LIFE CYCLE ASSESSMENT OF PRECAST CONCRETE BELOWGROUND INFRASTRUCTURE PRODUCTS. Final Report

Transcription

1 LIFE CYCLE ASSESSMENT OF PRECAST CONCRETE BELOWGROUND INFRASTRUCTURE PRODUCTS Final Report Presented to the Precast/Prestressed Concrete Institute, the Canadian Precast/Prestressed Concrete Institute, and the National Precast Concrete Association This report has been prepared by Morrison Hershfield, the Athena Institute, and Venta, Glaser & Associates. May 11, 2010

2 TABLE OF CONTENTS Executive Summary...v List of Tables... vii List of Figures... viii 1. Introduction Life Cycle Assessment Results disclosed to the public Goal and Scope of the Study Functional Unit System Boundary, Cut-Off Criteria, and Allocation Rules System Boundary Cut-off Criteria Data Sources U.S. LCI Database Portland Cement Association (PCA) surveys and reports Precast concrete Steel LCI data Product transportation On-site construction effects Waste treatment and end-of-life management Primary Data Collection from Precast Concrete Plants Precast concrete participating plants Primary data collection system for the precast concrete plants LCI Model of The Underground Infrastructure Products Life Cycle Impact Assessment Indicators and Methodologies Co-Product Allocation Co-Product Allocation Rules in General Background data (energy, electricity and transportation): U.S. LCI Database Precast concrete products Ecoinvent dataset adjusted to North America Co-Product Allocation Rules for Comparative Commodities Steel Data Quality Requirements...23 ii

3 6.1. Precision and Completeness Consistency and Reproducibility Representativeness Life Cycle Impact Assessment Results Cradle-to-Gate LCIA Results for Precast Concrete Used in Belowground Infrastructure Products LCIA Results For Belowground Infrastructure Products Life Cycle Interpretation Process Contribution Analysis for the Cradle-to-Installation Belowground Infrastructure Products Process Contribution Analysis for the Cradle-to-Grave Belowground Infrastructure Products Influence Analysis for Precast Concrete Used in Belowground Infrastructure Products Sensitivity Analysis for Precast Concrete Used in Belowground Infrastructure Products Conclusion Critical Review Conclusion of the Study Critical Review...42 Acknowledements...43 References...44 Acronyms and Abbreviations...46 Synopsis...48 Keywords...48 About the Authors...48 Appendix A: Description of Belowground Infrastructure Products...A2 Appendix B: Concrete Mix Designs...A8 Appendix C: Precast Concrete Plant Survey Results...A10 Appendix D: Material Quantity Take-Offs...A13 Appendix E: Cradle-to-Gate Life Cycle Impact Assessment (LCIA) Results for Precast Concrete Unit Volume Basis...A15 Appendix F: Cradle-to-Grave Life Cycle Impact Assessment (LCIA) Results for Precast Concrete Products Absolute Basis and Relative Basis...A17 Appendix G: Sensitivity Analysis and Influence Analysis...A22 Appendix H: Cradle-to-Installation Life Cycle Impact Assessment (LCIA) Profiles for Precast Concrete Products Absolute Basis and Relative Basis...A24 iii

4 Appendix I: Breakdown of End-of-Life LCIA Profiles...A33 Appendix J: Data Quality...A42 Appendix K: Data Sources...A45 iv

