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Ecological Indicators 58 (2015) 392–401

Contents lists available at ScienceDirect

Ecological Indicators

jo ur nal ho me page: www.elsev ier .com/ locate / ecol ind

xergy based renewability assessment: Case study to ecologicalastewater treatment

ing Shaoa,b,∗, G.Q. Chenc,d,∗∗

School of Humanities and Economic Management, China University of Geosciences, Beijing 100083, ChinaKey Laboratory of Carrying Capacity Assessment for Resource and Environment, Ministry of Land and Resource, Beijing 100083, ChinaLaboratory of Anthropogenic Systems Ecology (LASE), College of Engineering, Peking University, Beijing 100871, ChinaNAAM Group, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia

r t i c l e i n f o

rticle history:eceived 5 May 2015eceived in revised form 1 June 2015ccepted 6 June 2015

eywords:

a b s t r a c t

The renewability assessment has seldom been a core issue in previous studies. This work presents aframework to assess the renewability of a production system based on the unified ecological evaluationmethod of embodied cosmic exergy analysis. For the first time, both historical renewable and nonrenew-able resources uses of each social product input of a system are individually and completely traced andmeasured by the embodied cosmic exergy as available energy. A set of indicators have also been devised

enewability assessmentxergymergyastewater treatment

onstructed wetland

to assess the resources utilization efficiency and renewability of a production system. To demonstratethe framework, a case study is carried out for a pilot constructed wetland wastewater treatment systemin Beijing. The resources utilization style and renewability of the case system are analyzed and assessed.The presented framework can be easily transplanted to assess the renewability of other products, whichcould contribute a lot to meet the goal of sustainable development.

© 2015 Elsevier Ltd. All rights reserved.

. Introduction

.1. Renewability assessment of a production system

Renewability assessment is of great importance for sustain-ble development, which often has two implications. One isirectly related to renewable resource, which tries to calculate the

nput/output ratio of a specific renewable resource based on ben-fit analysis. It is only applicable to these renewable systems, e.g.,ind farm as renewable energy technology and wastewater treat-ent as renewable water technology (Chen et al., 2011b,c; Malc a

nd Freire, 2006; Shao and Chen, 2013; Yang and Chen, 2012; Yangt al., 2013).

The other is to investigate the sustainability of a concerned sys-em by identifying the renewable resources component from itsotal historical resources use, whose scope is much larger than that

∗ Corresponding author at: School of Humanities and Economic Management,hina University of Geosciences, Beijing 100083, China. Tel.: +86 10 62767167;

ax: +86 10 62754280.∗∗ Corresponding author at: Laboratory of Anthropogenic Systems Ecol-gy (LASE), College of Engineering, Peking University, Beijing 100871, China.el.: +86 10 62767167; fax: +86 10 62754280.

E-mail addresses: lingshao@pku.edu.cn, shaoling@cugb.edu.cn (L. Shao),qchen@pku.edu.cn (G.Q. Chen).

ttp://dx.doi.org/10.1016/j.ecolind.2015.06.010470-160X/© 2015 Elsevier Ltd. All rights reserved.

of the former one. It can be carried out for all kinds of productionsystems and can provide us with the specific renewability index foreach final product. As it can be very useful for sustainable develop-ment by means of renewability labeling strategy for all products,the present work aims at contributing a universal framework toassess the renewability of various production systems.

Thermodynamic accounting methods, especially emergy anal-ysis developed by Odum, have been widely applied to analyze thehistorical resources uses of various systems (Björklund et al., 2001;Chen et al., 2009, 2011d; Grönlund et al., 2004; Vassallo et al., 2009).A set of indicators have been proposed, among which the indicatorof RI (renewability index) concerning the original renewable nat-ural resources was devised to carry out renewability assessment.However, only a part of the natural renewable resources directlyutilized by the concerned system, such as sunlight and rain, havebeen identified as renewable resources in previous studies, with thehistorical renewable resources uses of various purchased productsbeing ignored or misdeemed as nonrenewable resources.

As a matter of fact, only a few energy sources can be regardedas complete renewable or nonrenewable resources according totheir replenishing time. For example, sunlight and wind energy are

renewable resources and fossil fuels are nonrenewable resources.As for almost all the economic products and social services (termedas social products hereafter), both renewable and nonrenewableresources have been consumed during their productions. In order

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L. Shao, G.Q. Chen / Ecologic

o assess the overall renewability of a production system supportedy various kinds of social products, the renewable resources use ofach product or service input should be concerned.

.2. The method of embodied cosmic exergy analysis

Emergy was initially proposed by Odum to evaluate the energyf one kind previously required to generate a product or serviceOdum, 1988, 1996). Since solar energy is conventionally believedo be the primary driving force of the ecosphere, solar emergy inerms of embodied solar energy has been prevailing in previousmergy studies. Most of the existing renewability related studiesave applied the solar emergy analysis method. But solar emergyased on embodied energy has suffered from the intractable prob-

em of double counting and is incapable to measure the depletionf energy since energy can never be consumed. Odum and othersame to realize this and exergy embodiment emphasizing avail-ble energy has been proposed to re-explain and re-define emergyBastianoni et al., 2007; Odum, 1996; Sciubba and Ulgiati, 2005).t has soon become popular on a par with emergy analysis inesources accounting field (Chen et al., 2014; Dai et al., 2014, 2015;hao et al., 2013a; Yang and Chen, 2014; Yang et al., 2009).

