Extended Exergy Accounting Research Articles

Improving urban ecosystem holistic sustainability of municipal solid waste-to-energy strategy using extended exergy accounting analysis

Waste-to-energy technologies play a crucial role in integrated waste management strategies to reduce waste mass and volume, disinfect the waste, and recover energy; different technologies have advantages and disadvantages in treating municipal solid waste under urban conditions. This paper applies the extended exergy accounting method to develop an analytical framework to identify the optimal waste-to-energy strategy from an urban ecosystem holistic sustainability perspective. In the analytical framework, urban ecosystem costs and revenues are formulated as a multi-criteria cost-benefit quantitative model. The urban ecosystem cost is divided into five categories, and the urban ecosystem revenues consist of direct and indirect parts. The direct part is the chemical exergy of the waste-to-energy plants produced product, and the indirect part includes equivalent exergy content of power generation substitution, human health risk elimination, disamenity impact removal and environmental degradation avoidance. Proposing an indicator system to evaluate the waste-to-energy strategy impact on the sustainability of the urban ecosystems and social, economic and environmental sub-ecosystem. Detailed analysis of food waste treatment scenarios of a food center in Singapore was done as a case study to illustrate this analytical framework. Base scenario is current practice that food waste disposal in incineration plant. Anaerobic digestion and gasification are proposed as potential technological solutions for on-site food waste treatment in scenario I and II respectively. In different scenarios, the urban ecosystem costs are estimated to be 71,536.01, 61,854.87 and 74,190.34MJ/year respectively, and the urban ecosystem revenues are estimated to be 135,312.66, 405,442.53 and 298,426.81MJ/year respectively. We show that the scenario where food waste is treated by anaerobic digestion outperforms both the base scenario and scenario II in terms of urban ecosystem costs and revenues, technical energy conversion efficiency, contribution to urban ecosystem holistic sustainability, and natural, social, and economic subsystems improvement, making it the optimal municipal solid waste-to-energy strategy choice.

Ecological accounting of the Chinese society 2012–2020 based on extended exergy

China's social system has undergone unprecedented economic transformation in the past decade. It is essential that the relationship between the country's socio-economic development and natural ecosystem be revealed, thereby revealing the evolutionary trajectory of its biophysical sustainability. The extended exergy accounting (EEA) method offers a thermodynamics-based tool to evaluate the structure and function of a social system and objectively estimate the impacts of human activities on sustainable development and broader ecosystems. This study aims to perform extended exergy analysis to trace the flows of resources, labor, capital, and environmental remediation exegetics in China's society from 2012 to 2020. During the accounting period, the average annual growth rate of total extended exergy (TEE) was just 1.2%. The TEE in the conversion and tertiary sectors ew noticeably faster than those in other sub-sectors, while the TEE in the extraction and agriculture sectors showed a declining trend. The TEE in 2020 reached 764.50 EJ, of which 179.13 EJ were attributed to Cumulative Exergy Consumption, 74.89 EJ were attributed to labor, 68.85 EJ to capital, and 441.63 EJ to environmental remediation costs. The indicator assessment reflects an enhancement in the sustainability of the Chinese social system, particularly the rapid improvement in labor and capital-related indicators. Comparing the results with other countries demonstrates that the gap between China and developed nations has narrowed, with China's indicators for balancing resource production and capital flows rivaling those of the U.S. and the U.K. The objective revelation of the developmental and transitional trajectory of Chinese society, based on the EEA approach, provides valuable insights for other developing countries in achieving sustainable development.

Assessment of coal supply chain under carbon trade policy by extended exergy accounting method.

Within an uncertain environment and following carbon trade policies, this study uses the Extended Exergy Accounting (EEA) method for coal supply chains (SCs) in eight of the world's most significant coal consuming countries. The purpose is to improve the sustainability of coal SCs in terms of Joules rather than money while considering economic, environmental, and social aspects. This model is a multi-product economic production quantity (EPQ) with a single-vendor multi-buyer with shortage as a backorder. Within the SC, there are some real constraints, such as inventory turnover ratio, waste disposal to the environment, carbon dioxide emissions, and available budgets for customers. For optimization purposes, three recent metaheuristic algorithms, including Ant Lion Optimizer, Lion Optimization Algorithm, and Whale Optimization Algorithm, are suggested to determine a near-optimum solution to an "exergy fuzzy nonlinear integer-programming (EFNIP)." Moreover, an exact method (GAMS) is employed to validate the results of the suggested algorithms. Additionally, sensitivity analyses with different percentages of exergy parameters, such as capital, labor, and environmental remediation, are done to gain a deeper understanding of sustainability improvement in coal SCs. The results showed that sustainable coal SC in the USA has the lowest fuzzy total exergy, while Poland and China have the highest.

