Mineral Resources Management and the Environment

U. Aswathanarayana

• Publisher: CRC Press
• Year: 2003
• ISBN:
  9781135292058
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria civile

Through an exploration of the links between geologic setting, mining and process technologies, economics, environment and stakeholder communities, this text addresses ways in which the mineral industry can be made safe, efficient and ecologically sustainable, focusing in particular upon the following key themes: a review of the current status of t

CHAPTER 1
Introduction

1.1 STATUS OF THE WORLD MINING INDUSTRY

1.1.1 Introduction

Förstner (1999, p. 1–3) gave an evocative vision of the directions in which the mining industry will have to make progress in order to cope with the increasingly serious environmental impacts of mining.

The volume of non-fuel minerals consumed during the five decades since the Second World War has exceeded the total extracted from the earth during all the previous history of mankind. While the world population doubled during the period 1959–1990, the production of six major non-ferrous metals (aluminium, copper, lead, nickel, tin and zinc) increased eight-fold. The most serious problem facing the mining industry presently is the enormous mass of the mine tailings (about 18 billion m³/y), which incidentally is the same order as the quantity of sediment discharge into the oceans. As progressively lower grades are worked, the mass of the mine tailings is expected to double in the next 20–30 years. Great attention is being paid to the mitigation of the sulphidic mining wastes, which produce acidic leachate containing heavy metals that could contaminate soils and water. Multidisciplinary, multi-institutional research is going on countries like Canada (MEND project) and Sweden (MiMi project) to mitigate the adverse consequences of Acid Mine Drainage (AMD).

The Industrialised countries are going in a big way for miniaturization, economies of scale, recycling and substitution. Consequently, the consumption of raw materials in the Industrialised countries is actually going down. The new trend in this regard has been described as “dematerialisation”, whereby less virgin material is used for extraction, the production of waste materials is minimized, and useful materials are recycled to the maximum extent possible. Future development will strongly depend upon the extent and the efficacy of recycling.

Enhanced environmental awareness around the world has profound consequences. In future, an orebody will be mined only when it is found to be viable after the social and remediation costs are incorporated in the price of the product. Several industrialized countries have become strong adherents of the concept of “ecologically sustainable development”, so much so that Ranger Uranium in Australia has placed A$ 2 billion in the bank to cover the final closure of the mining

Zimmerman’s dictum, “Resources are not, they become”, has profound technosocioeconomic implications. According to him, what constitutes a resource is governed by two considerations: (1) knowledge and technical means must exist to allow its extraction and utilization, and (2) there must be a demand for materials and services produced. It is therefore perfectly possible that what was yesterday a non-resource, can now become a resource today because advances in science and technology made it possible for that substance to be put to economic use.

This can be illustrated with the example of nickel. In 1887, when Sudbury (Canada) started producing nickel, they had trouble selling it – the total world demand for nickel at that time was less than 1000 t. During the twentieth century, the demand for nickel rose about 900 fold (to 900,000 t). This came about because numerous new uses were found for nickel (Ni-steels, Ni-Cd batteries, Ni plating, nichrome filaments, cupronickel compounds, etc.).

A mineral resource is “a concentration of naturally occurring solid, liquid or gaseous material in or on the earth’s crust in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible” (U.S. Bureau of Mines, 1989).

Traditionally, mineral resources are divided into three categories: (1) metallic minerals (e.g. iron ore), (2) non-metallic minerals (also known as industrial minerals) (e.g. clays), and (3) fuels (e.g. coal). Until the early part of the twentieth century, metallic minerals dominated the mineral market. Presently, non-metallic minerals and fuels exceed the metallic minerals both in terms of quantity and the value of world production.

More than two-thirds of the 92 natural elements are metals. Some of them, such as, Au, Ag, Cu, Pb, Sn, Hg, S, etc., have been known and used since ancient times. Improvements in analytical techniques led to the identification of a large number of metals. The specialized and exacting requirements of modern industries led to profound changes in the ways metals are detected, extracted, alloyed and used. New applications for metals are being found all the time, e.g., use of germanium in semiconductors, use of cerium in high temperature superconductors, development of zircalloys in nuclear industry, titanium alloys in aerospace industry, metal glasses, etc. On the other hand, some traditional metals (e.g., Fe and Cu) are being substituted by plastics, fiberglass, ceramics, etc., thus increasing the demand for industrial minerals. The non-metallic minerals are being increasingly used as insulating material, fillers, glasses, and construction material. The ever-increasing need for more fertilizers (due to the need to grow more food for the increasing population of the world) will greatly increase the consumption of fertilizer raw materials, like apatite, potash feldspar, etc.
Thus, the demand for a given mineral depends upon technology and markets.

