Geology Reference
In-Depth Information
imum circle). If the solar radiation incident on the top of the Earth's atmosphere
is 1:74 10
17
W, in fact, life on Earth received each second 1:74 10
17
J. Hence,
an anthropic energy/time universal equivalence is proposed as:
1s = 1:74 10
17
J
(2.2)
Time hence becomes energy-on-Earth and energy per unit surface of Earth can
be converted into time through this constant. Ultimately, “Time may be the uni-
versal measure of natural resources” (Valero, 1995).
On the other hand, Giampietro and Pimentel (1991) consider that fossil fuels and
fertilisers represent a bonus of space-time for society. They propose that 1000 kcal
of energy derived from fossil fuel equals 0.7 m
2
/yr of biosphere space-time activity
(0.016 MJ=m
2
=day). Equally, 1 kg of nitrogen chemically produced fertiliser is
equivalent to 823 m
2
/yr of biosphere space-time activity.
That is to say, natural productivity indices relate the natural energy cost of
producing something within the space required in a time unit. Hence, land, energy
and time can be theoretically interconverted through these indices. Accordingly, all
natural processes can be eventually converted into time units by simply dividing an
accumulated energy density [E]/[L
2
] by a natural productivity [E]/[L
2
]/[t] as shown
in Eq. (2.2). Furthermore, all artificial processes can also be converted into time by
dividing power into energy. The time needed to manufacture products can then be
calculated as the time to produce resources plus the residence time of the process.
This can be done because spent time is additive.
In real world systems, the direction of time is perceived as an irreversible increase
of entropy or exergy destruction. Therefore, one can construct time balance-sheets
in the same way as one does for exergy or money. There is no reason for excluding
such units. Knowledge, culture and civilisation have all been obtained at the cost
of natural resources which required time, space and energy to be produced.
Time is the most limited resource one has, as one only has one life to live. The
only manner to save “time” is via an improvement in e
ciency, conservation and
an increasing use of renewable resources. A finite world with finite natural capital
and a deadly slow replacement speed needs more time. This fact must in turn be
demonstrated by accounting tools so that mankind collectively, its governments,
corporations and individuals become increasingly conscious of the fact that time is
being lost. Ironically, the faster humankind move, the more (accumulated planetary)
time is lost.
Yet time as a unit of measure provides more a philosophical message than a
practical one. Its use as an accounting magnitude is complex and would require
much more in-depth development. Therefore, the authors proposal is to resort to
the exergy indicator, which provides an objective and integrated measure of the
quality of resources and can be easily incorporated into the realm of Economics
through the Thermoeconomics approach as explained next.
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