Improving the Sustainability of Residue Management Practices — Alcoa World Alumina Australia

Abstract

Alcoa World Alumina Australia is the world’s leading producer of aluminium and alumina, with three alumina refineries in Western Australia and a further six refineries located in Europe, the Caribbean, North and South America. During the refining process, an alkaline residue is produced and is deposited in lined storage areas designed to protect ground and surface waters. As early as 1977, Alcoa recognised the need to investigate alternative residue management strategies. The company made a significant commitment to continuous improvement in tailings management through the establishment of a focussed research and development group charged with the responsibility of “establishing Alcoa’s reputation as a leading company in the management of bauxite tailings”. Through ongoing research and field trials, a range of significant improvements to residue storage methods have been developed and implemented. Recent work has focussed on investigating ways to modify the residue, in particular decreasing its alkalinity to further lessen its potential environmental impact. Residue carbonation has been developed and tested at the Kwinana refinery and is currently being expanded to a full scale operation. It is a process which is easily integrated with the current thickening and dry stacking process, offering a range of operational and environmental benefits. The potential to progressively implement the process at Alcoa’s other refineries worldwide is currently being evaluated. It is anticipated that residue carbonation will become the alumina industry’s best practice benchmark for residue treatment and storage worldwide. Alcoa has also been focussed on potential re-use opportunities for the residue. A number of potential uses have been progressed through to pilot and demonstration phase, opening the way for the re-use of considerable volumes of residue. This paper will describe these more recent developments in residue management practices, and outline the sustainability case for progressing their implementation.