Production of alumina from bauxite ore results in the production of bauxite residues that might further be processed into valuable by-products thereby reducing the quantity of residue requiring final storage. These storage areas occupy a significant area of land and require final closure, rehabilitation and ongoing management. To reduce the volumes of this residue, CSRP research has been developing beneficial uses for bauxite residue in construction and agriculture with potentially very significant ecological advantages.
The program aimed to reduce the ecological footprint of minerals processing through the development of various by-products, avoiding the need for residue storage and maximising the overall benefit from any given ore body. The program investigated the cost-effective recovery of the valuable components in "red mud" using a variety of processes. Trials of promising products were undertaken in field demonstrations, along with broad-based sustainability assessments. Commercialisation frameworks and market assessments were then developed for these products.
"Waste is a product made to poor specifications" – Dr Evan Jamieson
ReSand® is sand extracted from mineral residues and used a replacement for virgin mined sand. Coarse bauxite residue (Red Sand™) and other mineral processing by-products have been identified as potential sources of construction sand. Research has identified methods of separation of bauxite residue, its neutralisation through carbonation and its ability to be washed low in salt to produce a ReSand®. Looking much like any other sand, this ReSand® has little if any dust, has great drainage and wetting properties, requires only light grading, and compacts well. ReSand® can be used as a replacement for virgin mined sand from a conventional quarry – with a significantly reduced ecological footprint. A pilot plant was constructed, commissioned and successfully demonstrated the separation, washing and carbonation processes.
ReLime™ is an alternative lime source used as a replacement for mined or manufactured lime. Bauxite residue contains solid alkalinity that can be separated as a by-product. Production of the alternative lime source involved implementation and operation of a pilot plant at Alcoa's Kwinana refinery. The pilot was completed on time for commencement of field trials. Sites were selected by the Department of Food and Agriculture WA for their ability to represent a range of typical farming environments. Lime agents were incorporated in time for the growing season. The aim of the trials was to compare the effectiveness of the two agricultural liming agents with conventional agricultural limes in high-rainfall pasture and medium-rainfall cropping farming systems.
ReSoil™ is a soil ameliorant produced from fine bauxite residue and used to improve soil structure. A catchment-wide environmental monitoring program was designed and implemented to investigate the safety of the use of Alkaloam, and the extent and duration of phosphorus retention achieved through its use. The Department of Food and Agriculture WA was the proponent of the project and has conditional approval from the Environmental Protection Authority to undertake the widespread release of Alkaloam for use as a soil amendment in the Peel-Harvey Coastal Plain Catchment. The research shows that the amendment of soils with Alkaloam to address nutrient leaching issues has no measurable adverse impacts on water quality and continues to be effective in reducing nutrient leaching through sandy catchments.
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Dr Evan Jamieson
Technology Delivery Group
Alcoa
p. 08 9410 3852
e. evan.jamieson@alcoa.com.au