ENVIRONMENTAL LIFE CYCLE DRIVEN DECISION MAKING IN PRODUCT DESIGN

Transcription

1 ENVIRONMENTAL LIFE CYCLE DRIVEN DECISION MAKING IN PRODUCT DESIGN A Dssertaton Presented to The Academc Faculty by DI LU In Partal Fulfllment of the Requrements for the Degree Ph.D. n the School of Chemcal and Bomolecular Engneerng Georga Insttute of Technology August, 2010

2 ENVIRONMENTAL LIFE CYCLE DRIVEN DECISION MAKING IN PRODUCT DESIGN Approved by: Dr. Matthew J. Realff, Advsor School of Chemcal and Bomolecular Engneerng Georga Insttute of Technology Dr. John Muzzy School of Chemcal and Bomolecular Engneerng Georga Insttute of Technology Dr. Fred Cook School of School of Polymer, Textle & Fber Engneerng Georga Insttute of Technology Dr. Jane C. Ammons School of Industral and Systems Engneerng Georga Insttute of Technology Dr. Pradeep Agrawal School of Chemcal and Bomolecular Engneerng Georga Insttute of Technology Date Approved: March 17, 2010

3 To My Parents, Jngdong Lu and Yanlng He To My Husband, Yanbng Yu and Son, Davd Yu Wth Love

4 ACKNOWLEDGEMENTS Frst I want to sncerely express my deepest grattude to my advsor, Dr. Matthew Realff, for hs support, gudance, encouragement, and patence throughout my Ph.D. study. Dr. Realff s a truly remarkable advsor who grants me a lot of freedom to explore new deas, but at the same tme nteract closely wth me. Dscussons wth Dr. Realff always kept me refreshed and excted to thnk new deas. He has suggested many orgnal deas and taught me how to thnk, research, create, and explan. I would lke to acknowledge the helpful comments and advce I receved from the professors who took the tme to serve on my thess commttee: Professors Fred Cook, John Muzzy, Pradeep Agrawal, and Jane Ammons. Also, I want to thank Professor. Mchael Overcash, Dr. Yong L, and Dr. Evan Grffng for provdng data for the carpet recyclng case study. My frends at Georga Tech were always there when I needed them. I thank them for our memores and frendshp: Delong Song, Cheng Chen, We Zhang, Lngyan Ruan, Lehong L, Chunpeng Xao, Zhengca Ye, Yuja Wang, Yaguang We, Farmnder Anand, Pe Yoong Koh, Qunta Nwanoske, Krystle Chaves, and Mchelle Kassner. Most mportantly, I would lke to thank and express my deepest love from the bottom of my heart to my parents, Jngdong Lu and Yanlng He, for ther endless love and support. I also want to thank my husband, Yanbng Yu, who s my lfe-tme soul mate and always understands and encourages me. I could not obtan ths Ph.D. degree wthout hm. Last but not the least, I want to thank to my adorable son, Davd Yu, born n Dec., He could cheer me up wth hs fabulous smles. v

5 TABLE OF CONTENTS Page ACKNOWLEDGEMENTS LIST OF TABLES LIST OF FIGURES SUMMARY v x x x CHAPTER 1 INTRODUCTION Background Problem Statement: Establshng the Systems Scence Base for Carpet Recyclng and Sustanablty Cradle-to-Gate LCI System Synthess Modelng for Sustanablty Standards n Optmzaton Desgn Sustanablty Standards Usng LCI nformaton Thess Objectves Dssertaton Overvew 7 CHAPTER 2 LITERATURE REVIEW Lfe Cycle Assessment Hstorcal Background Lfe Cycle Assessment Methodology Process-Based LCA Method Optmzaton of Process-Based LCA Economc Input Output LCA Comparson of Process-Based wth EIO-LCA Models Lfe Cycle Assessment for Envronmental Decson Makng Lfe Cycle Assessment Tools Lfe Cycle Assessment Databases 31 v

6 CHAPTER 3 LIFE CYCLE STUDIES FOR CARPET SYSTEM Carpet Lfe Cycle Carpet Manufacturng Nylon Carpet Recyclng Transparent and Representatve LCI Data LCI Calculaton of PET Depolymerzaton Lfe Cycle Impact Assessment 47 CHAPTER 4 A MATHEMATICAL PROGRAMMING TOOL FOR LCI-BASED PRODUCT DESIGN Introducton Two-Phase Framework Methodology for Process Synthesze Overvew Phase-I: Process Tree Buldng Process-Tree-Bulder Algorthm Process-Tree-Bulder Implementaton Phase-II: Development of LCI Optmzaton Summary Case Study EcoWorx TM Carpet System Input and Output for Process-Tree-Bulder Module Results and Dscusson Optmzaton wth Dfferent Energy Type Optmzaton wth TRACI Method Optmzaton wth Dfferent Post-Consumer Materal Capacty Summary and Conclusons Concluson 86 v

7 CHAPTER 5 POINT-BASED STANDARD OPTIMIZATION WITH LIFE CYCLE ASSESSMENT FOR PRODUCT DESIGN Introducton Methodology Pont-Based Standards NSF-140 Sustanablty Assessment of Carpet Pont-Based Standard Optmzaton Pont-Based Standard Optmzaton Modelng Lfe Cycle Assessment Background Case Study-NSF-140 Carpet Products The TRACI Method Lfe Cycle Inventory Optmzaton and Pont-Based Standard Optmzaton Results and Concluson 105 CHAPTER 6 STANDARD DESIGN USING LCI INFORMATION Introducton General Issues n Standards Desgn Prncples and Requrements n Standards Desgn Defntons Actvty-Based Verses Category-Based Standard From LCI to LCIA n the Standard Desgn Category-Based Standard Desgn Actvty-Based Standard Desgn Case 1 Sngle Category Actvty-Based Desgn Case 2 Multple Category Actvty-Based Desgn Case 3 Dealng wth Uncertanty n Actvty Impact 137 v

8 6.4 Case Study Dscusson and Concluson 148 CHAPTER 7 CONTRIBUTIONS AND FUTURE WORK Contrbutons Future Work Product Portfolo Desgn Standards Desgn Standard Desgn and Mappng LCI to LCIA 158 REFERENCES 160 v

9 LIST OF TABLES Table 2.1: Input-Output Table of a Natonal Economy (n physcal unts) 22 Table 2.2: Process-Based LCA Verses EIO-LCA Method 23 Table 2.3: Comparson of Major LCA Tools 31 Table 2.4: Advantages and Dsadvantages for Dfferent LCI Databases 34 Table 3.1: Inputs of PET Depolymerzaon 46 Table 3.2: Products of PET Depolymerzaon 46 Table 3.3: Energy Consumpton of PET Depolymerzaon 46 Table 4.1: A Matrx of Paths wth Raw Materals 57 Table 4.2: Recycled Materals Avalablty 69 Table 4.5: Case Study Summary of Energy Consumpton wth Dfferent Objectve 81 Table 4.6: Case Study Summary of Major Raw Materal Usage wth Dfferent Objectve 82 Table 4.7: Recycled Content Combnaton and Percentage of Energy Savng (Compare wth Vrgn Process) wth Dfferent Recycled Content Percentage 83 Table 5.1: Ponts Awarded for Manufacture s Use of Renewable Energy and/or Energy Reducton 92 Table 5.2: Ponts Awarded for Manufacture s Use of Bo-based, Recycled Content, or EPP Materals 93 Table 5.3: Ponts Awarded for Product Reclamaton 93 Table 5.4: Ponts Awarded for the Reducton of Specfed Lfe Cycle Impact Categores 96 Page Table 5.5: Lfe Cycle Impact Factor Value for Common Emssons n Carpet Products103 Table 5.6: Results of the LCI Optmzaton Verses the Pont-Based Standard Optmzaton 107 Table 5.7: Major Emssons from the LCI Optmzaton and the Pont-Based Standard Optmzaton on a Square Yard of Carpet Bass 109 x