Cumulative exergy was proposed by Szargut et al. to analyze theum of direct and indirect exergy inputs embodied in supply chainf a product and service (Szargut et al., 2002). Based on both theoncepts of emergy theory and cumulative exergy method, Cheneveloped embodied cosmic exergy (or cosmic emergy) to measurehe energy transformation hierarchy of each production process.ccording to the theory, earth is a cosmic heat engine operatingetween the solar radiation as a heat source and the cosmic back-round microwave (CBM) field as a cold sink, and the cosmic exergyriginated in the thermal difference between solar and CBM radi-tions is proved to be the ultimate driving force of the ecospherenstead of solar energy (Chen, 2005, 2006).

The embodied cosmic exergy synthesis successfully overcomeshe double counting problem of solar emergy by renovating emergyower base and is more systematic than cumulative exergy methody including the contribution of natural environment instead ofole non-renewable resources (Jiang et al., 2010). Chen has ana-yzed the global cosmic exergy budget in his original framework,n the basis of which a lot of studies have been carried out to assesshe resources uses of various ecosystems (Chen et al., 2010, 2011d;iang et al., 2010).

Considering that macro-economic statistic based input–outputnalysis can cover all transaction activities of social products withinn economy by means of a network modeling, Chen and hisollaborators have integrated the embodied cosmic exergy intonput–output framework and achieved fruitful results (Chen andhen, 2010, 2011). These studies have not only evaluated theesources use style of the concerned economy through a top-downnalysis, but also provided us with an average embodied cosmicxergy database for all products and services within the economy.urthermore, they have distinguished clearly between renewableesources and nonrenewable resources inputs in the basic model-ng process, whose results can be utilized to systematically identifyoth historical renewable and nonrenewable resources uses of eachroduct or service within a specific economy.

With the application of embodied cosmic exergy analysis andnput–output analysis based database, this work is to present

framework to assess the renewability of a production systemhrough tracing the historical renewable resources use along itsupply chains. The rest of the paper is organized as following:

ection 2 describes the method of embodied cosmic exergy, pro-edures and indicators of renewability assessment framework andaterials used in this study; a case study is performed by carry-

ng out embodied cosmic exergy analysis for a pilot constructed

icators 58 (2015) 392–401 393

wetland as ecological wastewater treatment engineering in Bei-jing, the results of which are presented and discussed in Sections3 and 4, respectively; finally the conclusions are drawn in Section5. The renewability assessment framework and related indicatorspresented in this paper can be utilized to trace lifecycle renew-able resources uses of various production systems, which wouldcontribute a lot to the sustainable development of the economy.

2. Methods and materials

2.1. Embodied cosmic exergy analysis

As developed by Chen, the method of embodied cosmic exergyanalysis has a solid theory basis, in which the global cosmic exergybudget with respect to main terrestrial processes has been sys-tematically studied (Chen, 2005, 2006). Subsequently, Chen andhis collaborators have developed a whole set of embodied cos-mic exergy scheme (Chen et al., 2010; Ji, 2008; Jiang, 2007; Jianget al., 2010). Revised from the energy circuit symbols developed byOdum, the exergy circuit symbols (see Fig. 1) have been devisedto illustrate the elements and flows within the ecosystem. In con-trast to the unit of solar Joule (sej) in solar emergy, the unit ofcosmic Joule (Jc) has been applied to measure the available energyas cosmic exergy.

The embodied cosmic exergy transformity (termed as trans-formity hereafter in this paper) is defined as the magnitude ofcosmic exergy input required for making one unit product or servicewith reference to emergy synthesis. Lots of works have been donepreviously to calculate the tranformity database for various natu-ral resources and social products. Nowadays researchers are ableto choose appropriate transformity data according to their needsrather than calculate the transformity of each concerning input bytheir own.

The embodied cosmic exergy transformities of the environ-mental inputs can be derived from classical references due to therelative stable balance of earth after the long-term evolution (Chen,2005, 2006; Ji, 2008; Jiang, 2007; Jiang et al., 2010). As for the socialproducts and services, in the light of different technical efficien-cies and economic structures, the same products from differenteconomy communities or different years have different transfor-mities. Special attention should be paid to choose an appropriatetransformity database for various inputs in order to perform a wellembodied cosmic exergy analysis.

The input–output analysis (IOA) is a network modelingapproach utilizing the statistics and organizing matrices of allthe intermediate inputs into goods and services of the wholeeconomic interactions (Leontief, 1970). It has been extended to ana-lyze the environmental impacts of an economic system soon afterits proposal, which has also been introduced to thermodynamicaccounting field (Baral and Bakshi, 2010; Chen and Chen, 2010,2011; Ukidwe and Bakshi, 2004). Recently the method of systemsIOA has been developed by Chen et al. to calculate the embodiedecological element intensities for all products and services withinthe economy (Chen and Chen, 2010, 2011). The embodied cos-mic exergy as an integrated measurement of resources use hasalso been concluded as one of the concerned ecological elements.Since the systems IOA based embodied cosmic exergy transformitydatabase can provide us with consistent and unified intensity data,it has been applied to estimate the renewable and nonrenewableresources uses of a production system in this work.

2.2. Procedure of renewability assessment and related indicators

The diagram for the embodied cosmic exergy based renewabil-ity assessment of a production system is shown in Fig. 2, which isdrawn by using the exergy circuit symbols illustrated in Fig. 1.

394 L. Shao, G.Q. Chen / Ecological Indicators 58 (2015) 392–401

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The whole earth ecosystem is essentially sustained by naturalenewable resources (RR) such as sunlight, wind power, geopo-ential power of stream, geothermal power, and wave power, and,onrenewable resources (NR) such as soil, fuels, and minerals, bothf which can be directly utilized by a production system (DR) byeans of environmental inputs. Besides DR, a production system

as indirectly consumed natural resources (IR) through economicurchase activities of products and services, which also involveenewable resources (PR) and nonrenewable resources (PN) flows.herefore the total resources use (U) of a production system is givens:

= DR + IR = (RR + NR) + (PR + PN).

