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Fig. 7.15. The utilisation coefficient as a function of the total amount of matter (a), and the rate of nutrient uptake by phytoplankton (b).

their actual energy content by their solar energy transformation ratios. The more transformation steps there are between two kinds of energy, the greater is the quality and the greater is the solar energy required to produce a unit of energy (Joule) of that type. When one calculates the energy of one type that generates a flow of another, this is sometimes referred to as the embodied energy (emergy) of that type.

Fig. 7.i6 presents the concept of embodied energy in a hierarchical chain of energy transformation and Table 7.i gives embodied energy equivalents for various types of energy.

H.T. Odum reasons that surviving systems develop designs that receive as much energy amplifier action as possible. The energy amplifier ratio is defined in Fig. 7.i7 as the ratio of output B to control flow C. H.T. Odum suggests that in surviving systems the amplifier effects are proportional to embodied energy, but full empirical testing of this theory still needs to be carried out in the future.

One of the properties of high-quality energies is their flexibility. Whereas low-quality products tend to be special, requiring special uses, the higher-quality part of a web is of a form that can be fed back as an amplifier to many different units throughout the web. For example, the biochemistry at the bottom of the food chain in algae and microbes is diverse and specialised, whereas the biochemistry of top animal consumer units tends to be similar and general, with services, recycles and chemical compositions usable throughout.

Fig. 7.16. Energy flow, solar equivalents and energy transformation ratio (embodied energy equivalents) in a trophic chain (from J0rgensen, 2002b).

Hannon (1973, 1979, 1982) and Herendeen (1981) applied energy intensity coefficients as the ratios of assigned embodied energy to actual energy to compare systems with different efficiencies.

The difference between embodied energy flows and power, defined as in phenomenological thermodynamics

Table 7.1

Embodied energy equivalents for various types of energy

Table 7.1

Embodied energy equivalents for various types of energy

Type of energy

Embodied energy equivalents

Solar energy

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