10 Table 5.8: Major Raw Materals from the LCI Optmzaton and the Pont-Based Standard Optmzaton on a Square Yard of Carpet Bass 111 Table 6.1: A Standard Table Structure n the Standard Framework 126 Table 6.2: Algorthm of Awarded Ponts Accordng to Equvalent Percentage Reducton among Dfferent Actvtes 130 Table 6.3: Actvty 0's Standard Table Structure 131 Table 6.4: Actvty 's Standard Table Structure 0<<=m 131 Table 6.5: An Example of Energy Reducton Table 133 Table 6.6: Percentage Combnaton of Multple Recyclng Process System 133 Table 6.7: Actvty 's Standard Table Structure 0<<=m 135 Table 6.8: Impact Category 1 Standard Table for Actvty Table 6.9: Impact Category 2 Standard Table for Actvty Table 6.10: Integrated Actvty Standard Table 137 Table 6.11: Actvty 0 Standard Table 143 Table 6.12: Example of Actvty 0 Standard Table 143 Table 6.13: Example of Actvty 1 Standard Table 143 Table 6.14: Example of Actvty 2 Standard Table 143 Table 6.15: Manufacturer s Use of Renewable Energy and/or Energy Reducton 143 Table 6.16: Ponts Awarded for Manufacturer s Use of Bo-Based, Recycled Content, or EPP 144 Table 6.17: Case study of Awarded Ponts Accordng to Equvalent Percentage Reducton among Dfferent Actvtes 145 Table 6.18: The Post Industral Materals Table 146 Table 6.19: The Post Consumer Backng Materals Table 147 Table 6.20: The Post Consumer Face Fber Materals Table 147 x

11 LIST OF FIGURES Fgure 2.1: A Techncal Framework for Lfe Cycle Assessment 11 Fgure 2.2: A Process Flow Dagram for PET Depolymerzaton 12 Fgure 2.3: General LCI Block 13 Fgure 2.4: Typcal LCA Scope through Product Lfe Cycle 14 Fgure 2.5: Process-Based LCA 16 Fgure 2.6: Interactons between LCA and LP Modelng 18 Fgure 2.7: The methodologcal Framework for Optmum LCA Performance 19 Fgure 2.8: GaB Database Manager 26 Fgure 2.9: Varables of a Flow n GaB 4 27 Fgure 2.10: Dervng the BEES Overall Performance Score 29 Fgure 2.11: Settng BEES Analyss Parameters 30 Fgure 3.1: General Carpet Structure 37 Fgure 3.2: Nylon 6 Carpet Recyclng Processes 39 Fgure 3.3: PET Depolymerzaton Process Flow Dagram 44 Fgure 4.1: The Generc Two-Phase Synthess Optmzaton Framework 54 Fgure 4.2: Smple Illustratve Process Transformatons wth Molar Unts 55 Fgure 4.3: Example of a Process Tree for Process Transformaton 55 Fgure 4.4: The Pseudo-Code Algorthm of the Process Tree Constructon 58 Fgure 4.5: The Structure of the EcoWorx TM Tle wth Recycled Alternatves 67 Fgure 4.6: Selected Raw Materals, Energy, and Emssons from Phase-I 70 Fgure 4.7: Major Raw Materals and Energy Usages for Mnmzng Electrcty Consumpton 72 Page x

12 Fgure 4.8: The Major Raw Materals and Energy Usages for Mnmzng Steam Consumpton 73 Fgure 4.9: Major Raw Materals and Energy Usages for Mnmzng Fuel Consumpton 74 Fgure 4.10: Major Raw Materals and Energy Usages for Mnmzng Total Energy Consumpton 75 Fgure 4.11: Major Raw Materals and Energy Usages for Mnmzng Sold Waste Emsson 78 Fgure 4.12: Major Raw Materals and Energy Usages for Mnmzng Global Warmng Impact 79 Fgure 4.13: Major Raw Materals and Energy Usages for Mnmzng Fossl Fuel Depleton Impact 81 Fgure 5.1: Ponts Dstrbuton n the NSF-140 Sustanable Carpet Standard 94 Fgure 5.2: The Output Matrx of the Phase-I 101 Fgure 6.1: General Product Cradle-to-Gate LCI Block 123 Fgure 6.2: Category-Based Standard Frameworks 125 Fgure 6.3: An Example of Multple Recyclng Process System 132 Fgure 6.4: Multple Category-Based Standard Frameworks 134 x

13 SUMMARY There s growng nterest n the assessment of products from a lfe cycle perspectve. Product lfe cycles are often domnated by extensve chemcal supply chans that lead up to the materals contaned n the products and the overwhelmng contrbuton that the producton of these chemcals make to the overall lfe cycle due to ther energy ntensty. Hence, chemcal engneers are unquely postoned to carry out sgnfcant components of ths assessment because of ther sklls n chemcal process desgn and analyss. Furthermore, the complexty and extent of lfe cycle concerns creates opportuntes for new process systems tools to be developed to support product desgn and analyss. The specfc thess objectves are threefold. The frst s to develop a systematc methodology to optmze materal selectons for a product based on lfe cycle nventory (LCI) characterstcs. The second s to use ths methodology combned wth sustanablty assessment standards to assess whether these standards are congruent wth lfe cycle assessment. The thrd s to develop an approach to desgn product sustanablty assessment standards that are clear and consstent wth lfe cycle prncples. The overall contrbutons wll be n the appled doman of lfe cycle assessment and ts ntegraton nto standards settng, and n contrbutons to optmzaton tools and methods. The three objectves wll be llustrated n the doman of carpet systems. Prevous research has generated a substantal database of gate-to-gate (GTG) lfe cycle nventores for varous chemcals that make up carpet, extendng from the nputs to the fnal carpet mll back to the natural resources such as ol, natural gas and mned calcum carbonate. x

