27-17 Mineralogical and Chemical Evaluation of Basaltic Feedstocks for CO₂ Sequestration and Agricultural Soil Amendments

Session: Environmental Geochemistry and Health (Posters)

Presenting Author:

Authors:

Abstract:

Enhanced rock weathering (ERW) has emerged as a nature-based solution that accelerates the natural breakdown of silicate minerals to capture and store atmospheric carbon dioxide. When finely ground silicate rock is applied to soils, it weathers over time, drawing down CO₂ and converting it into stable forms that can be stored in the soil or eventually transported to the oceans. Basaltic weathering also remineralizes soil and has important benefits for agricultural soils. Basaltic (mafic) rocks are typically preferred due to their abundance, relatively elevated concentrations of Mg, Ca, and other key plant nutrients, and lower concentrations of potentially toxic elements compared to other rocks, making them safer for use in agricultural soils. Despite these advantages, relatively little attention has been paid to how differences in the mineralogy, chemical composition, and degrees of alteration and metamorphism of the feedstock affect ERW performance. In this study, we evaluated a range of commercially available basaltic feedstocks (basalts, basaltic andesite, diabase etc.) from relatively fresh material to those showing more advanced alteration and or metamorphism to understand how these factors influence their CO₂ removal (CDR) potential and soil health benefits. We used X-ray diffraction (XRD), scanning electron microscopy (SEM), and polarized light microscopy to examine mineralogy. Major elements were analyzed using X-ray fluorescence (XRF), and trace elements were measured with inductively coupled plasma mass spectrometry (ICP-MS).  Modeling these parameters predicted increasing CDR over time for all feedstocks. Material with the highest reactive mineral content (fresh igneous phases) and minimal alteration achieved the greatest CDR (~5 t CO₂/ha) for application rates of 20 t/ha. In contrast, those with fewer reactive minerals showed the lowest (~3 t CO₂/ha after 15 years). The least altered material is the most suitable for CDR-based soil amendment, while another, slightly more altered but rich in highly reactive phases, released the most P and K, making it ideal for nutrient enrichment. For a balance between CDR, soil enrichment, and fertilizer replacement, this rock offers the best overall performance, maintaining strong CDR in both the short and long term. These findings emphasize that not all quarried material commercially referred to as basalt is actually basalt, and not all are equally effective for ERW. Understanding feedstock mineralogy and chemistry is key to effective and safe CDR.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5613

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.