Based on the embodied cosmic exergy theory, the resourcesccounting as the basis procedure of renewability assessment of

production system can be divided into five steps.

tep 1. Itemize all the inputs of the concerned system, includingboth environmental inputs as DR sources and social prod-ucts and services as IR sources to form an inputs inventory.

tep 2. List the quantity of each input in the inventory. The quantityof environmental inputs (QE) should be in Joule unit fol-lowing the usual practice. Since the input–output analysis

based transformity database (in monetary unit) is applied inthis study to calculate the embodied cosmic exergy of socialproducts and service inputs, their quantity (QP) should bein monetary unit.

ig. 2. Diagram for embodied cosmic exergy analysis of a production system.

uit symbols.

Step 3. Determine the embodied cosmic exergy transformities ofthe environmental inputs (TE) with reference to classicalreferences as aforementioned (Chen, 2005, 2006; Ji, 2008;Jiang, 2007; Jiang et al., 2010).

Step 4. Considering that the same products from different economycommunities or different years have different transfor-mities, choose an appropriate embodied cosmic exergytransformity database for the products and services inputsof the concerned system according to the place and yearwhere and when the system was built. In order to makesubsequent renewability assessment possible, a databasecovering both renewable and nonrenewable embodied cos-mic exergy transformity data of each product or serviceinput is necessary.

Determine the corresponding transformity for each prod-uct or service input with reference to compilation rulesof corresponding economy input-output table, and theembodied cosmic exergy transformity (TP) can be promptlyobtained. For example, the Farming sector as the first listedindustry of economic input–output table of Chinese econ-omy in 2007 (Sector 1) includes (1) crop planting; (2)vegetable and landscape planting; (3) fruit, nut, drink andperfume crops planting; and (4) Chinese medicinal plantplanting. Therefore the vegetation input comes from Farm-ing sector, and the transformity of Sector 1 listed in thedatabase is determined as the transformity of the vegeta-tion input.

Step 5. The embodied cosmic exergy of each input can be promptlyobtained by multiplying the transformity by its quantity.Sum the embodied cosmic exergy of environmental inputsand products or services inputs together to result the totalembodied cosmic exergy input of the concerned system:

U =n∑

i=1

TEi × QEi +n∑

i=1

TPi × QPi

A set of indicators have been devised to evaluate the resourcesutilization efficiency of an artificial system in previous emergy andcosmic exergy studies (Brown and Ulgiati, 1997; Ji, 2008; Jiang,2007; Jiang et al., 2010; Ulgiati et al., 1995). They are transplantedto assess the efficiency as well as renewability of a production sys-tem in this work, whose symbols, algorithms, and definitions areshown in Table 1. Although the expressions of some indicator seem

like those in previous studies, for example, the key indicator of RI.But their connotations have been updated and enlarged. Instead ofsimply regarding a social product as complete renewable or com-plete unrenewable, both renewable and nonrenewable resources

L. Shao, G.Q. Chen / Ecological Ind

Table 1Indices for embodied cosmic exergy analysis of a production system.

Indicator Algorithm Definition

Renewability index (RI) RI = (RRa + PRb)/Uc The ratio of renewableresources use to totalresources use

Purchased embodiedcosmic exergy ratio(PER)

PER = (PR + PNd)/U The ratio of purchasedresources use to totalresources use

Embodied cosmicexergy emmoneye

ratio (EER)

EER = U/Yef The total resourcesinvest per unit ofoutput

Embodied cosmicexergy yieldefficiency (EYE)

EYE = Yrg/U The resources returnon invest

a RR: natural renewable resources.b PR: purchased renewable resources.c U: total resources use.d PN: purchased nonrenewable resources.e Emmoney: it is developed from Odum’s Emdollar (Odum, 2002), indicating the

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oney circulation whose buying power is supplied by use of a quantity of emergy.f Ye: total economic yield.g Yr: total resources yield.

se of each product or service input of a production system haseen emphasized and concerned in the present work.

.3. Case description and data source

In order to illustrate the embodied cosmic exergy analysis basedenewability assessment framework, a case study is carried outor assessing the renewability of a wastewater treatment sys-em. Accompanied with the fast growing population and rapidmproving living standard, the anthropogenic wastewater becomes

key factor hindering the sustainable development of the econ-my. Wastewater treatment is therefore considered as a promisingechnology and a fundamental infrastructure to remove pollutantrom wastewater and to assure available water resources withuman society, whose economic input and output, contaminantemoval efficiency, pollutant emission, environmental impact, andesources use style have been comprehensively and intensivelytudied (Brown and Ulgiati, 1997; Chen et al., 2009, 2011a,d; Seckinnd Bayulken, 2013; Shao et al., 2014a,b; Shao et al., 2013b; Wut al., 2015). Located in the north of the country, the water resourcesf Beijing are much less than those of most southern cities in China.s the capital of China, Beijing City has experienced rapid economicevelopment and fast population growth in the past decades, whichas exacerbated the pressure on its fragile ecological environment.astewater treatment, especial constructed wetland as ecologicalastewater treatment therefore becomes the best choice of Beijing.