5 EXECUTIVE SUMMARY In order to better understand precast concrete's environmental performance in the context of belowground infrastructure products, a life cycle assessment (LCA) of four typical belowground infrastructure products has been conducted. Life cycle assessment is an analytical tool used to comprehensively quantify and interpret the energy and material flows to and from the environment over the entire life cycle of a product, process, or service. This study consists of a cradle-to-grave LCA study of four belowground precast concrete products. Belowground products in this study refer to structures for providing services related to drainage, electric utility equipment, residential septic systems, and municipal sewer systems. Each of the four belowground products are modeled separately: manhole, septic tank, utility structure, and pipe. The LCA does not compare the belowground products to alternative products. The infrastructure products in this study are analyzed using the same functional unit and equivalent methodological considerations, such as performance, system boundary, data quality, allocation procedures, decision rules for evaluating inputs and outputs, and completion of the impact assessment. Since the LCA includes results intended to be disclosed to the public, an independent external committee of LCA and technical experts critically and concurrently reviewed the methodology and results. The functional unit is the products themselves and not the services they provide. The study system boundary includes the inputs and outputs of energy and material from cradle-toinstallation, demolition, and disposal. Transporting materials to and from the construction site is also included. But the actual use phase of the products (the service the products provide) is excluded from the assessment. The life cycle inventory (LCI) data are from a combination of primary sources (survey of cement, concrete, and precast concrete plants) and secondary sources (U.S. LCI Database, World Steel Association, Ecoinvent LCI Database, Athena Database, and the American Chemistry Council). The LCI and LCA modeling software used in the project is SimaPro version Each product is modeled independently from cradle-to-grave. The environmental impact categories and assessment methods are the mid-point indicators from the U.S. EPA Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI). The methodologies underlying TRACI reflect state-of-the-art developments and best available practice for life-cycle impact assessment (LCIA) in the United States. The goal of this study is to better understand precast concrete s environmental life cycle performance in belowground infrastructure products by applying the ISO LCA Standards, ISO 14040:2006 and 14044:2006. The interpretation phase should deliver results that are consistent with the defined goal and scope and explain limitations and provide recommendations. North American LCI datasets in the U.S. LCI Database do not provide data uncertainty; therefore, the LCA team could not conduct an overall quantitative uncertainty analysis of the v

6 results. Instead we have provided a qualitative analysis in Section 6 and a Data Quality Matrix in Appendix J to qualitatively cover the data uncertainty aspects of the study. The cradle-to-installation LCIA results for the four infrastructure products vary considerably across the four products. Across the four products the total primary energy ranges between 6.8 to 24.6 GJ and the global warming potential varies from less than 0.7 up to 2.3 metric tons of C0 2 - equivalent. Total primary energy use is comprised almost entirely of non-renewable fossil fuels and the impact indicators relative order of magnitude mirror primary energy use. Further, there is a strong proportional relationship between a product s concrete use and the resulting LCIA values. From cradle-to-installation and from cradle-to-grave, most of the environmental impacts are associated with precast concrete as it exits the precast concrete plant including the upstream profiles of materials that go into making precast concrete, such as portland cement, and the precast plant operations themselves. Of these, precast plant operations only contribute 16% of the global warming impact and 27% of the primary energy use. From cradle-to-installation precast concrete as it exits the precast concrete plant is responsible for 47 to 61% of the primary energy use and 60 to 71% of the global warming potential. From cradle-to-grave precast concrete as it exits the precast concrete plant is responsible for 42 to 49% of the primary energy use and 55 to 61% of the global warming potential. of the finished product as it exits the precast concrete plant gate to the construction site is responsible for approximately 20% of the environmental impacts associated with global warming, acidification, eutrophication, photochemical smog, and primary energy use. vi

7 LIST OF TABLES Table 1. Main Data Sources...8 Table 2. Concrete Mix Designs and Properties (U.S. Customary Units)...10 Table 3. Constitute Elements of the Underground Infrastructure Product Assembly...14 Table 4. Impact Categories in Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI)...15 Table 5. Selected Impact Indicators...17 Table 6. Cradle-to-Gate LCIA Results for Precast Concrete Used in Belowground Infrastructure Products...25 Table 7. Cradle-to-Grave LCIA Results for Four Belowground Infrastructure Products Absolute Basis...26 Table 8. Cradle-to-Installation LCIA Contribution Analyses of Major Materials and Processes for Manhole Absolute Results...28 Table 9. Cradle-to-Installation LCIA Contribution Analyses of Major Materials and Processes for Septic Tank. Absolute Results...30 Table 10 Cradle-to-Installation LCIA Contribution Analyses of Major Materials and Processes for Utility Structure Absolute Results...32 Table 11. Cradle-to-Installation LCIA Contribution Analyses of Major Materials and Processes for Pipe Absolute Results...34 Table 12. Cradle-to-Grave LCIA Contribution Analyses of Major Materials and Processes for Utility Structure Absolute Results...36 Table 13. Cradle-to-Grave LCIA Contribution Analyses of Major Materials and Processes for Utility Structure. Percentage Results...37 Table 14. EOL LCIA Contribution Analyses of Major Materials and Processes for Utility Structure. Absolute Results...38 Table 15. EOL LCIA Contribution Analyses of Major Materials and Processes for Utility Structure. Percentage...39 Table 16. LCIA Influence Analysis for the Precast Concrete Used in Belowground Infrastructure Product...40 Table 17. Primary Energy Use and Global Warming Potential Sensitivity Analyses (Sensitivity Parameter: 10% Reduction of the Cement Use)...41 vii

