Page 276 - Materials Chemistry, Second Edition

262 R.K. Rosenbaum et al.

While being very reproducible and also easy to determine, the relevance of exergy
loss to the scarcity and future availability of the resource is not obvious and
therefore these methods are not recommended by the European Commission
(EC-JRC 2011). However, the cumulative energy demand (CED) method
(Frischknecht et al. 2015) is still used frequently as a resource accounting method in
LCA studies and is also part of various comprehensive LCIA methods like CML-IA
for fossil fuels (Guinée et al. 2002), ReCiPe (Goedkoop et al. 2012) and the
Ecological Scarcity method (Frischknecht and Büsser Knöpfel 2013).
Viewing resource use from a sustainability perspective, the characterisation at
midpoint level in the environmental mechanism (Fig. 10.28) should address its
impact on the future availability of the resource for human activities. Several cat-
egory 2 methods do this through incorporating a measure of the scarcity of the
resource, expressed by the relationship between what is there and what is extracted,
i.e. between the size of the stock or fund and the size of the extraction. However,
there are different measures to determine the size of the stock or fund yet to be
extracted.
Figure 10.29 shows a terminology for classifying a stock resource into classes
according to their economic extractability and whether they are known or unknown.
Here we will describe those most used in LCIA. The reserves are the part of the
resource which are economically feasible to exploit with current technology. The
reserve base is the part of the demonstrated resource that has a reasonable potential
to become economically and technically available if the price of the resource
increases or if more efficient extraction technology becomes available. Ultimate
reserves are the resources that are ultimately available in the earth’s crust, which
include nonconventional and low-grade materials and common rocks. This reserve

Fig. 10.29 Resource/reserve classification for minerals [taken from U.S. Geological Survey
(2015)]