14 Carpet recyclng s a promsng alternatve approach for reducng lfe cycle mpacts and s beng practced at a growng scale n the U.S. Ths thess uses the specfc ndvdual LCI gate-to-gate blocks for vrgn materals and for mportant carpet recyclng and general polymer recyclng processes. A database for the GTG LCI wll be used to construct a vrtual chemcal tree that automatcally that represents the potental cradle-togate (CTG) use of resources. The alternatves for each possble route for the product wll be generated, and optmzaton approaches wll be appled to optmze the performance of the carpet system accordng to lfe cycle objectves. Sustanablty assessment standards are currently beng developed for a range of buldng products, such as carpet, reslent floorng, commercal textle coverngs and offce furnture. Ths actvty has been stmulated through the consderable success of the U.S. Green Buldng Councl s (USGBC) LEED TM standard. The LEED TM Standard s ponts-based: the buldng desgn and constructon earns ponts for havng certan attrbutes or promotng certan actvtes. The ponts are totaled and then the buldng earns a ratng based on the total beng above a certan threshold. The second thess objectve s met through extendng the LCI optmzaton methodology to represent pontbased standards. A product can then be optmzed to maxmze the number of ponts t earns or to mnmze ts lfe cycle attrbutes. Ths approach can be used to evaluate the effectveness of an emergng carpet sustanablty standard, NSF-140, n ntegratng LCI nto the standard. The last objectve, standard desgn, s approached through desgnng the tables that award ponts n the standard to be consstent wth lfe cycle nformaton. Certan mnmum prncples of consstency are artculated and then the desgns shown to be xv

15 consstent wth these prncples n the case that the lfe cycle mpact assessment method maps the lfe cycle nventory to mpact through a lnear weghtng. xv

16 CHAPTER 1 INTRODUCTION 1.1 Background In the Unted States, carpet s the major floor coverng materal. Approxmately bllon square yards of carpet were produced n the U.S. (The Carpet and Rug Industry Statstcs). Accordng to the annual report from CARE (Carpet Amerca Recovery Effort, 2008), 5,038 mllon pounds of used carpet were generated as muncpal sold waste (MSW), and only mllon pounds of the used carpet were recycled. In addton, the used carpet does not sgnfcantly degrade, and the hgh performance synthetc fber polymers from face and back of a carpet have sgnfcant economc value. Therefore, waste landfll (Doka, G., 2005) s a poor choce for the management of the used carpet from a sustanable development vewpont. From the envronmental responsblty and the cost savng perspectve, recyclng technque s becomng an mportant opportunty for the used carpet (Polk, M., 1994, and Craghll, A, 1996). As a result, an average of about 2 to 25 percent of used carpet recycled materals s currently nvolved n the carpet producton system accordng to the Carpet Industry s Sustanablty Report (2003). Addtonally, mllon pounds of post-consumer carpet were dverted from landfll n 2008, wth mllon pounds beng recycled as a consequence of the government and companes efforts (Carpet Amerca Recovery Effort Annual Report, 2008) From the state and the federal regulatory perspectve, a Memorandum of Understandng (MOU) s sgned between the ndustry, a number of states, and the Federal 1

17 EPA as a non-bndng voluntary agreement to reach certan recyclng targets by A thrd party non-proft organzaton, the Carpet Amerca Recovery Effort (CARE) has been establshed by the ndustry to coordnate the actvtes to reach the MOU targets. In addton, the ndustry has made vgorous efforts to establsh an ANSI standard for sustanable carpets. The ANSI standard s developed through a consensus process wth the efforts of state and federal government, archtectural specfcatons and carpet buyers, and envronmental consultants. As part of the standard, the ndustry s especally engaged n lfe cycle nventory studes of carpet producton systems and recyclng processes. 1.2 Problem Statement: Establshng the Systems Scence Base for Carpet Recyclng and Sustanablty Lfe cycle assessment (LCA) s a commonly used method for evaluatng envronmental mpact. Envronmental mpacts can dffer sgnfcantly from process to process even n the same ndustry. Moreover, the chemcal process tself s complcated wth dverse operatng equpments and varous reacton condtons. Therefore, how to model and study the envronmental mpact of complex processes effectvely usng LCI nformaton s a key ssue. In vew of the fact that chemcal processes are nvolved wth numerous nformaton, even though t s straght forward to model the system n the mathematcal expresson, when comes to the stage of solvng the problem, t s dffcult and tme consumng due to the complex nature of the expresson whch nvolved wth the nteger and the non-lnear programmng. There are two ways to cope wth the dffculty. One of them s to dg nto the optmzaton algorthm and come up wth a novel mechansm to 2

18 solve the mxed nteger nonlnear programmng (MINLP) problem, and the other method s to express the problem properly at the begnnng so that the exstng solver nstead of a new algorthm can solve the problem. In ths dssertaton, I wll focus on the second method to manage the dffculty Cradle-to-Gate LCI System Synthess The development of Gatet-to-Gate blocks that are representatve and transparent s one prerequste for the scentfc study of lfe cycles. The development of new recyclng processes or the adopton of new materals leads to alternatves for products that nvolve dfferent confguratons of GTG blocks. Furthermore, t s mportant to ensure that dfferent producton pathways can be captured systematcally, so that any potental alternatves wll be ncluded. Ths leads to the problem of constructng the network of GTG blocks that connects raw materals wth products. Therefore, how to buld the GTG network automatcally s an nterestng and mportant ssue. Once the GTG network s bult, all the possble routes for producng the desred product are found. Whch route s the best accordng to the envronmental requrement? What s the system mpact regardng envronmental concern? Is current producton system optmal for mnmzng energy consumpton? How can we analyze the system and make some mprovements? How does recyclng technology nfluence the confguraton of the supply chan? These questons wll be answered through the development of an optmzaton formulaton Modelng for Sustanablty Standards n Optmzaton Sustanablty standards are an mportant drvng factor for product development n certan ndustres, such as carpet and buldngs. Also, standards are helpful for 3

19 procurement by large commercal organzatons and government agences. Standards are developed through a consensus process that often places emphass on the categores of mpacts whch are based on stakeholders prevous experences n the envronmental felds. For nstance, emphass s often placed on the avodance of sold waste through recyclng and release of materals to other meda durng manufacturng. However, emphass on energy effcency, use of renewable materals, and socal equty metrcs, s ncreasng due to rsng concerns about other human mpacts on the envronment and on global nequty. The emergng paradgm for sustanablty standards s to establsh a ponts-based reward system to allow the combnaton of multple attrbutes of the product s performance. The products are then categorzed nto dscrete levels based on crossng a certan threshold n the sum of ponts earned across categores. A key problem n ths ponts system s allocatng the ponts between performance attrbutes. Ths problem s mportant and rases some mportant questons. 1. Gven an exstng standard, s there any connecton between the ponts dstrbuton and lfe cycle nventory and assessment data? 2. If there s agreement that certan categores of ponts should reflect lfe cycle assessment, how should the results be mapped to ponts n dfferent categores? To examne these questons we wll choose the specfc example of the NSF 140 Sustanable Carpet Standard whch s a ponts-based standard. The questons wll be approached through the development of an LCI optmzaton tool to ncorporate the evaluaton and optmzaton of standards based products. Ths wll contrbute both to answerng the above questons, and potentally lead to some nterestng questons from a methodology perspectve. 4

