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Applications of Exergy to Enhance Ecological and Environmental Understanding and Stewardship

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Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09) Applications of Exergy to Enhance Ecological and Environmental Understanding and Stewardship MARC A. ROSEN Faculty of Engineering and Applied Science University of Ontario Institute of Technology 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 CANADA Email: [email protected] http://www.uoit.ca Abstract: Methods can be used which combine thermodynamics with environmental and ecological disciplines to understand ecological systems and environmental impact. Such assessments of ecological and environmental factors are better understood using the thermodynamic quantity exergy even though most consider thermodynamics in terms of energy. Here, applications are presented of many analysis techniques which integrate exergy and ecological and environmental factors (e.g. exergy-based ecological indicators). The examples considered include the application of exergy to water-based ecosystems for understanding, predicting and improving their health. Thermodynamic, ecological and environmental data are examined, and show that correlations exist between exergy and environmental and ecological parameters. The existence of such correlations likely implies that exergy factors into environmental improvement and ecological stewardship. Keywords: ecology, environment, energy, exergy, efficiency, sustainability 1 Introduction dissipation, biodiversity, ecosystem health and Thermodynamics suggests that human economic quality, and water quality. Also, ecological indicators activity can convert highly-ordered self-producing for ecosystem development and health have been ecosystems with their rich accumulations of proposes based on eco-exergy, a modified form of resources into damaged and disordered ecosystems. exergy which measures a system’s deviation from Assessments of environmental and ecological impact chemical equilibrium (Jorgensen, 2006; Jorgensen for energy and other systems normally consider and Nielsen, 2007). Emergy, the solar energy energy quantities, but many suggest that the required directly and indirectly to generate a flow or thermodynamic quantity exergy, which stems from storage, has been proposed as an objective function the second law of thermodynamics, is a better for ecosystems, as it permits assessments of self- measure of the potential for environmental or organizing systems (Bastianoni and Marchettini, ecological impact and the wellness of ecological 1997). systems (Szargut et al., 2002; Szargut, 2005; Relations between exergy and the environment Jorgensen, 2000; Jorgensen and Fath, 2004; Dincer reveal underlying patterns affecting environment and Rosen, 2007). Decisions based on assessments changes. Increasing exergy efficiency reduces that ignore nature significant deteriorate the ability of requirements for energy resources and emissions. But ecosystems to provide the goods and services that are exergy also is linked to environmental impact since it necessary for human activity. The numerous exergy- is a measure of the departure of the state of a system based environmental and ecological analysis from that of the environment (Ayres et al., 1998; techniques that have been developed are reviewed in Berthiaume et al., 2001; Gunnewiek and Rosen, this article. 1998; Frangopoulos and von Spakovsky, 1993; Rosen and Dincer, 1997a, 1999; Dincer and Rosen, 2007; 2 Background Sciubba, 1999; Wall and Gong, 2001; Baumgärtner and de Swaan Arons, 2003; Jorgensen and Svirezhev, 2004). Further, exergy is a measure of potential of a 2.1 Exergy, Ecology and Environmental substance to cause change, perhaps on the Impact environment (Dincer and Rosen, 2007). Ecological indicators have been proposed based on Several environmental impacts are predictable via exergy and each of the following: structural changes, exergy, like resource degradation, waste emissions ecological processes, maturity, extremal principles and disorder/chaos creation. Numerous exergy-based and optimization, buffering capacity and constraints, environmental methods have been developed, such as ISSN: 1790-5095 146 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09) extended exergy accounting (Sciubba, 2004), parameters and species composition, with exergy cumulative exergy consumption (Szargut et al., used as a measure of build-up of biological structure 2002), exergetic life cycle assessment (Granovskii et of a lake ecosystem (Salomonsen and Jensen, 1996). al., 2007), exergy-based industrial ecology (Dincer Xu (1997) applied exergy and structural exergy as and Rosen, 2007), exergy-based ecological footprint ecological indicators to assess the