Exergy evolution of the mineral capital on earth - circe

12 STARTING POINT, OBJECTIVES AND SCOPE
Additionally, two PhD <strong>the</strong>sis accomplished in <strong>the</strong> CIRCE institute <strong>of</strong> <strong>the</strong> University <strong>of</strong>
Zaragoza and directed by Antonio Valero, have applied and have fur<strong>the</strong>r developed
<strong>the</strong> exergoecology approach. The first one entitled “Análisis De Los Costes Exergéticos
De La Riqueza Mineral Terrestre. Su Aplicación Para La Gestión De La Sostenibilidad”
[276] (<strong>Exergy</strong> cost analysis <strong>of</strong> <strong>the</strong> <strong>mineral</strong> wealth on earth. Applicaton for <strong>the</strong>
management <strong>of</strong> sustainability), was carried out by Lidia Ranz in 1999. The second
one was written by Edgar Botero one year later: “Valoración Exergética De Recursos
Naturales, Minerales, Agua y Combustibles Fósiles” [34] (<strong>Exergy</strong> assessment <strong>of</strong>
natural resources, <strong>mineral</strong>s, water and fossil fuels).
Ranz developed an approximation <strong>of</strong> <strong>the</strong> R.E., based on <strong>the</strong> methodology proposed
by Szargut [336] and calculated <strong>the</strong> chemical exergy <strong>of</strong> some important <strong>mineral</strong>
commodities. Her reference environment was chosen according to <strong>the</strong> abundance
criterion, i.e. <strong>the</strong> components <strong>of</strong> <strong>the</strong> R.E. should be <strong>the</strong> most abundant ones found
currently in nature. For that purpose, she carried out a comprehensive and systematic
analysis <strong>of</strong> <strong>the</strong> most abundant <strong>mineral</strong>s on earth for each chemical element. An
important message <strong>of</strong> her study was that exergoecology is irrevocably connected to
geology. A problem with Ranz’s proposed R.E. is that if we assign zero exergy to <strong>the</strong>
most abundant substances, we are decreasing arbitrarily <strong>the</strong> natural <strong>capital</strong>, because
many abundant <strong>mineral</strong>s like sulfides naturally evolute to <strong>the</strong> most stable species.
Botero extended <strong>the</strong> exergy analysis to o<strong>the</strong>r natural resources such as water and
fossil fuels. In his PhD, <strong>the</strong> concept <strong>of</strong> exergy replacement costs was fur<strong>the</strong>r developed,
and <strong>the</strong> exergy abatement costs, were firstly applied. The exergy replacement cost
was first calculated as <strong>the</strong> exergy required for replacing a resource from <strong>the</strong> R.E.
to <strong>the</strong> current conditions found in nature, with <strong>the</strong> best available technology. The
exergy abatement cost was proposed as a physical way to measure <strong>the</strong> exergy cost for
avoiding <strong>the</strong> environmental externalities associated to <strong>the</strong> use <strong>of</strong> fossil fuels, with
<strong>the</strong> best available technology.
Both PhD <strong>the</strong>sis, <strong>the</strong> book <strong>of</strong> Naredo and Valero [239], and <strong>the</strong> first paper describing
<strong>the</strong> exergoecological method (Valero [365]), constitute <strong>the</strong> basis and starting point
<strong>of</strong> <strong>the</strong> present study. The fundamental concepts described in <strong>the</strong> previous works are
used in this <strong>the</strong>sis and are fur<strong>the</strong>r developed.
1.6 Scope, objectives and structure <strong>of</strong> this PhD
The aim <strong>of</strong> this PhD is <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> state <strong>of</strong> <strong>the</strong> <strong>mineral</strong>’s exergy on earth and
its degradation velocity, due to <strong>the</strong> human action. As opposed to Botero’s and Ranz’s
PhDs, where <strong>the</strong> exergoecological analysis was applied in a static way, in this <strong>the</strong>sis
<strong>the</strong> time factor constitutes a fundamental variable. For that purpose, an exhaustive
analysis <strong>of</strong> <strong>the</strong> geochemistry <strong>of</strong> our planet and its past, current and future declining
resources needs to be carried out.