Extended exergy accounting theory to design waste-to-energy management system under uncertainty

This paper seeks to study the waste-to-energy facility location planning problems under uncertainty from an integrated perspective. The extended exergy accounting method is first used to develop a multi-criteria decision analysis framework that unique in unifying multiple criteria of material, energy, social, economic and environmental aspects into homogeneous exergy terms, thus employing multiple criteria to obtain an integrated decision-making result.Robust optimization and mixed-integer linear programming mathematical techniques are applied to formulate the problem as a two-stage robust waste-to-energy facilities location model based on this framework to minimize the exergy expenditure, and determine the technology type, location and capacity size of waste-to-energy facilities over a large urban region. The uncertainty of municipal solid waste supply quantity in each waste generation site is considered.The proposed model was demonstrated using a case study for household food waste treatment in Shanghai, and two treatment scenarios are proposed. Under the same uncertainty, the deployment strategy in scenario II feeds annual 2,655,140 GJ more equivalent primary exergy into the urban ecosystem than the scenario I, indicating that the only deployed on-site biogas plant to disposal household food waste performs better than the centralized incineration and on-site biogas plant combined deployment.A further sensitivity analysis reveals several valuable insights into municipal solid waste management. If the uncertainty is not considered, it may result in a municipal solid waste treatment capacity gap of up to 11.5% and a waste-to-energy system breakdown. Introducing the uncertain budget and range can help the decision-maker adjust the planning scheme flexibly, but the results become more conservative as their values increase. In this case study, it is optimal for decision makers to choose uncertain range mˆi=12.5% and uncertain budget Γ=30.

Application of net zero extended exergy buildings concept for sustainable buildings analysis

Different Zero-Energy Building (ZEB)-related definitions considering its four main dimensions, such as zero energy, zero carbon, zero exergy and zero cost, have been proposed by different investigators. Among these, exergy-based definitions are relatively low in numbers. In this regard, the main objective of this present study is to propose net zero extended exergy buildings as a new concept, which combines extended exergy and net zero exergy building concepts and is a measure of the exergetic footprint. This concept setups a balance between extended exergy accounting of electricity from the grid and electricity generated in building. The proposed methodology is applied to a building available in the literature for heating and cooling seasons. Results show that 450Wp peak power and 44.181 kWh electrical energy must be obtained for meeting the electricity demand of the building. Another novel result is that the extended exergy accounting of the electricity generated by PV panels is bigger than the extended exergy of the electricity taken from the gird meaning that exergetic footprint of the electricity generated by PV panels is bigger. However, this result must be interpreted for the whole life time of the system.

Integrate exergy costs and carbon reduction policy in order to optimize the sustainability development of coal supply chains in uncertain conditions

The coal supply chain in developing countries is supposed to have the lowest cost overall; however, in terms of sustainability (social, economic, and environmental aspects) and considering Joules rather than monetary objectives, does this assumption remain accurate? This research develops a sustainable model for coal supply chain in five countries by integrating exergy costs and carbon tax policy using the extended exergy accounting (EEA) method under an uncertain environment. This sustainable model is a single vendor multi-buyer economic order quantity (EOQ) model for coal supply chain with the objective of the least total exergy with the maximum carbon and imperfect quality items decrease. Additionally, some realistic suppositions such as waste disposal to the environment, the obtainable budget of buyers and stockout in the model are considered. Following this, four metaheuristic algorithms, such as WOA, GA, ACO, and SA, are suggested to solve the model, and their results are validated by the exact method (GAMS). Finally, to improve the model's sustainability, a sensitivity analysis with different exergy values is offered for coal supply chain in each country. According to the results, coal supply chains in Canada and Germany have better sustainability performance (in Joules) than Iran and Turkey.

