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Identifying scales of dissipation for integrative sustainability scienceMeisterling et al.

Proceedings of the International Symposium on Sustainable Systems and Technologies, v2 (2014)

Identifying scales of dissipation for integrative sustainability science

Kyle Meisterling Environmental Studies and Institute for Energy Efficiency, University of California, Santa Barbara, kyle.meisterling@gmail.comWayne Christiansen Dept of Physics and Astronomy, University of North Carolina-Chapel HillMel Manalis Environmental Studies and Institute for Energy Efficiency UC Santa Barbara Abstract. Processes that occur over a vast range of scales support human economies and the earth system. This paper presents a taxonomy of dissipation in the human-environment system. Because it is conceptually simple and physically meaningful, dissipation as a common currency can bridge diverse models and thus facilitate the collaboration required for integrative and transdisciplinary scholarship and decision-making. We quantify dissipation by estimating entropy production rates for planetary, climatic, biospheric and anthropogenic processes. The taxonomy we present spans six orders of magnitude. It includes dissipation of photo-thermal, chemical, and kinetic gradients, as well as dissipation due to information management. Thermalization of low-entropy solar radiation to heat at the environmental temperature is the major dissipation process on earth. The dissipation that occurs via temperature gradients and material transfer is about 10 and 100 times smaller, respectively, than for solar radiation thermalization. We hope this work can help to identify the scaling factors required to better quantify the overlaps, modules, and hierarchies operating in complex human-environment systems.Proceedings of the International Symposium on Sustainable Systems and Technologies (ISSN 2329-9169) is published annually by the Sustainable Conoscente Network. Melissa Bilec and Jun-Ki Choi, co-editors. ISSSTNetwork@gmail.com.Copyright 2014 by Kyle Meisterling, Wayne Christiansen, and Mel Manalis. Licensed under CC-BY 3.0.

Cite as:K. Meisterling, W. Christiansen, M. Manalis. Identifying scales of dissipation for integrative sustainability science Proc. ISSST. v2 (2014), doi:XXIntroduction. This paper presents a taxonomy of dissipation in the human-environment system. Dissipation is conceptually simple and physically meaningful in many circumstances. Thus, is may serve as a common currency to link diverse models and facilitate the collaboration required for "integrative" and "trans-disciplinary" scholarship and decision-making (Seager 2008; Guine et al. 2011). Our work is aimed at helping to account for the complex and adaptive properties of economies, ecosystems, and societies (Gasparatos, El-Haram, and Horner 2008; Singh et al. 2009; Seager et al. 2013; Sexton and Linder 2014). It is our goal to provide a tool that helps define context for sustainability assessment, and to better situate interdependent systems (e.g. oxygen, carbon, "nutrient" cycles, climate) to facilitate an integrated view.

One lesson from thermodynamics is the critical importance of system definition. Exergy or free energy refer to a property of the system and its environment, defined as the amount of work that can be extracted from a system as it comes to equilibrium with some environment. The determination of free energy (hereafter exergy for brevity) requires accurate system definition. A change in the surroundings can affect exergy and entropy flows, so the definition of the surrounding is critical. In the realm of both engineering and the sustainability sciences, a representative background environment (e.g. temperature, chemical composition) has been defined to allow exergy calculations (Szargut, Morris, and Steward 1988; Ao, Gunnewiek, and Rosen 2008). However, over some scales (spatial or temporal), a change in the surroundings can act as a "back-reaction" (feedback) for the process of interest.

The notion of scale is important in many realms of science, including networks (Ravasz et al. 2002), ecosystems (Lavorel and Grigulis 2012; Cardinale et al. 2012; Jrgensen and Nielsen 2013; Pasari et al. 2013; Guerrero et al. 2013), and physics (Wilson 1975). Processes that occur over a vast range of scales support human economies and the earth system. (Young 1994; Schimel 2004; Kleidon 2010; DeFries et al. 2012; Hughes et al. 2013; Cumming et al. 2013); understanding these scales can support a coherent understanding of complex human-environment systems (Giampietro, Mayumi, and Ramos-Martin 2009; Burger et al. 2012; Cumming et al. 2013). Sol et al. state that we "need to identify the scales at which technological hierarchies operate" to better assess the prospects for economic growth (Sol et al. 2013) (p26). We take this to include the scales of interactions within and between systems, as well as the flows to and from the environment.

Scale is also important in biology (Bassett et al. 2010; Kempes, Dutkiewicz, and Follows 2012), and the metabolism of animals is a power law function of size (Thomas 1917; West, Brown, and Enquist 1997; Bejan 1997). Similarly, the efficiency of engines and generators is a power-law function of capacity (Caduff et al. 2011). Economies of scale have been identified since at least Adam Smith, whereby larger economic enterprises are able to more efficiently conduct their business. A common framework for economies of scale has been proposed based on Boltzman-Gibbs statistics of the "costs" of a particle joining a network (Peterson, Dixit, and Dill 2013). In the global economic network, certain regional sub-networks are particularly important for supporting trade (Duchin and Levine 2013).

