Commonwealth of Australia 2010
Background 2.1International perspective
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- 2.1.1International assessments
- 2.2Australian perspective
2.Background2.1International perspectiveSodium cyanide (NaCN) is a significant nitrogen-based commodity chemical, used worldwide for a range of industrial manufacturing and processing purposes. It is generally manufactured from the gas hydrogen cyanide (HCN) and may be used as a chemical intermediate for industrial purposes where there is no local supply of HCN (Suresh and Kishi, 2003a), or to generate HCN for fumigation purposes (IPCS, 2004), as well as directly for various purposes. While chemical uses predominate in Japan and Europe, the major application for NaCN in Australia, North and South America, South Africa and China is use as a lixiviant (leaching solution) in the beneficiation and processing of gold and silver ore (Suresh and Kishi, 2003b). The cyanidation reaction that this involves was first discovered by Scheele in Europe in 1783. It was developed into a practicable mining process in the 1880s, and sodium cyanide is now the most generally used lixiviant for extracting gold from ore. Sodium cyanide is also used in other mining and metal industries, as a depressor agent in base metal flotation, for electroplating copper and other metals to metal surfaces, for surface hardening of iron and steel, and as a metal cleaning agent. There are various purposes for which sodium cyanide has evidently been used in the past, but where other alternatives are now preferred, e.g. photography (ATSDR, 2006). According to World Health Organization (WHO) data cited by various sources (Buffington, 2002; Morna and Clarke, 2002; MCA, 2005), global production of hydrogen cyanide is ~1.4 million tonnes annually. Of this, ~20% is used to produce sodium cyanide (i.e. ~280 000 tonnes HCN, or ~500 000 tonnes NaCN – a figure consistent with more recent estimates by Suresh and Kishi, 2003ab), of which 90% (~450 000 tonnes NaCN) is used in the mining industry, primarily for gold and silver mining. According to Mudder and Botz (2000), ~13% of HCN production (i.e. ~330 000 tonnes NaCN) is converted into sodium cyanide for use in beneficiation of gold and silver ores (i.e. ~66% of NaCN production). At the turn of the 21st century, there were about 875 gold and silver operations throughout the world, of which about 460 utilised cyanide (Mudder and Botz, 2000). Internationally, there have been various environmental incidents involving sodium cyanide or cyanide compounds derived from sodium cyanide (breakdown products) including spill incidents, transportation accidents, and tailings dam overflows and failures (e.g. Baia Mare, Romania, 2000). These have led to international focus on the uses of sodium cyanide and the environmental protection measures employed at facilities manufacturing and using sodium cyanide, their emissions and waste management practices. Internationally, regulatory approaches to the management of cyanide in gold mining vary among jurisdictions depending on local conditions, the level of public concern and past incidents. A range of environment protection guidelines have been published covering most aspects of cyanide management in mining such as handling, transportation, storage, use, tailings storage facilities (TSF) design and construction, water and wastewater management, TSF and tailings management, reporting, occupational safety and emergency response. Of note is the recent and comprehensive International Cyanide Management Code for the gold mining industry prepared by the International Cyanide Management Institute (ICMI, 2006) in consultation with the United Nations Environmental Program (UNEP), the then International Council on Metals and the Environment (ICME – now the International Council on Mining and Metals (ICMM)), the Gold Institute, the International Finance Corporation (IFC) and the Worldwide Fund for Nature (WWF). Chemical industry initiatives, such as the Responsible Care® program provide a comprehensive risk management framework for sodium cyanide management (refer Section 88.1).
There is one manufacturing facility in Western Australia (WA) and one (formerly two) in Queensland (Qld). Production at these facilities uses relatively modern technology, with production facilities having been established in the last seventeen years. Both liquid and solid forms of sodium cyanide are produced in Australia, with exports in solid form. Sodium cyanide is primarily used in Australia by the gold mining industry, where it is used in the cyanidation process to extract gold from ore. About 98% of Australia’s gold production is dependent on the use of sodium cyanide for gold ore beneficiation. This process enables relatively high recovery of gold (and other precious metals) from ore. A lesser amount of sodium cyanide is used in Australia for ore flotation and in the electroplating, metal cleaning and metal hardening industries. In recent years, there have been a few environmental incidents in Australia involving sodium cyanide arising from inappropriate or inadequate planning, design, storage, handling, transportation, use, and waste management. These and overseas incidents have raised community concerns. The major industries, including chemical and mining, and environment protection agencies have responded with reviews of procedures and development of new guidance, codes of practice, procedures and regulations to minimise safety and environmental risks. Although there have been restrictions on the manufacture, handling, transport, storage and use of sodium cyanide in Australia, this report represents the first comprehensive environmental risk assessment by a national agency.
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