8 LIST OF FIGURES Figure 1. The four stages of life cycle assessment are an iterative process: the results of each phase can influence the phases that come before and after....2 Figure 2. The system boundary of the underground infrastructure products defines the limits of the life cycle assessment....5 Figure 3. The system boundary of precast concrete production plant defines the unit processes included in the product system (this system boundary is a subset of the building system boundary in Fig. 2 and is included as the upstream profile of concrete and other portland cement-based materials)....6 Figure 4. Simplification of the LCA process by aggregating manufacturing and end of life information on scrap Figure 5. Cradle-to-installation LCIA contribution analyses of major materials and processes for manhole percentage results...29 Figure 6. Cradle-to-installation LCIA contribution analyses of major materials and processes for septic tank percentage results...31 Figure 7. Cradle-to-installation LCIA contribution analyses of major materials and processes for utility structure percentage results...33 Figure 8. Cradle-to-installation LCIA contribution analyses of major materials and processes for pipe percentage results...35 viii

9 LIFE CYCLE ASSESSMENT OF PRECAST CONCRETE BELOWGROUND INFRASTRUCTURE PRODUCTS By Medgar L. Marceau, Jamie K. Meil, Lindita Bushi, Wayne B. Trusty, Mark Lucuik, George J. Venta, and Matt Bowick 1. INTRODUCTION In order to better understand precast concrete's environmental performance in the context of belowground infrastructure products, a life cycle assessment (LCA) of four typical belowground infrastructure products has been conducted. This cradle-to-grave * LCA study has been completed over a period of approximately one year: for the study team the project began in February 2009, and the final report was submitted in May This LCA does not include comparative assertions; however, it may lead to future studies with comparative assertions disclosed to the public. Therefore, an independent external committee of LCA and technical experts critically and concurrently reviewed the methodology and results Life Cycle Assessment Life cycle assessment is an analytical tool used to comprehensively quantify and interpret the energy and material flows to and from the environment over the entire life cycle of a product, process, or service. 1 Environmental flows include emissions to air, land, and water, as well as the consumption of energy and material resources. By including the impacts throughout the product life cycle, LCA provides a comprehensive view of the environmental aspects of the product and a more accurate picture of the true environmental trade-offs in product selection. Two international standards, ISO 14040:2006 and ISO 14044:2006, describe an iterative four-stage or phased methodology framework for completing an LCA, as shown in Fig. 1: (1) goal and scope definition, (2) life cycle inventory, (3) life cycle impact assessment, and (4) interpretation. 1, 2 An LCA starts with an explicit statement of the goal and scope of the study; the functional unit; the system boundaries; the assumptions and limitations; the allocation methods used, and the impact categories chosen. The goal and scope includes a definition of the context of the study, which explains how and to whom the results are to be communicated. The ISO standards require that the goal and scope of an LCA be clearly defined and consistent with the intended application. The functional unit defines what is being studied. The purpose of the functional unit is to quantify the service delivered by the product system and provide a reference to which the inputs and outputs can be related. Allocation is the method used to partition the environmental load of a process when several products or functions share the same process. * A "cradle-to-grave" assessment considers impacts at each stage of a product's life-cycle, from the time natural resources are extracted from the ground and processed through each subsequent stage of manufacturing, transportation, product use, recycling, and ultimately, disposal (Source: 1

