Exploitation of the world’s mineral deposits has defined human development and lies at the very heart of modern industrial society. But the mining of our mineral deposits has serious environmental consequences. The quest for mineral riches has damaged vast tracts of otherwise unspoiled land, and today threatens national parks and other ecologically sensitive areas. The waste produced by mining far exceeds that from all other sources, and even outstrips the natural erosion of the world’s streams. The extraction and processing of ore consume huge amounts of energy and so are major partners in the problem of climate change caused by the burning of fossil fuels. The refining of ore releases huge quantities of toxic gases into the atmosphere, and is a major contributor to acid rain. As a result, the environmental impact of our exploitation of mineral deposits can be severe.
The amount of rock waste produced by mining activities is truly staggering, particularly when low-grade ores are recovered by surface or “open pit” methods. The Bingham Canyon copper mine in Utah, for example, has removed an entire mountain and excavated a pit over 3 kilometers (2 miles) across and 1 kilometer (3300 feet) deep (Fig. 18B). This mine alone has removed 3.3 billion metric tons of material, an amount seven times greater than was excavated in the building of the Panama Canal. At the height of its production, the mining operation removed 400,000 metric tons of material every day, three-quarters of which was rock waste. At only 0.3 percent copper, the remaining 100,000 metric tons of ore that the mine processed daily produced a further 97,000 metric tons of waste. Worldwide, close to 30 billion metric tons of material a year, or almost twice the estimated amount of sediment carried by the world’s streams, is moved by mining activities.
Figure 18B: Bingham Canyon Mine.
The Bingham Canyon copper mine in Utah is one of the largest in the world, having excavated over 3 billion metric tons of rock. At peak production 400,000 metric tons of material were moved daily to recover just 3000 metric tons of copper.
Moving such vast quantities of material and processing the extracted ore requires huge amounts of energy. Aluminum production and steelmaking, for example, are particularly energy-intensive processes. Worldwide, the excavation and refining of ore uses up to one-tenth of all the energy produced each year—enough to supply 80 percent of the world’s annual electricity use! Because most of this energy is supplied by the burning of fossil fuels, mining is a major contributor to the environmental problems caused by energy use, such as air pollution, acid rain, and the climate changes linked to increased atmospheric carbon dioxide levels.
Serious contamination problems are also associated with leaching of the waste material produced by mining and with the refining process known as smelting, which extracts metal from its ore. Although most rock waste is chemically inert, the finely ground tailings left behind after ore has been concentrated can be highly reactive, producing acid mine drainage and contaminating surface waters with toxic metals. Up to 16,000 kilometers (10,000 miles) of streams are estimated to have been affected in this way in the United States alone. When mining efforts necessitate deforestation of vast areas, silting of lakes and streams can occur as a result of the resulting increased erosion.
The smelting of ore releases huge quantities of pollutants into the atmosphere. The extraction of metals from metal sulfide ores, for example, is estimated to be responsible for the annual emission of 6 million metric tons of sulfur dioxide, the primary cause of acid rain. Smelting also emits arsenic, lead, and other toxic chemicals, and when unchecked, can produce environmental disaster areas in which little of no vegetation will grow. A disaster area around the old nickel smelters in Sudbury, Ontario, for example, once occupied over 100 square kilometers (almost 40 square miles).
The damage caused by the exploitation of mineral deposits is significant and poses one of the major dilemmas facing modern society. Mining is an inherently destructive industry that does not readily lend itself to environmental mitigation by pollution control. Put another way, mining is a very dirty business! Yet mining is an economic activity upon which civilization depends. The very prosperity of industrial nations like the United States and Canada, and the high standard of living that their inhabitants enjoy, depend on the use of mineral products.
If the devastating environmental impact of mineral extraction is to be lessened, it cannot be done simply by demanding cleaner mines. Instead, more mineral-efficient economies are needed that emphasize the recycling, repairing, and remanufacturing of mineral products. Also needed are substitutes for mineral products that can be produced with less damage to the environment. A particularly successful example of such a substitute is the replacement of copper wire by fiber optics made from glass.
Environmental issues associated with resource exploitation have led many citizens and groups to call for fundamental changes to our consumer-driven society. For example, although residents in the United States now recycle 65 percent of the aluminum they use, they still throw away 16 million metric tons of metal each year. Only by learning to reuse and recycle metals more efficiently while lessening our dependence on mineral products can we significantly reduce the environmental impact of their production.