There are also "dis-economies" of scale that limit size by making operation un-economic. For example, centralized commodity production incurs larger distribution losses, because a given product must be shipped from its point of production to the point of use, and this distance gets longer as production is scaled-up and centralized (Lorente et al. 2012). In addition to losses associated with material and energy flows, the trade-offs that define optimal system size involve information management as well (Altman, Nagle, and Tushman 2013). Finally, distributed systems, as opposed to centralized ones, can be more resilient in the face of disturbance (Farrell, Zerriffi, and Dowlatabadi 2004).

Dissipation, entropy, and the 2nd Law. Entropy and information have deep physical connections (Szilard 1929; Brillouin 1962; Landauer 1991). Entropy is a measure of the number of states available to a system and is often described as the 'lack of information' one system has about another. The 2nd Law of Thermodynamics describes the macroscopic "impossibility" of seeing a closed system evolve to have fewer quantum configurations, that is, lower entropy. The more restrictive, and probably more common, statement of the 2nd Law is that in the real world, entropy in closed systems only increases. This describes the ubiquitous presence of dissipative losses associated with flows. The tendency for entropy increase lies at the heart of the drive toward equilibrium, including the free energy of mixing and the tendency for a polymer to curl up (also known as "entropic elasticity"). When constraints are relaxed, a system will tend toward arrangements with more realizable configurations. Just as the arrangement of symbols represents information (e.g. written language), so does the arrangement of energy. The concept of dissipation is perhaps more easily conceptualized with energy than with information (e.g. symbols), but it applies to both.

One reason why dissipation is applied more easily to energy than to information may be because we are accustomed to engineered systems to manage energy. These types of machines led scientists to study energy in a structured, constrained way, which allows quantitative, predictive analysis. However, when it comes to information, the illustrative examples of information dissipation seem more concocted than what we are used to in the relatively less restricted area of personal communication. However, again, the technology to transmit, process and store (i.e. manage) information led scientists to study information in a more constrained, analytical way (Shannon 1948) and has led to an explosion of technological information management tasks.

Methods. Dissipation is a concept that applies to information, material and energy. We quantify dissipation by estimating annual entropy production rates for planetary, climatic, biospheric and anthropogenic processes. Since entropy is fundamentally a measure of (lack of) information, it quantifies both energy and information-based tasks.

For chemical processes, we make a distinction between thermo- and physio-chemical dissipation. Reduction-oxidation reactions involve re-arrangement of atomic nuclei and electrons. These processes can liberate or absorb heat to and from the environment; this heat is what we call "heating value" in the context of fuel. In addition to this thermal energy, the difference in concentration (partial pressures or concentrations) between reaction products and the surroundings is a gradient of "type", and is associated with exergy. Thus the exergy of a fuel is composed of a thermal component and a component of "type" (note, however, that since exergy is dependent on the environment, a change in the surroundings can change the magnitude of a compound's thermo-chemical and physio-chemical exergy) (Szargut, Morris, and Steward 1988).

Photo-thermal dissipation. When high-energy (low-entropy) solar photons encounter the earth system, many are almost immediately absorbed by matter (whether in the atmosphere or surface). The absorbed energy is re-radiated as photons at temperatures characteristic of the earth environment. In the process, many more photons are produced, but with lower per photon energy, and higher overall entropy. Some dissipation of the exergy of solar photons is delayed by "hangups" in the earth system (see (Dyson 1971) for an enlightening discussion of cosmic hangups).

We take the dissipation due to thermalization at the surface and in the atmosphere from Kleidon, along with dissipation due to light scattering and heat diffusion, and the effective surface and atmospheric temperatures of 288K and 252K, respectively (Kleidon 2010) (values corroborated with (Peixoto et al. 1991; Szargut 2003; Trenberth, Fasullo, and Kiehl 2009; Pascale et al. 2011)).

Material flows. Following Pascale et al., we view the thermalization process as separate from the material climate system because the radiative entropy production "is not relevant to the operation of the material climate system", since providing the system "at every point with heat sources and sinks equal to shortwave absorption and net longwave emissionwould not affect the evolution of the climate system, since the fluid equations are concerned only with the amount of heat gained or lost." (Pascale et al. 2011) (p1194-1195). We take evaporation from Schlesinger and Bernhardt (Schlesinger and Bernhardt 2013), and atmospheric turbulent dissipation from Makarieva et al. (Makarieva et al. 2013) and Pauluis and Dias (Pauluis and Dias 2012).

Biomass and primary productivity. Through photosynthesis, primary producers ("plants" for brevity) convert some of the exergy of sunlight into chemical exergy. The fate of primary production is shown in Table 1. Terrestrial and aquatic photosynthesizers both use about 50% of the chemical exergy for their own respiration. Most of the remainder is available to the ecosystem to be consumed.

Table 1. Fate of primary production in ocean and land ecosystems. From (Schlesinger and Bernhardt 2013),, with page numbers indicated. Note that 15% of ocean NPP is "exported" to the deep ocean (some of which is respired or dissolved, p356).

OceanLand

"plant" respiration50%50%

Respiration by "decomposers"30% (p355)48% (p150)

Respiration by "herbivors"15% (p355)2% (p150)

Dissolved5% (17% of 15-20%; p355)