Page 235 - Materials Chemistry, Second Edition

4.5 Impact Categories, Impact Indicators and Characterisation Factors 219

For a derivation of Equations 4.4–4.6 a continuous annual consumption is
presumed that may be valid as a rough approximation. For all resources it is
difficult to determine the supplies or world reserves. Known supplies depend on
the respective status of exploration which again depends on economic factors.
Beyond that there are estimations of world reserves justifying exploitation and
estimations of entire occurrences (those justifying exploitation at present + those
not (yet) justifying exploitation). The problem remains that a justification of
exploitation is a function of the price of the respective raw material. If the demand
rises, for example, due to a real or politically caused shortage, the reserves increase
because less productive resources or those difficult to obtain will also be exploited.
However, even a free-market economy needs some time to transact the investments
necessary for the discovery of new resources and an operation of mines, and hence,
reliability of data cannot be assumed. Because many metals, for example, relatively
noble ones like copper are not really consumed but are accumulated in the
technosphere 100) , it is unclear whether these stocks are to be included as reserves
or not. Another question arises: Where is the starting point for mine exploitation
of, for example, landfills (‘waste mining’)?
Furthermore, the employment of weighting factors requires tables, which lists
data on reserves and consumption for as many raw materials as possible. For
this reason, mostly explored (safe) reserves are used for the determination of the
‘static range’. For oil this ‘time’ amounts to approximately 40–45 a, that is, it is as
much newly explored as consumed. By comparison with comparable figures for
coal it is nevertheless possible to state that the static ranges for coal are twice (hard
coal) or 10 times (lignite) as large as those of oil. For an aggregation, relative data
are completely sufficient as long as they were procured by uniform methods. In
Table 4.7 the static ranges and resource scarcity factors for the most important
abiotic resources are provided.
For the following elements ‘high to extremely high’ static ranges are indicated by
Crowson 101) : beryllium (Be), gallium (Ga), kaolin, lithium (Li), magnesium (Mg),
phosphate, rare earths and silicon (Si); ‘large’ for germanium (Ge). These elements
and minerals, therefore, do not have to be included in the weighting of resources.
The inclusion of the rare earths in this list has recently been challenged because a
scarcity of several of these elements is beginning to cause serious concerns. This
scarcity seems to be economically/politically caused and not due to a real physical
shortage. A shortage of lithium seems to be possible, too, if production and use of
electric cars increase.
A large static range can also occur because of very small annual consumptions
that may increase with new technologies, for example, indium in the cell phone
technology or if gallium were largely used as semiconductor material in the future.
On the basis of resources consumption in agriculture (e.g. phosphates) Brentrup
and co-workers do not recommend an untimely aggregation of abiotic resources

100) Brunner and Rechberger (2004).
101) Crowson (1992).