Municipal solid waste (MSW) decomposition in landfills generates landfill gas (LFG) emissions, primarily methane (CH4) and carbon dioxide (CO2), accompanied by trace amount of hydrogen sulfide (H2S) and other non-methane organic compounds. Despite using gas collection systems and conventional soil covers in MSW landfills, fugitive CH4 and CO2 emissions persist. In this regard, researchers from the University of Illinois Chicago (UIC) developed a biogeochemical cover (BGCC) to mitigate CH4, CO2, and H2S emissions. It consists of biochar-amended soil as the biocover layer for microbial oxidation of CH4 and basic oxygen furnace (BOF) slag as the layer for CO2 and H2S removal through carbonation and sulfidation, respectively. However, implementation of BGCC on large scale may face challenges due to limited availability of BOF slag near landfills. Therefore, there is a need to identify alternative materials that can replace BOF slag in BGCC while maintaining comparable carbonation capacity. Cement kiln dust (CKD), a byproduct of cement industry, can be a potential alternative to BOF slag, owing to its high calcium content. Hence, a series of batch experiments were conducted with CKD under typical ambient conditions, with varying moisture content levels. The selected moisture content levels for the batch experiments for CKD were 10, 20, 30, and 40%, all of which were below the water holding capacity of CKD (62.3%). Additionally, batch experiments with BOF slag were also conducted at 10 and 20% moisture content under same ambient conditions for comparison purpose. The experimental results showed that the highest short-term (24 h) and long-term (ultimate) CO2 removal capacities were achieved at 30% moisture content, measuring 171.2 mg/g and 225.1 mg/g of CO2, respectively. Notably, the ultimate carbonation capacity of CKD at 30% moisture content surpassed that of BOF slag, which achieved its highest capacity at 20% moisture content, by a factor of 2.25.