Embodied energy

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Embodied Energy is the sum of all the energy required to produce any goods or services, considered as if that energy was incorporated or 'embodied' in the product itself. The concept can be useful in determining the effectiveness of energy-producing or energy-saving devices, or the "real" replacement cost of a building, and, because energy-inputs usually entail greenhouse gas emissions, in deciding whether a product contributes to or mitigates global warming. One fundamental question is: does the device produce more energy or save more energy than it took to make it?

Embodied energy is an accounting method which aims to find the sum total of the energy necessary for an entire product life-cycle. Determining what constitutes this life-cycle includes assessing the relevance and extent of energy into raw material extraction, transport, manufacture, assembly, installation, dis-assembly, deconstruction and/or decomposition as well as human and secondary resources. Different methodologies produce different understandings of the scale and scope of application and the type of energy embodied.

History[edit]

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,[1] and later the agricultural energetics of Sergei Podolinsky, a Ukrainian physician,[2] and the ecological energetics of Vladmir Stanchinsky [3]

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".[4] According to Tennenbaum[5] Leontief's Input-Output method was adapted to embodied energy analysis by Hannon[6] 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.

Embodied energy methodologies[edit]

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. 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.[7] 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.

Standards[edit]

The SBTool, UK Code for Sustainable Homes and USA LEED are methods in which the embodied energy of a product or material is rated, along with other factors, to assess a building's environmental impact. Embodied energy is a 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 University of Bath Embodied Energy & Carbon Material Inventory[8]) 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[9] 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.

Related methodologies[edit]

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.

Embodied energy in common materials[edit]

Selected data from the Inventory of Carbon and Energy ('ICE') prepared by the University of Bath (UK) [8]

Material Energy MJ per kg Carbon kg CO2 per kg Density kg /m3
Aggregate 0.083 0.0048 2240
Concrete (1:1.5:3) 1.11 0.159 2400
Bricks (common) 3 0.24 1700
Concrete block (Medium density) 0.67 0.073 1450
Aerated block 3.5 0.3 750
Limestone block 0.85 2180
Marble 2 0.116 2500
Cement mortar (1:3) 1.33 0.208
Steel (general, av. recycled content) 20.1 1.37 7800
Stainless steel 56.7 6.15 7850
Timber (general, excludes sequestration) 8.5 0.46 480–720
Glue laminated timber 12 0.87
Cellulose insulation (loose fill) 0.94–3.3 43
Cork insulation 26 160
Glass fibre insulation (glass wool) 28 1.35 12
Flax insulation 39.5 1.7 30
Rockwool (slab) 16.8 1.05 24
Expanded Polystyrene insulation 88.6 2.55 15–30
Polyurethane insulation (rigid foam) 101.5 3.48 30
Wool (recycled) insulation 20.9 25
Straw bale 0.91 100–110
Mineral fibre roofing tile 37 2.7 1850
Slate 0.1–1.0 0.006–0.058 1600
Clay tile 6.5 0.45 1900
Aluminium (general & incl 33% recycled) 155 8.24 2700
Bitumen (general) 51 0.38–0.43
Medium-density fibreboard 11 0.72 680–760
Plywood 15 1.07 540–700
Plasterboard 6.75 0.38 800
Gypsum plaster 1.8 0.12 1120
Glass 15 0.85 2500
PVC (general) 77.2 2.41 1380
Vinyl flooring 65.64 2.92 1200
Terrazzo tiles 1.4 0.12 1750
Ceramic tiles 12 0.74 2000
Wool carpet 106 5.53
Wallpaper 36.4 1.93
Vitrified clay pipe (DN 500) 7.9 0.52
Iron (general) 25 1.91 7870
Copper (average incl. 37% recycled) 42 2.6 8600
Lead (incl 61% recycled) 25.21 1.57 11340
Ceramic sanitary ware 29 1.51
Paint - Water-borne 59 2.12
Paint - Solvent-borne 97 3.13
Photovoltaic (PV) Cells Type Energy MJ per m2 Carbon kg CO2 per m2
Monocrystalline (average) 4750 242
Polycrystalline (average) 4070 208
Thin film (average) 1305 67

Embodied energy in automobiles[edit]

Treloar, et al. have estimated the embodied energy in an average automobile in Australia as 0.27 terajoules as one component in an overall analysis of the energy involved in road transportation.[10]

Embodied energy in Telecommunication[edit]

Embodied energy in telecommunications began in Mayaguez. Recently the embodied energy is going to used also in other sectors as ICT and telecommunication.[11] The ICT energy consumption, in the USA and worldwide, has been estimated respectively at 9.4% and 5.3% of the total electricity produced.[12] The Embodied Energy concept can help to evaluate the impact of devices and networks.

See also[edit]

References[edit]

  1. ^ Mirowski, Philip (1991). More Heat Than Light: Economics as Social Physics, Physics as Nature's Economics. Cambridge University Press. pp. 154–163. ISBN 978-0-521-42689-3. 
  2. ^ Martinez-Alier, J. (1990). Ecological Economics: Energy Environment and Society. Oxford: Basil Blackwell. ISBN 0631171460. 
  3. ^ Weiner, Douglas R. (2000). Models of Nature: Ecology, Conservation, and Cultural Revolution in Soviet Russia. University of Pittsburgh Pre. pp. 70–71, 78–82. ISBN 978-0-8229-7215-0. 
  4. ^ Leontief, W. (1966). Input-Output Economics. New York: Oxford University Press. p. 134. 
  5. ^ Tennenbaum, Stephen E. (1988). Network Energy Expenditures for Subsystem Production (PDF) (MS). OCLC 20211746. Docket CFW-88-08. 
  6. ^ Hannon, B. (October 1973). "The Structure of ecosystems" (PDF). Journal of Theoretical Biology 41 (3): 535–546. doi:10.1016/0022-5193(73)90060-X. 
  7. ^ Lenzen 2001
  8. ^ a b G.P.Hammond and C.I.Jones (2006) Inventory of (Embodied) Carbon & Energy (ICE), Department of Mechanical Engineering, University of Bath, United Kingdom
  9. ^ CSIRO on embodied energy: Australia's foremost scientific institution
  10. ^ Treloar, Graham J.; Love, Peter E. D.; Crawford, Robert H. (January–February 2004). "Hybrid Life-Cycle Inventory for Road Construction and Use". Journal of Construction Engineering and Management 130 (1): 43–49. doi:10.1061/(ASCE)0733-9364(2004)130:1(43). Retrieved 2010-06-29. 
  11. ^ Puglia, Virgilio (January 2013). "Energy indices for environmental sustainability". International Journal of Technology Marketing 8 (1/2013). 
  12. ^ "ICTs for e-Environment Guidelines for Developing Countries, with a Focus on Climate Change". International Telecommunication Union. 2008. 

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