A LIFE CYCLE ASSESSMENT METHOD FOR BUILDINGS BELES

Transcription

1 Proceedngs: Buldng Smulaton 2007 A LIFE CYCLE ASSESSMENT METHOD FOR BUILDINGS Daojn Gu 1, Ljng Gu 1, Yngxn Zhu 1 1 Department of Buldng Scence, Tsnghua Unversty, Bejng , Chna ABSTRACT Green buldng has come to be a goal of buldng desgn now. Snce sustanable performance of buldng nvolves lots of aspects, an ntegrated ndex s needed to evaluate t comprehensvely. Buldng envronmental mpact assessment (EIA) based on lfe cycle assessment (LCA) theory s a well-known method to do ths. However, when t s used n Chna, two man dffcultes should be overcome: lack of unform assessment method and lack of basc data. Amng at ths and combnng Chnese specal stuaton, EIA based on damage orented method s propounded and Buldng Envronment Load Evaluaton System (BELES) s founded. All of the envronmental mpacts are fnally classfed nto four endponts: Resource Exhauston, Energy Exhauston, Human Health Damage and Ecologcal Damage. Resource scarcty factor and energy qualty coeffcent are consdered. Weght system s determned by nvestgaton to natonal experts. Ths method and framework can be useful gudance to buldng desgn, especally to green buldng assessment. KEYWORDS lfe cycle assessment, envronmental mpact, BELES, buldngs BACKGROUD Sustanable development concept brngs forward new requrement for buldngs, and then green buldng becomes one of the hot topcs n buldng feld. Sustanable performance of green buldngs nvolves several aspects of buldng performance, such as energy consumpton, resources consumpton and emsson. Dfferent scheme may have advantage n dfferent aspect, then how to evaluate buldng wth an ntegrated ndex becomes focus of scholars. Buldng sustanable performance s evaluated comprehensvely manly by analyss of ts envronmental load (EL) both home and abroad, whch s the numercal result of envronmental mpact assessment (EIA) of object or process. The total EL of the buldng can be obtaned through EIA n all aspects of the buldng. The hgher the total EL s, the larger the envronmental mpact of the buldng s. At present, buldng EIA can be classfed nto two categores: one s qualtatve assessment wth part quanttatve assessment, for example, green buldng evaluaton, EL s expressed wth score; the other s totally quanttatve assessment, for example, buldng lfe cycle assessment (LCA), EL s expressed wth amount or polluton level. There are far more qualtatve assessment researches than quanttatve ones, but qualtatve assessment s not able to show the real amount of EL, concluson from t s always dsputed. Therefore, more and more quanttatve assessments based on LCA have been adopted n recent years. Some scholars n Chna have done some researches about buldng LCA. Data collecton work and nventory analyss on energy resource and man buldng materals have been carred out. There are also methodology study and some applcaton study. But generally speakng, buldng LCA n Chna s stll at the begnnng phase. Lack of data s the man problem. Besdes, there s no unform EIA method, weghtng defnton method, formatted database or tools for LCA framework and applcaton. Amng at the above problems of domestc buldng LCA and combnng the specal stuaton of Chna, EIA based on endpont damage method s proposed and envronmental load evaluaton system for buldngs n Chna, Buldng Envronmental Load Evaluaton System (BELES), s founded n ths paper. BELES Lfe cycle assessment (LCA) s an nternatonally recognzed method to evaluate envronmental mpacts. It s a process to evaluate the envronmental burdens assocated wth a product, process, or actvty throughout ts lfe cycle. LCA framework conssts of goal and scope defnton, lfe cycle nventory analyss, mpact assessment, and nterpretaton (ISO. 1997). BELES s an applcaton of LCA theory on buldngs. Goal and scope defnton The object of BELES s buldngs and ther actvtes n Chna, manly ncludng buldng materals, equpment, energy, whole buldng etc. Dfferent object has dfferent assessment scope. As for a whole buldng, ts lfe cycle ncludes extractng and processng of raw materals, buldng materals producton, transportaton, buldng constructon, operaton, mantenance, recyclng and fnal demolton; as for buldng materals, ts lfe cycle ncludes raw materals extractng, transportaton, buldng materals producton, use, recyclng and demolton. Fg.1 shows the research scope of BELES. Insde the boundary s the object, the actvtes n buldng crcle; outsde the boundary s the natural ecologcal crcle. All of the substance and energy exchange between the two crcles should be studed. Based on the stuaton

