ABSTRACT
The mining industry has been an important driver of economic growth and has helped to facilitate the rapid development of many countries for decades. However, the ever-increasing demand for mineral and metal resources in order to meet the highly dynamic technological landscape has led to most of the richest mines being rapidly depleted. Reports by the United Nations Environment Programme (UNEP) on ‘Critical Metals for Future Sustainable Technologies and Their Recycling Potential’ (Buchert et al., 2009) and the U.S. Environmental Protection Agency (EPA) about ‘Rare Earth Elements: A Review of Production, Processing, Recycling and Associated Environmental Issues’ (Weber and Reisman, 2012) and a number of international initiatives show that global governments have concerns on the security of supply of certain metals. As a result, many mining companies are re-evaluating the current sources of metals, turning to deposits with lower-grade ores. For example, in the nineteenth century, copper was being mined from deposits with 10% ore grade (Gordon, 2002), whereas, today, the world average copper grade is about 0.6%. This trend applies to a number of various other metals such as gold, silver and cobalt. This means the extraction of the metals from such lower-grade ores generates more mine waste per unit extracted as more tonnes of inert materials must be physically removed, crushed, screened and later dumped to yield a reasonable concentrated fraction. This adds to the already extensive quantities of waste currently in existence and, thus, further impacts negatively on the environment and also affects the communities living in the locality of these mines.
