Cumbre Mundial sobre Desarrollo Sostenible

the diagram to denote changes in energy quantity and quality. An important aspect of natural energy flows he shows here are flows to heat loss, and energy feedback loops in a system where some energy is converted to higher quality levels, and some energy being fed back. Odum (Howard Thomas Odum, 1956) found from his field studies that systems develop storages of high quality energy and those storages are then fed back as an energy source at a lower level to increase the efficiency of the inflow mechanisms. Each system also sets up exchanges for needed materials with more and less complex systems and so contributes to work at the next larger system scale and acts as on contributing systems.

To help elucidate the complexity of interaction Odum created a systems language, using a toolbox of symbols borrowed heavily from electrical circuitry diagrams into which he substituted the electrical componentry with his own systems language symbols as shown in Figure 7. His systems methodology has gone largely unnoticed since its creation in the early 1970’s. Diagrams like Figure 6 provide an uncluttered macro view of energy flows through living systems, and account for the total inflows balanced against outflows and where every stage of the process results in heat loss. In taking this approach Odum’s thesis is that ‘complexity must be reduced to essentials if complexity is to be overcome as an impediment to understand and correct action, and this means modelling’6 _(M.

6 _{The development and the potential utility of models and modelling was an argument that had to be made in}

the 1960s in a number of disciplines, see for instance Chorley and Haggett 1967, and specifically in relation to ecological modelling and its analogies see Stoddart (1967) in that book.

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T. Brown, 2004, p. 91). Odum called the models he developed macroscopic mini-models to suppress detail and capture the ‘subjective qualitative essence of facts and figures’ (2004, p91).

Odum reasoned that the use of macro diagrams that developed and quantified flows of energy of different qualities and at different scales might apply to more than ponds and forests and

developed an argument that they applied equally as well to human economic and social systems. He found that flow in networks is not random movement, but movement as feedback that reinforces systems that efficiently transform the most energy into useful work. Where feedback action occurred their worked to capture more resources or to improve the efficient use of resources feeding into the process. Figure 8 shows how feedback processes are depicted using his symbolic language. It is a network of interactions and not an isolated activity as benefits also flow to

surrounding systems (Howard Thomas Odum & Odum, 1976). He stated this as the power principle as ‘during self-organisation, system designs develop and prevail that maximise power intake, energy transformation, and those uses that reinforce production and efficiency’ (Howard Thomas Odum, 1995, p. 311).

Odum identified similarities in different systems and at different scales, and used the tools he had developed to model a range of systems’ behaviour (Howard Thomas Odum, 1971, 1974). He found evidence that common designs following common principles exist in all thermodynamic systems and at all scales (Howard Thomas Odum, 1996b). That scale extends both upward and downward (see Figure 10) from the ecological scale of

human habitat and on that basis Odum predicted that chemical and biological entities would be found to have similar structure. Schneider and Kay also examined thermodynamic evolution of evolving systems and concluded that they comprise similar processes that are

phenomenological manifestations of the

second law of thermodynamics (Schneider & Kay, 1994). Odum’s (1971, p. 9) macro analysis of the scale of all things known places the human world at about the mid-point (See figure 10). This is very significant if it is accepted that patterns of transport within thermodynamic systems look much the same at different scales. However, even within the humanly accessible world there is so much detail, diversity, and activity that it can look like there is no organisation or principles at work. This has the effect of suppressing the search for macro and micro patterns in the behaviour of matter,

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but is fast changing as information about activity at other scales is revealed using the tools of modern science

How physical mechanisms actually bring about a change in energy quality and material structure are the least explained part of Odum’s work. Odum provided an extensive blueprint for the

development of energy systems, but a Google search of research literature for his name and the term ‘emergy’, the term he used to denote the idea of embedded energy, show that he has remained outside the mainstream scope of enquiry for the ensuing fifty years.

Odum’s cumulative ‘emergy’ approach to energy transformation needed a new way to measure levels of energy quality and so he settled on joules of sunlight as the common energy denominator for all energy flows. He called it emergy because ‘energy in systems is converged while being transformed onto smaller but more valuable forms’ (Howard Thomas Odum, 1987). A practical way that emergy analysis can be used is as an environmental accounting device that values the

contribution of ecosystem goods and services expressed in one currency and this makes the comparison of different forms of energy flow meaningful. It is a more complex measure of energy quality than is used in life cycle analysis (LCA) (Reddy, Kurian, & Ardakanian, 2015), as that measure includes energy of production and manufacture only. A significant problem with emergy is that measurements are difficult to collect, and quantify, and so, as a concept, economists, physicists, and engineers have largely ignored it.

A feed forward process results in increased stores of higher quality energy, which in turn is influenced by a feedback process in a way that increases the performance of the system. Systems have a finite capacity to store high quality energy can only feed small amounts of energy forward. At times the amount available is large that the system cannot cope and so the system changes the way it operates, and energy is released out of the process. When it happens in natural systems - as a

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