2 Proceedngs: Buldng Smulaton 2007 of Chna, BELES manly analyze three types of envronmental mpacts: energy exhauston, resources exhauston and polluton, and the nvolved substances manly are fossl fuel resources, mneral resources and. Natural crcle Fossl fuel mnerals Metal mnerals Nonmetal mnerals Gas Energy producton Raw materal extractng Lqud Transportaton Buldng materal and component producton Sold Buldng crcle Buldng operaton Recyclng and demolton Fg.1 research scope of BELES Date models Two data models are used n BELES: nventory model and emboded energy model. Inventory model s the deal and most common LCA data model descrbed wth detaled nput and output amount of substances. But nventory data of many products n Chna are very hard to get, so emboded energy model s proposed. In ths model, emboded energy s used as lfe cycle energy consumpton of the product; envronmental polluton from emboded energy use process n Chna s used as lfe cycle envronmental polluton of the product; Amount of man raw materals of the product s used as ts lfe cycle resources consumpton. In BELES, nventory data model s used for man buldng materals, but emboded energy model for other general buldng materals, equpment and components. EIA based on end-pont damage method EIA s classfed nto two categores, one s Md-pont mpact assessment, the other s End-pont mpact assessment. The former only evaluate the drect envronmental mpacts, but not the ndrect ones. It s the common assessment method at present, ncludng three steps: classfcaton, characterzng and quantfcaton. The latter track to evaluate the termnal of envronmental mpact chan, ncludng four steps: classfcaton, damage classfcaton, characterzng and quantfcaton. BELES use End-pont damage assessment method to quantfed envronmental load. There s no nternatonally unform end-pont classfcaton now. In ths paper, the end-ponts are classfed nto four categores: Resource Exhauston (RE), Energy Exhauston (EE), Health Damage (HD) and Ecologcal Damage (ED). 1. Resource exhauston Producton of buldng materals and components consume large amount of raw materals, so RE s an mportant part of envronmental mpact of buldngs actvtes. Some researches evaluate RE by addng up the weght of consumed man buldng materals drectly (Tong 2003), however, ths can not show the dfference among varous resources. In ths paper, resources scarcty factor (SF) s ntroduced for RE assessment. There s stll no unform defnton of SF; some are determned by reserves, and some by consumng speed. Besdes, some renewable resources, such as land, forest, water and so on, are very scarce at current perod because of the specal stuaton of Chna. Therefore evaluaton of these resources should be dfferent from that of mneral resources. In BELES, SF s used to descrbe the exhaustng extent of resources, and dfferent calculaton model for dfferent knd of resources. As for unrenewable mneral resources, SF s the drect rato of resources consumng speed. Accordng to the statstc data of mneral resources n Chna, the resduary avalable years (RAY) of each knd of resource can be worked out. Assumng SF of 1t ron s 1, than SF λ of resource can be calculated wth equaton (1). Where L Fe s RAY of ron (yr); L s RAY of resource (yr). LFe λ = (1) L Table1 SF of unrenewable resources resources Reserve (t/per.) RAY (yr) SF ron tn copper alumnum cement lme slca gel salt gypsum marble