Ore is defined as a “mineral or rock that can be recovered at profit”. Gangue is the useless material associated with the ore. Protore is mineralized rock that is too lean to be economically minable. The above definition of ore has the economic criterion built into it. Thus, a mineral does not remain an ore or non-ore for all time. A mineral can be regarded as ore so long as technology and market demand make it economical to mine it. Alternately, what was yesterday a non-ore may become ore today as technology and market demand make it economically worthwhile to mine it now.

1.1.2 Status of the metal mining industry

Appendix B carries a country-wise listing of about 400 large (>1 Mt/y production) metal mines in the world (source: Mining Magazine, Jan. 2000; M = million = 10⁶). Appendix C gives the world production of minerals/metals in 1998 (source: Minerals Yearbook, 1998, v.1, US Geological Survey, 2000). The information in the Appendix B is extracted and tabulated in Table 1.1. It may be noted that the production figures given for different kinds of mining are only estimates (based on the mean production level of a particular category of mines multiplied by the number of mines in that category).

The following conclusions may be drawn from Appendices B & C:

1. The following ten countries have more than ten large metal mines: Australia (114), USA (81), Canada (67), South Africa (54), Chile (49), Brazil (30), Zimbabwe (23), Peru (21), Mexico (20), India (18).

2. Opencast mining is the most prevalent form of mining. It accounts for 60% of the number of mines (236 out of 395), and 69% (1095 Mt/y out of 1569 Mt/y) of the ore production.

3. Mining of iron ore: Virtually all the major iron ore mines (50 out of 52) are opencast. The only underground iron ore mine in the world is in Kiruna, Sweden. Opencast mining accounts for 95% of the production from large mines (267 Mt/y out of 281 Mt/y). Small-scale and artisanal mining of iron ore is invariably opencast. The gross production of iron ores (1020 Mt in 1998) from all types of mining is about 3–4 times that of the production from large mines.

4. Mining of ores of gold and silver (occasionally copper): Most commonly gold occurs in the form of intermetallic compound of Au-Ag, known as electrum. Opencast mining accounts for 59% of the number of mines (105 out of 178) and 68% of the production (422 Mt/y out of 619 Mt/y). It is significant that though the number of underground mines is 23% (41 out of total of 178 mines), they account for 14% of the production (88 Mt/y out of 619 Mt/y). The world production of gold from different types of mining in 1998 was 2480 t. Artisanal gold mining is almost invariably opencast, and has certain characteristics, which have a profound impact on mining. In the lateritic occurrences of gold, the metal tends to be enriched in the mottled zone, which occurs 3–5 m below the surface layer of red loam (“murram”). Artisanal miners use sluice boxes and panning to concentrate gold, and mercury amalgam method to extract gold. As against this, cyanidation is the most common method of extracting gold from ores produced in large mines. The environmental implications of different methods of mining and extraction of gold are discussed elsewhere (Section 7.6).

Table 1.1 Important metal mines in the world (Source: Mining Magazine, Jan. 2000).

5. Mining of ores of base metals (Cu, Pb, Zn), Ni, Cr, PGM, As, etc.: Though the number of opencast mines (65) and underground mines (60) for these metals is comparable, the production from the opencast mines (325 Mt/y) is almost double that of the production from the underground mines (166 Mt/y).

6. Mining of bauxite: As bauxite deposits are usually surficial alteration blankets, they are invariably mined by opencast methods. Thus, all the 16 large mines producing 71 Mt/y of bauxite are opencast mines. Incidentally, the world production of bauxite in 1998 (122 Mt) is about six times the quantity of bauxite produced in 1980 (about 19 Mt) (Archer et al., 1987, p. 70).