20 1. How should a ponts-based standard be represented n an optmzaton problem? 2. How can the above questons be represented and answered usng optmzaton methods? As standards begn to drve product desgn and marketng, t s consderate to reward approprately aspects of lfe cycles. The nformaton from lfe cycle contrbutes the most to resource usage and scentfcally based measures of envronmental mpact. As a result, lfe cycle nventory contans lots of useful nformaton that could help us to make the standards more comprehensve. Therefore, the research queston s how to map lfe cycle nformaton nto standards and solve the optmzaton problem of desgnng a standard to encourage overall envronmentally benefcal systems Desgn Sustanablty Standards Usng LCI nformaton Desgn of sustanablty standards has taken place wthout a frm systematc understandng of the envronmental decsons and lfe cycle nformaton nvolved. In partcular, the standard has evolved through several generatons of stakeholder nput to have a certan number of ponts awarded n dfferent categores of actvty, wthout a systematc understandng of whether the pont allocatons actually reflect mproved envronmental performance. In the carpet ndustry, the postve role of recyclng, and n partcular closed-loop recyclng of materals from carpet back nto new carpet, s not clear, snce the energy nvolved could be more or less when examned from a cradle-tocradle perspectve. On the other hand, the GTG lfe cycle nformaton would help to construct the mult-attrbute standard. Carpet s not the only product for whch multattrbute standards are beng developed and for whch lfe cycle nventory s beng 5

21 suggested as the underpnnng evaluaton method. For example, sustanable forestry, other floorng surfaces, textles, offce furnture, and the Leadershp n Energy and Envronmental Desgn (LEED TM ) green buldng standard are all evolvng standards and many of them have lfe cycle assessment components. Ths motvates a systematc and normatve approach to ncorporatng lfe cycle assessments nto standards. 1.3 Thess Objectves The objectves of ths thess are 1). To develop a set of transparent and representatve GTG LCI blocks for carpet recyclng that can be used n the optmzaton models. These blocks wll represent both closed loop and open loop optons for the use of carpet materals. A focus on the depolymerzaton of carpet materals wll be explored for closed loop optons along wth polymer re-extruson for the backng components. These GTG blocks wll contrbute to the growng body of scentfc LCI data based chemcal engneerng prncples. 2). To develop a lfe cycle optmzaton framework that can construct a GTG network and operate over a transparent and representatve set of GTG lfe cycle blocks. Ths framework wll generate a complete process network whch can be optmzed to meet dfferent objectves, such as mnmzng energy consumpton, mnmzng emssons, and mnmzng use of vrgn raw materals. Ths model wll be used to test the hypothess that closed loop recyclng can be sgnfcantly sub-optmal when objectves relatng to overall energy and mass consumpton of a product are used to drve the decsons. Ths framework wll contrbute to smplfyng the optmzaton process and use lfe cycle nformaton to help desgn early n the product lfe cycle. 6

22 3). To develop a normatve optmzaton model that can explore the relatonshp between standards settng and lfe cycle nventory calculatons. Ths model wll be tested n the context of a carpet standard under development through a consensus ANSI standards body. The model wll be used to test the hypothess that the standard pont reward system and lfe cycle nventory measures are not completely algned for carpet. The optmal soluton wll be used to suggest changes to the pont allocaton scheme that could brng the standard and lfe cycle assessment nto closer agreement. Ths method wll answer the queston: gven an exstng pont dstrbuton, how do we assess the perverse ncentve for products to ncrease ther lfe cycle mpact to ncrease the number of ponts they get? 4). To develop a normatve methodology that can desgn standards settng usng lfe cycle nventory nformaton. How sustanablty standards and lfe cycle assessment are related wll be well establshed through ths method. Also the followng queston wll be answered: If one could desgn a standard, how could lfe cycle assessment data be used to desgn the standard to acheve consstency between the ponts and the assessment to avod creatng perverse ncentves? Ths wll contrbute to dentfy regulatory needs and address publc concerns for chemcal ndustry. 1.4 Dssertaton Overvew The chemcal ndustry puts great emphass on mprovng the energy effcency wth renewable materals and reducng the amount of emssons that enter the envronment. The sustanable development across the extensve chemcal supply chan s employed by syntheszng the lfe cycle nventory nformaton. The study from the LCI of how each process cooperates n the lfe cycle supply chan and how to optmze the entre 7

23 chemcal system through ndvdual processes s a necessary and meanngful subject. Namely, we wll focus on the complexty wth respect to model of both the system and processes usng a back searchng approach to evaluate the envronmental mpacts throughout the product s entre lfe cycle. Importantly, except for obtanng the objectve value, the content and the sequence of the processes can also gude us on how to evaluate and mprove the system for decson makng. The approach wll be llustrated n the doman of the EcoWorx TM carpet system from the Shaw Industry & Inc. Ths dssertaton s comprsed of seven chapters. Chapter 2 carres out the lterature revew of lfe cycle assessment, process-based and economc nput-output lfe cycle assessment methodology, and LCA for envronmental decson makng. Chapter 3 descrbes usng transparent and representatve LCI data for GTG blocks modelng and the lfe cycle mpact assessment (LCIA) method, whch are the foundatons for the carpet case study. Chapter 4 explans our approach to modelng the chemcal system usng a mathematcal programmng technque that nvolves process network constructon and lnear programmng optmzaton. Chapter 5 llustrates how to ntegrate lfe cycle nventory wth mult-attrbute standard through mxed nteger lnear programmng (MILP) optmzaton and the process network constructon. Chapter 6 explores more applcatons of combnng LCI and optmzaton tools to help the envronmental polces and regulatons decson makng scentfcally. Addtonally, our studes can be extended to show how sustanablty assessment standards can be redesgned to make them congruent wth lfe cycle measures. Fnally, Chapter 7 dscusses the future work of usng lfe cycle nformaton to help envronmental decson makng. 8

24 CHAPTER 2 LITERATURE REVIEW In ths chapter we gve a broad overvew of lfe cycle assessment whch s the foundaton of our study. Ths chapter focuses on the lterature revew of lfe cycle assessment wth four sectons. Secton 2.1 ntroduces the hstorcal background of the lfe cycle assessment approach. Secton 2.2 descrbes the lfe cycle assessment methodology n detal ncludng process-based LCA approach, optmzaton of the process-based LCA, economc nput-output LCA method, and LCA for envronmental decson makng. Secton 2.3 descrbes the major advanced LCA tools used by both researchers and ndustry such as GaB, SmaPro, TEAM TM, and BEES. Secton 2.4 dscusses well-known exstng LCA databases ncludng the Econvent database, the GaB U.S. extenson database, the database from NREL, and the EIO-LCA database. 2.1 Lfe Cycle Assessment Hstorcal Background The frst documented lfe cycle studes date from the late 1960s (Mettnen, P., 1997), and the ntal studes were focused on drect envronmental mpact such as energy requrements and sold wastes. Later on, other potental envronmental effects were ncluded n lfe cycle studes. From Hunt, R. (1996) and Fnk, P. (1997), the emssons nto ar, water, or sol, and other envronmental concerns such as human health and global warmng began to play an ncreasng role n lfe cycle studes. Lfe cycle assessment was formalzed by the Socety of Envronmental Toxcology and Chemstry (Fava, J.A., 1991); wth the goal of capturng all the envronmental mpacts of a product. Fnally, 9