development state analysis (Chen and Chen, 2007) and environomics of the ecosystem of Lake Chao, a eutrophic in China, (Frangopoulos and von Spakovsky, 1993). and the restoration of riparian wetlands and macrophytes in Lake Chao. It was observed that 2.2 Extending Relations to Economics macrophyte restoration could decrease phytoplaniton The ties of exergy to environment and ecology can biomass and increase fish biomass, exergy, structural be extended to economics. For instance, exergy, zooplankton/phytoplankton ratio and environmental impact and protection costs can be transparency, implying that macrophyte restoration included in exergy-based economic assessments. A can purify lake water, regulate lake biological thermoeconomic method to increase the efficient use structure and control eutrophication (Xu et al., 1999). of exergy resources based on a carbon exergy tax is Ludovisi and Poletti (1999) also applied exergy and proposed (Santarelli, 2004). To obtain exergy-based structural exergy as ecological indicators for the indicators of sustainable development, Ferrari et al. development state of homogeneous lake ecosystems. (2001) integrate thermodynamics and economics, Exergy and structural exergy were used to assess the while Sciubba (2005) has also proposed aquatic ecosystem consisting of the mesocosms and exergoeconomics as a thermodynamic foundation for microcosms of Lake Baikal (Silow and Oh, 2004). rational resource use. Furthermore, an ecological That work supported the use of structural exergy as a economics perspective of economic development and measure of ecosystem health in that the structural environmental protection is provided by Rees (2003), exergy of the communities decreased: 1) after the noting that pristine ecosystems are typically observed addition of allochtonous compounds (peptone, diesel to be ordered and have high exergy while damaged oil) to the mesocosms, 2) after the addition of ecosystems are disordered and have low exergy. toxicants to the microcosms, and 3) after discharges from Baikal Pulp and Paper, which polluted the area 3 Applications of Exergy in Ecology (based on the exergy contents for benthos in polluted and unaffected regions). and the Environment Exergy and structural exergy were demonstrated to be feasible ecological indicators of system-level 3.1 Exergy and Ecology Applications responses of lake ecosystems to chemical stresses via Exergy-based ecological models and methods have tests of the system-level responses of experimental been applied to various ecosystems, particularly lake ecosystems to three chemical stresses: aquatic ones. The stresses in ecosystems from acidification, copper and pesticide contamination pollution have made it important to have meaningful were determined (Xu et al., 2002). Large changes indicators for assessing the effects of pollution in occurred in some instances, indicating the those communities. Exergy-based indicators of ecosystems were seriously contaminated by the ecosystem integrity facilitate detection and chemical stressors while small changes were evaluation of environmental responses to pollution, observed at other times suggesting the lake mitigation of the harmful impacts and effective ecosystems were not significantly impacted. The ecosystem management. observed changes in exergy and structural exergy were consistent with expectations of reduced food 3.1.1 Lakes chains, resource-use efficiency, stability, information Applying exergy in the ecological modelling of a and exergy in stressed aquatic ecosystems. lake environment has demonstrated that exergy act as The pelagic trophic food chain in Lago Maggiore, an object function in ecological models for lakes and Switzerland was examined from 1978-1992 in part reservoirs, an ecological indicator for the by determining the exergy content in the food chain development and evolution of lake ecosystems and a (de Bernardi and Jorgensen, 1998). The approach component of structural dynamic models that account helped better describe functioning mechanisms for for ecosystem changes (Zhang and Wang, 1998). the food chain, predict the most significant factors Additional support for exergy being an object affecting ecosystem function, estimate the efficiency function in lake models was provided by an of the food chain in utilizing available resources and examination for a generic lake of the exergetic verify ecological models. response to changes in phytoplankton growth ISSN: 1790-5095 147 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09) 3.1.2 Lagoons ecosystems, and exergy can act as an effective The exergy index and specific exergy provide useful ecological indicator. information on community structure when applied as ecological indicators of organically enriched regions 3.2
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