7. The annual production of important metallic ores in the world (in millions of tonnes – Mt) are: bauxite (122), chromite (13), copper (12), iron (1020), lead (3), Mn-ore (19), nickel (1), titanium (5), zinc (8), totaling about 1203 Mt. The annual production of important industrial minerals in the world (in terms of Mt) are: asbestos (2), barite (6), boron minerals (4), cement, hydraulic (1520), clays (43), diatomite (2), feldspar (8), fluorspar (5), gypsum (107), lime (115), magnesite (11), nitrogen (106), peat (26), perlite (2), phosphate rock (145), potash (25), pumice (12), salt (192), sand and gravel (110), soda ash (32), sulphur (58), talc & pyrophyllite (8), totaling about 2539 Mt. Thus, the production of industrial minerals is more than double that of the metallic minerals.

1.1.3 Status of coal mining industry

An examination of the energy consumption (in the form of primary, commercially-traded fuels) in different regions of the world in 2000 (Table 1.2; source: Mining Magazine, Sept. 2001, p. 103) leads to the following conclusions: (1) North America

Table 1.2 Energy* production and consumption (2000) (Mt of oil equivalent) (source: Mining Magazine, Sept. 2001, p. 103).

Table 1.3 Particulars of important of coal producing countries in the world (source: Mining Magazine, Sept. 1999). Proven reserves of coal in Mt in 1998; Coal production in Mt in 1998.

(USA, Canada and Mexico) account for about 30% of the total global energy consumption, with roughly equal contribution from oil, natural gas and coal, (2) The important consumers of energy in the Asia-Pacific region, are China, Japan and India, and because of the strong dependence of China and India on coal, the energy contribution from coal in their case far outweighs that from oil and natural gas.

Table 1.3 carries the particulars of reserves and production of hard coal (anthracite and bituminous coal) and brown coal (sub-bituminous coal and lignite), arranged country-wise and region-wise (such as, North America, Latin America, Europe, Former Soviet Union countries, Africa and Middle East, Asia-Pacific).

An analysis of the data given in Table 1.3 leads to the following conclusions:

1. The following eleven countries which have reserves of more than 10 Bt of coal each (all grades): USA (247), Russian Federation (157), China (115), Australia (90), India (75), Germany (67), South Africa (55), Kazakhstan (34), Ukraine (34), Poland (14) and Brazil (12), with aggregate reserves of 900 Bt, account for 91% of the total coal reserves of the world (984 Bt) (B = billion = 10₉).
2. The following eight countries which produce more than 100 Mt/y of coal each (all ranks): China (1236), USA (1014), Australia (356), India (323), Russia (232), South Africa (222), Germany (208), Poland (180), with aggregate production of 3771 Mt, account for 82% of the global production of about 4600 Mt.

Interestingly, two countries, China and USA, produce half of the coal in the world. As we will see later, the large quantities of coal produced and consumed in China has profound adverse consequences on the quality of environment in that country.

1.2 MINING AND THE ENVIRONMENTAL AGENDA

1.2.1 Environmental challenges facing the mining industry

An Environmental impact may be defined as a change in the environmental parameters, over a specified period, and in a specified geographical area, resulting from a particular activity compared to the situation which would have existed had the activity not been performed.

It is no longer possible for a mine to be started merely because its technoeconomic viability has been demonstrated. The mining project has to be socially acceptable as well. Sengupta (1993, p. 22–23) has drawn attention to the “shadow effect” of a mine site. Apart from the degradation of land directly connected to the mine site itself (due to the mine, supporting facilities, waste disposal arrangements, etc.), the shadow effect of the mine site may extend to large areas around the mine site as a consequence of the infrastructure (rail, road, housing, power plants, water storage, etc.) necessary for the performance of the mining operations. Thus, the responsibility of the mining company is not confined to the mine site, but to a large area around it. The mining company has thus to work harmoniously with a variety of land use authorities, concerned with (say) wildlife, forestry, recreation and tourism, fisheries, environmentally-sensitive habitats (e.g., corals, mangroves), parks, reserves, historical sites, native reserves and rights of the indigenous people, urban growth, etc.

Khanna (1999) gave a succinct account of the environmental challenges facing the mining industry.

The adverse effects of mining on the geological environment include changes in the landscape, landslides, subsidence, pollution of water and soil, lowering of groundwater,...