3 Proceedngs: Buldng Smulaton 2007 Because annual data are qute dffcult to get, the result of reserve (Natonal Statstc Agency, 2004) dvdng the output of typcal year (Anon.) s used to as the RAY after that typcal year. The SFs of some resources are shown n table 1. It can be seen that metal mneral resources are relatvely scarcer, but nonmetal mneral resources are abundant wth RAY more than 200. When RAY exceeds 500, t s set to be 500, because reserve data are approxmate data. The producton of some buldng materals, such as clay brck, wll destroy the land. Land has been destroyed serously n Chna, the area decreasng year after year, although t s renewable resources. Therefore these destroyed parts should be consdered as the exhauston of land resource, and be descrbed wth SF. The prme use of land s food producton, servng raw materals s just addtonal use. So the two parts should be dfferentated when calculatng SF, as equaton (2) shows. LFe λ s = (2) ( GS P PS ) / ΔS Where G s s total land area n Chna (ha), P s s land area needed for mnmum food producton level (ha/per.), P s the populaton of Chna (per.), S s the annual decreasng land area (ha/a), L Fe s RAY (yr) of ron. The value of these parameters s obtaned from relevant references (Chen 2002, Feng 2005), and fnally λ s s fgured out to be 4.37 Smlar to land, Forest (except that can renew n a short perod) and water are also renewable but currently scarce resources. Although there s no concept of RAY for them theoretcally, SFs are assumed to be the nverse rato of ther reserves to ndcate ther scarcty and to unfy SF concept. Then SF of forest and water can be determned wth equaton (3), also assumng SF of ron s 1. Where λ j s SF of resources j, G j s the reserve of resources j (t/per.); G Fe s the reserve of ron (t/per.). SFs of renewable but currently scarce resources are show n table 2. GFe λ j = (3) G j Table 2 SF of renewable but currently scarce resources resources Reserve (t/per.) RAY (yr) SF land forest water Then buldng RE (kgfe eq) can be calculated wth equaton (4). Where G s the consumed amount of buldng materal (kg); R j s the amount of resources j consumed by unt buldng materal mass (kg/kg); λ j s the SF of resources j. RE = ( G ( λj Rj )) (4) j 2. Energy exhauston Energy exhauston caused by consumpton of fossl fuel resources. Although fossl fuel resources are also mneral resources, they should be evaluated respectvely for ts specal use as energy. The tradtonal assessment only consders the dfference of heat value among dfferent energy resources, but gnore the dfference of energy qualty. Jang Y et al (2004) proposed energy qualty coeffcent (QC) based on exergy analyss method of second law of thermodynamcs. QC s the rato of the useful work the energy could make over ts total energy. To be used n buldngs, the prmary energy needs to be converted to be secondary energy by some dynamcal equpment, lke power plant, boler, and dstrbuton system. There s energy loss n convertng process, so convertng effcency η should be consdered. Then QC can be defned wth equaton (5). Where Q s the total energy the energy contans (MJ), W s the useful work the energy resource could make (MJ). Accordng to heat-work converson arthmetc of thermodynamc, QCs can be worked out, shown n table 3. W λ = η (5) Q Table3 energy qualty coeffcent energy QC energy QC coal 0.35 geothermc water 0.07 ol 0.46 natural gas 0.52 Then EE (kgce eq) of buldng actvtes can be calculated wth equaton (6). Where E s the consumed amount of energy (equvalent coal amount converted by heat value, kgce eq), λ s QC of the energy resource. EE = E λ (6) 3. Health damage Human Health Damage (HD) expresses the bad effect that envronmental s have on human health drectly or ndrectly. HD can be quantfed. Murray et al (1994) collaborated wth World Health Organzaton, wth more than 100 experts n the world, worked on the global dsease burden, and propounded an ntegrated ndex, Dsablty-Adjusted Lfe Year (DALY), to evaluate HD. Among envronmental polluton relevant to buldng actvtes, clmate change, ozone layer depleton and respratory system damage are man factors resultng n human health damage. Scholars n relevant feld have done some research on the change of dsease ncdence and human mortalty caused by these envronmental mpacts. Based on these researches, Eco-Indcator99 (Goedkoop 2001) calculated DALY. Clmate change manly attrbuted to greenhouse gases. The research of Eco-Indcator99 ndcates global

