Sustainability Reporting and Water Resources: a Preliminary Assessment of Embodied Water and Sustainable Mining

This paper presents a preliminary compilation and analysis of the water reported to have been consumed by a range of various mineral commodities and compares it to mine production data. This has been undertaken to assess and quantify the 'embodied water' of mineral products-a key aspect of sustainability (embodied water is the total water required to produce a good or service). At present, although the use of formal reporting protocols such as the global reporting initiative (GRI) is increasing, there are still critical weaknesses. Some key aspects to facilitate proper water accounting are not listed in sustainability reports, including the extent of recycled water used, mine site water inventories, the quality of various waters, and impacts on water resources. Based on the data compiled, there is wide variation in the water used for different mineral commodities as well as for the same commodity. There is little evidence for 'economies of scale' in base metals and bulk minerals, though for precious metals (gold, platinum), greater throughput does tend to lead to greater efficiency. For many mines, there is little evidence of improving efficiency over time, although some mines have made substantive improvements in reducing water consumed. The grade of ore being processed is clearly critical in understanding the embodied water of minerals, with declining ore grades leading to an increased chance of higher embodied water in the future. Given that many metals are declining in average ore grade, the sensitivity of embodied water to ore grade provides a major sustainability challenge for mining generally. In summary, the embodied water of minerals is clearly significant, and will likely gradually increase in the future, and so must be more completely accounted for to understand a fundamental aspect of sustainability and mining-that of water resources.