25 LCA was standardzed by the Internatonal Standardzaton Organzaton through ISO and ISO standards n Snce then, researchers have developed varous lfe cycle mpact assessment methods to evaluate the envronmental mpact. In addton, economc nput-output analyss s also appled to lfe cycle studes. Nowadays, LCA method s wdely used by many ndustres. LCA s the assessment of the envronmental mpact such as energy (Km, S., 2003) and emsson of a product through ts lfe cycle. The framework of LCA (Consol, F., 1993) contans four phases n sequence as shown n Fgure Goal and scope defnton determnes the system boundares, assumptons of a study, and functonal unt accordng to the goal of evaluatng potental envronmental mpacts. 2. Lfe cycle nventory analyss s the bass of LCA, whch quantfes materal consumpton and envronmental emssons nsde the defned boundary of the producton system. 3. Lfe cycle mpact analyss evaluates the potental mpacts, such as global warmng and fossl fuel depleton, based on the manpulaton of LCI results. 4. Interpretaton ncludes senstvty and uncertanty analyss for the study, and what can be learned about the system, or what may be mproved n the future. 10

26 Fgure 2.1: A Techncal Framework for Lfe Cycle Assessment Among the four phases of LCA, lfe cycle nventory analyss s the foundaton of LCA and has the followng procedures: 1. Data Collecton s typcally the most data-ntensve part of LCI. a) Construct the partcular process flow dagram; b) Descrbe each detaled process unt; c) Document the data and nformaton sources. 2. Calculaton through the applcaton of conservaton laws and thermodynamc propertes. a) Calculate mass balance to capture all the materal flow; b) Calculate energy balance to trace all the energy consumpton throughout the system boundary. 11

27 3. Valdaton of Data revews and revses the results from common experence and experts' comments. The process flow dagram n Fgure 2.2 s an example of flow dagram wth varous unt processes for PET depolymerzaton. 4 (l) Ethylene Glycol 25 o C P2 5 (l) 25 o C HX 2 S6 6 (l) 230 o C P3 7 (l) 230 o C P5 9 (g) 230 o C C1 HX3 10 (s) 25 o C Polyethylene S5 8 (g) 230 o C C2 1 (s) Contamnated PET 25 o C S1 HX 1 S2 2 (l) 230 o C P1 3 (l) 230 o C S3 11 (l) 230 o C R S4 P4 C3 12 (l) 230 o C HX4 13 (l) 25 o C C4 Flter 1 15 (s) 25 o C 14 (l) 25 o C BHET Sand Fgure 2.2: A Process Flow Dagram for PET Depolymerzaton 12

28 For each general LCI block, nputs are materal and energy, whle outputs are fnal product and emsson as descrbed n Fgure 2.3. Energy Raw Materal Emsson Unt Process Fnal Product By Product Fgure 2.3: General LCI Block In addton, the LCA glossary that s used n the followng chapters wll be explaned below, and Fgure 2.4 shows a typcal LCA scope through a product lfe cycle. Functonal unt s a quantfed reference unt for performance descrpton of the product system. It provdes a reference to relate the nputs and outputs and facltates comparson of dfferent systems. Raw materal s a prmary or secondary (recovered and/or recycled) feedstock used n a manufacturng process. 13

29 Intermedate materals are the mddle materals made from raw materals n order to make fnal products. Cradle-to-grave s the LCA of the whole product lfe cycle from raw materals to use phase and dsposal. Cradle-to-gate s the LCA of the lfe cycle from raw materals to the factory product. Gate-to-gate s the LCA of the part lfe cycle from one factory product to another factory product. Cradle Gate to Grave Energy Energy Energy Energy Energy Raw materals acquston Materals manufacturng Product manufacturng Product use phase Landfll Waste and Emsson Waste and Emsson Waste and Emsson Waste and Emsson Waste and Emsson Reuse Remanufacture Recycle Fgure 2.4: Typcal LCA Scope through Product Lfe Cycle 14

30 The GTG LCI captures the unt operatons of manufacturng from an ntermedate product. The chemcal product s ether a commerce artcle or s an dentfable chemcal ntermedate. Consequently, numerous GTG LCI blocks can buld up a process path for one product. In addton, f the orgnal resources of the process path are raw materals such as crude ol, natural gas, or mnerals, the LCI wll be termed as a CTG LCI. 2.2 Lfe Cycle Assessment Methodology The major LCA methods are process-based LCA and economc nput-output LCA. The process-based LCA method s also named as "classcal" or "tradtonal" LCA approach, whch s developed by the effort of Socety of Envronmental Toxcology and Chemstry (SETAC), U.S. Envronmental Protecton Agency (EPA), and Internatonal Organzaton for Standardzaton (ISO). The process-based LCA approach uses physcal process flow nformaton through a product lfe cycle to capture resources, energy, and envronmental mpacts. The EIO-LCA method has been developed at Green Desgn Intatve from Carnege Mellon Unversty. The EIO-LCA method uses the structure of the flows of money n the economy to brng economc actvty as quanttatve nput and estmate correspondng envronmental mpacts Process-Based LCA Method The Process-Based LCA model shown n Fgure 2.5 s based on process mass and energy balances for systems contaned wthn the boundary. Throughout the process analyss, data and ste nformaton at varous levels of detal, whch reflect real systems and knowledge about specfc systems, are used. 15

31 Raw Materal Energy Unt Process Raw Materal Energy Unt Process Emsson Product Emsson Product Raw Materal Energy Unt Process Raw Materal Energy Unt Process Raw Materal Energy Unt Process Raw Materal Energy Unt Process Emsson Product Raw Materal Energy Emsson Unt Process Product Emsso n Product Emsson Fnal Product Raw Materal Energy Unt Process Emsson Product Energy Raw Materal Unt Process Raw Materal Energy Unt Process Raw Materal Emsson Energy Product Unt Process Emsson Raw Materal Emsson Energy Product Unt Process Product Emsson Product Emsson Product Fgure 2.5: Process-Based LCA Km, S., and Overcash, M. (2003) utlze sources that represent accumulated engneerng practce such as scentfc artcles, chemcal encyclopeda, and patents to fnd relevant data for the process-based LCA. 16

32 2.2.2 Optmzaton of Process-Based LCA Among lfe cycle assessment, lfe cycle nventory s based on lnear relatonshps between the amount of actvtes and a set of drect measurement of envronmental burdens such as energy consumpton, materal usage, and emssons. Therefore, lnear programmng can be used to model the LCA relatonshps for envronmental studes. Fgure 2.6 shows the connectons between lfe cycle assessment and lnear programmng modelng. Envronmental burden can be allocated n the nventory stage. The optmal soluton of the lnear programmng presents how to mprove the system from an envronmental perspectve. The beneft of usng lnear programmng wth LCA s that we can analyze the lfe cycle more accurately and evaluate how to mprove the system effcency accordng to dfferent requrements. Furthermore, when addtonal system performances, such as economc or socal performance are evaluated, mult-objectve lnear programmng can be appled (Azapagc, A., 1999). 17

33 Fgure 2.6: Interactons between LCA and LP Modelng (Azapagc, A., 1995) Azapagc, A. (1999) proposed an optmum LCA performance (OLCAP) methodology whch ntegrates LCA nto an optmzaton system n four steps as shown n Fgure 2.7: 1. Prepare the completed LCA study; 2. Formulate the optmzaton model wth LCA nformaton; 3. Perform mult-objectve optmzaton (MO) on envronmental and economc crtera; 4. Make decson from mult-crtera decson analyss and choose the best compromse soluton. 18

