Review of carbon sequestration by alkaline industrial wastes: potential applications in landfill biogeochemical cover systems

Abstract

The surge in global industrialization has significantly increased greenhouse gas concentrations in the Earth's atmosphere, with carbon dioxide (CO₂) being the predominant contributor to about two-thirds of the greenhouse effect. Landfill gas (LFG), resulting from the biodegradation of municipal solid waste (MSW), mainly consists of methane (CH₄) and CO₂. To counteract uncontrolled CO₂ emissions from waste decomposition, an innovative, low-cost biogeochemical cover (BGCC) system for landfills utilizing biochar-amended soil and basic oxygen furnace (BOF) slag for CO₂ carbonation has been developed. Despite the effectiveness of BOF slag in CO₂ removal, its limited availability near landfill sites presents sustainability challenges, necessitating the search for viable alternatives within the BGCC system that can achieve efficient CO₂ sequestration through direct aqueous mineral carbonation. This review explores various carbon sequestration techniques, identifying potential alkaline industrial solid wastes as substitutes for BOF slag, and evaluates these materials—namely cement kiln dust (CKD), blast furnace (BF) slag, coal fly ash (CFA), and concrete waste—for their compatibility with the BGCC system. CKD is highlighted as having the highest carbonation potential based on its capacity for direct aqueous carbonation, with a comparative analysis revealing substantial differences in the carbonation capacities of the materials. Given the fine-grained nature of the selected materials, the review also emphasizes the need to integrate them into barrier soil layers or use them as standalone layers within the BGCC. In conclusion, this review accentuates the potential of alternative materials in achieving effective CO₂ sequestration within BGCC, thereby addressing the challenges related to the availability of BOF slag and promoting sustainable landfill management practices.