Emergy

Emergy is the amount of energy consumed in direct and indirect transformations to make a product or service. Emergy is a measure of quality differences between different forms of energy. Emergy is an expression of all the energy used in the work processes that generate a product or service in units of one type of energy. Emergy is measured in units of emjoules, a unit referring to the available energy consumed in transformations. Emergy accounts for different forms of energy and resources (e.g. sunlight, water, fossil fuels, minerals, etc.) Each form is generated by transformation processes in nature and each has a different ability to support work in natural and in human systems. The recognition of these quality differences is a key concept.

History

The theoretical and conceptual basis for the emergy methodology is grounded in thermodynamics, general system theoryvon Bertalanffy. L. 1968. General System Theory. George Braziller Publ. New York 295 p. and systems ecology.Odum, H. T. 1983. Systems Ecology: An Introduction. John Wiley, NY. 644 p. Evolution of the theory by Howard T. Odum over the first thirty years is reviewed in Environmental Accounting and in the volume edited by C. A. S. Hall titled Maximum Power.Odum, H.T., 1995. Self organization and maximum power. Chapter 28, pp. 311-364 in Maximum Power, Ed. by C .A. S. Hall, University Press of Colorado, Niwot.

Background

Beginning in the 1950s, Odum analyzed energy flow in ecosystems (e.g. Silver Springs, Florida;Odum, H. T. 1957. Trophic structure and productivity of Silver Springs, Florida. Ecol. Monogr. 27:55-112. Enewetak atoll in the south Pacific;Odum, H. T. and E. P. Odum. 1955. Trophic structure and productivity of a windward coral reef at Eniwetok Atoll, Marshall Islands. Ecol. Monogr. 25:291-320. Galveston Bay, TexasOdum, H. T. and C. M. Hoskin. 1958. Comparative studies of the metabolism of Texas Bays. Pubi. Inst. Mar. Sci., Univ. Tex. 5:16-46. and Puerto Rican rainforests,Odum, H. T. and R. F. Pigeon, eds. 1970. A Tropical Rain Forest. Division of Technical Information, U.S. Atomic Energy Commission. 1600 pp. amongst others) where energies in various forms at various scales were observed. His analysis of energy flow in ecosystems, and the differences in the potential energy of sunlight, fresh water currents, wind and ocean currents led him to make the suggestion that when two or more different energy sources drive a system, they cannot be added without first converting them to a common measure that accounts for their differences in energy quality. This led him to introduce the concept of "energy of one kind" as a common denominator with the name "energy cost".Odum, H. T. 1967. Energetics of food production. In: The World Food Problem, Report of the President's Science Advisory Committee, Panel on World Food Supply, Vol. 3. The Whitehouse. pp. 55-94. He then expanded the analysis to model food production in the 1960s, and in the 1970s to fossil fuels.Odum, H. T. et al. 1976. Net Energy Analysis of Alternatives for the United States. In U.S. Energy Policy: Trends and Goals, Part V – Middle and Long-term Energy Policies and Alternatives. 94th Congress 2nd Session Committee Print. Prepared for the Subcommittee on Energy and Power of the Committee on Interstate and Foreign Commerce of the U.S. House of Representatives, 66-723, U.S. Govt. Printing Office, Wash, DC. pp. 254–304.Odum, H. T. and E. C. Odum. 1976. Energy Basis for Man and Nature. McGraw-Hill, NY. 297 pp

Odum's first formal statement of what would later be termed emergy was in 1973: Energy is measured by calories, btu's, kilowatthours, and other intraconvertable units, but energy has a scale of quality which is not indicated by these measures. The ability to do work for man depends on the energy quality and quantity and this is measurable by the amount of energy of a lower quality grade required to develop the higher grade. The scale of energy goes from dilute sunlight up to plant matter, to coal, from coal to oil, to electricity and up to the high quality efforts of computer and human information processing.Odum, H. T. 1973. Energy, ecology and economics. Royal Swedish Academy of Science. AMBIO 2(6):220-227.

In 1975, he introduced a table of "Energy Quality Factors", kilocalories of sunlight energy required to make a kilocalorie of a higher quality energy,Odum, H. T. 1976. 'Energy quality and carrying capacity of the earth. Response at Prize Ceremony, Institute de la Vie, Paris. Tropical Ecology 16(l):1–8. the first mention of the energy hierarchy principle which states that "energy quality is measured by the energy used in the transformations" from one type of energy to the next.

These energy quality factors, were placed on a fossil-fuel basis and called "Fossil Fuel Work Equivalents" (FFWE), and the quality of energies were measured based on a fossil fuel standard with rough equivalents of 1 kilocalorie of fossil fuel equal to 2000 kilocalories of sunlight. "Energy quality ratios" were computed by evaluating the quantity of energy in a transformation process to make a new form and were then used to convert different forms of energy to a common form, in this case fossil fuel equivalents. FFWE's were replaced with coal equivalents (CE) and by 1977, the system of evaluating quality was placed on a solar basis and termed solar equivalents (SE).Odum, H. T. 1977. Energy analysis, energy quality and environment. In Energy Analysis: A New Public Policy Tool, M. W. Gilliland, ed. American Association for the Advancement of Science, Selected Symposium No. 9, Wash. DC. Westview Press. pp. 55–87.

Embodied energy

The term "embodied energy" was used for a time in the early 1980s to refer to energy quality differences in terms of their costs of generation, and a ratio called a "quality factor" for the calories (or joules) of one kind of energy required to make those of another.Odum, E. C., and Odum, H. T., 1980. Energy systems and environmental education. Pp. 213–231 in: Environmental Education- Principles, Methods and Applications, Ed. by T. S. Bakshi and Z. Naveh. Plenum Press, New York. However, since the term embodied energy was used by other groups who were evaluating the fossil fuel energy required to generate products and were not including all energies or using the concept to imply quality, embodied energy was dropped in favor of "embodied solar calories", and the quality factors became known as "transformation ratios".

