A/HRC/21/48 B. Extraction of resources - current practices 5. Mining for the extraction of resources generally fall within two categories of activities: excavation and beneficiation. Each of these activities generates its own waste stream and management issues. Excavation techniques entail surface, underground and solution mining. Underground (or sub-surface) mining involves the construction of tunnels or shafts to reach buried ore deposits, and can extend several miles underground. Solution mining (or in situ, leaching or recovery) involves the injection of a liquid (e.g. water, sulphuric acid, nitric acid, hydrogen peroxide or carbonates) leaching solution into porous rock through a borehole to dissolve the desired resource. 6. Around the world, underground mining is the method most commonly used for coal extraction. The use of solution mining techniques for uranium has been increasing, up from approximately 36 per cent in 2009 to 41 per cent in 2010. While the use of solutions may have a less destructive impact on the surface ground, these toxic and hazardous substances bring with them chemical management challenges related to their use, distribution, storage and disposal. 7. Beneficiation refers to the variety of processes, used to separate desired resources from material of no commercial use. The methods of primary concern for the scope of this report are the chemical processes involving cyanide leaching and mercury amalgamation. The predominant method used to beneficiate gold ore and other metals is cyanide leaching. This technique uses aqueous solutions of sodium or potassium cyanide as leaching agents (lixiviants) to extract the desired metal from the ore. In the amalgamation of gold, metallic gold is wetted with mercury to form a solution of gold in mercury. The amalgam is later roasted in open air, releasing elemental mercury emissions into the atmosphere. Artisanal and small-scale gold mining (ASGM or ASM), supplying an estimated 13 per cent of the world gold production, is the largest demand sector for mercury globally. 5 Another process that uses chemicals is the Bayer process for the beneficiation of bauxite for recovery of alumina to be used in aluminium production. 8. Hydraulic fracturing may be used to enhance or enable the recovery of oil and gas, and it is the process by which a mixture of water, sand and chemicals is injected into a well at high pressure to create fractures in geological formations, thereby collapsing small pockets of oil and gas into larger reserves for enhanced recovery. The excess water from oil or gas production (produced water) and drilling fluids constitute hazardous wastes and are sometimes re-injected into the reservoir. In some countries where the practice is not banned, produced water is disposed of in waste ponds, which may not be lined with impermeable barriers, or even dumped directly into streams or oceans. 9. A controversial source of fossil fuel is “oil shale,” a sedimentary rock that contains solid kerogen, which can release oil and gas when heated. Extraction may be through surface mining or by the in situ method. Waste materials remaining after the extraction of shale oil and tar sands are not unlike the waste of mining activities, including spent rock, hazardous solids and toxic solutions. Tar sand production is similar to developing oil shale. To bring extracted oil and gas to refineries for processing, pipelines requiring access routes are used on land, underground, or below the sea and can break, leak or explode, allowing oil or gas to spill out and seep into aquifers and other freshwater resources.6 In addition, thousands of tankers are used to transport at least half of the oil produced offshore. 5 6 4 United Nations Environment Programme (UNEP), Environment for development perspectives: Mercury use in ASGM, (Geneva, 2011). See Paul R. Epstein and Jesse Selber, eds., Oil: A Life Cycle Analysis of its Health and Environmental Impacts, Centre for Health and the Global Environment Harvard Medical School (2002), p. 21.