4 Proceedngs: Buldng Smulaton 2007 human health damage factor (HDF) of CO 2 from 2000 to 2100 s 2E-7 DALY/kg. HDFs of other greenhouse gases can be calculated, accordng to the global warmng characterzng factors n equvalent potental model of EPA (Agency of US Envronment Protecton 1995). CFC-11 s a typcal knd of polluton depletng ozone layer, HDF of t s 8.5E-4 DALY/kg. HDFs of other polluton depletng ozone layer can also be calculated accordng to the ozone layer depletng characterzng factors. HDF of CO that may damage respratory system s 7.31E-7 DALY/kg. Some substance have more than one knd of damage, for example, CO s a knd of greenhouse gas and may also lead to respratory dseases, so ts HDF should be the sum of HDF of each knd. HDFs of polluton relevant to buldng actvtes are shown n table 4. Table 4 global HDF of s HDF HDF (DALY/kg) (DALY/kg) CO E-7 TSP 8.03E-5 CH E-6 CFC E-3 NO x 1.51E-4 CFC E-3 CO 1.13E-6 CFC E-4 SO E-5 HCFC-141b 1.54E-4 PM E-4 NMVOC 1.28E-6 Then HD of buldng actvtes can be fgured out wth equaton (7). Where G s the amount of (kg), H s HDF of ths (DALY/kg). HD= G H (7) 4. Ecosystem damage Ecosystem Damage (ED) refers to the effect on bodversty of bosphere caused by emsson and ecologcal envronment occupancy. There are manly two ways n buldng actvtes that wll lead to ecosystem damage. One s acd and eutrophc substances emsson when usng energy. In Chna acdfcaton and eutrophcaton are manly caused by norganc substances due to deposton of SO2, NOx, such as sulphate, ntrate. The other s land occupancy or type change, for example, pavng ppelnes, buryng waste, usng as raw materals and so on. Hamers et al (1996) propounded Ecosystem Damage Factor (EDF) to quantfy and evaluate ecosystem damage. EDF s defned as the potentally dsappeared fracton (PDF) of speces n some regon durng some perod, wth unt PDF m 2 yr. Where, PDF s the rato of dsappeared speces number over former speces number. Snce there s no research to quantfy the effect of SO 2, NO x, or other on ecosystem n Chna, the research results of Eco-Indcator99 are adopted n BELES, whch are shown n table 5. Type change of land wll lead to regonal bodversty change. Combnng PDF, bodversty change s used to evaluate ED of land occupancy n BELES, and smplfed method s proposed based on the stuaton of Chna. In ths method, the average speces number of urban land s assumed as the speces number of reference land. When the land s occuped, f ts speces number ncreases, then the ecosystem s mproved; f ts speces number decreases, then PDF (α) of land use can be calculated wth equaton (8) and EDF (ε) wth equaton (9). Where C r s land speces number before occupancy, C u s land speces number after occupancy, T s lastng tme of occupancy (yr), S s the area of occuped land (m 2 ). C C r u α = (8) Cr ε = α T S (9) In our research, ED of land occupancy s evaluated by land plant dversty. Ths s because land damage always destroy plants drectly, plant speces number s bgger than anmal speces number, and s easer to obtan and more relable. In EDF calculaton, plant speces number data of dfferent type of urban land comes from reference (Meng X 2004), occupyng tme s assumed 50 years, and the results are show n table 5. For EDF calculaton of sold wastes, assume that wastes are dsposed wth landfll, 20 m 3 buldng wastes wth densty 1500 kg/m 3 accumulated on per m 2 land. Table 5 Ecosystem Damage Factor Impact factor (1m 2 ) EDF (PDF m 2 yr) SO 2 (1kg) NO x (1kg) Sold waste(1kg) Pavng road(1m 2 ) 9.32 Everglade or natral water occupancy Shallow land-cover occupancy Plantaton and woodland depleton Landfll land occupancy Normalzaton Meanngs and Unts of the four endponts of envronmental mpacts are not same, so they need to be normalzed by ther background value for comparson and weghtng. To fnd how much the envronmental mpact of the research object s n buldng ndustry s, the whole buldng ndustry should be taken as the background, and then the total envronmental load (EL) per unt buldng area of Chna s taken as the background value n ths paper. Buldng ndustry EL of Chna manly comes from two parts, one s buldng materal producton, and the other s buldng operatng energy and water consumpton. Output of buldng materals and lvng water consumpton are obtaned from natonal statstc almanac (2004), buldng constructon and operatng energy consumpton s assumed to be 25% of the total energy consumpton of the country, and the area of exstng buldngs n Chna s mllon m2. The