10 Life cycle assessment framework Goal and scope definition Inventory analysis Interpretation Direct application: Product development and improvement Strategic planning Public policy making Marketing Other Impact assessment Figure 1. The four stages of life cycle assessment are an iterative process: the results of each phase can influence the phases that come before and after. In inventory analysis a flow model of the technical system is constructed using data on inputs and outputs. The flow model is often illustrated with a flow chart that includes the activities that are going to be assessed and gives a clear picture of the technical system boundary. The input and output data needed for the construction of the model are collected (such as materials and energy flows, emissions to air and water, and waste generation) for all activities within the system boundary. Then, the environmental loads of the defined system are calculated and related back to the functional unit and the flow model is finished. Inventory analysis is followed by impact assessment, where the life cycle inventory (LCI) data are characterized in terms of their potential environmental impacts; for example, resulting in acidification, ozone depletion, and global warming. The impact assessment phase of LCA is aimed at evaluating the significance of potential environmental impacts based on the LCI flow results. Classical life cycle impact assessment (LCIA) consists of the following mandatory elements: selection of impact categories, category indicators, and characterization models; and continues with the classification stage, where the inventory parameters are sorted and assigned to specific impact categories. The categorized LCI flows are then characterized using one of many possible LCIA methodologies into common equivalence units and then are summed to provide an overall impact category total. This equivalency conversion is based on characterization factors as prescribed by the selected LCIA methodology. In many LCAs, characterization concludes the LCIA analysis; this is also the last compulsory stage according to ISO 14044: However, in addition to the mandatory LCIA elements (selection, classification, and characterization), other optional LCIA elements (normalization, 2

11 grouping, and weighting) may be conducted depending on the goal and scope of the LCA study. In normalization, the results of the impact categories from the study are usually compared with the total impact in the region of interest. Grouping consists of sorting and possibly ranking of the impact categories. During weighting, the different environmental impacts are weighted against each other to get a single number for the total environmental impact As per ISO 14044:2006, weighting, shall not be used in LCA studies intended to be used in comparative assertions intended to be disclosed to the public. Since, this is a comparative assertion study, weighting and other optional LCIA elements are excluded to be consistent with the goal and scope of this LCA study and the ISO 14044:2006 protocol. The results from the inventory analysis and impact assessment are summarized during the interpretation phase. The outcome of the interpretation is conclusions and recommendations of the study. According to ISO 14040:2006 the interpretation should include: Identification of significant issues based on the results of the LCI and LCIA phases of LCA; Evaluation of the study considering completeness, sensitivity, and consistency checks; and Conclusions, limitations and recommendations. The working procedure of LCA is iterative as illustrated by the back-and-forth arrows in Fig. 1. The iteration means that information gathered in a latter stage can cause effects in a former stage. When this occurs, the former stage and the following stages have to be reworked taking into account the new information. At the end, the results and conclusions of the LCA will be completely and accurately reported to the intended audience. The data, methods, assumptions, limitations, and results will be transparent and presented in sufficient detail to allow the interested parties to comprehend the complexities and trade-offs inherent in the LCA. The report will also allow the results and interpretation to be used in a manner consistent with the goals of the study Results disclosed to the public. Per the ISO referenced standards, specific requirements are applied to an LCA that makes comparative assertions that are intended to be disclosed to the public. Given that the products in this LCA are not compared to competing products, a critical review is not required. However, this LCA may lead to future comparative studies intended to be disclosed to the public and a critical review was performed in conjunction with another PCI LCA study that did require critical review. The infrastructure products in this study are analyzed using the same functional unit and equivalent methodological considerations, such as performance, system boundary, data quality, allocation procedures, decision rules for evaluating inputs and outputs, and completion of the impact assessment Goal and Scope of the Study The goal of this project is to better understand precast concrete s environmental life cycle performance relative to the life cycle performance of belowground infrastructure precast concrete products by applying and following the ISO 14040:2006 and 14044:

12 There are two possible approaches to LCA 1. This study uses an attributional approach, where average industry data is employed throughout the value chain. In the attributional approach, the elementary flows and potential environmental impacts are assigned to a specific product system typically as an account of the history of the product. This differs from the consequential method, which seeks to model a cause-and-effect chain by using marginal data in the value chain. The reason for doing this work is to disseminate information on the LCAs of precast concrete products that are based on the most complete and up-to-date life cycle inventory data for cement and concrete products. The intended audience is architectural, engineering, specifying professionals, academia, governmental organizations, and other interested parties who require reliable information on sustainable building design practices. The scope of the LCA is defined by the function of belowground precast concrete products, the functional unit, and the system boundary including cut-of criteria and allocation rules. Belowground products in this study do not refer to building foundations (which are cast-in-place as an integral part of the building); but rather to structures for providing services related to drainage, electric utility equipment, residential septic systems, and municipal sewer systems. These belowground products are considered separately because they are not an essential part of building the same way the roof or structural systems are. This LCA study does not include comparing the belowground products to competing products Functional Unit The definition of the functional unit, which is the basis for comparison, is defined in ISO 14040:2006, 1 as the quantified performance of a product system for use as a reference unit. The functional unit of each belowground infrastructure product (manhole, septic tank, utility vault, and concrete pipe) is described in detail in Appendix A. According to the U.S. Army Corps of engineers concrete pipe has a service life of 70 to 100 years with most installations having a 100-year life. 4 In this study, the functional unit is one-piece typical precast concrete belowground infrastructure product (manhole, septic tank, utility vault, and concrete pipe) with the specifications as presented in Appendix A and the average service life of 100 years. 2. SYSTEM BOUNDARY, CUT-OFF CRITERIA, AND ALLOCATION RULES 2.1. System Boundary The system boundary is the interface between the product system under the study and the environment, and it determines which unit processes shall be included within the LCA. The system boundary in this work, shown in Fig. 2, includes the inputs and outputs of energy and material from construction, transportation, and maintenance over the life span of 100-years, demolition, and end-of-life (EOL) disposal. Transporting materials to and from the construction site is also included. As per communication with the sector specific U.S industry experts, no maintenance is performed on these products while they are in-service. For that reason, in this LCA study, the environmental load of maintenance phase is considered null. 4

13 Input materials and products: Cradle-to gate upstream profiles of materials and products: e.g. steel, aggregate, precast concrete Input energy supply: (e.g. electricity generation, fossil fuels pre-combustion, heat generation, etc.) of input materials, products, fuels, and waste Construction Maintenance End-of life waste disposal (recycling, landfill) Emissions to air, water, and soil included excluded Figure 2. The system boundary of the underground infrastructure products defines the limits of the life cycle assessment. The system boundary excludes the impact of capital goods manufacturing (such as bulldozers, dump trucks, and other construction machines), human labor, and impacts caused by people. The ISO standard 14044:2006, Clause , indicate that inputs to a product or process do not need to be included in an LCI if (1) they do not represent a significant fraction of the total mass of processed materials or product, (2) they do not contribute significantly to an environmental impact category, and (3) they do not represent a significant amount of energy. This project also involves collecting data from precast concrete plants; therefore, the system boundary for precast concrete plants is also included. The precast concrete system boundary is shown in Fig. 3. It is a subset of the underground infrastructure products boundary in Fig. 2 and is included as the upstream profile of precast concrete. It is chosen to include cement manufacture; aggregate production; transportation of fuel, cement, supplementary cementitious materials (fly ash), and aggregates to the plant; and plant operation, which includes forming, reinforcement, and curing processes. The upstream profiles of portland cement and aggregates are imported into the concrete system boundary. The energy used to heat, cool, and light plant buildings is included in plant operations. The upstream profiles of fuels and electricity are imported into the system boundary. 5

