[Fis] Exergy analysis and ascendancy

  Dear All,

Sorry for my silence during last weeks. I have seen very interesting
postings but I was unable to participate. Now, please, let me return to the
problem of “measuring” sustainability.

I agree with Sergio that there are different and very valuable methods
(Emergy, exergy, material flow accounting, ecological footprint…) capable
of accounting for a resource intrinsic value on a physical measurable basis
but, since I know, there is not yet any method that could be in a similar
extent 'sensitive to life'. Or in other words, I do not know, from a global
perspective, any method that could inform us about the health of
ecosystems, or how far away from the collapse (death) an ecosystem is.

The previously referred methods provide an accounting of scarce natural
resources used or consumed in whatever activity, and from this information
we can indirectly estimate their importance on sustainability of the Earth.
I like very much Emergy approach, because it considers the total energy
income of Earth and it allows to know the maximum amount of energy that we
have available for a sustainable development (am I right, Sergio?). There
is another approach not mentioned yet, which corresponds to the Exergy
Replacement Cost, proposed by Valero and Botero, that goes a step further
of conventional accounting of natural resources. Very quickly, the 'exergy
replacement cost' measures the amount of natural resources that would be
required to restore to Nature, with our present technology, the resources
that have been taken from her (See for more details Proceedings of the
International Conference ECOS’02, Berlin July 2002). This approach not only
informs about the amount of natural resources consumed for producing
whatever good or commodity, but also closes the loop and provides a measure
of the resources that we should consume for returning to nature the
materials we have taken from it.

The problem of measuring the health of ecosystems (or their carrying
capacity) is in my opinion related with some aspects of the FIS discussion
about molecular recognition held a few months ago. In that discussion Shu
Kun explained that he was working on the problem of integrating information
in the process of molecular recognition and entropy. In very poor words (I
am not specialist in biology) I understood that when the state of an
organic molecule varies in the molecular recognition process, it is
necessary for its detection and measurement, not only entropy but also
information:

“Molecular recognition was the very first case which forces us to expand
thermodynamic entropy concept to be an information theory entropy concept,
because the mixing of two idea gases (mixing of oxygen and nitrogen, for
instance) cannot be described by any detectable change of thermodynamic
parameters (no heat change, no pressure change, no volume change and no
temperature change). Therefore, the related Gibbs paradox regarding ideal
gas mixing can never be logically discussed within the frame of
thermodynamics...”

I think that the problem of measuring the health of ecosystems, or their
carrying capacity, is similar in some extent. Pure physical properties,
such as entropy, exergy, energy, emergy… are not enough. I particularly
work with exergy, which informs us about how far away from the equilibrium
a system is. In this sense, exergy is also an interesting property for the
measurement of living beings, because all of them depart from thermodynamic
equilibrium. However, whatever non-living structure which is not in
equilibrium with the environment has also exergy content, e.g. oil, coal...
Further, some organic molecules with a given configuration are very
relevant for living beings, but the same chemical component in other
slightly different configuration, containing in measurable terms the same
amount of exergy, can be a poison. Thus, exergy is a good measurement of
non-equilibrium with respect the environment, but clearly it is not enough.

Exergy is crucial for thermoeconomic analysis, applied to industrial plants
(very different from ecosystems), where it informs about how the resources
consumed in a plant are distributed among the different plant devices. This
is an informational problem. As the thermoeconomic analysis techniques
inform us about the productive process inside the plant and about the
interactions among the different plant devices. Through the re-arrangement
and simplification of physical information (temperatures, pressures, mass
flow rates, compositions...) of different plant devices and mass flow
streams in the plant, one obtains a new, abstract perspective of the
industrial processes, informing about the interactions among the different
plant devices from a productive viewpoint.

If we could find a (several) physical property(ies) in ecosystems, similar
to exergy in industrial processes, that could be relevant for the analysis
of the interactions among the different living beings maybe we would be
able of measuring their carrying capacity and their health since the
viewpoint of their sustainability. My central point is that, in analogy
with thermoeconomic analysis, it would not be necessary to go in depth to
the details of the behavior of each living being, but to its interactions
with respect to the others.

Since ascendency is able of informing us about the organizational level of
an ecosystem, maybe the combination of exergy analysis and ascendency could
provide a more “sensitive to life” information about the carrying capacity
of ecosystems? And maybe the work of Shu Kun could also be applied to the
information-evaluation of the health of ecosystems?

I would highly appreciate your comments respect these speculations
(particularly on how to develop them formally).

Best regards

Luis
Received on Wed Dec 3 12:06:55 2003