Carbon sequestration amount evolution characteristics and reaction mechanisms in coal-based solid waste backfill: A new whole-process carbon sequestration technique

Abstract

Underground carbon sequestration (CS) by solid waste backfill (SWB) offers an effective pathway for collaborative disposal of coal-based solid waste and CO₂, where the amount of carbon sequestration is an important evaluation parameter. In this study, the concept of whole-process carbon sequestration using coal-based solid waste and CO₂, including sequential stirring and curing stages, was proposed to evaluate the performance evolution of CS. The results showed that CO₂ pressure and ambient temperature positively correlated with the CS amount from coal-based SWB. In particular, CO₂ pressure prevailed in the stirring stage, while the ambient temperature effect was more significant in the curing stage. The CS amounts obtained during the stirring stage alone, the curing stage alone, and two sequential stages ranged from 0.66 %-3.10 %, 3.53 %-5.09 %, and 5.12 %-6.02 %, respectively. The functional group and micromorphology analyses revealed that the prevailing mechanism at the CS stirring stage was the stirring-driven gas dissolution-leaching-mineralization reaction, while that at the curing stage was the hydration-driven gas permeation-dissociation-CS reaction. Both were essentially solid-liquid-gas multiphase chemical reactions. The results are instrumental in substantiating the coal-based SWB carbon sequestration evolution patterns and mechanisms and providing data support for waste disposal and carbon emission reduction in the coal industry.

Keywords

Whole-process carbon sequestration / Stirring stage / Curing stage / Carbon sequestration performance evolution / Ambient temperature / CO₂ pressure

CRediT authorship contribution statement

Nan Zhou: Writing - review & editing, Writing - original draft, Methodology, Funding acquisition. Jixiong Zhang: Supervision. Yuzhe Zhang: Software, Data curation. Hao Yan: Validation.

Declaration of competing interest

The authors declare that they have no known competing finan-cial interests or personal relations hips that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the National Key R&D Program of China (No. 2023YFC3904304), the National Natural Science Foun-dation of China (No. 52304158) and Jiangsu Key Laboratory for Clean Utilization of Carbon Resources Research Project (No. BM2024007).

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