14 Cement manufacture Aggregate production Fly ash transportation Handling and storage Handling and storage Electricity generation Fossil fuels pre-combustion Plant operations Plant waste disposal Emissions to air, water, and soil Admixtures production Reinforcing production Mixer wash-out/off Precast plant Water to construction site Process included Process excluded Cradle-to-gate (precast concrete plant exit gate) system boundary Figure 3. The system boundary of precast concrete production plant defines the unit processes included in the product system (this system boundary is a subset of the building system boundary in Fig. 2 and is included as the upstream profile of concrete and other portland cement-based materials). Precast concrete operations generally offer economies of scale and a high level of quality control. Precast concrete components for walls, columns, floors, roofs, facades, pipe, utility vaults, manholes, septic tanks and other applications are made by placing concrete and steel reinforcement into forms at the plant and curing the product. Production procedures vary between the different categories of precast concrete products. These precast concrete components are usually made with conventional reinforcement in custom-made individual forms. These forms can be made of wood, fiberglass, concrete, or steel. Wood or fiberglass forms can generally be used 40 to 50 times without major maintenance while concrete and steel forms have practically unlimited service lives. Form-release agents are applied to forms prior to placing the concrete to prevent the concrete from sticking to the forms when they are removed. The steps in the precast production process include: (1) concrete mixing; (2) conveying to the form in ready mix trucks, specially designed transporters with a dumping mechanism that places the concrete in the form, or concrete buckets carried by overhead cranes; (3) placing the concrete in the form; (4) consolidation by vibration, leveling, and surface finishing; (5) curing; and (6) form stripping. Plant operations are described in greater detail below. The energy, materials, and emissions associated with construction of concrete plant equipment and buildings are not included in the LCI. The system boundary also excludes the creation of infrastructure, accidents, human resources, and environmental burdens caused by the work force. 6

15 Fly ash is a coal combustion by-product (waste generated from producing electricity and steam for industrial processes) that is used in concrete without transformation. Fly ash is generally captured from the chimneys of coal-fired power plants. Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO 2 ) (both amorphous and crystalline) and calcium oxide (CaO). Owing to its pozzolonic properties, fly ash is used as a replacement for some of the Portland cement content of concrete. In this LCA study, we are using generic datasets from the U.S. LCI Database for electricity and heat generation, transportation and other commodities. Current profiles from the U.S. LCI Database for electricity generation in the US do not take into account beneficial reuse of waste materials from coal combustion process (such as fly ash, bottom ash, boiler slag, and flue gas desulphurization materials); that is, 100% of the environmental load of coal combustion process is allocated to the electricity generation; therefore, to count the upstream environmental burden of fly ash (mass or economic allocation basis) would be double counting when electricity is also used in the product system. Therefore, the LCA only includes the burden of transporting the fly ash to the precast concrete plant gate Cut-off Criteria As per ISO series, the cut-off criteria includes the specification of the amount of material or energy flow or the level of environmental significance associated with unit processes or product system to be excluded from a study. The cut-off criteria for input flows to be considered within each system boundary are as follows: Mass all input flows that cumulatively contribute less than 1% of the total mass input of the product system being modeled can be excluded, providing its environmental relevance is minor. Energy all input flows that cumulatively contribute less than 1% of the total product system s energy inputs can be excluded, providing its environmental relevance is minor. Environmental relevance if an input flow meets the above two criteria but is determined (via secondary data analysis) to contribute 2 % or more to any product life cycle impact category (see below), it is included within the system boundary. Similar cut-off criteria may also be used to identify which outputs should be traced to the environment, for example, by including final waste treatment processes Data Sources The LCI data sources are shown in Table 1. Secondary data are drawn from the U.S. LCI Database, PCA reports, PCI surveys, World Steel Association, Ecoinvent LCI database, Athena Database, and the American Chemistry Council. This project draws on the latest North American LCI data for upstream processes related to various products and it consistently utilizes the U.S. LCI Database for pre-combustion and combustion LCI data for thermal, electricity, and transportation energy carriers. The American Chemistry Council s 2007 LCI data for plastic resins and precursors, as provided within the US LCI Database, are used to prepare the LCI of 7