Against the background of Green Olympics, a verticalubsurface-flow constructed wetland, Longdao River constructedetland (LRCW), is constructed in 2004. It is located in the suburb

f Beijing and near the Longdao River. As the stream has been pol-uted by domestic sewage received from the resident areas alonghe upstream of the river, the LRCW is devised to purify the riverater before it mingling into the main stream of Wenyu River. As

pilot engineering, the daily treatment capability of the LRCW is00 m3 and its lifetime is designed as 20 years. The diagram of theRCW is shown in Fig. 3 (Chen et al., 2008). Its bed area is 602 m2

nd the length and width are 28 m and 21.5 m, respectively.The appropriate embodied cosmic exergy transformity database

or various products and services inputs of the LRCW needs toe determined. Firstly, the database should concern the Chinese

conomy since the case system is located in China. However, asoncerning the time, no economic input–output table of China wasublished in 2004. Among the available tables nearby, i.e., the eco-omic input-output tables of China in 2005, 2002 and 2007, the

icators 58 (2015) 392–401 395

table in 2005 is taken no account of because it is an extended tablerather than a formal one. Given that the sectors of table in 2007 aremore detailed than that of table in 2002 (135 vs. 42), the embod-ied cosmic exergy database for the Chinese economy in 2007 isfinally applied to estimate the historical resources use associatedwith social inputs of the case constructed wetland (Chen and Chen,2010).

135 sectors, i.e., 135 typical products and services of Chineseeconomy in 2007 have been covered by the database, including 5for agriculture; 5 for mining; 81 for manufacture; 3 for electricity,gas, and water production and supply; 9 for transportation, stor-age, and post; 2 for construction and real estate; and 30 for otherservices. In the database, cosmic exergy have been accounted interms of eighteen sources of six groups, i.e., solar based source (sun-light, wind power, chemical power of rain, geopotential power ofrain, chemical power of stream, geopotential power of stream, andwave power), deep earth based source (geothermal power), gravi-tation based source (tide power), soil source (topsoil loss), fossil fuelsource (coal, crude oil, and natural gas), and mineral source (fer-rous metal ore, non-ferrous metal ore, non-metal ore, cement, andnuclear fuel). The former three groups are considered as renewableresources while the rest are nonrenewable resources.

3. Results

3.1. Inputs inventory and corresponding embodied cosmic exergytransformities

Due to data limitation, only construction and operation stagesof the case system have been concerned. On the basis of projectdata, the lifecycle inputs inventory of the case system is listed inTable 2. The raw data of environmental inputs have been calculatedfrom the system’s area and the climate and geology data of Beijing,which can be found in Chen et al. (2009). Most of inputs of the casesystem are consumed in construction stage, and only two inputsas the electricity and labor have been concerned for the operationstage. Two social services, i.e., design in construction stage and laborin operation stage have been concerned.

With reference to classical references as aforementioned (Chen,2005, 2006; Ji, 2008; Jiang, 2007; Jiang et al., 2010) and compilationrules of Chinese economic input–output table in 2007, the embod-ied cosmic exergy transformity of each input can be promptlyobtained (see Table 2).

3.2. Resources use of the case system

The results of embodied cosmic exergy accounting of the casesystem are listed in Table 3. The case system has consumed4.23E+13 Jc resources during its lifecycle.

The structure of embodied cosmic exergy inputs of the casesystem is shown in Fig. 4. It can be seen that electricity is thelargest resources source of the case system, accounting for 38.83%of the total embodied cosmic exergy. The cosmic exergy embod-ied in labor ranks the second, which is responsible for about 15%of the total resources use. Although construction stage involvesmore kinds of inputs than operation stage, the resources use ofoperation stage is a bit larger than that of construction stage. Thesubstrates and vegetation together share about 1/3 of the totalresources use, which has verified the key role of biomass in a con-structed wetland to function as ecological wastewater treatment.The contribution of environment inputs to the total resources use

is negligible, revealing that the case system barely relies on directenvironmental resources to treat wastewater.

Two services as design and labor together share about 1/5 of thetotal resources use. The service has seldom been paid attention to

396 L. Shao, G.Q. Chen / Ecological Indicators 58 (2015) 392–401

Fig. 3. Diagram of the case constructed wetland.

Table 2Inputs inventory and corresponding embodied cosmic exergy transformities.

Item Sector codes andcontents

Embodied cosmicexergy transformity

Solarbased

Deep earthbased

Gravitationbased

Soil Fossilfuels

Minerals Unit

Environment inputSunlight 1.02E−05 Jc/JWind, kinetic 3.12E−02 Jc/JRain, chemical 6.08E−01 Jc/JRain, geopotential 3.51E−01 Jc/JEarth cycle 7.82E−03 Jc/J

Social and economic inputOrganic substrate 5 Services in support

of agriculture3.38E+10 7.23E+07 4.05E+06 2.12E+11 2.34E+11 6.56E+10 Jc/104

ChineseYuan (CNY)

Geotextile 49 Manufacture ofplastic

1.28E+10 2.34E+07 8.76E+05 8.25E+10 7.59E+11 1.84E+11 Jc/104 CNY

Mineral substrate 10 Mining andprocessing ofnonmetal ores andother ores

1.16E+10 2.09E+07 1.24E+06 5.89E+10 5.48E+11 2.67E+12 Jc/104 CNY

Other substrate 52 Manufacture ofbrick, stone andother buildingmaterials

1.26E+10 2.27E+07 9.47E+05 7.67E+10 1.21E+12 4.18E+11 Jc/104 CNY

Vegetation 1 Farming 5.14E+10 1.11E+08 5.68E+05 5.07E+11 2.77E+11 8.69E+10 Jc/104 CNYPump 67 Manufacture of

pump, valve andsimilar machinery

1.08E+10 1.98E+07 9.76E+05 6.22E+10 5.86E+11 5.67E+11 Jc/104 CNY

Electric control 78 Manufacture ofequipments forpowertransmission anddistribution andcontrol

