The Environmental Costs of Platinum-PGM Mining: An Excellent Case Study In Sustainable Mining

The platinum group of metals (PGMs) possess a range of unique chemical and physical properties and are increasingly finding important uses in a wide variety of environmentally-related technologies (eg. catalytic converters, fuel cells, electronics). The typical ore grade for PGM mineralisation is similar to gold (g/t) but the processing is more akin to base metals (at percent). The typical scheme for a PGM project is a mine, flotation concentrator, smelter and refinery. The environmental costs could therefore expected to be more significant than gold mining – in contrast to the uses for PGMs in many environmentally focussed technologies. The global production of PGMs is dominated by South Africa due to their large economic PGM resources in the Bushveld Complex, while other countries play a minor but important role. Concerns are being raised about the long-term ability to supply PGMs to meet future technological needs, as well as allegations of significant environmental and social impacts such as water pollution, unfair village relocation and compensation issues. This paper presents a detailed review of the platinum-PGM industry and major environmental costs such as water, energy and greenhouse emissions. The relationships between production statistics and environmental or ‘sustainability metrics’ are then investigated with a view to understanding the current trends in PGM mining and potential future implications. The paper presents a unique case study for a group of metals which are uniquely concentrated in one major region of the earth and pose some intriguing and difficult sustainability issues for the future. Full Reference: Mudd, G M & Glaister, B J, 2009, The Environmental Costs of Platinum-PGM Mining: An Excellent Case Study In Sustainable Mining. Proc. “48 Annual Conference of Metallurgists”, Canadian Metallurgical Society, Sudbury, Ontario, Canada, August 2009. INTRODUCTION The platinum group of metals (PGMs) have shown one of the highest long term growth rates of numerous mineral commodities over the past 50 years, due to their unique physical and chemical properties which make them ideal for a wide variety of technologies. Applications for PGMs include catalysts for chemical process facilities (eg. oil refineries), catalytic converters for vehicle exhaust control, hydrogen fuel cells, electronic components, jewellery, and a variety of specialty medical uses. Given the need to expand many of these uses to meet environmental challenges such as resource efficiency and pollution control, PGMs demand can reasonably be expected to be sustained for a significant period of time. The typical ore grade for PGM mineralisation is similar to gold, at grams per tonne (g/t), but the processing is more akin to base metals (at percent). The typical scheme for a PGM project is a mine, grinding, gravity-based separation, flotation concentrator, smelter and refinery. The environmental costs could therefore be expected to be more significant than gold mining – in contrast to the uses for PGMs in many environmentally focussed technologies. Some PGMs are also extracted as a by-product (or coproduct) from the processing and smelting of base metal ores (eg. Ni, Cu ores). The global production of PGMs is dominated by South Africa due to their large economic PGM resources in the Bushveld Complex, while other countries such as Russia, Canada, Zimbabwe, and the United States play a minor but useful role. Although known economic resources continue to reflect current production growth, concerns are being raised about the long-term ability to supply PGMs to meet future technological needs (eg. [1-2]), as well as allegations of significant environmental and social impacts such as water pollution, unfair village relocation and compensation issues (amongst others) [3]. This paper presents a detailed review of the PGM industry and major environmental costs such as water, energy and greenhouse gas emissions, and focussing on South Africa. A range of data is compiled, including annual production, major inputs ands outputs, and analysed with respect to unit efficiencies or ‘sustainability metrics’. The relationships between production statistics and sustainability metrics are then investigated with a view to understanding the current trends in PGM mining and potential future implications. The paper presents a unique case study for a group of metals which are uniquely concentrated in one major region of the earth and pose some intriguing and difficult sustainability issues for the future. PLATINUM-PGM MINING AND PROCESSING Overview The six platinum group metals have similar physical and chemical properties, divided according to their densities into a heavier category, comprising platinum (Pt), iridium (Ir) and osmium (Os), and a lighter group, consisting of palladium (Pd), rhodium (Rh), and ruthenium (Ru) [4]. Due to their high corrosion and oxidation resistance and relative scarcity in the earth’s crust, along with gold (Au) and silver (Ag), PGMs are classified as noble and precious metals. Common abbreviations used are ‘4E’ (or 3E+Au) which includes Pt, Pd, Rh and Au, while 6E (or 5E+Au) includes Pt, Pd, Rh, Ru, Ir and Au. In 2007, global PGM production was about 509 tonnes, consisting of 165.8 / 86.5 t Pt/Pd from South Africa, 27 / 96.8 t Pt/Pd from Russia, 6.2 / 10.5 t Pt/Pd from Canada, 5.3 / 4.2 t Pt/Pd from Zimbabwe and 3.9 t Pt and 12.8 t Pd from the United States [5]. Historical production and price is shown in Figure 1. The PGMs are one of the very few metals which have stayed relatively constant in their real price over time [6]. According to the USGS [7], global economic reserves are about 71,000 t PGMs, with an additional 81,000 t PGMs in the reserve base category – about 88% is in South Africa, with 8% in Russia. Platinum-PGM Mining and Processing There are broadly considered to be four main types of economic PGM mineral deposits [4]: • Norite intrusions – where meteoritic impact has been instrumental in PGM emplacement; eg. Sudbury Irruptive Complex in Ontario, Canada (~10-1000 Mt, 1-3 g/t, ~2-3% Ni+Cu). 0 100 200 300 400 50