Authors: Scullett-Dean, G; Stockwell, K; Myers, L; Nyeboer, H; Santini, TC

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Scullett-Dean, G, Stockwell, K, Myers, L, Nyeboer, H & Santini, TC 2022, 'Accelerating soil formation in bauxite residue: a solution for long-term tailings management and storage', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: 15th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1027-1036,

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Bauxite residue is the highly alkaline (pH ~12) and saline tailings material produced during the Bayer process for alumina production. Australia is currently responsible for the management of approximately 750 million tonnes of bauxite residue and produces an additional 30 million tonnes each year. Currently only 2% of bauxite residue produced is recycled (International Aluminium Institute 2017, Di Carlo et al. 2019a); however, there is growing interest in reusing residue by transforming this byproduct into a productive soil material through in situ remediation. This aims to transform the bauxite residue into a soil-like medium, by adding amendments to the residue to reduce pH and salinity and improve other unfavourable conditions. Our work has focused on optimising the amendment application used to accelerate soil formation, using field scale lysimeters to test a combination of treatments. Here we provide an overview of a successful year-long field trial to promote soil formation, and our key insights from the trial. Combining microbially-driven bioremediation with common amendments compost and tillage accelerated pH neutralisation of the residue and leaching of excess salts, creating a material amenable to plant growth. The trials were completed under harsh Australian climatic conditions utilising available mine site water and cost-effective amendment rates, ensuring that this technology is applicable for further industrial scale-up. The data from this study will allow development of best practice remediation strategies for bauxite residue deposits based on their climate and desired end land use and is also applicable to other alkaline tailings and waste materials. Our results with bauxite residue show that in situ remediation is an innovative solution for rapid, cost-effective long-term tailings management.

Keywords: remediation, pH neutralisation, red mud, alumina refining, amendments, gypsum, compost, tillage, alkaline

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