From slag to green: Aided-phytoremediation as a sustainable tool to rehabilitate land contaminated by steel slag and assessment of CO sequestration.

Steel slag (SS) has many applications, but its immediate reuse is not possible due to its inherent swelling potential and presence of toxic metals. Therefore, it can only be used after the aging process, which can be either natural or artificial. While few large-scale steel plants afford artificial aging, many small-scale ones opt for natural aging through stockpiling of SS. This results in an increase in soil pH to over 12, thus damaging the ecosystem and making it unviable for plant growth. This research focuses on the reclamation of land affected by SS through the formation of a Phyto-barrier using 22 native plant species aided by the application of a 2 % (v/v) solution of the organic amendment. Furthermore, the superior performance of plants belonging to the Fabaceae family was ascertained, while establishing Sesbania grandiflora as an able species for aided-phytoremediation due to its remarkable growth (≈ 10 ft tall and 33 cm in circumference) during the study period. The CO sequestered by the plantation showed that maximum sequestration has been done by Sesbania grandiflora (49.96 kg CO / tree/ year), and least by Azadirachta indica (0.35 kg CO/tree/year). The overall CO sequestered by the plantation stood at 3.85 tons/year. A cost-benefit analysis of using aided-phytoremediation indicates an expense of 90 $ per year as the recurring expense, while carbon credits if monetized, would yield 154 $ to 308 $ as returns. The investigations of this study established a new approach to vegetation over SS-affected land, through native species and the application of organic amendment.