1.22E+10 2.29E+07 1.25E+06 6.81E+10 5.37E+11 5.83E+11 Jc/104 CNY

Pipe and valve 49 Manufacture ofplastic

1.28E+10 2.34E+07 8.76E+05 8.25E+10 7.59E+11 1.84E+11 Jc/104 CNY

Steel griller 63 Manufacture ofmetal products

1.45E+10 2.68E+07 1.21E+06 8.78E+10 6.82E+11 6.61E+11 Jc/104 CNY

Bricks and cement 50 Manufacture ofcement, lime andplaster

1.24E+10 2.09E+07 8.49E+05 7.17E+10 1.15E+12 3.25E+11 Jc/104 CNY

Design 118 Professionaltechnical services

9.04E+09 1.83E+07 1.44E+06 4.02E+10 2.08E+11 1.29E+11 Jc/104 CNY

Electricity 92 Production andsupply of electricpower and heatpower

2.31E+10 1.49E+07 7.33E+05 4.70E+10 1.76E+12 1.42E+11 Jc/104 CNY

Labor 123 Management ofpublic facilities

2.34E+10 4.89E+07 1.15E+06 1.95E+11 3.17E+11 1.26E+11 Jc/104 CNY

L. Shao, G.Q. Chen / Ecological Indicators 58 (2015) 392–401 397

Table 3Embodied cosmic exergy accounting of the case system (Unit: Jc).

Item Solar based Deep earth based Gravitation based Soil Fossil fuels Minerals Total

Environment inputSunlight 5.06E+08 5.06E+08Wind, kinetic 2.27E+08 2.27E+08Rain, chemical 1.39E+10 1.39E+10Rain, geopotential 1.73E+08 1.73E+08Earth cycle 1.78E+08 1.78E+08

Social and economic inputOrganic substrate 1.61E+11 3.45E+08 1.93E+07 1.01E+12 1.12E+12 3.13E+11 2.60E+12Geotextile 2.53E+10 4.63E+07 1.73E+06 1.63E+11 1.50E+12 3.64E+11 2.06E+12Mineral substrate 1.64E+10 2.96E+07 1.76E+06 8.34E+10 7.76E+11 3.78E+12 4.66E+12Other substrate 2.49E+10 4.49E+07 1.88E+06 1.52E+11 2.40E+12 8.28E+11 3.41E+12Vegetation 1.46E+11 3.16E+08 1.62E+06 1.44E+12 7.89E+11 2.48E+11 2.63E+12Pump 3.24E+09 5.94E+06 2.93E+05 1.87E+10 1.76E+11 1.70E+11 3.69E+11Electric control 1.34E+09 2.52E+06 1.38E+05 7.49E+09 5.91E+10 6.41E+10 1.32E+11Pipe and valve 5.22E+09 9.55E+06 3.57E+05 3.37E+10 3.10E+11 7.51E+10 4.24E+11Steel griller 7.25E+06 1.34E+04 6.05E+02 4.39E+07 3.41E+08 3.31E+08 7.25E+08Bricks and cement 5.46E+09 9.20E+06 3.74E+05 3.15E+10 5.06E+11 1.43E+11 6.86E+11Design 5.33E+10 1.08E+08 8.50E+06 2.37E+11 1.23E+12 7.61E+11 2.28E+12

06

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fossil fuels related to mechanization process have been consumed

Electricity 1.93E+11 1.24E+08 6.11E+Labor 2.34E+11 4.89E+08 1.15E+Total 8.85E+11 1.53E+09 5.36E+

n previous ecological accounting studies of a constructed wetland.lthough a few studies have concerned them in the accounting,

he transformity applied is neither specific nor precise (Chen et al.,011d). The input–output analysis based transformity databasepplied in this study realizes a complete modeling for all productsnd services of the economy community, which enables us to accu-ately and systematically trace the complete historical resourcesses of various services.

Six sources of embodied cosmic exergy have been traced in thisork, whose components are shown in Fig. 5. As high as 97.91% of

he total resources use is originated from nonrenewable resourcesources, i.e., soil, fossil fuels and minerals. The renewable resources,.e., solar based source, deep earth based source and gravitationased source, have a tiny share of the total resources supply, amonghich the solar based sources has contributed almost all the renew-

ble resources (99.82%). It is also revealed that the fossil fuels arehe main source of nonrenewable resources of the case system.

As concerning the stage, except for fossil fuels, all the otherources supply more resources to construction stage than to oper-tion stage. For instance, more than 70% of the embodied cosmicxergy of minerals has been supplied to construction stage. Theeason can be attributed to the electricity input in operation stage

ince the electricity has consumed a lot of fossil fuels resources ints production. Meanwhile, fossil fuel is the largest resources source

Fig. 4. Components of embodied cosmic exergy of the case system.

3.92E+11 1.47E+13 1.18E+12 1.64E+131.95E+12 3.17E+12 1.26E+12 6.62E+125.53E+12 2.67E+13 9.19E+12 4.23E+13

of the case system, which shares more than a half (63.25%) of thetotal resources input.