Environmental sustainability and exergy return on investment of selected solar dryer designs based on standard and extended exergy approaches

ABSTRACT Different solar dryer designs are available in the literature. However, it is essential to understand how the performance of the dryer designs contributes to environmental sustainability by reducing waste in the exergy-loop and mitigate CO2 emission into the atmosphere. The exergy-based sustainability indices include waste exergy ratio, lack of productivity (LOP), sustainability index, environmental destruction coefficient and exergy recovery ratio. The paper also introduces exergy return on investment (ExRoI) by applying an extended exergy accounting approach with the inclusion of exergy influx of material resources, capital and labor in the exegetic computations of the sustainability index. Four solar dryers consisting of an indirect solar-cabinet dryer, mix-mode solar dryer, hybrid solar dryer and a double-partitioned single-pass-collector solar dryer with a wind generator were used as a case study. Comparatively, the ExRoI is lower than the standard exergy-efficiency for the four dryers by 6.87 to 91.61%. In contrast, the standard exergy-based sustainability index was higher by 5.4 to 61.2%. Total invested exergy ranged from 0.04TJ to 0.081TJ. The values of waste exergy ratio, LOP, ERR, EDC, and carbon credit ranged from 0.47 to 0.79, 0.566 to 16.45, 5.44 × 10−4 to 1.37 × 10−1, 1.57 to 17.45 and 231.45 to $2908, respectively.

The Thermoeconomic Environment Cost Indicator (iex-TEE) as a One-Dimensional Measure of Resource Sustainability

This paper presents a conceptual development of sustainability evaluation, through an exergy-based indicator, by using the new concept of the Thermoeconomic Environment (TEE). The exergy-based accounting methods here considered as a background are Extended Exergy Accounting (EEA), which can be used to quantify the exergy cost of externalities like labor, monetary inputs, and pollutants, and Cumulative Exergy Consumption (CExC), which can be used to quantify the consumption of primary resources embodied in a final product or service. The new concept of bioresource stock replacement cost is presented, highlighting how the framework of the TEE offers an option for evaluating the exergy cost of products of biological systems. This sustainability indicator is defined based on the exergy cost of all resources directly and indirectly consumed by the system, the equivalent exergy cost of all externalities implied in the production process and the exergy cost of the final product.

Evaluating the urban metabolism sustainability of municipal solid waste management system: An extended exergy accounting and indexing perspective

In this study, Extended Exergy Accounting was adopted to develop an accounting model to evaluate the performance of a Municipal Solid Waste Management System. Furthermore, urban metabolism sustainability index for waste was also proposed to represent the unified society-economy-environment impacts of the MSWMS under the framework of a comprehensive sustainability evaluation. A detailed analysis of wood and horticultural waste treatment scenarios in Singapore was done as a case study. It was found that the gasification scenario theoretically performs significantly better than the incineration scenario, in terms of energy carrier consumption, emissions, thermodynamic efficiency and sustainability. Analysis results show that, if extrapolated to Singapore’s total wood and horticultural waste, gasification technology has potential to reduce energy consumption and increase electricity output. An uncertainty analysis was carried out and it was found that the main extended exergetic parameters of the two scenarios considered were in the range of 3–8%, thus confirming the reliability of the accounting results. A sensitivity analysis of the urban metabolism sustainability index for waste was conducted for the gasification scenario to identify key influencing factors and seek potential improvements; this was done by considering changes in four variables: transportation distance, electrical efficiency, working hour increment and gross capital cost per ton waste treated. It was found that, to ensure the feasibility and sustainability of gasification scenario, the following are required: keeping the electricity production efficiency greater than 21.33%; the transportation distance between the gasification power plant and source of wood and horticultural waste should be kept within 17.08 km; employment of per kton annual treatment capacity should be less than 0.14 workers; wood and horticultural waste source should control the waste collection frequency of no more than 3 times per day and the number of workers participating in the collection each time is less than 4 persons, totaling to 12 workers per day.

