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Emergy is any of several concepts, or all of them at the same time. It was originally coined by Dr. David M. Scienceman in collaboration with the late Professor Howard T. Odum as a means of making it distinct from other embodied energy methodologies. In this context, "emergy" is a contraction of the term "embodied energy". However Scienceman also used emergy to refer to the concept of energy memory, and H.T.Odum used it to mean both sequestered energy and emergent property of energy use. Some researchers maintain that it can be expressed as a scientific unit which is called the "emjoule", a contraction of "emergy joule", or "embodied energy joule". In 1986, H.T.Odum also used the word 'enmergy' briefly, before using 'emergy' as a standard. Because it can be confused with the word 'energy', some authors use the 'eMergy', and 'EMERGY' notations to emphasize the difference.

Emergy: a systems concept

According to the Emergy Systems school, like the concept of sustainability, "Emergy is a systems concept that is context driven, and cannot be fully understood or utilized outside of systems context." This school has therefore promoted emergy as a concept that is useful for establishing the metric for a rigorous and quantitative sustainability index. According to Laganisa and Debeljakb:

The emergy synthesis method was introduced from

Odum in the 1980s ... with the aim of taking into account the different quality of driving forces supporting a process and allowing their comparison on the same basis. It attempts to solve the problem of multi-quality inputs by transforming them to an equivalent of energy of a single quality, which is usually solar energy. (Laganisa & Debeljakb 2006, pp. 287-288).

Definition in words

Emergy can be defined as the total solar equivalent available energy of one form that was used up directly and indirectly in the work of making a product or service (H.T.Odum 1996, H.T. & E.C.Odum 2000).

Emergy expresses the cost of a process or a product in solar energy equivalents. The basic idea is that solar energy is our ultimate energy source and by expressing the value of products in emergy units, it becomes possible to compare apples and pears. (S.E.Jorgensen 2001, p. 61)

S.E. Jorgensen, S.N.Nielsen and H.Mejer write, "Emergy calculations have the same aim as exergy: to capture the energy hidden in the organization and construction of living organisms." (1995, p. 103). H.T.Odum said that the notion of embodied exergy could be used to evaluate structure (1994, p. 266), and Chen (in press) goes further to define embodied exergy as emergy.

Emergy measures value (see below) of both energy and material resources within a common framework. Embodied in the emergy value are the services provided by the environment which are free and outside the monied economy. By accounting for quality and free environmental services, resources are not valued by their money cost or society’s willingness to pay, which are often very misleading. Non-emergy approaches to the evaluation of ecological, sociopolitical-economic, and industrial processes most often evaluate only nonrenewable resources, depending on what human technologies are able to extract from them (user-side quality). Furthermore, non-emergy approaches do not account for the free services that a system receives from the environment (e.g., the photosynthetic activity driven by the solar radiation, the dilution of pollutants by the wind, etc.) which are just as much a requirement for the productive process as are fossil fuels for example. Very few, if any evaluation methodologies have an accounting procedure for human labor, societal services and information. That is, for those flows which carry negligible energy but are supported by a huge indirect flow of resources and perform high quality control, innovation and maintenance actions. Emergy includes all of this, perhaps not perfectly, but in a way to help us understand that there is a huge network of supporting energies necessary to support any particular economic activity in our societies, and thereby provide better framework for making policy decision. For Shu-Li Huang and Chia-Wen Chen (2005)

intensive and diversified emergy sources build up the structure and enhance metabolism in urban areas. (p. 49)

Mathematical Definition

To understand the concept of emergy it is first necessary to understand Exergy: the real proportion of the energy that can drive mechanical work.

${\displaystyle E_{x}=(Gibbs\ free\ energy)+(gravitational\ potential\ energy)+(kinetic\ energy)}$

The Gibbs free energy is the available thermodynamic/chemical energy. Forms of energy such as radiation and thermal energy can not be converted completely to work, and have exergy content less than their energy content, see entropy.

The exergy power is the rate of change of exergy with time

${\displaystyle P_{x}={dE_{x} \over dt}}$

an equivalent of the concept of power for exergy.

Emergy is then defined as the integral of the exergy power over time

${\displaystyle E_{m}=\int _{t=-\infty }^{t_{0}}P_{x}dt}$

i.e. the total change in exergy until ${\displaystyle t_{0}}$. This is a slight simplification of the formula in (Giannantoni 2002).

