Abstract
In addition to materials and direct energy, accounting for embodied energy is essential to understand how the biophysical economy operates, because it provides an indication of the distribution of intra-economy energy demand created by consumption of goods and services. Furthermore, the energy embodied in manufactured capital provides, to first approximation, an estimate of the energy required to replace depreciated capital. This chapter begins by developing, for the first time in the literature, a rigorous, thermodynamically-based definition of embodied energy. We then show that energy embodied in the products of an economic sector is the sum of all direct energy consumed along the supply chain, including all upstream processing stages. We note that waste heat from a sector is additive to the energy embodied within products of a sector, thereby providing the mechanism for accumulating embodied energy along the manufacturing supply chain. Equations that describe the accumulation and flow of embodied energy through economies are developed through a series of increasingly-disaggregated model economies. Finally, we discuss embodied energy in the context of our running example, the US auto industry. We find that there are very few estimates in the literature of energy embodied within automobiles.
One of the main sinks of energy in the “developed” world is the creation of stuff. In its natural life cycle, stuff passes through three stages. First, a new-born stuff is displayed in shiny packaging on a shelf in a shop. At this stage, stuff is called “goods.” As soon as the stuff is taken home and sheds its packaging, it undergoes a transformation from “good” to its second form, “clutter.” The clutter lives with its owner for a period of months or years. During this period, the clutter is largely ignored by its owner, who is off at the shops buying more goods. Eventually, by a miracle of modern alchemy, the clutter is transformed into its final form, rubbish. To the untrained eye, it can be difficult to distinguish this “rubbish” from the highly desirable “good” that it used to be. Nonetheless, at this stage the discerning owner pays the dustman to transport the stuff away. [1, p. 88]
—David MacKay
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Notes
- 1.
To the authors’ knowledge, this is the first appearance in the literature of a systematic, detailed, and mathematically-rigorous derivation of embodied energy accounting equations derived from the laws of thermodynamics.
- 2.
The amount of energy embodied in an entire economy may be an indicator of its level of “development.” See Sect. 8.3 for a discussion of several indicators of economic “development.”
- 3.
Outputs from agricultural sectors will be similar: both (a) the direct energy component (comprising chemical potential energy) and (b) the embodied energy component (representing upstream energy consumed in food production) will be nonzero.
- 4.
Total energy can be neither created nor destroyed.
- 5.
Of course, waste heat exists and is accounted by the first law of thermodynamics. However, waste heat is ignored when accounting for total energy.
- 6.
But little direct energy accumulation actually occurs. We use energy as quickly as we make it available to society.
- 7.
Because we have substituted the first law of thermodynamics into the total energy accounting equation, \(\dot{Q}_{out}\) is a proxy for direct energy consumption by the sector.
- 8.
Note that γ B will, in general, be different from \(\gamma_{K}\) defined in Sect. 3.2. \(\gamma_{B}\) will equal \(\gamma_{K}\) if and only if the depreciated capital has an embodied energy content that is identical to the average embodied energy content of the sector on a per-unit-mass basis.
- 9.
Exceptions to this assumption may be the direct energy content of rubber, plastic and other petroleum products, e.g., motor oils which are used as resource inputs to the auto industry.
- 10.
The “energy cost” estimated by Berry and Fels is the energy embodied in a single automobile. The “energy cost” (in kW-hr/automobile) multiplied by the the production rate (in automobiles/year) gives the rate of gross embodied energy outflow in the product stream of the auto sector (\(\dot{B}_{\dot{P}_{gross}}\)). A limitation of the process-based approach employed by Berry and Fels is trucation error for upstream energy demand. See Sect. 7.1 for details.
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Heun, M., Carbajales-Dale, M., Haney, B. (2015). Stocks and Flows of Embodied Energy. In: Beyond GDP. Lecture Notes in Energy, vol 26. Springer, Cham. https://doi.org/10.1007/978-3-319-12820-7_5
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