Introduction of the term "emergy"

Use of the term "embodied energy" for this concept was modified in 1986 when David Scienceman, a visiting scholar at the University of Florida from Australia, suggested the term "emergy" and "emjoule" or "emcalorie" as the unit of measure to distinguish emergy units from units of available energy.Scienceman, D. M., 1987. "Energy and Emergy," in G. Pillet and T. Murota (eds), Environmental Economics: The Analysis of a Major Interface, R. Leimgruber, Geneva, pp. 257–276. (CFW-86-26) The term transformation ratio was shortened to transformity in about the same time. Throughout these twenty years, the baseline or the basis for evaluating forms of energy and resources shifted from organic matter to fossil fuels and finally to solar energy.

After 1986, the emergy methodology continued to develop as the community of scientists expanded and as new applied research into combined systems of humans and nature presented new conceptual and theoretical questions. The maturing of the emergy methodology resulted in more rigorous definitions of terms and nomenclature and refinement of the methods of calculating transformities. The International Society for the Advancement of Emergy Research and a biennial International Conference at the University of Florida support this research.

Chronology

+Table 1: Development of emergy, transformity and conversion ratios. Years Baseline Unit Emergy Values Units Reference 1967–1971 Organic matter the baseline. All energies of higher quality (wood, peat, coal, oil, living biomass, etc.) expressed in units of organic matter. Sunlight equivalent to organic matter = 1000 solar kilocalories per kilocalorie of organic matter. g dry wt O.M.; kcal, conversion from OM to kcal = 5kcal/g dry wt. Odum, H.T. 1971. Environment, Power and Society. John Wiley, NY. 336 pp. 1973–1980 Fossil fuels and then coal the baseline. Energy of lower quality (sunlight, plants, wood, etc.) were expressed in units of fossil fuels and later in units of coal equivalents. Direct sunlight equivalents of fossil fuels = 2000 solar kilocalories per fossil fuel kilocalorie Fossil fuel work equivalents (FFWE) and later, coal equivalents (CE) 1980–1982 Global solar energy the baseline. All energies of higher quality (wind, rain, wave, organic matter, wood, fossil fuels, etc.) expressed in units of solar energy 6800 global solar Calories per Calorie of available energy in coal Global solar calories (GSE). Odum, H. T., M. J. Lavine, F. C. Wang, M. A. Miller, J. F. Alexander Jr. and T. Butler. 1983. A Manual for Using Energy Analysis for Plant Siting with an Appendix on Energy Analysis of Environmental Values. Final report to the Nuclear Regulatory Commission, NUREG/CR-2443 FINB-6155. Energy Analysis Workshop, Center for Wetlands, University of Florida, Gainesville. 221 pp. 1983–1986 Recognized that solar energy, deep heat, and tidal momentum were basis for global processes. Total annual global sources equal to the sum of these (9.44 E24 solar joules/yr) Embodied solar joules per joule of fossil fuels = 40,000 seJ/J Embodied solar equivalents (SEJ) and later called "emergy" with nomenclature (seJ) Odum, H. T. and E. C. Odum, eds. 1983. Energy Analysis Overview of Nations. Working Paper WP-83-82. International Institute for Applied Systems Analysis, Laxenburg, Austria. 469 pp. 1987–2000 Further refinements of total energy driving global processes, Embodied solar energy renamed to EMERGY Solar Emergy per Joule of coal energy ~ 40,000 solar emjoules/ Joule (seJ/J) named Transformity seJ/J = Transformity; seJ/g = Specific emergy 2000–2016 Emergy driving the biosphere reevaluated as 15.83 E24 seJ/yr raising all previously calculated transformities by the ratio of 15.83/9.44 = 1.68 Solar emergy per Joule of coal energy ~ 6.7 E 4 seJ/J seJ/J = Transformity; seJ/g = Specific emergy Odum, H. T., M. T. Brown and S. B. Williams. 2000. Handbook of Emergy Evaluation: A Compendium of Data for Emergy Computation Issued in a Series of Folios. Folio #1 – Introduction and Global Budget. Center for Environmental Policy, Environmental Engineering Sciences, Univ. of Florida, Gainesville, 16 pp. Available on line at: .2016-presemtEmergy driving the biosphere reevaluated as 12.0 E24 seJ/yr, raising the previously calculated transformities based on 9.44 with 12.0/9.44 = 1.27, and diminishing the previously calculated transformities based on 15.83 by the ratio of 12.00/ 15.83 = 0.76

Definitions and examples

Emergy— amount of energy of one form that is used in transformations directly and indirectly to make a product or service. The unit of emergy is the emjoule or emergy joule. Using emergy, sunlight, fuel, electricity, and human service can be put on a common basis by expressing each of them in the emjoules of solar energy that is required to produce them. If solar emergy is the baseline, then the results are solar emjoules (abbreviated seJ). Although other baselines have been used, such as coal emjoules or electrical emjoules, in most cases emergy data are given in solar emjoules.

Unit Emergy Values (UEVs) — the emergy required to generate one unit of output. Types of UEVs: Transformity — emergy input per unit of available energy output. For example, if 10,000 solar emjoules are required to generate a joule of wood, then the solar transformity of that wood is 10,000 solar emjoules per joule (abbreviated seJ/J). The solar transformity of the sunlight absorbed by the earth is 1.0 by definition.