34 Fgure 2.7: The methodologcal Framework for Optmum LCA Performance (Azapagc, A., 1999) In Fgure 2.7 a mult-objectve optmzaton model wth LCA for the step has the followng structure: 19

35 mn f ( x, y) = [ f1, f2,..., f y Y Z q ]...(1) s. t. h( x, y) = 0...(2) g( x, y) 0...(3) n x X R...(4)...(5) A lnear programmng (LP) or a mxed nteger non-lnear programmng (MINLP) s formed n Equatons (1) to (5) (Azapagc, A., 1999). The objectve functon f(x,y) ncludes economc and envronmental factors. h(x,y) represents equalty constrants such as materal and energy balances, and g(x,y) represents nequalty constrants such as materal avalablty and system producton capacty. A vector of dmenson n has contnuous varables for materal and energy flows, whle a vector of dmenson q has nteger varables representng alternatve processng routes or substtute materals. mn F = c mn B mn E j K = = T N y + f ( x)...(6) n= 1 J b j = 1 k, j p x...(7) j, n n e B...(8) j Other objectve functons can be formed as Equatons (6) to (8). In Equaton (6), c s a vector of cost, and F s an economc objectve functon. In Equaton (7), b j,n represents coeffcents of emsson lnked wth contnuous varables x n, and B j s the envronmental objectve functon. In Equaton (8), e k,j represents the relatve contrbuton of the envronmental burden B j to mpact E k, and E k represents the mpact functon. Take the global warmng potental (GWP) as an example, b j,n s the coeffcent of transferrng mass rate of emsson to CO 2 equvalent wth lnear characterstc, and e k,j s the 20

36 coeffcent of transferrng CO 2 equvalent to global warmng potental wth lnear characterstc. Stefans, Lvngston, and Pstkopoulos (1997) presented a methodology for ncorporatng envronmental consderatons n the optmal desgn and schedulng of batch processes. Stefans, S. K., (1995,1996) and Pstkopoulos, E. N. (1998) presented methods for mnmzng the envronmental mpact (MEIM) of process systems by embeddng LCA prncples wthn a formal process optmzaton framework. Process-based LCA method s commonly used for specfc processes whch have detaled and accurate process flow data for lfe cycle nventory. Snce the lfe cycle nventory has a lnear characterstc for mass and energy balances, lnear programmng model and optmzaton method are used as a tool for process-based LCA. Gullen- Gosalbez, G. and Grossmann I.E. (2009), and You, F. and Grossmann, I.E. (2009) perform studes on the uncertanty of supply chans from an LCI perspectve n chemcal ndustry. In addton, varous applcatons of optmzaton-based approaches exst n chemcal engneerng process synthess supply, such as heat-exchanger network synthess, dstllaton sequencng, mass exchanger networks and reactor network synthess Economc Input Output LCA Economc nput-output model was developed by Leontef, W. (1970), who won the Nobel Prze for ts development n The model utlzes economc transacton data from ndustry sectors to explore the economc relatonshps among them. In the EIO model, the producton economy s dvded nto sectors and represented as a table or 21

37 matrx nvolvng ndvdual economc sectors. Table 2.1 s an example of the nput-output transacton table representng purchase flow between sectors. Table 2.1: Input-Output Table of a Natonal Economy (n physcal unts) (Leontef, W., 1970), Into From Sector 1 Agrculture Sector 2 Manufacture Sector 1 Agrculture Sector 2 Manufacture Households Total Output 100 bushels of wheat 50 yards of cloth In order to examne the envronmental mpact based on the economc actvty of a product, researchers at Carnege Mellon Unversty developed an EIO-LCA model (Hendrckson, C., 1998) to combne envronmental nformaton and economc nput output data for envronmental lfe cycle assessment. EIO-LCA can trace out the emssons of other related processes such as transportaton and manufacturng throughout the supply chan. X drect supplers = ( I + D) F...(1) X = ( I + D + DD + DDD +...) F...(2) X = ( I D) 1 B = R X = R ( I D) F...(3) 1 F...(4) X s the drect suppler process nputs vector and can be obtaned from Equaton (1). I s an dentty matrx. D s a drect requrements matrx, and F s a desred output vector. In Equaton (2), X takes all suppler nput levels nto account. In Equaton (4), B s 22

38 a vector of envronmental output. denotes the type of envronmental burden, and R s a matrx that has dagonal elements representng the envronmental mpact per dollar of output for each process. Snce R s a gven coeffcent from dollar value, the model s lnear related wth nput X and output B. Knowng R, B can be obtaned from Equaton (4) Comparson of Process-Based wth EIO-LCA Models The EIO-LCA model evaluates the mpact for an ndustry sector, whch contans several ndustry types. However, the sectoral aggregaton of EIO-LCA s not adequate to model a specfc ndustral manufacturer. On the other hand, the major lmtaton for Process-Based LCA s the lack of detaled and accurate process data. Table 2.2 shows the advantages and dsadvantages between process-based LCA and EIO-LCA (Hendrckson, C., 2006). Table 2.2 Process-Based LCA Verses EIO-LCA Method Advantages Dsadvantages Process-based LCA method Detaled and process specfc results Specfc product comparsons Process mprovements Tme ntensve for LCI Usng confdental or propretary data Data avalablty for envronmental mpact Economc Input-output LCA method Comprehensve assessments for economc usage Systems-level comparsons Results publcly avalable Economc boundares Dffcult for process assessments Uses aggregated data Data avalablty for envronmental mpact Tmelness of ndustral structure 23

39 2.2.5 Lfe Cycle Assessment for Envronmental Decson Makng Lfe cycle assessment s used wdely as a tool for envronmental mprovement, strategc plannng, publc polcy makng, and decson support. There are manly two applcatons (Mettnen, P., 1997): publc and corporate. The publc applcatons are focused on polcy makng, for example, to support the development of envronmental regulaton and legslaton. On the other hand, corporatons use LCA to analyze products lfe cycle and to support marketng clams around the envronmental performance of products. From the survey (Smth, J.C., 2006), LCA s commonly used to support busness strategy (18%) and research and development (18%), for product or process desgn (15%), for academa (13%), and for product declaratons or labelng (11%). 2.3 Lfe Cycle Assessment Tools Many ndustres and companes have appled the LCA approach to optmze and mprove resource management, whch leads to a more effcent use of energy and materals. Therefore, LCA s used for comparng dfferent optons and as a support tool n decson makng. Ths has led to an ncreased effort to develop lfe cycle assessment tools. Accordng to the evaluaton of lfe cycle assessment tools fnal report by Menke, D.M (1996), 37 lfe cycle assessment tools exsted n LCA software tools have broad applcatons n dfferent areas. For nstance, the tools are desgned for many ndustres such as plastc materals, buldng materals and food ndustry. In addton, as the growth of computer engneerng, the graphc user nterface (GUI) makes the tools easer to use and can present the results clearly. The crtera for evaluatng the LCA tools are: hghly detaled and representatve lfe cycle nventory, mpact assessment 24

