Embodied energy

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Embodied energy is defined as the available energy that was used in the work of making a product. Embodied energy is an accounting methodology which aims to find the sum total of the energy necessary for an entire product lifecycle. This lifecycle includes raw material extraction, transport,[1] manufacture, assembly, installation, disassembly, deconstruction and/or decomposition.

Different methodologies produce different understandings of the scale and scope of application and the type of energy embodied. Some methodologies are interested in accounting for the energy embodied in terms of oil that support economic processes.

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[edit] Embodied energy methodologies

Different methodologies use different scales of data to calculate energy embodied in products and services of nature and human civilization. International consensus on the appropriateness of data scales and methodologies is pending. This difficulty can give a wide range in embodied energy values for any given material. In the absence of a comprehensive global embodied energy public dynamic database, embodied energy calculations may omit important data on, for example, the rural road/highway construction and maintenance needed to move a product, human marketing, advertising, catering services, non-human services and the like. Such omissions can be a source of significant methodological error in embodied energy estimations [2]. Without an estimation and declaration of the embodied energy error, it is difficult to calibrate the sustainability index, and so the value of any given material, process or service to environmental and human economic processes.

[edit] Classifications

There appear to be three main differences in contemporary embodied energy methodologies. Following Tennenbaum[3] these may be identified as ‘anthropocentric’ and ‘capitalcentric’, with a third identified as ‘ecocentric’. According to Tennenbaum, the difference in methodologies is determined by how they treat, and where they attribute energy depreciation in a network of ecological system energy flows. In all the methods, depreciation is taken away from the production process under consideration and reassigned elsewhere in the total system. What characterises a method is where they assign this energetic loss. According to David M. Scienceman[4], the principal point of difference is whether embodied energy is partitioned at work intersections and apportioned among pathways.

[edit] Anthropocentric analysis

Anthropocentric embodied energy analysis is interested in what energy goes to supporting a consumer, and so all energy depreciation is assigned to the final demand of consumer but not to storages of ‘assets’ or ‘capital stocks’. It is associated with Hannon’s work. There is no requirement that energy must be expressed as one energy form or quality.

[edit] Capital-centric analysis

Capital-centric embodied energy analysis is interested in what supports assets. Energy depreciation is therefore assigned to storage of ‘assets’ or ‘capital stocks’, but not to final demand. This method is associated with Herendeen's and Costanza's works, where embodied energy is apportioned among pathways and partitioned at work intersections, and is therefore additive just like heat energy. As with the anthropocentric view, there is no requirement that energy must be expressed as one energy form or quality.

[edit] Ecocentric analysis / Emergy evaluation

"Embodied energy is an energy function that is intended to make energy flows of different types comparable"[5]

In ecocentric embodied energy analysis, depreciation is assigned to a unit of production, that is, assigned to both storages of ‘assets’ or ‘capital stocks’, and to final demand. This method is associated with Howard T. Odum's works, where embodied energy is not apportioned among pathways and is therefore not additive like heat energy. Energy is only partitioned at work intersections that are diverging, and flexible. The notions of feed back, and energy amplifier effect as used in electronic circuits inform the theory behind this definition.

"Energy used in developing energy of higher quality is 'embodied energy'"[6]

In the emergy methodology there is a requirement that energy must be expressed in one energy form or quality. Other approaches most often evaluate only nonrenewable resources, depending on what human technologies are able to extract from them (user-side quality). The Energy Systems Language is used to help make emergy algorithms transparent.

[edit] Standards

The UK Code for Sustainable Homes and USA LEED Leadership in Energy and Environmental Design are standards in which the embodied energy of a product or material is rated, along with other factors, to assess a buildings environmental impact. Embodied energy is a new concept for which scientists have not yet agreed absolute universal values because there are many variables to take into account, but most agree that products can be compared to each other to see which has more and which has less embodied energy. Comparative lists (for an example, see the Bath University Embodied Energy & Carbon Material Inventory below) contain average absolute values, and explain the factors which have been taken into account when compiling the lists.

Typical embodied energy units used are MJ/kg (megajoules of energy needed to make a kilogram of product), tCO2 (tonnes of carbon dioxide created by the energy needed to make a kilogram of product). Converting MJ to tCO2 is not straightforward because different types of energy (oil, wind, solar, nuclear and so on) emit different amounts of carbon dioxide, so the actual amount of carbon dioxide emitted when a product is made will be dependent on the type of energy used in the manufacturing process. For example, the Australian Government[7] gives a global average of 0.098 tCO2 = 1 GJ. This is the same as 1 MJ = 0.098 kgCO2 = 98 gCO2 or 1 kgCO2 = 10.204 MJ.

[edit] Related methodologies

In the 2000s drought conditions in Australia have generated interest in the application of embodied energy analysis methods to water. This has led to use of the concept of embodied water.

[edit] Terminology

David M. Scienceman coined the term 'emergy' to make the ecocentric method distinct from other types of analysis. "The prefix em- can, fortuitously, even be taken to indicate an energy memory property, a record of source energy transformed."