Solar emergy
The unit of solar emergy is ${\displaystyle U}$. Brown and Ulgiati (2001) define the solar emergy of a flow coming out of a given process as the solar energy that is directly or indirectly required to drive the process itself.

${\displaystyle U=\sum _{i}Tr_{i}E_{i}}$

Where ${\displaystyle E_{i}}$ is the available energy (or free energy) content of the i th independent input flow to the process, and ${\displaystyle Tr_{i}}$ is the solar transformity of the i th input flow. The solar transformity of direct solar radiation (${\displaystyle Tr_{s}}$) is set equalt to 1.

Development

Ten years after proposing the emergy nomenclature in 1987, D.M.Scienceman wrote that his suggestion came as a consequence of studying H.T.Odum's book Systems Ecology (later published as Ecological and General Systems 1994) for a period of about 2 years. With a background in mathematics and nuclear physics, Scienceman had never before heard of the 'embodied energy' concept, and found Odum's use of it very confusing. It was out of this confusion that Scienceman proposed the emergy nomenclature as a means of unifying and simplifying scientific discussions.

"Owing to great confusion in the scientific literature, and in order to clearly distinguish the theories of H.T.Odum, new concepts - energy memory, emergy, transformity, informity, empower, emtropy, emformation, emtelligence, emprice, emdollars, emtrons and soals - are introduced plus their appropriate units." (Scienceman 1987, p. 275)

With this new terminology, Scienceman sought to clarify two issues: 1/ the combining of energies of different forms; 2/ the process of embodying energies of different forms, or using them up. Scienceman (1997) noticed that the efficiency ratios used in engineering thermodynamics to quantify the transformations of energies from one form into another form were the same kind of ratios that H.T.Odum referred to as energy quality ratios. However in 1986 the National Bureau of Standards did not include any symbol for the notion of 'energy quality', a concept which is pivotal for understanding emergy, and later referred to by the term "energy transformation ratio", or " transformity". Scienceman and H.T.Odum subsequently collaborated on a linguistic project of simplifying and unifying the scientific lexicon by introducing and clarifying new terms. As H.T.Odum later noted,

"In 1983 our concept of embodied energy (the available energy of one kind previously used up directly and indirectly in transformations to make a product or service) was given the name “EMERGY” and its unit names the “emjoule” or “emcalorie.” What is called an “energy transformation ratio” in this chapter was renamed the “ transformity” with the unit “emjoule per Joule” (not a dimensionless ratio.)" (H.T.Odum 1994, p. 251.)

Energy memory, energy in a body

Scienceman's inclusion of the term energy memory in the definition of the word emergy implies that the properties of physical-biological-chemical materials can be included within the domain of the emergy schema.

"I now describe 'emergy' as meaning 'energy memory', meaning a measure of the quantity of original form energy which has been totally used up or transformed into a new form of energy. The original form has disappeared and has become only a memory, a memory stored up in emergent properties and transformity." (Scienceman 1997, p. 210-211).

As it is used by Scienceman, the term "energy memory" implies a "memory algebra" (1997, p.211), which does not appear to obey the "energy conservation algebra" (Ibid.). The energy conservation algebra simply states that the sum of the mass and energy must be conserved in any energy transformation, so that the sum of mass and energy in the universe remains constant forever (see for example Ohta 1994, p.3). However, while the sum of mass and energy in the universe remain constant forever, distributions of mass and energy in the universe do not remain constant forever. For example, the earth accumulates energy through the energy transformations carried out during photosynthesis. Another example is the hypertrophic growth of a heterotrophic organism. Consider also a simple closed electronic circuit with battery, and resistor. Because this circuit is closed, the quantity of electrons is constant. This is to say that the electrical form energy is conserved. However the chemical form of energy that provides the force to move electrons in this circuit is not conserved. The heat energy form dissipates across the resistor as the chemical form of energy performs the work of moving electrons. Depending how one understands the concepts of open and closed systems, the circuit can be called closed to electron flow, but open to heat flow. In thermodynamics it is considered a closed system, but one that is isolated to electron flow, and not isolated to heat flow.

The memory algebra was designed to give a quantitative account of non-conservative energy transformations. The memory algebra also seems to have a connection with the physiological application of the cybernetic concept of "error" which is sometimes referred to as "memory". In addition to this H.T.Odum offered the theory that the toxic action of any substance is proportional to the emergy. This theory was partly based on research which found that pollution stress was greater on organisms with higher transformity (H.T.Odum 1994, p. 529). G.P.Genoni, E.I.Meyer and A. Ulrich (2003) used the transformity measure to examine the hypothesis of a positive relationship between the “rarity” of a chemical element and its tendency to bioaccumulate.