Extended Exergy Analysis (EEA) of Italy, 2013–2017

In recent years, many studies have been published on the applications of exergy analyses to complex systems, including entire countries. Oddly, the results, although consistent, appear to lead to divergent conclusions. The underlying problem is that in a “pure” thermodynamic analysis, the so-called “externalities”, i.e., labor, capital, and environmental costs, are often neglected or only approximately included in the picture. In 1998, an extension of the theory that included the exergy content of the externalities was introduced, called “extended exergy accounting” (EEA). Its novelty consisted of the explicit inclusion of the exergy embodied in the externalities. The aim of this work is to use the results of the extended exergy accounting to obtain an indicator that can be used to assess the sustainable development of a country. First, a novel methodological approach to the theory is presented, based on the exploitation of a very large dataset obtained from several national and European statistical institutions. After a brief discussion of the theory, an application to the case of Italy is developed over a 5 years time window (2013–2017). The paper includes a comparison with the concurrent evolution of other sustainability indicators and of the gross domestic product (GDP) indicator. The results show a consistent trend for EE as compared with those of other indicators, and also convincingly proves that this trend is incompatible with that of the GDP. The EE indicator is called the exergy footprint, which also displays a remarkable sensitivity to both environmental and economic factors.

Sustainability analysis of a solar driven hydrogen production system using exergy, extended exergy, and thermo-ecological methods: Proposing and comparing of new indices

This paper aims at investigating and comparing some sustainability indices in the literature while proposing some new indices. A solar driven hybrid system made of a PV cell, an alkaline electrolyzer and a PEM fuel cell is chosen to apply these indices because renewable-based stand-alone hybrid systems for generating electricity seem to be very promising for the future. Some sustainability indices and methods, such as sustainability index, exergetic sustainability index, extended exergy accounting and thermo ecological cost analysis, exist in the literature. In addition to these indices, new indices proposed in this paper contain thermo-ecological cost (TEC) of irreversibilities, extended TEC, extended exergy-based sustainability index and the extended exergetic ecological index. A daily dynamic performance analysis is made for one year. According to the results, exergy efficiency values range from 0.027 to 0.121 while extended exergy efficiencies vary between 0.08 and 0.14. Finally, the proposed indices are classified for designing environmental cycles, assessing environmental effects under operation conditions, and evaluating sustainability in every aspect.

A new systematic decision support framework based on solar extended exergy accounting performance to prioritize photovoltaic sites

Determining locations is important for researchers and policymakers involved in developing photovoltaic (PV) plants. Here, solar extended exergy accounting performance is proposed as a new systematic decision support framework for prioritizing PV sites from environmental, technical, financial, and social viewpoints. The space-time solar extended exergy accounting performance of a 500 kW grid-connected PV system is determined for different Iranian climates as an example to show how the proposed tool can enhance site selection for PV power systems. The simulations are carried out for all 12 months of the year using the actual climatic, technical, economic, environmental, and social databases. Results for January, April, July, and October, representing winter, spring, summer, and autumn, respectively, are discussed in detail. The outcomes of the proposed method are compared with those for total irradiance, solar irradiance exergy, power generation, and exergy efficiency. In addition, several space-time ‏maps are developed for facilitating comparison among PV installation priorities obtained using various criteria. The average monthly total irradiance and solar irradiance exergy in Iran respectively varies in the range 120–184 kWh/m2/month and 112–172 kW/m2/month, respectively. The average monthly power generation, exergy efficiency, and extended exergy accounting performance of the developed plant are respectively found to be in the range of 45.3–66.0 MWh/month, 13.6‒14.8%, and 9.46–10.5% for different Iranian climates. Overall, southeast, central, and northwest cities of Iran are shown to be promising candidates for solar PV power systems based on the extended exergy accounting approach. The outcomes show that the proposed tool can be much more helpful than conventional methods for ranking candidate locations for building PV plants. The proposed extended exergy accounting performance framework can be applied for other stand-alone and hybrid renewable energy systems for various environmental and climatic conditions.