40 capabltes and flexblty, and extent of use wthn ndustry. There are manly two groups who use the LCA software: researchers and busness users. Researchers and scentsts have hgh expectatons for LCA tools, because they have a good understandng of the features of the LCA method and need to create ther own data to model and compare dfferent complex systems. On the other hand, the busness users apply LCA tool to mprove ther envronmental performance, product development, and process optmzaton. Therefore, analyzng and presentng results and the easy-to-use feature are mportant for decson makers. The prmary advanced LCA tools used by both researchers and ndustry are GaB 4, SmaPro and TEAM. These are dscussed n more detal below. GaB s the popular LCA software developed by PE Internatonal n Germany. GaB has hghly sophstcated functons and frendly user nterface, whch makes t useful for quckly analyzng data-ntensve and complex systems for envronmental lfe cycle assessment. GaB 4 has the functon of lfe cycle assessment (LCA), lfe cycle engneerng (LCE), desgn for envronment (DfE), energy effcency/benchmark studes, strategc rsk management, and carbon footprnts. Fgure 2.8 shows the GaB database manager, and Fgure 2.9 shows the nput of varables of a flow. To desgn the LCA model of a process or a system n the GaB 4, plans, processes, flows, parameters, unts, and quanttes are created and nput n the tool. After fnshng modelng, the balance of energy and materal flow can be calculated and assessed by mpact. The tool also can create multple scenaros to compare mpacts of dfferent condtons. The database of GaB s large and manly for the use of product manufacturng and specfcally the car ndustry. The clents of GaB are dvded nto three groups: ndustry, unversty, and 25

41 government. GaB has more than 150 users such as Mercedes Benz AG, DuPont, General Motors, Motorola, Noka, Semens and Tmberland (GaB, 2009). Fgure 2.8: GaB Database Manager (GaB 4, 2006) 26

42 Fgure 2.9: Varables of a Flow n GaB 4 (GaB 4, 2006) SmaPro 7 s a lfe cycle tool to collect, analyze, and montor the envronmental performance of products and servces developed by Pre Consultants. SmaPro 7 offers ultmate flexblty of accessng to and unrestrcted edtng of dfferent database fles, parameterzed modelng, nteractve results analyss and a large ncluded database. Valuable features of SmaPro 7 are the ablty to lnk database entres and access to numerc and vsual ndcatons of mpact for each stage, process, and materal n a product lfe cycle. Lmtatons of SmaPro 7 are the lack of senstvty analyss and the 27

43 graphcal user nterface for system development. SmaPro 7 has more than 300 users such as Phlps and ABB (SmaPro, 2009). Tool for Envronmental Analyss and Management, TEAM, s a flexble and powerful lfe cycle assessment software tool developed by the Ecoblan Group n Pars, France. TEAM s a powerful tool used to comple lfe cycle nventores usng dfferent data, ncludng your own data and perform senstvty analyss. Lmtatons of TEAM are the lack of support for user-defned weghtng factors for mpact assessment and the comparson of results capabltes. TEAM has sophstcated functonalty and a large database. TEAM has more than 100 users such as BMW (TEAM, 2008). Buldng for Economc and Envronmental Sustanablty (BEES) tool s developed from the Natonal Insttute of Standards and Technology s (NIST) BEES program. The BEES model s a publcly avalable software tool for buldng desgners, archtects, and specfers. The BEES model takes a lfe cycle approach to buldng materals and focus on both lfe cycle envronmental and cost data. The BEES model s based on consensus standards ncludng: Lfe-Cycle Costng (ASTM E917), Buldng Element Classfcaton (ASTM E1557), Envronmental Lfe-Cycle Assessment (ISO 14040), and Mult-Attrbute Decson Analyss (ASTM E1765). Fgure 2.10 shows the steps to derve the BEES overall performance score. A total of 23 buldng elements are represented n BEES 3.0, wth 118 generc products and 80 brand-specfc products from 14 companes (Revew of BEES). The lmtatons of the BEES are the tool only compares the performance of buldng products, not permts comparatve analyss of entre buldng components assembles and ultmately entre buldngs. And the BEES overall performance scores do not represent absolute performance. Fgure 2.11 shows the user 28

44 nterface of settng BEES analyss parameters. The BEES tool s a software program especally valuable for selectng envronmentally frendly buldng products. The database ncludes actual envronmental and economc performance data for 230 buldng products. Up to now, over 22,000 copes of BEES 3.0 requested by ndvduals from more than 80 countres (BEES, 2002). Fgure 2.10: Dervng the BEES Overall Performance Score (BEES, 2002) 29

45 Fgure 2.11: Settng BEES Analyss Parameters (Lppat, B. C., 2001) Table 2.3 shows a comparson of dfferent LCA tools. The dscussed LCA tools have advantages at user nterface and graphcally presentng the data. The weakness for all exstng LCA tools s that lack nformaton for detaled process desgn. 30

46 Table 2.3: Comparson of Major LCA Tools GaB SmaPro TEAM BEES Doman Manufacturng, Transportaton Energy, Transportaton, Packagng Materals Chemcals and Plastcs Buldng Materals LCI Extensve, Hgh-Qualty GaB Databases Detaled Inventory Prmarly European Data Propretary Informaton LCIA Methods No Eco-Indcator 99 EPS 2000,and CML IPPC, CML, and Eco-99 TRACI Useablty User frendly Careful study of examples s needed Steep Learnng Curve Easy to Use 2.4 Lfe Cycle Assessment Databases LCA analyss s data ntensve. The demand for LCA databases has ncreased rapdly n a short amount of tme. The qualty and accuracy of the LCA based nformaton play a sgnfcant role n the study of LCA. The content of database ncludes whch economc sectors to cover, whch pollutants are measured. These contents should be consstent as well, for example, they should have the same boundares and modelng prncples. Data n the database should be representatve LCI data, up-to-date, clearly defned, and from a relable source. Last, but not the least, the format of data and f data s exportable are mportant to users. Generally, the LCI databases are dvded nto two areas: comprehensve commercal databases such as Econvent, GaB, and publc LCI 31

47 databases ncludng U.S. lfe cycle nventory databases, European reference lfe cycle data system. A lst of the well-known exstng lfe cycle nventory databases s shown as follows: 1. The Econvent database s generated by Swss Center contans up-to-date and consstent lfe cycle nventory data for more than 2700 ndustral processes on materal supply, resource extracton, energy, chemcals, metals, agrculture, waste management servces, and transport servces (Hscher R., 2002 and Frschknecht, R., 2004)). The Econvent database s used by more than 1500 users n more than 40 countres worldwde and s ncluded n varous eco-desgn tools for product desgn, buldng, and constructon. Man characterstcs of the database are ts relable coherent set of LCI data and transparency n reportng to enable ndvdual assessment of data approprateness. In addton, the Econvent database s an onlne database wth nterlnked data whch has full access to unt process data and rolled-up data and s open for nternatonal collaboraton. 2. The GaB U.S. Extenson Database has over 500 cradle-to-gate nventores for energy supples, commonly used materals, and transportaton systems. Ths s the largest LCI database avalable on the market focused on LCI nformaton n the U.S. The database ncludes over 200 cradle-to-gate datasets based on the U.S. LCI database. In addton, the U.S. LCI Basc Database from GaB s a free database that contans over 180 products and processes gate-to-gate nventores (Spatarb, S., 2001). 3. Natonal renewable energy laboratory (NREL) provdes the U.S. lfe cycle nventory database for researchers to study n the format of Excel. The NREL database s generated from a publc/prvate partnershp. In the begnnng, Athena Insttute started a buldng LCI project n Canada n 1990s, whch caught the U.S. DOE s attenton. Later n 32

