Effect of basic oxygen furnace slag type on carbon dioxide sequestration from landfill gas emissions

This study investigates the carbon dioxide (CO₂) sequestration potential of three different basic oxygen furnace (BOF) slags (IHE-3/15, IHE-9/17, and Riverdale) subjected to simulated landfill gas (LFG) conditions (50% CH₄ and 50% CO₂ v/v) in a series of batch and column experiments. Batch experiments were performed at different moisture contents (0%, 10%, 15% and 20% moisture by weight) and temperatures (7 °C, 23 °C and 54 °C) to examine the effect of moisture and temperature on the CO₂ sequestration potential of the BOF slags. The column experiments were conducted under continuous humid gas flow conditions. The results from the batch experiments show that the CO₂ sequestration was significantly higher in a moist state (10%, 15%, 20% moisture (w/w)) versus the dry state (0% moisture). The optimum moisture content (w/w) for CO₂ sequestration was different for each BOF slag; IHE-3/15 (10%), IHE-9/17 (20%) and Riverdale (20%). The variation in ambient temperature did not show any significant effect on the CO₂ sequestration capacity of the BOF slags. The CO₂ sequestration capacity of IHE-3/15, IHE-9/17 and Riverdale BOF slags determined by long-term batch experiments were 105 mg/g, 80 mg/g and 67 mg/g, respectively. The IHE-3/15 slag demonstrated the highest carbonation potential and was attributed to its finer particle size and higher free lime, portlandite and larnite content. The IHE-9/17 and Riverdale slags showed significantly lower CO₂ sequestration capacity in comparison to the IHE-3/15 slag. The amount of free lime, portlandite and larnite, which are considered to be the most reactive minerals during carbonation, was nearly 1.3 times less than that of the IHE-3/15 slag in the IHE-9/17 and Riverdale slags. Also, the Riverdale slag showed relatively lower CO₂ sequestration in column experiment in comparison to the batch experiments, perhaps due to a high in-situ density which limited CO₂ diffusion and hence the CO₂ uptake. Overall, this study provides a means to analyze the suitability of the use of BOF slags in landfill covers for mitigating fugitive CO₂ emissions from landfills.