Transformity: the rationalization of quality

Like the emergy concept, the concept of transformity was first introduced by Dr.D.M.Scienceman in collaboration with the late Howard T. Odum. In 1987 D.M.Scienceman proposed that the phrases, "energy quality", "energy quality factor", and "energy transformation ratio", all used by H.T.Odum, be replaced by the word "transformity" (p. 261). This approach aims to solve a long standing issue about the relation of qualitative phenomena to quantitative phenomena often analysed in the physical sciences, which in turn is a synthesis of rationalism with phenomenology. That is to say that it aims to quantify quality.

Definition of transformity in words

Scienceman then defined transformity as,

"a quantitative variable describing the measurable property of a form of energy, its ability to amplify as feedback, relative to the source energy consumed in its formation, under maximum power conditions. As a quantitative variable analogous to themodynamic temperature, transformity requires specification of units." (1987, p. 261. My emphasis).

In 1996 H.T.Odum defined transformity as,

"the emergy of one type required to make a unit of energy of another type. For example, since 3 coal emjoules (cej) of coal and 1 cej of services are required to generate 1 J of electricity, the coal transformity of electricity is 4 cej/J"

G.P.Genoni expanded on this definition and maintained that, "the energy input of one kind required to sustain one unit of energy of another kind, is used to quantify hierarchical position" (1997, p. 97). According to Scienceman, the concept of transformity introduces a new basic dimension into physics (1987, p. 261).

Definition as a ratio

One part of the rationalist viewpoint associated with modernity and science is to contrast qualitatively different phenomena under transformation through quantitative ratios, with the aim of uncovering any constancy amidst the transformation change. Like the efficiency ratio, transformity is quantitatively defined by a simple input-output ratio. However the transformity ratio is the inverse of efficiency and involves both indirect and direct energy flows rather than simply direct input-output energy ratio of energy efficiency. This is to say that it is defined as the ratio of emergy input to energy output.

Original version: ${\displaystyle Transformity={\frac {emergy\;input}{energy\;output}}}$

Development

However, it was realised that the term "energy output" refers to both the useful energy output and the non-useful energy output. (Note: that as given by P.K.Nag, an alternative name for 'useful energy' is 'availability' or exergy, and an alternative name for 'non-useful energy' is 'unavailability', or anergy (Nag 1984, p.156)). But as E.Sciubba and S.Ulgiati observed, the notion of transformity meant to capture the emergy invested per unit product, or useful output. The concept of Transformity was therefore further specified as the ratio of "input emergy dissipated (availability used up)" to the "unit output exergy" (Sciubba and Ulgiati 2005, p. 1957).

Revised version: ${\displaystyle Transformity={\frac {emergy\;input}{exergy\;output}}}$ or ${\displaystyle Tr={\frac {E_{m}}{E_{x}}}}$ (after Giannantoni 2002, p. 8)

Substituting in the mathematical definition of emergy given above.

${\displaystyle Tr={\frac {\int _{t=-\infty }^{t_{0}}P_{x}dt}{E_{x}}}}$

Empower and maximum empower

Empower refers to the flow rate of emergy: "The time rate of change of emergy is empower, analogous to the time rate of change of energy, power." (Scienceman 1987, p. 262.) Maximum empower therefore refers to the maximum flow rate of emergy. Considered as a principle, maximum empower has been proposed as a corrolary of the maximum power principle, and is assumed to describe the organisational law of evolution. Accordingly H.T.Odum suggested that Lotka's maximum power principle be restated as the "Maximum Empower Principle"

The "Maximum Em-Power Principle" (Lotka-Odum) is generally considered as the "Fourth Thermodynamic Principle" (mainly) because of its practical validity for a very wide class of physical and biological systems (C.Giannantoni 2000, § 13, p. 155)

Citing H.T.Odum, J.L.Hau and B.R.Bakshi say that, "this principle determines which systems, ecological and economic, will survive over time and hence contribute to future systems" (2004, p.15).

Definition of the maximum empower principle in words

In the self-organizational process, systems develop those parts, processes, and relationships that maximize useful empower. (H.T. & E.C. Odum 2000, p. 71).

