Compaction as a cost-effective strategy to upgrade the disposal of MSWI fly ash: feasibility and potential

Highlights

	● Cost-effective compaction is introduced into the stabilized fly ash disposal process.
	● After compaction, SFA density is more than doubled, and > 60% of the volume is saved.
	● Huang Peiyun & Heckel equations are the most suitable to describe compaction process.
	● The mechanical strength of the green compact meets the MU10 lime-sand brick standard.

Abstract

Landfilling remains the primary disposal method for fly ash produced from municipal solid waste incineration (MSWI) following stabilization/solidification. However, the increasing generation of stabilized fly ash (SFA) is accelerating the depletion of landfill capacity. Furthermore, the small particle size and low bulk density of SFA present significant environmental risks during handling and transportation. To mitigate these issues, a cost-effective compaction method was introduced into the SFA disposal process. The results show that SFA from both grate furnaces and fluidized bed incinerators exhibited high porosity, loose structure, and irregular particle morphology, indicating substantial potential for compaction. Key parameters influencing compaction effectiveness included compaction pressure, holding duration, and moisture content, with optimal values identified as 100–200 MPa, 20 s, and 10%–15% moisture, respectively, depending on the incinerator type. After compaction treatment, the density of SFA more than doubled, while its volume was reduced by over 60%, significantly increasing landfill capacity and enhancing the efficiency of SFA disposal. The compaction process was effectively modeled using the Huang Peiyun equation for gerate furnace ash and the Heckel equation for fluidized bed ash. Furthermore, the unconfined compressive strength and three-point bending strength of compacted SFA met the MU10 standard for lime-sand bricks, making the material suitable for transportation and disposal. Finally, the compaction-based disposal method for SFA demonstrated clear techno-economic advantages and significant potential for broader application in waste management strategies.

Graphical abstract

Keywords

Stabilized fly ash / Compaction process / Volume reduction / Disposal upgrading

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CRediT Authorship Contribution Statement

Shijin Dai: Conceptualization, Methodology, Formal analysis, Writing - original draft. Fafa Xia: Visualization. Bo Yang: Review & editing. Deli Wu: Review & editing. Dongjie Niu: Funding acquisition, Review & editing. Youcai Zhao: Review & editing. Xunchang Fei: Writing - review and editing. Zhanbo Cheng: Writing - review and editing. Hongping He: Funding acquisition, Writing - review and editing.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 52100152), the Natural Science Foundation of Shenzhen Science and Technology Commission (China) (No. RCBS20210609103644013), and the Stable Support Program of Shenzhen Colleges and Universities (China) (No. 20220810172813001). The Foundation of the State Key Laboratory of Pollution Control and Resource Reuse Foundation (Tongji University, China) is also acknowledged (PCRRF20013).

Conflict of Interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-025-1955-1 and is accessible for authorized users.

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