation via wollastonite weathering in soil. Wollastonite ore-amended soil promoted good plant growth, thus the co-benefits of wollastonite ore soil amendment (CO2 sequestration and improved crop yield) would encourage producers to effectively use this mineral to contribute towards global climate change mitigation, without compromising their produce.