"The maximum empower principle is a unifying concept that explains why there are material cycles, autocatalytic feedbacks, successional stages, spatial concentrations in centers, and pulsing over time. Designs prevail that maximize empower" (H.T.Odum 2002, p. 60). This is to say that "those elements or individuals whose patterns of action do not result in maximum production tend to be replaced eventually" (H.T. & E.C.Odum 2000, p.71). M.T.Brown and S.Ulgiati both maintain that "The total available emergy flow drives the system behaviour according to the Maximum Empower Principle, determining the size of the system itself and its growth rate." (2001, p. 109).

Mathematical definition of the maximum empower principle

As a corrolary of maximum power efficiency, a mathematical statement of the maximum empower efficiency principle still needs to be clarified - see discussion

Acceptance

Giannantoni maintains that the maximum empower principle is generally accepted as the fourth thermodynamic principle (see above quote and reference). However, for some scientists, there are two fundamental requirements for something to be considered a thermodynamic or energetic principle. Firstly is an experimental technique, or instrument, used to quantitatively measure the phenomenon of interest. In the case of maximum empower this would mean the specification of an instrument that measures 'empower'. A second requirement is a set of mathematical equations that demonstrate, in the current case, an experimentally testable relationship of the phenomenon of "empower" to other thermodynamic variables. A consequence of the first criteria is that serious scientific scholarship using the emergy nomenclature will need something like an "empower meter". Giannantoni has attempted to give the mathematics, however does not appear to have specified an empower meter by which to quantitatively measure empower. In conclusion, although the concept of maximum empower has been used in peer-reviewed journals to model and quantify the ecological-economic sustainability of a region and nation, the question remains as to whether it qualifies as the 4th thermodynamic law, and apparently will not be resolved until an empower meter or equivalent is constructed. While this remains the case, scientists may have difficulty accepting and using the concept to unify disciplines like physics, biology and chemistry.

Emergy accounting and emergy "analysis" vs emergy synthesis

Emergy accounting is a GLOBAL method of accounting concerned with the input of solar energy equity at the global level. The emergy accounting methodology seeks to account for the energy used in developing energy of higher quality, which are capable of controlling ecosystem and economic functions. M.T.Brown and S.Ulgiati say that emergy accounting is a "method of valuation" that, "uses the thermodynamic basis of all forms of energy and materials, but converts them into equivalents of one form of energy, usually sunlight." (1999, p. 4). Emergy "analysis", therefore aims to identify how this energy, and its comparable inputs as fossil fuels etc., are distributed. Emergy accounting assumes three things:

1. That every sector of the world economy is, in the final analysis, dependent on the total global energy budget.

2. None of the sectors of the world economy overlap in their function.

3. Non-human sectors (i.e. non-human ecological systems) are included in the world economy

The sum result of these assumptions is that all sectors considered together produce a "complete" economy. It therefore includes energy, emergy, commodity and money flows. The method rests heavily on H.T.Odum's use of the "maximum power principle". In an evolutionary sense the use of this principle to analyse the world economy implies that the global economy will run close to optimal efficiently if and only if competition is unimpeded by cultural, communication, geographical, legal or other matters. However because emergy involves the combination of hetrogenous energy forms, D.M.Scienceman now only refers to Emergy Synthesis, preferring to see the notion of "emergy analysis" as an oxymoron.

Emergy policy, environmental ethics and value theory

Value theory

A controversial application of the concept is with respect to Value theory. For H.T.Odum, “embodied energy is a measure of value, in one of the meanings of the word 'value'” (H.T.Odum 1994, p.251 - In this quote the term "embodied energy" is synonymous with "emergy", see Embodied energy). H.T.Odum (1996) understood emergy to encompass not only the above considerations, but also the human notion of utility as a "donor-type value." This conception has not yet received wide support or critical analysis by value theorists. In fact it is this application which seems to act as a block to the wider appeal of Emergy Synthesis in the sciences and arts. This could be due to the attitude which regards the arts, qualitative aesthetics, and spiritual systems of value as incommensurable with rational scientific systems of quantitative value measurement and prediction.

Environmental ethics

Further controversial implications of this conception of value are in the fields of legal theory and policy where H.T.Odum suggests a consequentialist ethic. The kind of consequentialism employed is utilitarianism which seeks the quantitative maximization of value. Policies and laws that aim at long term sustainability are, according to this ethic, those that maximize value. From the perspective of emergy synthesis, "value" is defined as "empower". Therefore, from the perspective of emergy evaluation, policies and laws that aim at long term sustainability by maximizing value, consequently aim to maximize empower. Semantically speaking then, emergy theorists imbue the concept of empower with both scientific, and normative content. In this context the division between social and physical sciences melts into air.