4. Discussions

4.1. Resources utilization efficiency and renewability assessmentof the case system

The values of proposed indices of the case system have beenshown in Table 4. By summing the renewable resources embod-ied in both environmental and purchased inputs together, the RIof the case system has been calculated. It is revealed that only2.09% of the total resources use of the case system are originatedfrom renewable resources. The result is much less than that inChen et al. (2011d) investigating the same constructed wetland bymeans of embodied cosmic exergy analysis. It is mainly becausethat the previous study mistook some social product inputs as com-plete renewable resources sources. However, under the industrialproduction background nowadays, the production of each socialproduct would certainly involve a lot of nonrenewable resources.Taking vegetation as an example, various kinds of fertilizers and

during its growth. And it cannot be 100% renewable as was assumedin Chen et al. (2011d). As a matter of fact, the average renew-able resources percentage of agriculture industry for the Chinese

0.00E+0 0

5.00E+1 2

1.00E+1 3

1.50E+13

2.00E+1 3

2.50E+1 3

3.00E+1 3Operation

Const ruct ion

Fig. 5. Components of six sources of embodied cosmic exergy for the case system.

398 L. Shao, G.Q. Chen / Ecological Indicators 58 (2015) 392–401

Table 4Embodied cosmic exergy indices for the case system.

Parameter Value Indicator Value

Natural renewable resources (RR) 1.50E+10 Jc Renewability index (RI) 2.09%Natural nonrenewable resources (NR) 0.00E+00 Jc Purchased embodied cosmic exergy ratio (PER) 99.97%Purchased renewable resources (PR) 8.71E+11 Jc Embodied cosmic exergy Emmoney ratio (EER) 3.62E+07 Jc/CNYPurchased nonrenewable resources (PN) 4.14E+13 Jc Embodied cosmic exergy yield efficiency (EYE) 3.14

etat

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iseppcwpAsperwn

Total resources use (U) 4.23E+13 Jc

Total economic yield (Yr) 1.168E+06 CNY

Total resources yield (Ye) 1.33E+14 Jc

conomy in 2007 is only 5.58% (Chen and Chen, 2010), much lesshan 100%. Since electricity having a low renewability index (1.17%)ccounts for about 2/5 of the total resources use of the case system,he low RI of the case system is reasonable.

As RI is an important and essential indicator in screeningnvironment-friendly product, improving its RI is very necessaryor a production system upgrading its competitiveness in sustain-ble economic development. Two possible measures are suggestedere. Firstly, since some kinds of natural resources are 100% renew-ble (e.g., solar energy, wind energy), use them as much as possible.econdly, choose products of high RI. For example, the pipe asssential material of wastewater treatment can be made from plas-ic, cement or metal. But the three kinds of pipes have different RIs1.23% for plastic pipe, 0.89% for cement pipe and 1.01% for metalipe), and obviously the plastic pipe is preferred.

The other three indicators mainly represent the resources uti-ization style (PER) and efficiency (EER and EYE) of a productionystem. Indicating by the high value of PER (99.97%), almost all ofhe resources need of the case system has been met by purchasednputs, with the resources of environmental inputs sharing a negli-ible part. At the meanwhile, most of the purchased resources areonrenewable resources while all environment inputs are renew-ble resources.

The EER as the monetary-based transformity of the case sys-em is calculated as 3.62E+07 Jc/CNY, indicating that in average.62E+07 Jc cosmic exergy resources has been consumed by thease system to output 1 CNY outcome. It is relative less (ranking the0th smallest) than those of the 135 typical products and services

temized in the embodied cosmic exergy transformity database ofhinese economy in 2007 (see Appendix A), which shows that thease system has an efficient resource utilization style. By regardinghe cosmic exergy transformity of freshwater resources as the cos-

ic exergy content of one unit purified water, the total resourcesield of the case system has been estimated as 1.33E+14 Jc. Theigh value (3.14) of the EYE has again indicated a high resourcestilization efficiency of the case system.

.2. The differences between this study and the other studies

The indicator of RI has been applied to assess the renewabil-ty of various systems including wastewater treatment in previoustudies (Chen et al., 2009, 2011d; Grönlund et al., 2004; Vassallot al., 2009). However, these studies are suffered from the followingroblems. On the one hand, most of these studies only concerned aart of the natural renewable resources directly utilized by the con-erned system, such as sunlight and rain as renewable resources,ith the historical renewable resources uses of various purchasedroducts being ignored or misdeemed as nonrenewable resources.nd on the other hand, some studies erroneously believed thatome product inputs were totally renewable resources. For exam-le, vegetation was regarded as total renewable resources in Chen

t al. (2011d). However, in fact each social product consumes bothenewable and nonrenewable resources in its production. Thisork has contributed a framework tracing historical renewable andonrenewable resources of a production system. It is proved that

–––

each social product has its renewable and nonrenewable compo-nents, although the latter is revealed as much larger than the formerfor most products.

One of our former studies has assessed the renewability ofwastewater treatment (Shao and Chen, 2013) based on water foot-print analysis. Despite both studies concerned the renewabilityof wastewater treatment from a historical view by tracing theresources use along the supply chain, the previous study and thepresent study have following two differences:

(1) In the former study, considering that a wastewater treat-ment plant is to renew wastewater and deliver available waterresources to human society, the indicator of WIWP (waterinvestment in water purified) as the ratio of freshwater inputto purified water output has been devised on the basis ofwater footprint analysis to assess the renewability of wastewa-ter treatment. However, this method concerning input/outputratio of a specific renewable resource can only be applicableto renewable technologies. For example, the renewability ofrenewable energy can be investigated by the ratio of nonre-newable energy invest to renewable energy supply. As for thesegeneral production systems, it is meaningless.

