Environmental feasibility of soil amendment with flue gas desulfurization gypsum (FGDG) for terrestrial carbon sequestration

Technologies for increasing carbon storage in soils are gathering attention as a means for mitigating atmospheric CO₂ emissions. Carbon sequestration can be achieved by controlling the organic carbon stock in soil and by accelerating mineral carbonation. In this study, carbon sequestration capacity was measured in soil columns treated with flue gas desulfurization gypsum (FGDG), a by-product of electric power generation. The feasibility of using FGDG as an environmentally benign alternative to gypsum or anhydrite was examined using a toxicity characteristic leaching procedure and Microtox bioassay. While no toxic leachate was generated from the FGDG treatment, some toxic elements in the soil were removed through absorption reactions. Test results for carbon sequestration based on unsaturated soil column experiments suggest that the application of FGDG for soil treatment holds promise of less microbial CO₂ emission from soil. The net benefits of carbon sequestration from the FGDG treatment were calculated as 87 and 621 g C/m²/m of infiltrated water, for the 1 % calcite-added column and 3 % calcite-added columns, respectively. The presented test results show that the FGDG treatment for soil carbon sequestration holds a promise when it is applied to slightly alkaline soils.