Emergy and policy

In terms of energy, and environmental resource policy, the main outcome of emergy theory is, according to H.T.Odum, that one should choose policies that maximise empower (i.e. maximize the flow rate of embodied energy). When sequestered energy is substituted for emergy, this means that policies with highest utility maximise sequestration.

Notes

1. M. Leone (2005). "The Quest for an Environmental Metric: Gazing at weather systems, a ground-breaking scientist spawned an ecological accounting standard that Wall Street might one day embrace". CFO Publishing.
2. B.R. Bakshi (2000). "The A thermodynamic framework for ecologically conscious process systems engineering" (PDF). Computers and Chemical Engineering. 24: 1767–1773.
3. Heui-seok Yi, Jorge L. Hau, Nandan U. Ukidwe, and Bhavik R. Bakshi (2004). "Hierarchical Thermodynamic Metrics for Evaluating the Environmental Sustainability of Industrial Processes" (PDF). Environmental Progress. 23 (4): 302–314.{{cite journal}}: CS1 maint: multiple names: authors list (link)
4. M.T. Brown and S. Ulgiati (1997). "Emergy-based indices and ratios to evaluate sustainability: monitoring economies and technology toward environmentally sound innovation" (PDF). Ecological Engineering. 9: 51–69.
5. M.T. Brown and S. Ulgiati (1999). "Emergy Evaluation of the Biosphere and Natural Capital" (PDF). Ambio. 28 (6).

