GEO-6 Chapter 4: Cross-Cutting Issues

and mining industry produced around 90 billion tons of mine waste, excluding construction materials (Mudd and Jowitt 2016). This massive mining scale requires an acute focus on environmental assessment, monitoring and management for primary resource extraction (Hudson-Edwards 2016; Mudd and Jewitt 2016). Currently, much of the mine waste is stored, exposed to changing environmental and management conditions. The 2015 Samarco tailings dam failure in Brazil, among other events, demonstrated how long-term storage strategies are not solutions (Philips 2016; Roche, Thygesen and Baker 2017). Some mined resources are widely distributed around the world, including sand, gold, copper and lead-zinc; other resources, such as nickel, rare earth elements and phosphorous, are concentrated in a small number of countries. Given the fundamental contribution of mineral resources to modern social systems, technologies and infrastructure, these materials need to be assessed for their role in modern society. This analytical approach is known as criticality – examination of the potential implications of supply disruption, resource substitution, recyclability and environmental impacts (Graedel et al. 2015) For example, many metals such as iron, copper, gold and lead are recyclable. Other minerals, such

Traditionally, the discovery of new and accessible deposits of non-renewable resources has kept pace with or even outpaced growing extraction, so concern over the depletion of such resources would not be considered highly important (Mudd, Weng and Jowitt 2013; Mudd and Jowitt 2014; Weng et al. 2015; Mudd and Jowitt 2017). However, as a measure of their quality, the grades of most mined ores are in gradual decline, meaning that the most easily and economically refined ores have already been exploited (Ruth 1995; Mudd 2010). Larger amounts of lower grade ore have to be extracted and processed to meet global demands, as can be shown by tracking exploitation of copper ore deposits (Figure 4.10) . When declining ore grades are combined with the larger project scales needed to extract enough ore to supply market demand, greater risks threaten the natural environment. More land is cleared, or simply removed and shipped away, as mountain-top removal illustrates. Larger volumes of mine waste accumulate, with heavy metals and reactive agents recombining into noxious compounds. Water pollution risks, especially from acid and metalliferous drainage, increase. Threats to biodiversity become more complex. Energy demand intensifies, along with associated greenhouse gas emissions (Norgate and Haque 2010). To meet global demands in 2014, the global metals

Figure 4.10: Example of ore grade decline over time for copper mining, showing world annual copper production and estimated tailings generated annually

4 000

20

18

3 600

16

3 200

2 800

14

12

2 400

10

2 000

4

8

1 600

6

1 200

Tailings Production (Mt/year)

800

Ore Grade (%Cu), World Production (Mt Cu/yr) 4

400

2

Mt - million metric tonnes

0

0

1770

1795

1820

1845

1870

1895

1920

1945

1970

1995

Year

Estimated Copper Tailings (Mt/year)

World Copper Production (Mt Cu/year)

Copper Ore Grade (%Cu)

Source: Ruth (1995); Crowson (2012); Mudd, Weng and Jowitt (2013); Mudd and Jowitt (2016).

92

Setting the Stage