Research on Extended Carbon Emissions Accounting Method and Its Application in Sustainable Manufacturing

Carbon-Emission Accounting (CEA) is an important assessment method for sustainable manufacturing, which mainly focuses on raw materials, energy and waste disposal factors but ignores labor and capital factors. However, the generation process of labor and capital inevitably produce Carbon Dioxide Emissions (CDE). Referring the Extended Exergy Accounting method, the calculation model of extended carbon dioxide emissions factors of capital and labor is established based on the standard CDE per capita, total population, annual working hours, intermediate money M2 and total annual wage S, etc. Then the Extended Carbon-Emission Accounting (ECEA) method is proposed based on the current CEA method, accounting labor, capital, raw materials, energy and all other environmental related factors. Comparatively analyzing on grinding and hard-turning process of a lathe spindle part is studied, the result shows ECEA method is more reasonable and suitable for sustainable manufacturing than CEA method.

An integrated full cost model based on extended exergy accounting toward sustainability assessment of industrial production processes

Existing methods for the sustainability assessment of industrial production processes have considered the values of natural resource use and ecosystem services. However, these methods mainly focus on monetary measures of natural capital cost and ignore some other costs, including human health effects, biodiversity loss and indirect exergy consumption in labor employment. The integrated ecological cumulative exergy consumption accounting method was proposed to improve the existing extended exergy model and provide a comprehensive perspective of the full cost of production including natural resources, human resources and environmental cost. The improved model is illustrated by its application for the steel-making process in China. Of the total cost of the steel-making process, the human resources cost (investment) accounts for only 9.7%. Contrary to the traditional cost evaluation, the result of this case study shows that classical economic assessment cannot reflect an overall ecological sustainable level of the steel-making process. The integrated method framework can be used to assess sustainability in a different spatial scale.

Exergy-based ecological indicators: From Thermo-Economics to cumulative exergy consumption to Thermo-Ecological Cost and Extended Exergy Accounting

This paper presents a summary of the conceptual development and the practical applications of exergy-based Environmental Indicators. After a brief historical introduction, the two most popular methods are presented and discussed: the Exergo-Environmental Analysis (here TEA, as a memento of Jan Szargut's original denomination “Thermo-Ecological Analysis”, currently adopted also by Valero's school) and the Extended Exergy Accounting (EEA). Both emerged from Szargut's idea of the existence of a consumption index, the Cumulative Exergy Consumption (CExC), which can be used to quantify the consumption of primary resources “embodied” in a final product or service. The extension introduced by both methods with respect to CExC consists in the explicit inclusion in the exergy budget of one or more of the Externalities, lumped in the original CExC formulation into the exergetic material contents of the single commodities. The differences between the three formulations are obviously reflected in the numerical values of the resulting indicators. The Thermo-Ecological Cost (TEC) and the CExC differ because of the inclusion in the former of the exergetic resources that reflect the “penalty” in the use of primary non-renewable consumption caused by the anthropic intervention. The CExC index and the Extended Exergy Cost EEC differ because the latter explicitly includes in the calculation a “Labour and Capital equivalent exergy consumption” that allows for the survival of the individuals in a given region according to the respective life standards (variable in space and time). Another difference is the way the Environmental Externality is computed: while TEA takes an ex-post assessment, EEA introduces a calculation of the -ideal or real-remediation costs.

The Way Forward in Quantifying Extended Exergy Efficiency

Extended exergy accounting (EEA) is a methodology which estimates the extended exergy cost (EEC) of a product or a service or the extended exergy efficiency (EEE) of a country or economic sector taking into account materials, energy, labour, capital, and environmental impact. The use of EEA results for policy or planning purposes has been hampered by: (1) the lack of data to quantify the EEC of most of the inputs, making it almost impossible to quantify the EEC of a product or service and (2) the lack of a conceptual framework to quantify in a consistent way the exergy of labour and capital. In this paper, we make a review of past studies to identify, synthesize, and discuss the different EEA methods. We identified 3 different EEA methods, that we further compare using the Portuguese Agriculture, Forestry, and Fishery (AFF) sector from 2000 to 2012. The equivalent exergies of labour and capital estimated for the AFF sector vary widely among the three EEA methodologies. We propose and test a new EEA methodology to estimate EEE which accounts for these fluxes in a more restricted scope but more consistently and that includes the Environmental Benefit (EB) that represents the capability of the forestry to capture carbon dioxide. Results show that the EEE of the Portuguese AFF sector has increased by 32% from 2000 to 2012.

