21 AUG 2025 (THU) 10:35-11:05

Global Carbon Sequestration and Offset Potential of Alkaline Wastes

Ms LIANG Xindan 

( Supervisor: Prof Peng Gong )

Abstract:

Alkaline wastes, generated in excess of 20 Gt annually as byproducts of mining, metallurgy, and chemical industries, remain insufficiently utilized, yet their enrichment in calcium- and magnesium-bearing silicate minerals endows them with significant negative-carbon potential, enabling natural and accelerated mineral carbonation processes that together could sequester more than 1 Gt CO₂ per year, a mitigation potential equivalent to offsetting approximately 10% of industrial and fossil-fuel emissions. By integrating carbonation kinetic models with LCA-based carbon emission accounting methodologies, the study characterizes pathways of CO₂ uptake at the global scale under both natural and engineered conditions, thereby elucidating differences in sequestration potential, pathways, and associated environmental benefits. It also assesses the strategic role of alkaline solid wastes within the broader portfolio of carbon neutrality and negative emission technologies. Under natural conditions, alkaline wastes can gradually capture atmospheric CO₂ through mineral carbonation, whereas accelerated carbonation technologies can markedly enhance both sequestration efficiency and resource utilization. Although recent research has clarified the mechanisms, kinetics, and enhancement strategies of mineral carbonation, existing work remains largely restricted to specific minerals or case studies and lacks a systematic framework integrating diverse utilization pathways across regions. In addition, the baseline contribution of natural carbonation is often overlooked, creating uncertainties in offset estimates and constraining the integration of alkaline wastes into climate mitigation policies and CCUS strategies. The findings are expected to advance understanding of the global carbon cycle and provide theoretical as well as empirical support for waste valorization and CCUS technologies, thereby contributing to industrial emission reduction and sustainable development.