MINING AND THE ENVIRONMENT

Mining and its Impact on the Environment

1. Energy Consumption

The mining industry is a large consumer of electricity. For example, in the USA in 1994, the mining industry, including primary metals production, consumed 158 TWh (i.e. 10¹² Wh) of electricity, which was 5% of total US electricity consumption. In South Africa, in 1995, the mining industry accounted for approximately 25% of electricity consumption. The reason for these figures lies in the quantities of ore and rock that have to be transported by the industry, resulting in huge vehicles or extensive hoisting systems for underground mines. Cooling of deep underground mines is very energy intensive, as is pneumatic equipment, which is used extensively. Smelting of many metals requires large amounts of energy.

2. Air

Surface mines may produce dust from blasting operations and haul roads. Many coal mines release methane, which is a greenhouse gas. However, methane is generally captured, where it is economically feasible to do so. Since some cooling plants use CFCs, HCFCs and HFCs, there is the potential for the release of these ozone-depleting substances, but such releases are tiny. Tailings dams, if not vegetated or capped may also be a source of dust. Radiation is emitted from tailings dams where radioactive elements are found in the ore. Smelter operations with insufficient safeguards in place have the potential to pollute the air with heavy metals, sulphur dioxide, and other pollutants.

3. Water

The mining industry uses large quantities of water, though some mines are able to reuse much of their water intake. Mining brings sulphide-containing minerals into the presence of air, where they are oxidised and react with water to form sulphuric acid. This, together with various trace elements impacts groundwater, both from surface and underground mines. Tailings dams and waste rock heaps are also sources of acidic drainage water, affecting surface and underground water. The chemical deposits left behind by explosives are usually toxic, and they contaminate and increase the salinity of mine water. In situ mining, in which a solvent is allowed to percolate through unmined rock, leaching minerals directly, has the potential to contaminate groundwater. Artisanal mining may impact water where mercury is used to process gold.

4. Land

Since mining moves large quantities of rock, and, in the case of surface mining, overburden (material overlying a mineral deposit that must be removed before mining), land impacts are very large. These impacts may be temporary where the mining company returns the rock and overburden to the pit from which they were extracted. Many copper mines, for example, extract ore that contains less than 1% copper. For many non-ferrous metals, virtually all of the mined ore thus becomes waste. Artisanal mining,e.g. alluvial mining for gold and diamonds, often has an impact far greater than the size of the operation. Many areas are pock marked by thousands of small holes which have been indiscriminately dug in search of precious minerals. Trenches that scar the landscape are problems in some places where artisanal mining takes place. These activities may lead to erosion and the localised destruction of river banks.

5. Health and Safety

Mining operations range from extremely hazardous to being as safe or as dangerous as any other large scale industrial activity. Underground mining is generally more hazardous than surface mining because of the poorer ventilation and visibility and the dangers of rockfalls. The greatest health risks arise from dust, which may lead to respiratory problems, and from exposure to radiation (where applicable). The use of mercury for gold extraction in artisanal mining is very hazardous to health and fertility except without proper equipment.