The framework contributed in this paper, however, is appli-cable to all production system. It views a plant as an organicsystem, and tries to analyze its renewability by identifyingthe renewable component from the total resources input. Inorder to distinguish these two kinds of renewability assessmentstudies, the former one is suggested to add some determinatewords to indicate which renewable resource is concerned; forexample, the water resources renewability assessment for thewastewater treatment or the energy resources renewabilityassessment for the renewable energy technology.

(2) The previous study only concerned water resources. Aswastewater treatment is devised to mitigate water pollutionand assure us with available water resources, it is reasonablethat water resources should be given priority to. In contrast, thepresent study takes all resources into account (eighteen sourcesof six groups, see Section 2.3). All these resources have beenmeasured by embodied cosmic exergy as a uniform standardof available energy. In some certain contexts, it can provide uswith more comprehensive results as there are many other kindsof resources on the earth besides water resources. Furthermore,the cosmic exergy has been proved to be the original drivingforce of the earth (Chen et al., 2010, 2011d), which is the mostappropriate equivalent to measure the resources uses of bothnatural resources and human society products.

5. Conclusions

This study has for the first time presented a systems renewa-bility assessment framework for all production systems based

on embodied cosmic exergy analysis as an improved ecologi-cal thermodynamic method. After clearly describing the methodof embodied cosmic exergy analysis, corresponding renewabil-ity assessment procedures and related indicators of a production

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L. Shao, G.Q. Chen / Ecologic

ystem, a case study has been performed to illustrate the frame-ork. Eighteen sources of lifecycle resources uses have been traced

or each input of a pilot constructed wetland wastewater treatmentystem in Beijing.

It is revealed by the indicator of RI that the total renewableesources account for 2.09% of the total resources use of the caseystem, indicating a low renewability of the case system. At theeantime, some other cosmic exergy based indices have revealed

hat the case system has a relative efficient resource utilizationtyle. The presented method is considered as more comprehensivehan the previous single-resources based method, which can beasily transplanted to assess the renewability of other productionystems. The obtained renewability indexes of various products areery necessary to promote sustainable economic development aseople and firms can prioritize their options with regard to prod-ct’s renewability label.

cknowledgements

This work is supported by the State Key Program for Basicesearch of China (973 Program, No. 2013CB430402), the Fun-amental Research Funds for the Central Universities (Granto.2652015151) and the Natural Science Foundation of China

Grant No. 11272012).

ppendix A.

The transformity and renewability index for Chinese economyn 2007 (revised from Chen and Chen (2010)).

Sector Embodiedcosmic exergytransformity(Jc/104 CNY)

PR (%)

1 Farming 9.23E+11 5.582 Forestry 9.30E+12 8.613 Animal husbandry 2.82E+12 8.974 Fishery 1.69E+12 80.475 Services in support of agriculture 5.45E+11 6.206 Mining and washing of coal 9.30E+12 0.187 Extraction of petroleum and natural

gas2.65E+12 0.28

8 Mining of ferrous metal ores 5.58E+12 0.259 Mining of non-ferrous metal ores 7.31E+12 0.1710 Mining and processing of nonmetal

ores and other ores3.29E+12 0.35

11 Grinding of grains 7.80E+11 5.2312 Processing of forage 8.36E+11 16.6313 Refining of vegetable oil 7.68E+11 5.8614 Manufacture of sugar 7.49E+11 4.8115 Slaughtering and processing of meat 1.95E+12 8.8716 Processing of aquatic product 1.12E+12 67.3217 Processing of other foods 9.49E+11 8.3718 Manufacture of convenience food 8.20E+11 5.6519 Manufacture of liquid milk and dairy

products1.54E+12 7.40

20 Manufacture of flavoring and fermentproducts

9.44E+11 5.99

21 Manufacture of other foods 9.81E+11 7.5722 Manufacture of alcohol and wine 6.37E+11 3.9723 Processing of soft drinks and purified

tea7.89E+11 4.35

24 Manufacture of tobacco 2.97E+11 3.9425 Spinning and weaving, printing and

dyeing of cotton and chemical fiber8.23E+11 2.78

26 Spinning and weaving, dyeing andfinishing of wool

1.50E+12 7.07

27 Spinning and weaving of hemp andtiffany

8.09E+11 3.84

28 Manufacture of textile products 7.79E+11 3.6129 Manufacture of knitted fabric and its

products7.92E+11 3.07

icators 58 (2015) 392–401 399

Sector Embodiedcosmic exergytransformity(Jc/104 CNY)

PR (%)

30 Manufacture of textile wearingapparel, footwear and caps

7.24E+11 3.62

31 Manufacture of leather, fur, feather(down) and its products

1.12E+12 6.58

32 Processing of timbers, manufacture ofwood, bamboo, rattan, palm and strawproducts

2.71E+12 7.05

33 Manufacture of furniture 1.68E+12 5.8534 Manufacture of paper and paper

products1.02E+12 3.65

35 Printing, reproduction of recordingmedia

7.31E+11 2.90

36 Manufacture of articles for culture,education and sports activities

1.08E+12 2.96

37 Processing of petroleum and nuclearfuel

2.02E+12 0.38

38 Coking 3.68E+12 0.3039 Manufacture of basic chemical raw

materials1.79E+12 0.69

40 Manufacture of fertilizers 1.98E+12 0.6241 Manufacture of pesticides 1.16E+12 1.1742 Manufacture of paints, printing inks,

pigments and similar products1.28E+12 1.46

43 Manufacture of synthetic materials 1.41E+12 0.7144 Manufacture of special chemical

products1.65E+12 2.02

45 Manufacture of chemical products fordaily use

8.74E+11 2.85

46 Manufacture of medicines 8.16E+11 4.6447 Manufacture of chemical fiber 1.28E+12 0.8948 Manufacture of rubber 1.90E+12 4.8749 Manufacture of plastic 1.04E+12 1.2350 Manufacture of cement, lime and

