Metals recycling: economic and environmental
Robert U. Ayres *
INSEAD, Boule6ard de Constance, F-77305, Fontainebleau, France Received 17 July 1997; accepted 27 July 1997
We are in a period of economic transition. The ‘cowboy economy’ of the past is obsolescent, if not obsolete. Environmental services are no longer free goods, and this fact is driving major changes. Recycling is the wave of the (immediate) future. The potential savings in terms of energy and capital have long been obvious. The savings in terms of reduced environmental impact are less obvious but increasingly important. The obstacle to greater use recycling has been the fact that economies of scale still favor large primary mining and smelting complexes over (necessarily) smaller and less centralized recyclers. But this advantage is declining over time as the inventory of potentially recyclable metals in industrialized society grows to the point that efficient collection and logistic systems, and efficient markets, justify significant investments in recycling. Increasing energy and other resource costs, together with increasing costs of waste treatment and disposal, will favor this shift in any case. But government policies, driven by unemployment and environmental concerns, taken together, may accelerate the shift by gradually reducing taxes on labor and increasing taxes on extractive resource use. © 1997 Elsevier Science B.V.
Keywords: Pollution; Environment; Sustainability; Re-use; Re-manufacturing; Recycling; Metals; Mining; Overburden; Gangue
* Tel.: _33 1 64987672; e-mail: Ayres@INSEAD.FR
0921-3449:97:$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S0921-3449(97)00033-5
146 R.U. Ayres : Resources, Conser6ation and Recycling 21 (1997) 145–173 1. Background: the present situation
Economic development in the developing countries over the next half century, at recent growth rates, combined with unavoidable population growth, would require a many-fold (more or less) increase in the consumption of natural resources. But materials consumed by the industrial economic system do not physically disappear. They are merely transformed to less useful—or harmful—forms. In some cases (as with fuels) they are considerably transformed by combination with atmospheric oxygen. In other cases (such as solvents and packaging materials) they are discarded in more or less the same form as they are used. In the case of metals, the subject of this paper, they are chemically degraded and, in some cases, physically dissipated.
Enormous quantities of metal ores are extracted from the earth’s crust. Table 1 shows world production of concentrated (or selected) metal ores and metals.1 The rate of extraction is increasing rapidly (Fig. 1). Annual production (i.e. extraction) of just three metal ores—copper, gold and iron—in the US in 1994 was about 2.5 Table 1
World production of metal ores 1993 (MMT)
Gross weight of Metal content Net weight of Mine and mill waste ore MMT % metal MMT MMT
Aluminum 106 19 19.8 86
Chromium 10 30 3.0 7
Coppera \2500 0.4 9.4 \2 490
Goldb :466 0.0005 0.002 :466
Iron 989 52 517.0 472
Leada \45 6.5 2.9 \42
Manganese 22 33 7.2 15
Nickela \130 0.7 0.9 \129
Platinum groupb :50 0.0005 0.0002 :50
Uranium (1978)c 1900 0.002 0.04 1 900
Zinca \219 3.2 6.9 \212
Source: calculated from data in US Bureau of Mines, Minerals Yearbook 1993. a Extrapolated from US data on ore treated and sold vs marketable product for 1993, using same implied ore grade.
b Based on ore grades mentioned in text for mines in South Africa only. c Based on data from . No current data available.
1 The quantities of ore removed from the earth are normally much larger, but physical separation techniques leave much of the excess material at the mine, where it is piled up into small mountains, but not put back into the ground. For instance, copper ores mined in the western part of...