From Thermodynamics to Economics and Ecology - Thanatia: The Destiny of the Earth's Mineral Resources - page 75

attempts to mimic Nature he must use voltaic arc temperatures, such as those al-
ready reached by lightning in a thunderstorm. Further evidence of Man's inability
to imitate Nature is the working temperature (37 o C) of living tissue building and
chemical combustion of food. Such a low temperature is unthinkable in industrial
processes including distillation which requires thousands of more Joules in the sep-
aration than the mixing process. This is of course something which natural systems
are perfectly designed to accomplish. Indeed using manmade technology to separate
sugar from salt would necessitate a selective organic solvent for sugar, followed by
a period of evaporation and subsequent cooling of that same solvent. The expense
and effort involved would effectively mean that in the interests of time and resources
it would be better to throw away such mixture. It is this minimum reversible cost
which represents the exergy value - the authors' reference point for the physical cost
of things. It is however important now that the topic progresses to the exergy cost
concept, which is closer to the human perception of cost.
Many things society values are worthless from a thermodynamic point of view.
This is shown in the striking examples of a beautifully designed Bohemian glass or a
stone sculpture of say Rodin, or even gold. Their exergy content is zero in practical
terms. Glass, stone or gold are found in Nature as rocks or minerals and their
manipulation adds no additional exergy to the object itself. These examples clarify
that the source of an object's worth may not be related to its exergy content. In fact,
many monetary values juxtapose their equivalent physical value as prescribed by
Thermodynamics. How Physics can help is through a physical valuation of objects,
i.e. by stating the number of energy units required in the manufacture of a given
product (that is to say its embodied exergy or exergy cost). This is by no means
trivial information, since in contrast to the financial markets, natural sciences are
not affected by value manipulation and other somewhat subjective externalities.
3.3.2.2 Exergy cost definition and allocation rules
Exergy cost can be defined as the sum of all resources required to build a product
from its component parts, expressed in exergy units. The concept was internation-
ally presented by Valero et al. (1986) in their “General Theory of Exergy Saving”,
where a general matric procedure, able to be implemented into computer software,
was developed for the cost determination of energy systems 6 . This methodology
was further demonstrated to be isomorphous to the Input-Output theory of Leon-
tief (1951). Szargut (1987) proposed the concept of cumulative exergy consumption
almost simultaneously 7 with the exergy cost of Valero et al. (1986). Both in fact,
precisely define embodied exergy, which the authors will now go on to explain.
6 Such procedures were patterned from the ideas of systematic splitting of “Fuels and Products”
for exergoeconomic costing allocation in energy systems developed by Tsatsaronis and Winhold
(1985).
7 The cummulative exergy consumption was first formulated in Szargut (1978) (see Sec. 2.6.3.4)
but the international community was not aware of it until the publication of the topic Szargut et al.
(1988). In any case both exergy cost and cummulative exergy consumption are refined concepts
of the former “embodied energy” concept attributed to Hannon (1973).