plaster1.56E+12 0.79

51 Manufacture of products of cementand plaster

1.34E+12 0.89

52 Manufacture of brick, stone and otherbuilding materials

1.72E+12 0.73

53 Manufacture of glass and its products 1.50E+12 0.8454 Manufacture of pottery and porcelain 1.53E+12 0.9255 Manufacture of fire-resistant materials 1.43E+12 0.8256 Manufacture of graphite and other

nonmetallic mineral products1.44E+12 0.93

57 Iron-smelting 2.87E+12 0.3558 Steelmaking 2.07E+12 0.4059 Rolling of steel 2.13E+12 0.4760 Smelting of ferroalloy 2.47E+12 0.4261 Smelting of non-ferrous metals and

manufacture of alloys3.01E+12 0.35

62 Rolling of non-ferrous metals 2.07E+12 0.4963 Manufacture of metal products 1.45E+12 1.0164 Manufacture of boiler and prime mover 1.06E+12 1.0765 Manufacture of metalworking

machinery1.13E+12 1.05

66 Manufacture of lifters 1.16E+12 1.0067 Manufacture of pump, valve and

similar machinery1.23E+12 0.88

68 Manufacture of other general purposemachinery

1.19E+12 0.92

69 Manufacture of special purposemachinery for mining, metallurgy andconstruction

1.14E+12 1.00

70 Manufacture of special purposemachinery for chemical industry,processing of timber and nonmetals

1.15E+12 0.91

71 Manufacture of special purposemachinery for agriculture, forestry,animal husbandry and fishery

1.05E+12 1.42

72 Manufacture of other special purposemachinery

1.08E+12 1.12

73 Manufacture of railroad transportequipment

1.13E+12 1.20

74 Manufacture of automobiles 9.87E+11 1.4975 Manufacture of boats and ships and

floating devices9.14E+11 1.09

4 al Ind

00 L. Shao, G.Q. Chen / Ecologic

Sector Embodiedcosmic exergytransformity(Jc/104 CNY)

PR (%)

76 Manufacture of other transportequipment

1.04E+12 1.31

77 Manufacture of generators 1.19E+12 0.9378 Manufacture of equipments for power

transmission and distribution andcontrol

1.20E+12 1.02

79 Manufacture of wire, cable, opticalcable and electrical appliances

1.65E+12 0.64

80 Manufacture of household electric andnon-electric appliances

1.02E+12 1.21

81 Manufacture of other electricalmachinery and equipment

1.30E+12 0.92

82 Manufacture of communicationequipment

8.40E+11 1.44

83 Manufacture of radar and broadcastingequipment

8.49E+11 1.54

84 Manufacture of computer 7.70E+11 1.3585 Manufacture of electronic component 9.69E+11 1.2286 Manufacture of household audiovisual

apparatus7.89E+11 1.37

87 Manufacture of other electronicequipment

7.09E+11 1.34

88 Manufacture of measuring instruments 8.50E+11 1.4289 Manufacture of machinery for cultural

activity and office work9.23E+11 1.32

90 Manufacture of artwork, othermanufacture

1.28E+12 4.09

91 Scrap and waste 1.20E+11 1.0592 Production and supply of electric

power and heat power1.97E+12 1.17

93 Production and distribution of gas 2.22E+12 0.3794 Production and distribution of water 6.72E+11 1.4995 Construction 1.17E+12 1.3096 Transport via railway 4.63E+11 1.2097 Transport via road 6.46E+11 1.4898 Urban public traffic 6.44E+11 1.0299 Water transport 7.36E+11 0.77100 Air transport 9.98E+11 1.42101 Transport via pipeline 6.20E+11 1.34102 Loading, unloading, portage and other

transport services7.40E+11 1.03

103 Storage 7.13E+11 3.87104 Post 4.46E+11 1.60105 Telecom and other information

transmission services3.24E+11 1.68

106 Computer services 4.49E+11 2.36107 Software industry 3.76E+11 2.79108 Wholesale and retail trades 2.82E+11 3.04109 Hotels 5.32E+11 2.29110 Catering services 7.97E+11 22.71111 Banking, security, other financial

activities1.19E+11 3.27

112 Insurance 4.44E+11 4.17113 Real estate 1.43E+11 2.44114 Leasing 5.88E+11 1.89115 Business services 6.55E+11 2.32116 Tourism 4.65E+11 7.10117 Research and experimental

development7.11E+11 4.47

118 Professional technical services 3.86E+11 2.35119 Services of science and technology

exchanges and promotion4.27E+11 2.19

120 Geological prospecting 6.73E+11 1.99121 Management of water conservancy 3.31E+11 2.60122 Environment management 6.26E+11 2.01123 Management of public facilities 6.62E+11 3.55124 Services to households 4.57E+11 3.09125 Other services 6.40E+11 2.06126 Education 4.25E+11 3.72127 Health 6.26E+11 3.48

128 Social security 3.26E+11 5.55129 Social welfare 2.17E+11 3.27130 Journalism and publishing activities 4.66E+11 3.26131 Broadcasting, movies, televisions and

audiovisual activities6.14E+11 3.45

icators 58 (2015) 392–401

Sector Embodiedcosmic exergytransformity(Jc/104 CNY)

PR (%)

132 Cultural and art activities 5.05E+11 3.80133 Sports activities 5.38E+11 3.25134 Entertainment 3.75E+11 9.07135 Public management and social

organization4.12E+11 4.10

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