References

• B.R. Bakshi (2000) 'A thermodynamic framework for ecologically conscious process systems engineering', Computers and Chemical Engineering 24, pp. 1767-1773.
• S.Bastianoni (2000) 'The problem of co-production in environmental accounting by emergy analysis', Ecological Modelling 129, pp.187–193.
• S.Bastianoni, F.M.Pulselli, M.Rustici (2006) Exergy versus emergy flow in ecosystems: Is there an order in maximizations?', Ecological Indicators 6, pp.58–62
• M.T. Brown and S. Ulgiati (2004) Energy quality, emergy, and transformity: H.T. Odum's contributions to quantifying and understanding systems, Ecological Modelling, Vol. 178, pp. 201-213.
• T.T.Cai, T.W.Olsen and D.E.Campbell (2004) Maximum (em)power: A foundational principle linking man and nature', Ecological Modelling, Volume 178, Issue 1-2, pp. 115-119.
• D.E.Campbell (2001) Proposal for including what is valuable to ecosystems in environmental assessments', Environmental Science and Technology, Volume 35, Issue 14, pp. 2867-2873.
• G.Q. Chen (2006) 'Scarcity of exergy and ecological evaluation based on embodied exergy', Communications in Nonlinear Science and Numerical Simulation, 11, pp. 531–552
• B.D.Fath, B.C.Patten, and J.S.Choi (2001) Complementarity of ecological goal functions', Journal of Theoretical Biology, Volume 208, Issue 4, pp. 493-506.
• G.P. Genoni (1997) 'Towards a conceptual synthesis in ecotoxicology', OIKOS, 80:1, pp. 96-106.
• G.P. Genoni, E.I. Meyer and A.Ulrich (2003) 'Energy flow and elemental concentrations in the Steina River ecosystem (Black Forest,Germany)', Aquat. Sci., Vol. 65, pp. 143–157.
• C.Giannantoni (2000) 'Toward a Mathematical Formulation of the Maximum Em-Power Principle', in M.T.Brown (ed.) Emergy Synthesis: Theory and applications of the emergy methodology, Proceedings from the first biennial emergy analysis research conference, The Center for Environmental Policy, Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL.
• C.Giannantoni (2002) The Maximum Em-Power Principle as the basis for Theromodynamics of Quality, Servizi Grafici Editoriali, Padova.
• C.Giannantoni (2006) 'Mathematics for generative processes: Living and non-living systems' Journal of Computational and Applied Mathematics 189, pp. 324–340.
• Shu-Li Huang and Chia-Wen Chen (2005) 'Theory of urban energetics and mechanisms of urban development', Ecological Modelling, 189, pp. 49–71.
• J.L.Hau and B.R.Bakshi (2004) 'Promise and Problems of Emergy Analysis', Ecological Modelling, special issue in honor of H. T. Odum, vol. 178, pp. 215-225.
• S.E. Jorgensen, S.N.Nielsen, H.Mejer (1995) 'Emergy, environ, exergy and ecological modelling', Ecological Modelling, 77, pp. 99-109
• J.Laganisa, & M.Debeljakb (2006) 'Sensitivity analysis of the emergy flows at the solar salt production process in Slovenia', Journal of Ecological Modelling, 194, pp. 287–295.
• P.K.Nag (1984) Engineering Thermodynamics, Tata McGraw-Hill Publishing Company.
• H.T.Odum (1986) in N.Polunin, Ed. Ecosystem Theory and Application, Wiley, New York.
• H.T.Odum (1988) 'Self-Organization, Transformity, and Information', Science, Vol. 242, pp. 1132-1139.
• H.T.Odum (1995) 'Self-Organization and Maximum Empower', in C.A.S.Hall (ed.) Maximum Power; The Ideas and Applications of H.T.Odum, Colorado University Press, Colorado, pp. 311-330.
• H.T.Odum (1996) Environmental Accounting: Emergy and Environmental Decision Making, Wiley.
• H.T.Odum (2002) 'Material circulation, energy hierarchy, and building construction', in C.J.Kibert, J.Sendzimir, and G.B.Guy (eds) Construction Ecology; Nature as the basis for green buildings, Spon Press, New York.
• H.T.Odum and E.C.Odum (1983)Energy Analysis Overview of Nations, Working Paper, WP-83-82. Laxenburg, Austria: International Institute of Applied System Analysis. 469 pp. (CFW-83-21)
• H.T.Odum and E.C.Odum (2000) A Prosperous way Down: Principles and Policies, Colorado University Press, Colorado.
• D.M.Scienceman (1987) 'Energy and Emergy.' In G. Pillet and T. Murota (eds), Environmental Economics: The Analysis of a Major Interface. Geneva: R. Leimgruber. pp. 257-276. (CFW-86-26)
• D.M. Scienceman (1989) ' The Emergence of Emonomics'. In Proceedings of The International Society for General Systems Research Conference (July 2-7, 1989), Edinbrough, Scotland, 7 pp. (CFW-89-02).
• D.M. Scienceman (1991) Emergy and Energy: The Form and Content of Ergon. Discussion paper. Gainesville: Center for Wetlands, University of Florida. 13 pp. (CFW-91-10)
• D.M. Scienceman (1992) Emvalue and Lavalue, Paper Prepared for th Annual Meeting of The International Society for the Systems Sciences, University of Denver, Denver, Colorado, U.S.A.
• D.M. Scienceman (1997) 'Letters to the Editor: Emergy definition', Ecological Engineering, 9, pp. 209-212.
• E. Sciubba, S. Ulgiatib (2005) 'Emergy and exergy analyses: Complementary methods or irreducible ideological options?' Energy 30, pp. 1953–1988.
• S.E.Tennenbaum (1988) Network Energy Expenditures for Subsystem Production, MS Thesis. Gainesville, FL: University of FL, 131 pp. (CFW-88-08)
• S.Ulgiati, H.T.Odum, S.Bastianoni (1994) 'Emergy use, environmental loading and sustainability. An emergy analysis of Italy', Ecological Modelling, Volume 73, Issue 3-4, Pages 215-268.
• S.Ulgiati and M.T.Brown (1990) Emergy evaluation of natural capital and biosphere services.
• S.Ulgiati and M.T.Brown (2001) 'Emergy Accounting of Human-Dominated, Large-Scale Ecosystems', in S.E.Jorgensen (ed) Thermodynamics and Ecological Modelling, CRC Press LLC, pp. 63-113.

See also

• Emergy evaluation
• Embodied energy
• Emergy Synthesis
• Energy Systems Language
• Maximum power
• Systems ecology
• Energy quality
• Energetics

External links

• Emergy Systems
• Enrique Ortega has prepared a series of XML files that correspond to FOLIO 4: Emergy analysis of agricultural systems of the State of Florida (USA). For Emergy calculator links scroll down to 2. Emergy Evaluation Tables for Florida Agriculture.
• S.Maud (2005) Where to with 'Emergy' Literacy?
• "Thermodynamics, Availability, and Emergy", Wayburn, Thomas L., Proceedings Engineering and Architecture Symposium, March 15-16, 1993, College of Engineering and Architecture, Prairie View A&M University, Prairie View, Texas.

• Pseudoscience
• Emergy