Performance assessment of a wind power plant using standard exergy and extended exergy accounting (EEA) approaches

In this study, standard exergy and extended exergy accounting (EEA) approaches were applied and compared to evaluate the performance of a wind power plant located in the northern region of Iran. The efficiency of the whole wind plant was found to be 63.82% and 15.76% on the basis of the standard exergy and EEA approaches, respectively. This low exergetic efficiency obtained using the EEA concept was mainly due to the inclusion of non-energetic/immaterial terms, particularly the capital influx in the exergetic computations. The exergy destruction (irreversibility) on the basis of the standard exergy theory was remarkably lower than the EEA-based irreversibility due to overlooking the externalities in the standard approach. Overall and based on the findings of the present study, the EEA theory was found to be much more accurate to measure the sustainability and productivity of wind-driven power plants compared with the standard exergy analysis. The EEA-based thermodynamic framework concept developed herein could be employed for decision making on the implementation of renewable energy plants under different climate conditions such as wind-driven power plants with respect to their sustainability and productivity aspects.

Do the Different Exergy Accounting Methodologies Provide Consistent or Contradictory Results? A Case Study with the Portuguese Agricultural, Forestry and Fisheries Sector

Three exergy accounting approaches are used to evaluate exergy efficiency: the Energy Resources Exergy Accounting (EREA), the Natural Resources’ Exergy Accounting (NREA) and the Extended Exergy Accounting (EEA). To test the consistency of the results provided by these methodologies, we apply them to evaluate the Portuguese agricultural, forestry and fisheries (AFF) sector, from 2000 to 2012. EREA shows an increase of 30% in the efficiency of the Portuguese AFF sector, while NREA and EEA methodologies increases of 27% and 43%, respectively. Although the results are consistent for the AFF sector, the same does not happen in the fisheries subsector, whose exergetic efficiency increases 14% with the EREA but decreases 42% with the NREA approach. The ratio of output to useful exergy reveals that a better thermodynamic efficiency is not translated into a higher energy service efficiency because fishing vessels have to travel more to get the same fish. Thus, results provided by the EREA and NREA approaches are complementary and both are needed to provide a realistic picture of exergy efficiency. On the other hand, results obtained by the EEA approach are dominated by capital and environmental impacts, revealing the disproportionality between material and immaterial inputs in this methodology.

Life-cycle greenhouse gas emissions assessment and extended exergy accounting of a horizontal-flow constructed wetland for municipal wastewater treatment: A case study in Chile

The life-cycle greenhouse gaseous emissions and primary exergy resources consumption associated with a horizontal subsurface flow constructed wetland (HSSF) were investigated. The subject of study was a wetland for municipal wastewater treatment with a 700-person-equivalent capacity. The effects of two types of emergent aquatic macrophytes (Phragmites australis and Schoenoplectus californicus) and seasonality on greenhouse gas (GHG) gas emissions, the environmental remediation cost (ERC) and the specific environmental remediation cost (SERC) were assessed. The results indicate that GHG emissions per capita (12–22kgCO2eq/p.e/yr) and primary exergy resources consumed (24–27MJ/m3) for the HSSF are lower than those of a conventional wastewater treatment plant (67.9kgCO2eq/p.e/yr and 96MJ/m3). The SERC varied between 176 and 216MJ/kg biological oxygen demand (BOD5) removal, which should be further reduced by 20% for an improved BOD5 removal efficiency above 90%. The low organic matter removal efficiency is associated with a high organic load and low bacterial development. Seasonality has a marked effect on the organic removal efficiency and the SERC, but the macrophyte species does not.

Extended Exergy Accounting for Karachi

Exergy is stepping stone for thermos-economic analyses of complex system. In this paper, we presented an exergy-based resources accounting framework for urban systems. The cumulated exergy consumption in transformations of various resources and energy are presented in details. A case study of Karachi in Pakistan was conducted, in which the main energy supplier is found to be natural gas, followed by coal, nuclear Power and petroleum. The fluxes of labor and capital were also quantified by the exergy metrics, showing that the labor force input to Karachi is twice as much as that of the economy in context of the whole societal system.