Proceedings of the 4th IASME / WSEAS International Conference on & (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 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 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: , environment, energy, exergy, efficiency,

1 Introduction , , 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 (Jorgensen, 2006; Jorgensen for energy and other systems normally consider and Nielsen, 2007). , the 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 reduces that ignore nature significant deteriorate the ability of requirements for energy resources and emissions. But ecosystems to provide the 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 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 (Salomonsen and Jensen, 1996). al., 2007), exergy-based (Dincer Xu (1997) applied exergy and structural exergy as and Rosen, 2007), exergy-based 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 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 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 , 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 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 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 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 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 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 structure when applied as ecological indicators of organically enriched regions 3.2 Exergy and Environment Applications in the Mar Menor lagoon, a Mediterranean coastal Methods integrating exergy and the environment lagoon in south-eastern Spain (Salas et al., 2005). have been applied to devices, systems and processes These indicators were suggested to be insufficient in a wide range of fields, including heating, cooling, alone to act as ecological indicators because exergy power generation, cogeneration, chemical and specific exergy did not distinguish levels of processing, separation and production. organic enrichment or the effects of all types of pollution. 3.2.1 Heating and cooling Exergy assessments including environmental factors 3.1.3 Seas have been reported for a variety of thermal processes Exergy has been cited as a useful indicator for related to heating and cooling, including integrating the underlying recovery processes of psychrometric devices, heat pumps, drying systems benthic communities after disturbances, following an and cryogenic devices (Dincer and Rosen, 2007), as application of exergy as an ecosystem indicator well as thermal storage technologies (Rosen and during the recovery of marine benthic communities. Dincer, 2002). This conclusion was based on examinations of the An exergy-based economic optimization carried communities in the sandy and muddy bottoms of the out of the geometry of a precooling air reheater for North Adriatic Sea (Libralato et al., 2006). The air conditioning (Jassim et al., 2005). The total cost complex dynamics that occur in a disturbed function was optimized based on the optimum heat community during recovery processes are usually transfer area and the total irreversibilities. An difficult to assess with conventional indices, but assessment has also been undertaken of cold thermal exergy as a measure of the departure of a system system using a glycol working fluid from equilibrium has been proposed as a useful (Bakan et al., 2007). ecological indicator in this context. A controlled EXCEM analysis, an exergy-based technique that trawl fishing haul was the , and the local simultaneously considers cost, energy and mass, has exergy storage of the benthic community was used been applied to a range of thermal systems and and exergy was estimated with data for trophic processes (Rosen and Dincer, 2003), including a groups, coding genes of broad taxonomical groups greenhouse heating system using a solar-assisted and genome size. Local exergy content decreased in ground-source (Ozgener and Hepbasli, disturbed areas, peaking in sandy and muddy bottom 2005). EXCEM ssessments have also been carried one month after the disturbance and subsequently out of ground-source heat pump systems for building increasing to the reference or surrounding level. This applications (Ozgener et al., 2005) and of geothermal result is consistent with the dynamics of exergy district heating systems (Ozgener et al., 2007). storage during the development of systems. As anticipated, the dynamics of exergy in the two 3.2.2 Power generation and cogeneration differed. The results may be extendable to Numerous exergy-based environmental assessments biological systems (Libralato et al., 2006). have been reported for electrical power generation and processes that simultaneously produce multiple 3.1.4 Macroinvertebrate communities and products. The latter include cogeneration of Reis and Miguel (2006) reported an exergy balance and heat (i.e. combined heat and power) as of green leaves and Park et al. (2006) used self- well as trigeneration of electricity, heat and cold. organizing maps to pattern the exergy of benthic A complex Brayton cycle for power generation macroinvertebrate communities. The latter work was investigated considering ecological and utilized data for 650 sites in the Netherlands economic conditions (Tyagi et al., 2007). The including 855 species. The exergy was calculated ecological function was defined as the ratio of power using biomass data for five trophic functional groups: output to generation rate and the economic , , –, function as the ratio of power output to total cost. herbivores and . The response of the The cycle was optimized by adjusting several exergy of the different trophic groups varied with operating conditions, including cycle ecosystem characteristics, suggesting that patterning and reheat and intercooling ratios. Values changes of exergy is effective for evaluating were determined of turbine outlet and several pressure ratios at which the cycle is