48 2001, DOE and Athena ntated the U.S. LCI Database project at NREL. The NREL LCI Database has been avalable snce 2003 (NREL, 2004). The non-government organzatons nvolved n the NREL database are Athena Insttute, Frankln Assocates, Sylvatca, CORRIM, Vehcle Recyclng Partnershp, Amercan Plastcs Councl, Portland Cement Assocaton, Amercan Center for Lfe Cycle Assessment, USGBC, and others. Also, the nvolved government organzatons are DOE, GSA, USDA, EPA, NIST, and the Navy. In addton, government mantans the database and provdes common data and ndustry support wth LCI data and some fundng to develop the publcly avalable LCI database for commonly used materals, products, and processes. The common processes are standard transformaton processes (stampng, pressng, pantng, and other operatons), electrcty generaton, transportaton, and energy pre-combuston. 4. The EIO-LCA database nvolves of aggregate sector-level data quantfyng how much envronmental mpact can be drectly attrbuted to each sector of the economy and how much each sector purchases from other sectors n producng ts output. The data n the database are n the format of dollar per physcal unts. The economc nput-output tables n the EIO-LCA database are typcally produced by natonal governments. In the begnnng, the EIO-LCA database was based on the 1992 benchmark nput-output (IO) commodty tables from the Department of Census, Bureau of Economc Analyss. In addton, natonal-level data on materal or energy resources consumed by ndustry sectors, and data on ndustry releases to the envronment are ncluded n the database to estmate lfe cycle mpacts (Carnege Mellon Unversty Green Desgn Insttute, 2008). Table 2.4 shows the advantages and dsadvantages for dfferent LCI databases. 33

49 Table 2.4: Advantages and Dsadvantages for Dfferent LCI Databases Database Advantages Dsadvantages Econvent Databases -Interlnked database -Transparent and consstent -Wde breadth of data -User frendly nterface -Data n XML format GaB Database NREL Database U.S. EIOLCA Database -Wde breadth of data -Dsaggregated unt process data -Peer-revewed, publcly avalable LCI data -U.S. LCI database -Industry averages -Data n Excel format -Free and fast -Monetary data -Industry sector data -Requres purchase of LCA modelng tool -Process data not compatble wth certan modelng tools -Requres purchase of LCA modelng tool -Process data not compatble wth certan modelng tools -Process data not compatble wth certan modelng tools -Not compatble wth certan modelng tools -Product assessments contan aggregate data Further work on the LCI database may comprse work on the LCI modelng methodology, the database content, for example, new or more detaled nformaton covered n economc sectors, and the structure and features of the database system. Furthermore, buldng up nternatonal co-operatons n LCI data collecton and supply s the focus of future LCI database actvtes. 34

50 CHAPTER 3 LIFE CYCLE STUDIES FOR CARPET SYSTEM 3.1 Carpet Lfe Cycle The Unted States has the largest carpet ndustry n the world. The lfe cycle of a carpet accounts for every mpact on the envronment from the day the carpet s made untl the end of lfe when t s dsposed of or recycled. A carpet s lfe cycle mpact nclude chemcal emssons from manufacturng, depleton of petroleum and other natural resources, transportaton, ndoor ar qualty concerns, and dsposal at landflls and recyclng processes. A carpet lfe cycle conssts of four basc stages: carpet manufacturng, transportaton and nstallaton, use phase, and dsposal or recyclng. Each stage plays an mportant role n a carpet's lfe cycle. Most carpet n use today s made from petroleum based fbers such as nylon, polyester, and polypropylene, whose manufacturng often can contrbute to greenhouse gas emssons. Moreover, the economcally sgnfcant component n carpet products s nylon fbers, whch are also envronmentally sgnfcant n the lfe cycles of carpet products. Several alternatve green fbers exst such as recycled nylon and recycled P.E.T. polyester. Renewable resources also can be accounted for envronmental frendly n the manufacturng phase. Lke carpet fbers, carpet backng also can be made of recycled content and/or sustanable resources. In the phase of transportaton, the majorty of the carpet s manufactured n the U.S. n Dalton, Georga, a town known as the "Carpet Captal of the World." Most of the carpet s transported to ts destnatons by the use of trucks n the U.S. In terms of transportaton, 35

51 carpet tends to have a much lower carbon footprnt than floor coverngs lke bamboo, because the carpet s sgnfcantly lghter than most other types of floorng whch consumes less fuel. The use phase for offce buldng carpets s not dstnctly dfferent based on the constructon: carpets tend to be cleaned on a perodc schedule over the lfe, and replaced after a certan tme perod rrespectve of the wear. However, there has been heghtened nterest n recyclng of carpet n recent years, drven by a mult-stakeholder agreement between the carpet ndustry and varous government and non-government organzatons (NGOs). They sgned a memorandum of understandng for carpet stewardshp (MOU), a ten-year schedule to ncrease recyclng carpet and reduce carpet to landflls. Hence, one objectve s to ensure that the recyclng of carpet s benefcal from a lfe cycle perspectve compared to usng vrgn raw materals. 3.2 Carpet Manufacturng Most carpet manufactured n the U.S. s made of synthetc materals, especally nylon, polyester, and polypropylene face fbers. A large number of backngs are made as a sandwch of polypropylene fabrc and latex or PVC. Nearly all commercal carpets are made by bondng a face fber to a backng fber. Nylon 6 and nylon 6.6 account for nearly two-thrds of the face fber market, wth polyester as the next most commonly used fber. 95% of carpet has a tufted structure shows n Fgure 3.1. Based on the structure and composton of carpet tle product, a carpet tle s composed of three layers: fber, prmary backng, and secondary backng. Nylon s the most popular fber for commercal carpet because t s easy to clean and has a better stan-resstance. The backng s used to keep the tufts n place and has three elements: a prmary backng, an adhesve, and a secondary backng. 36

52 Fgure 3.1: General Carpet Structure Most carpet s made wth unsustanable or non renewable resources such as petroleum. Several types of offce carpet materals and structure constructon are exsted. In ths thess, we focus on one specfc constructon, a tle, and a specfc sute of materals used by a manufacturer, Shaw Industres, to produce EcoWorx TM, whose ntal desgn phlosophy and constructon was presented by Segars, J.W. (2003). Commercal tles have three man components of an archtecture, face fber, prmary backng fabrc, and secondary backng. The secondary backng s often composed of a sandwch of two polymer layers and a layer of glass fber. The polymer layers are often heavly flled wth an norganc materal to reduce the use of expensve polymer and provde mechancal 37