Environmental Engineering Reference
In-Depth Information
400 to 175 years- by ~55 % (Fig.
12.6
). This implies that a considerable quantity of
iron resources has disappeared within 10 years! Such a trend was significant until
1975 but the changes have become smaller after 1980. So why did this proved re-
source disappear?
One reason is that during the decades of 1960-1970, a major innovation occurred
in the iron & steel industry. Until then, it was usual to locate the steel-works near to
the mines of the main raw materials of iron ore or coal. But, a new business model
(seaside iron-making) became established mainly by Japanese steel makers. Its new
concept was to produce high-quality steel at low cost by importing high quality iron
ores and coals, and by using large-scale blast furnaces. In order to perform efficient
iron-making using a large blast furnace, it was necessary to ensure stable supplies of
large quantities of high-grade iron ores and coking coals. This required a reduction
in transportation costs for the raw materials from Brazil, India and Australia which
led to economic use of large ships for the long distance transportation necessary. As
such, seaside iron-making became popular, most of small pit-mines were closed,
thus reducing the economically viable resources; for instance, the last iron ore mine
in Japan was Kahaishi mine and was closed in 1993.
This illustrates the point that whether the material existing in nature is classed
as a 'resource' or not is dependent simply on whether production using that natural
material is economically justified or not. Thus, the same substance can be a 're-
source' or just simply 'rocks', depending on the economic and geographical con-
ditions, combined with technological progresses. It may thus be better to simply
define 'resource' as follows:
1. Located at a minable place;
2. Containing useful substances and concentrations;
3. Gathered in sufficient quantity; and of course,
4. Being capable of being exploited economically.
These days, the utilization of waste materials through recycling is widely promot-
ed. Such recycling materials are sometimes called 'secondary' resources but the
technological and economic viability of their recycle can vary significantly. Used
paper and steel scrap are representatives of secondary resources where their re-
cycle is both technologically and economically viable. On the other hand, many
wastes can be recycled only through significant additional expenses of preliminary
selection, separation, detoxification and so forth by the waste generators and/or
handlers. Such cases may be also regarded as broadly economically justified when
the costs of recycle are compared with costs for the proper disposals of the wastes
concerned. Not only iron & steel but also many base metals are used in large quan-
tities by society and therefore collection of such metal scraps is relatively easy, so
that base metals are suitable materials for recycling. It is thus important to balance
the amounts of metal production from ores and scraps to mitigate the degradation
of primary resources.