5 Proceedngs: Buldng Smulaton 2007 background of buldng ndustry n Chna can be calculated accordng to the above analyss method. Table 6 shows the result. Table 6 background value Background value HD (DALY/m 2 ) 8.84E-5 ED (PDF m 2 yr) 1.58 RE (kgfe eq/m 2 ) EE (kgce eq/m 2 ) steal, glass and so on. BELES has also been used to determne evaluaton ndex of green buldng materals through lfe cycle EL analyss of many offce and resdental buldngs. Besdes, t has been used to optmze buldng envelop desgn too. For nstance, Fg.2 shows the lfe cycle EL of cement calculated by BELES. It can be seen, EL of each endpont n each phase of cement lfe cycle has been carred out, and the man envronmental mpacts of each phase are not same. 6. Weghtng Weghtng factors ndcate the relatve mportance of the four endponts. In ths paper, weghtng factors are determned by nvestgaton of 57 expects from desgn nsttutons, government departments, real estate ndustry and unverstes. Weghtng factors are obtaned by analyss of vote result. Table 7 shows the result. Lfe Cycle EL of cement (pt/kg) explotaton and processng transportaton electrcty producton coal producton EE RE ED HD dsposal Table 7 weghtng factors of each endpont HD ED RE EE weght Envronmental load calculaton Accordng to the above method of classfcaton, characterzng, normalzng and weghtng, EL can be calculated wth equaton (10): RE EE HD ED EL = ωre + ωee + ωhd + ωed (10) BRE BEE BHD BED Where RE s the total resources exhauston value of the object (kgfe eq); EE s the total energy exhauston value of the object (kgce eq); HD s the total human health damage value of the object (DALY); ED s the total ecosystem damage value of the object; ω RE, ω EE, ω HD, ω ED are the correspondng weghtng factors; B RE, B EE, B HD, B ED are the correspondng buldng ndustry background value. To make t easy to be understood, the unt of EL s defned as envronmental load pont (pont, pt for short). APPLICATION An assessment tool named Buldng Envronmental Load Evaluaton System (BELES) for buldng LCA n Chna has been developed, based on the above theory framework. Users can update and expand the database and set new data modules of buldng materals, equpment, energy etc by themselves, and add new project to descrbe a sngle buldng wth ts consumpton of buldng materals, energy etc, and analyze EL of buldng materals, equpment or the whole buldng. BELES has been used to analyze EL of buldng energy producton and use, for example, coal-burned electrcty generaton, gas-burned heatng etc, and lfe cycle EL of man buldng materals such as cement, Fg.2 Lfe Cycle EL of cement CONCLUSION In ths paper, method to evaluate envronmental load of buldngs and ther relevant actvtes has been propounded, based on LCA theory and combnng the specal stuaton of Chna. EIA based on endpont damage has been explaned, and four endponts, RE, EE, HD, ED, have been proposed. Scarcty factors are used for RE assessment, and are defned respectvely for unrenewable resources and renewable but currently scarce resources. Qualty coeffcent s ntroduced n EE assessment to consder the dfference of energy qualty. In HD assessment, three md-mpact, global warmng, ozone layer depleton and respratory damage, are nvolved. In ED assessment, envronmental mpact of land occupancy s descrbed by the change of land plant dversty. The weghtng factors are determned by nvestgaton to experts of buldng ndustry. The total EL of buldng ndustry n Chna, ncludng EL of buldng materals producton, buldng constructon, operatng energy consumpton and lvng water consumpton, s used as background value. Fnally, an assessment tool, BELES, has been developed to assst calculaton and analyss. Ths assessment system has been proved feasble n many researches. It has been used for materals and energy consumpton evaluaton of green buldngs and buldng effcency desgn. In the future, wth the expanson of database, BELES wll be used n broader buldng feld, evaluate envronmental load of more buldngs and relatve actvtes, and promote sustanable development of buldng ndustry n Chna. REFERENCES Anonymty

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