ISSN: 1790-5095 148 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

maximized in terms of ecological and economic emissions from fossil . These objectives while minimizing the entropy generation comparisons, based on a previous analysis rate. Also, exergy and environmental analyses have (Gunnewiek and Rosen, 1998), help identify trends been reported of the power plants in transportation that may permit the exergy of a substance to be a systems like aircraft (Rosen and Etele, 2004) and useful indicator of potential environmental impact automobiles (Daniel and Rosen, 2002). and consequently to be a tool for establishing A combined power consisting of a solid emission limits that are rationally based rather than oxide and gas turbine was assessed using a formulated by trial and error. thermoeconomic method based on a carbon exergy Air pollution limits in Ontario are covered by the tax that directed at increasing the efficient use of provincial Environmental Protection Act, which aims exergy resources (Santarelli, 2004). Also, to ensure environmental conditions that do not hydroelectric and thermoelectric power generation endanger human health and the Earth ecosystem. In processes were analyzed with a comprehensive Ontario, the Ministry of the Environment implements method based on exergetic and economic parameters environmental legislation for industry. Allowable air as well as environmental emissions (Tonon et al., emission limits (i.e., pollutant mass per air 2006). A photovoltaic-hydrogen system for averaged over a specified time), which must be residential buildings was also assessed (Santarelli and achieved prior to discharge, are listed for numerous Macagno, 2004). substances. Point of Impingement (POI) air emission Methods for extending exergy accounting and limits are determined considering the best available thermoeconomics with environmental factors were pollution control technology. The potential of a applied to gas turbine-based cogeneration to optimize substance to impact the environment is evaluated by the design (Sciubba, 2003). An exergy analysis of ten parameters: cogeneration and district energy, with environmental benefits, was also reported (Rosen et al., 2005). • transport, • persistence 3.2.3 Chemical processes • , Processes for chemical and fuel processing and • acute lethality separation vary widely. Some of these have been • sub-lethal effects on mammals, investigated with exergy-based environmental • sub-lethal effects on plants, methods to improve understanding and designs. For • sub-lethal effects on non-mammalian , example, an analysis method based on exergetic, • teratogenicity, economic, environmental and other parameters has mutagenicity/genotoxictiy, and been applied to bioethanol production (Tonon et al., • 2006). Also, an exergetic evaluation of the • carcinogenicity. renewability of a biofuel has been carried out by Berthiaume et al. (2001). Also, an exergetic Two methods for developing environmental costs environmental assessment of life cycle emissions for for air emissions are considered. In the first method, various automobiles and fuels was reported (Daniel the cost is considered of removing pollutants from the and Rosen, 2002), and the exergy of the emissions waste stream prior to discharge to the environment, for two energy conversion technologies were from combustion emissions. This cost can contrasted, considering their potentials for be related to the exergy of the pollution, and is environmental impact (Crane et al., 1992). referred to as the Removal Pollution Cost (RPC). The removal cost for a waste emission is evaluated as the total fuel cost per unit fuel exergy multiplied by the 4 Case Study chemical exergy per unit fuel exergy, and divided by A case study of the correlation of exergy with other the exergy efficiency of the pollution removal process. indicators of environmental impact is presented to The exergy efficiencies for removing pollutants from illustrate the exergy-based ecology and waste streams vary. Some sources indicate that exergy environmental analyses and concepts discussed in efficiencies are below 5% when removal involves this article. Specifically, the exergy of waste mechanical separation. For simplicity, exergy emissions is compared to other selected measures to efficiencies of 1% for all pollutants are used here. assess or control the potential environmental impact In the second method for developing air-emission of emissions, including air emission limits environmental costs, environmental costs of pollutant, established by the government of Ontario, Canada, referred to here as Environmental Pollution Costs and two quantifications of “environmental costs” for (EPCs), are estimated. Such work is most advanced

ISSN: 1790-5095 149 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

for atmospheric emissions from fossil fuel from a waste stream prior to discharge into the combustion. Environmental costs for some emissions environment. have been estimated for Canada (see Table 1). Values for EPCs are based on quantitative and qualitative 5 Conclusions evaluations of the cost to correct or compensate for Exergy exhibits many interesting relations with environmental damage, and/or to prevent a harmful ecology and the environment, which provide a emission. foundation for exergy-based ecological and environmental methods. The applications considered illustrate that exergy almost certainly factors, or Table 1. Selected environmental pollution costs should factor, into environmental improvement Pollutant Environmental activities and ecological management. The pollution cost applications also illustrate how the insights gained 1 ($/kg pollutant) via exergy can assist in integrating thermodynamics 2 Particulates 4.95 into ecological and environmental management, CO 4.46 especially by exploiting the correlations with NOx 3.50 environmental and ecological parameters. Through SO2 3.19 the applications, the merits of exergy analysis over CH4 1.17 the more conventional energy analysis are Volatile organic compounds 0.54 highlighted from a thermodynamic perspective and CO2 0.036 also from a combined thermodynamic and 1 Values are in 2006 Canadian dollars. EPCs are environmental and ecological perspective. For based on 1990values, adjusted for inflation using instance, it is shown that exergy, but not energy, is the Price Index for all products. Statistics often a measure of the potential for ecological and Canada reports a 40% increase over the 16 years. environmental impact, and that exergy-based 2 Includes heavy metals like lead, cadmium, nickel, ecological and environmental indicators are chromium, copper, manganese and vanadium. meaningful and merit further investigation.

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