However some sources use emergy as a general synonym for embodied energy.[8]

[edit] History

The history of constructing a system of accounts which records the energy flows through an environment can be traced back to the origins of accounting itself. As a distinct method, it is often associated with the physiocrat's "substance" theory of value (Mirowski 1999, pp. 154-163), and later the agricultural energetics of Serhii Podolinsky, a Ukrainian socialist physician (Martinez-Alier 1990), and the ecological energetics of V.V.Stanchenskii (Weiner 2000, pp. 70-71, 78-82).

The main methods of embodied energy accounting as they are used today grew out of Wassily Leontief's input-output model and are called Input-Output Embodied Energy analysis. Leontief's input-output model was in turn an adaptation of the neo-classical theory of general equilibrium with application to, "the empirical study of the quantitative interdependence between interrelated economic activities" (Leontief 1966, p. 134). According to Tennenbaum[9], Leontief's Input-Output method was adapted to embodied energy analysis by Hannon[10] to describe ecosystem energy flows. Hannon’s adaptation tabulated the total direct and indirect energy requirements (the ‘energy intensity’) for each output made by the system. The total amount of energies, direct and indirect, for the entire amount of production was called the ‘embodied energy’.

[edit] References

  1. ^ Advances in free geographic mapping services can help reduce embodied energy of transportation in two ways. First. to choose a route that uses the least fuel and maintains vehicle velocities at their individual maximum fuel efficiency. Secondly, overlays can be used of determining: (i) raw material and products availability as a function of location, and (ii) modes of transportation as a function of emissions. These overlays enable manufacturers access to an easily navigable method to optimize the life cycle of their products by minimizing embodied energy of transportation. Pearce,J.M., Johnson, S.J., & Grant, G.B., 2007. “3D-Mapping Optimization of Embodied Energy of Transportation”, Resources, Conservation and Recycling, 51 pp. 435–453. [1]
  2. ^ Lenzen, 2001
  3. ^ Tennenbaum, 1988
  4. ^ Scienceman, 1987
  5. ^ Wang, Odum & Costanza 1980, p. 185
  6. ^ H.T.Odum 1994, p. 251
  7. ^ http://www.cmit.csiro.au/brochures/tech/embodied/ CSIRO on embodied energy: Australia's foremost scientific institution
  8. ^ Odum 1996, Environmental Accounting: Energy and Environmental Decision Making, Wiley
  9. ^ Tennenbaum, 1998
  10. ^ Hannon, 1973

[edit] Bibliography

  • D.H. Clark, G.J. Treloar and R. Blair (2003) 'Estimating the increasing cost of commercial buildings in Australia due to greenhouse emissions trading, in J. Yang, P.S. Brandon and A.C. Sidwell, Proceedings of The CIB 2003 International Conference on Smart and Sustainable Built Environment, Brisbane, Australia.
  • R. Costanza (1979) "Embodied Energy Basis for Economic-Ecologic Systems." PhD Dissertation. Gainesville, FL: Univ. of FL. 254 pp. (CFW-79-02)
  • B. Hannon (1973) "The Structure of ecosystems", Journal of Theoretical Biology, 41, pp. 535-546.
  • M. Lenzen (2001) "Errors in conventional and input-output-based life-cycle inventories", "Journal of Industrial Ecology", 4(4), pp. 127-148.
  • M. Lenzen and G.J.Treloar (2002) 'Embodied energy in buildings: wood versus concrete-reply to Börjesson and Gustavsson, Energy Policy, Vol 30, pp. 249-244.
  • W. Leontief (1966) Input-Output Economics, Oxford University Press, New York.
  • J. Martinez-Alier (1990) Ecological Economics: Energy Environment and Society, Basil Blackwell Ltd, Oxford.
  • P. Mirowski (1999) More Heat than Light: Economics as Social Physics, Physics as Nature's Economics, Historical Perspectives on Modern Economics, Cambridge University Press, Cambridge.
  • H.T. Odum (1994) Ecological and General Systems: An Introduction to Systems Ecology, Colorado University Press, Boulder 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)
  • S.E. Tennenbaum (1988) Network Energy Expenditures for Subsystem Production, MS Thesis. Gainesville, FL: University of FL, 131 pp. (CFW-88-08)
  • G.J. Treloar (1997) Extracting Embodied Energy Paths from Input-Output Tables: Towards an Input-Output-based Hybrid Energy Analysis Method, Economic Systems Research, Vol. 9, No. 4, pp. 375- 391.
  • G.J. Treloar (1998) A comprehensive embodied energy analysis framework, Ph. D. thesis, Deakin University, Australia.
  • G.J. Treloar, C. Owen and R. Fay (2001) 'Environmental assessment of rammed earth construction systems', Structural survey, Vol. 19, No. 2, pp. 99-105.
  • G.J.Treloar, P.E.D.Love, G.D.Holt (2001) Using national input-output data for embodied energy analysis of individual residential buildings, Construction Management and Economics, Vol. 19, pp. 49-61.
  • D.R.Weiner (2000) Models of Nature: Ecology, Conservation and Cultural Revolution in Soviet Russia, University of Pittsburgh Press, United States of America.
  • G.P.Hammond and C.I.Jones (2006) Inventory of (Embodied) Carbon & Energy (ICE), Department of Mechanical Engineering, University of Bath, United Kingdom

[edit] See also

[edit] External links

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