Sustainability and Waste Management in the Resource Industries
Fundamental science and engineering research at Monash University and The University of Melbourne in Australia has enabled the alumina industry worldwide to reduce the volume of waste produced by about fifty percent. Valuable raw materials are recovered, and the risk of storage failure is eliminated. Across the mining industry, there are at least two major storage failures annually worldwide, resulting in deaths and environmental disasters. The failure in Hungary of a storage facility for bauxite residue in October 2011 resulted in eight deaths and a fine of 472 million euro ($US648 million) and the arrest of the CEO (later released). The new technique called dry disposal produces a paste for stacking and drying instead of a water-like suspension to be stored in a dam or pond. Simply removing water from the suspension and reusing and recycling water represents a step toward a more sustainable practice in the industry. As the concentration of such a suspension is increased as a result of dewatering, the materials exhibit non-Newtonian behavior, characterized by shear thinning, a yield stress, and in some instances, thixotropic behavior. Such high concentration, nonideal (dirty) suspensions in the resource industries has meant that new rheological methods and techniques were needed for both shear and compression rheology to measure and interpret the basic flow properties. Also, some older empirical techniques needed to be modified and interpreted in a more fundamental way so that the results could be used in design. The paper reviews these techniques and illustrates how the industry itself has motivated their development. Understanding and exploiting this rheology has resulted in dramatic improvement in the waste disposal strategy for some industries, but many have failed to embrace the available technology. Why? Is regulation the answer? Probably not. The paper concludes that a greater positive change in the waste management practice will occur in the future, motivated by a number of factors, including public perception, water recovery, the necessity to earn the right to operate, and perhaps even by common sense accounting. The paper is a review of thirty years of work with the resource industries on environmental waste minimization. Aspects have been published in the Proceedings of Paste and Thickened Tailings Conferences held annually since 1999 (Jewell, R. J., Fourie, A. B., Eds.; Paste and Thickened Tailings?A Guide, Second ed.; Australian Centre for Geomechanics: Perth, 2006), in Chemical Engineering Science (Boger, D. V. Chem. Eng. Sci.2009, 64, 4525), and in the Proceedings of the Second International Future Mining Conference in 2011 (Jones, H.; Boger, D. V. Proceedings of the Second International Future Mining Conference 2011, Sydney, 22?23 November, 2011).