Sunday, September 23, 2012

Emergy Definition

   Emergy, method to valuing the environmental real wealth.  

Emergy spelled with an "m" is a different term from the word "energy" which we have known since we learn the thermodynamics law. Energy was defined as the potential ability of a physical system to do work on other physical systems (Harper, 2007).  Rather than the ability to do work, emergy is energy required to compose those system. Emergy is defined as “the available energy of one kind of previously used up directly and indirectly to make a service or product", its unit is the emjoule” (Odum, 1996). Emergy also often understood as "the energy memory" of one kind of product or service. Emergy analysis is a technique to measure the real value of a system of one kind product or service based on the total energy required to compose it system. In the emergy analysis, many kind of energy type which were involved in the process of a system will be converted into the same energy quality, so then the mathematical calculation could be perform on its.  The conversion from one energy type into another form of energy could be done through the conversion ratio, this ration called “transformity”. Base on the transformity, various kind of energy could be converted into the same kind of energy and can easily analyze each contribution to the system. Furthermore, emergy indices are used for better evaluation of the concerned system. These indices indicate various performance of the system in term of efficiency and sustainability (Campbell, 1997). Associated with the emergy analysis for fisheries production, some indices need to be calculate are Emergy Yield Ratio (EYR), Emergy Investment Ratio (EIR), Environmental Loading Ratio (ELR), and Environmental Sustainability Index (ESI) (Odum and Odum, 1983; Ulgiati et al., 1995; Odum, 1996; Brown and Ulgiati, 1997; Ulgiati and Brown, 1998)

1.      Emergy Concept
Biosphere in the earth surface where we are living on is a system which is supported by so many resources either renewable or nonrenewable. Along with the economic development, diminishing of earth resources has reached a new stage. Enterprises for private profit are consuming the environmental systems that are the basic of public welfare. The conflict between those intent on protecting the environmental and those intent on further economic development are becoming increasingly important in public policy discussion and politic development.

Trying to solve the problem and search the middle course between these two issues, H.T. Odum (Odum, 1996) introduces the “EMERGY” theory. Emergy is a science-based evaluation system to represent both the environmental values and the economic values with a common measure. Emergy measures both the work of nature and that of humans in generating product and services. While the available energy is potential energy which can do work, the Emergy is “energy memory”. That the meaning was, emergy is a measure of the available energy which has been used up to make the products or services.

2.      Definition
To build and maintain the products or services (energy storage) of available resources, environmental work has to be done, this proses certainly requiring energy use and transformation. The storage can be evaluated quantitatively by the work done in its formation.  Work of energy transformation can be measured by the availability of energy that is used up. Thus, real wealth can be measured by the work previously done. EMERGY is a scientific measure of real wealth in term of the energy required to do the work of production.

EMERGY is the available energy of one kind of previously used up directly and indirectly to make a product or service. Its unit is the emjoule   (H. T. Odum, 1986a, 1988; Scienceman, 1987)

However, on the further application of energy calculation, each energy source has different contribution as the energy of one kind is not equivalent in its ability to do work to energy of another kind. Therefore, in adding up the available energies of different kinds contributing process, all have to be expressed in unit of one kind of energy. In the development of emergy analysis, there are several energy type were used as the calculation base, yet commonly solar energy were used as the calculation base. In the solar energy base, all form of energies contributing on a system was expressed in unit of solar energy and it would be required to generate all the inputs.  The process of converting every kinds of energy contributing in the system into solar energy called “transformation” process. Transformation proses will involve the ratio of conversion which hereinafter referred to as transformity.  

3.      Transformity
 An energy transformation is a process that one or more kinds of available energy are converted to a different type of available energy. Most often, inputs to a process are the result of another process, in which energy has been concentrated and upgraded. In figure 2.1 its clearly shows that the quality of 1 joule of humans physical work equal with 10 joule of meat energy from cattle, and 10 joule of energy from cattle can be generated from 1.000 joule of energy from plant or 1.000.000 joule energy from sun and rain. 

Fig. 1. Emergy quality chain from cattle ranch supporting humans, with levels of energy transformation.

Further, the quotient of a product’s emergy divided by its energy is defined as its transformity (H. T. Odum. 1976b, 1988). In above figure (fig. 2.1), it’s explaining that transformity for plant is quotient of sun energy divided by energy produce by plant, its means 1.000.000 joule divided by 1.000 joule, and then the transformity is 1.000. As well as plants, cattle and humans energy also subjected with the same process and resulting the transformity number about 100.000 and 1.000.000 for cattle and humans respectively. The units of transformity are emjoules perjoule. As in the previous statement that commonly solar emergy were used as the calculation base, the units for this transformity are solar emjoules per joule (abbreviated sej/J).

Solar transformity is the solar EMERGY required to make one joule of a service or product. Its units are solar emjoule per joule (sej/J). A product’s solar transformity is its solar EMERGY divided by its energy. (H. T. Odum, 1996).

There have been a lot of transformities for various kinds of energies, materials, and services such as emergy per energy, emergy per mass, and emergy to money ratios. The more energy transformations there are contributing to a product, the higher is the transformity. This is because at each transformation, available energy is used up to produce a smaller amount of energy of another form. Thus, the emergy per unit energy increases but the energy decreases, and therefore the emergy per unit energy increased sharply. The human energy has a larger transformity than meat flash from cattle that contributed to produce it.

Fig. 2. Concepts of energy transformation hierarchy and transformity, (a) All units view together; (b) Units separated by scale; (c) Units as a web of energy flows; (d) Processes shown as an ordered series; (e) Flows of energy per unit time; (f) Transformities (Brown et al., 2004)

  All the energy transformations could be arranged in ordered series to form an energy hierarchy. The hierarchy is that many units at lower level generate a few units at higher level, with the higher level feeding controls back to lower level units. Transformity shows the position of an energy transformation in the energy hierarchy and increases gradually from left to right (Figure 2.2). Therefore, it can be considered as a comparison factor for different types of energy. High transformity means high quality, and vice versa. Many transformities have been determined by Odum and the other authors over the past years and used in emergy analyses. New transformities are based on emergy driving the biosphere reevaluated as 15.20 E+24 sej/yr.


  1. Thanks for posting. You've done a great job of explaining a complicated subject.