Global Metal Mining and Physical Water Stress
Water Impact Assessment of the Mining Industry Applying LCA and GIS within the Raw Materials Criticality Methodology (project period: 2016 - 2021)
Driven by growing demand and technological development, consumption of natural resources has been increasing rapidly within the last decades and is still expected to grow in the future. As a result of tight and unstable market situations, there is also raising concern about limited resource availability and more frequent supply shortages to the economy. Hence, so-called criticality assessment methods have recently been developed aiming at screening global commodity markets in order to identify potential supply risks of raw materials such as metals and minerals which are of rising importance for high technology industries, e.g. producing and providing modern energy technologies for the transition of fossil to renewable energy systems. But the global expansion of resource extraction, particularly metals, relevant for most technological applications, has also significant impacts on the environment such as hydrological systems which are essential for providing considerable amounts of freshwater feeding fundamental human and environmental needs. Especially ore mining and refining of metals consume large quantities of water. On a global and even national scale, however, consumption of freshwater for mining and refining activities accounts only for a small portion of the overall water use, particularly compared to agricultural water consumption as well as other industrial sectors such as the energy supply industry. But on regional and even local scale there are significant impacts on freshwater resources to be observed from the mining industry. Notably in relatively dry, mining intensive countries mine water usage is responsible for affecting both, the quantity and quality of freshwater availability, which is essential to domestic and industrial water supply as well as to sustaining ecosystems and environmental services.
Thus, latest criticality assessment methods of raw materials have been extended and advanced by environmental criteria to determine ecological impacts of mining activities. Due to reasons of practicality most assessment methods are based on Life-Cycle Analysis methods (LCA) also considering the freshwater consumption of mining and refining processes in relation to average national water scarcity indices, mostly neglecting spatial differences in water demand and supply on regional and even on local level. Additionally, nearly almost there is only a sectoral view given on the water usage of individually selected raw materials, e.g. iron, copper or gold, mostly without assessing their cumulative water impacts occurring within a particular region. As most of the metals are extracted and processed in combination with other metals, especially due to their geologically related occurrence, a cross-sectoral view of accumulated impacts of all minerals and metals being mined and refined within a particular hydrological region as well as a given time period is essential. Thus, the cumulative spatio-temporal assessment of mining’s overall impact on water availability and water scarcity provides profound knowledge about how metal extraction may affect other water needs within the particular mining area. For instance, assessment results of individual raw materials might contribute only small proportions to the overall mining impacts on regional ecosystems, however, in summary all mining activities together may have significant cumulative impacts that cannot be neglected compared to mining of single raw materials.
In conclusion, there are two mutually influencing concerns to be addressed: On the one hand, from the perspective of raw materials criticality assessment, there is only few data available about water-related risks such as water shortages may potentially affect the production and supply of global raw material markets. On the other hand, there is also lack of comprehensive information about the global mining industry’s water impacts on regional and spatially explicit level affecting both, regional water availability and supply as well as the ability of sustaining ecological systems in mining areas. With special regard to the increasing demand for a more environmental-friendly and sustainable use of raw materials and water as well, particularly addressed by the Sustainable Development Goals, this research project emphasizes on following questions:
- To which extend is the large scale mining industry exposed to water stress and what impact does industrial mining have on water resources on global, national and regional scale? And are there significant differences in exposure to water stress and water-related risks between the particular mining commodities and mining areas, respectively?
- How will climate change potentially affect the water situation in mining areas concerning changes of water availability and water stress as well as challenges of water supply mining probably will be confronted with in the future?
- What cumulative effects does the production of numerous raw materials have on regional water stress compared to observations of individual raw materials conducted in previous and existing assessment studies?
- And finally, how could increasingly established methods of raw materials criticality assessment be evolved by additionally including water-related impacts as a result of mining?
In order to provide more precise information about the mining’s exposure to water stress as well as the impacts of the global resource extraction on regional freshwater supply and availability, a GIS-based model was developed containing detailed data on water use from Life Cycle Inventory (LCI) Analysis of mining and refining activities. LCA-data, in particular water consumption inventories of mining processes, are being combined with spatial water risk and water impact characterization factors – both downscaled on major water basin and subbasin scale also considering seasonal variability of water demand and water supply affected by mining activities (see figure). This water impact assessment comprises detailed analysis of the global mining industry regarding 14 metal commodities at three different processing and refining stages, including the production of preprocessed and purified ores (bauxite and iron ore fines), metal concentrates (cobalt, copper, lead, manganese, molybdenum, silver, uranium [U3O8] and zinc), and refined metals (gold, nickel, palladium and platinum). Overall, almost 2,800 mining properties are considered in this survey. Depending on the commodity, the selected mining locations represent about 60 - 100 % of the global production of each particular commodity mentioned above. The water impact assessment was conducted commodity-wise by a correlation of mine-site production and water consumption comparatively with a water stress characterization factor on basin and subbasin level comprising >15,000 hydrological catchment units in order to determine water scarcity impacts of mining all over the world. Furthermore, a water impact assessment based on national average characterization factors was carried out in order to demonstrate improvements in accuracy and reliability which can be achieved by using precise GIS-models incorporating state-of-the-art water impact assessment methods. This primarily includes the water stress index (WSI) and the water (scarcity) footprint (WSFP), even aligning with assessment frameworks applied in the industry, e.g. DIN EN ISO 14046.
Figure: Structural design of the GIS-model to conduct spatio-temporal water impact assessment of metal mining at different spatial resolution scales
As a result, the comparative analysis of water consumption, water stress and water impacts in the mining sector, conducted on different spatial resolution scales, has shown that the application of currently used national mean impact factors in environmental criticality methods may lead to a bias to overestimate the impacts of water consumption of the mining industry on global level. Despite the assessment of mining-related water stress and scarcity, the influence of climate change on regional water availability and water stress in mining regions was also observed. Selected climate change predictions were implemented in GIS to show to which extent water stress will assumably be changing by 2030 and 2040 and thus mining will be confronted with potential water-related risks in the future. Exemplified by several IPCC-scenarios, particularly by the IPCC “business-as-usual”-scenario RCP 8.5 in combination with the Shared Socioeconomic Pathway SSP2 (“middle of the road”-scenario), it can be attested that the mean water stress will tend to deteriorate by 2040 for most of the areas in which mining is currently situated. Thus, there is noticeable trend in increasing water stress in average for almost the production of every mining commodity considered in this survey.
In summary, the methodological approach provided in this project, combining geographical methods (GIS) and methods of industrial ecology, primarily LCA and LCIA, enables comparative water impact assessment, particularly in terms of a water scarcity footprint. This was exemplified by 14 metal commodities of increasingly global relevance to the economy, and therefore contributing to a more advanced understanding of the extractive industry’s influence on water scarcity on both, regional and global scale. Thus, this transdisciplinary approach helps to significantly specify and improve criticality assessment of raw materials with respect to environmental and particularly water-related issues.
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