16 petrochemical-based material. The World Steel Association and U.S. and Canadian Steel Industry Associations are the primary sources for steel LCI data. Cement LCI data were sourced from the Portland Cement Association (PCA) via their latest industry survey from Concrete and precast concrete products LCI data were obtained from surveys of precast concrete plants and data from PCA s 2007 LCI data for concrete and concrete products. Additional material and construction process LCI data is taken from Athena Institute proprietary LCI building material and construction database and third-party sources to model selected finish components and other ancillary materials. Table 1. Main Data Sources LCI input data Common primary fossil fuels (including pre-combustion Electricity generation and delivery Time frame Geographical representative ness 8 Technological representative ness North America Average 2007 North America Average Source U.S. LCI Database US LCI Database, IEA & DOE Primary or secondary data Secondary Secondary Cement US & Canada Average PCA Primary Precast concrete 2008 North America Average Steel products 2000; 2007 Raw material and final product transportation Worldwide; adjusted to North America Average 2004/2009 North America Average On-site construction 2000/2007 North America Average End-of Life 2000/2007 North America Average CPCI, NPCA, and PCI surveys World Steel Association; U.S and Canadian Steel Industry Association Surveys, US Census, Statistics Canada Athena Database Athena Database ICF 2005* Primary Secondary Primary, Secondary Primary, Secondary Secondary * Source: ICF Consulting Determination of the Impact of Waste Management Activities on Greenhouse Gas Emissions: 2005 Update. Final Report Contract No. K Submitted to: Environment Canada and Natural Resources Canada. All European Ecoinvent process data has been modified according to the following methodology: (1) all electricity and fuel combustion has been substituted with U.S. LCI Database process data, and (2) significant material contributions (by mass) to Ecoinvent processes have been substituted by U.S. LCI Database process data, and otherwise substituted by modified Ecoinvent material processes. Where available, regional data have been used. However, regional cement data are not available and therefore could not be used in this project. Average U.S cement data are used and deemed appropriate for this attributional LCA, which is based on average cement industry data.

17 The terminology used in the report is based on the following definitions: Data collection is the acquisition of quantitative and/or qualitative values of a property, either by measurement, estimation or calculation. Primary data are data determined by direct measurement, estimation or calculation from the original source (typically for process emissions). Secondary data are data collected from literature or other published media (typically for physical constants, carbon content of fuels, etc.) U.S. LCI Database. The U.S. LCI Database 5 contains LCI data on various types of fossil (hydrocarbon) fuels combusted in both industrial and utility boilers. These data also include LCI profiles for the upstream extraction, production, and transportation of the fuels what is typically referred to as pre-combustion effects. Fuels consumed by various transportation modes on a tonne-kilometer (t-km) basis are also included in the database. The database also includes electricity generation by various methods (coal, natural gas, petroleum, nuclear, hydroelectric, and renewables) on a US average, eastern grid, and western grid basis Portland Cement Association (PCA) surveys and reports. The 2007 PCA cement plant survey data are the basis for the cement LCI profile for the study. 3 These data have been augmented by data from the Toxic Release Inventory (U.S. TRI) and National Pollutant Release Inventory (Canadian NPRI) for reporting plants to capture additional process and combustion emissions to air and water in the production of cement. Additional PCA reports are used to determine/calculate other emissions and ancillary materials use in the production of cement Precast concrete. Primary production flow data have been collected from three U.S. precast plants producing belowground infrastructure products (pipes, manholes, utility vaults, and septic tanks). The data were not report for specific belowground precast concrete products but rather they were reported for the entire plant even though the plant produced multiple types of precast concrete product. The study team has prepared a weighted average manufacturing profile for the product class of below ground infrastructure product. The manufacturing flows present an average profile for precast products. The upstream manufacturing flows have been itemized for each product (cement, SCMs, coarse and fine aggregates, additives, etc.), and a generic weighted average manufacturing profile has been applied to each of the products of interest. The concrete mix designs and properties are shown in Table 2 (see also Appendix B). The study team acknowledges that the use of a generic weighted average manufacturing profile is a limitation of the study; however, as the study team anticipated, the results show that the precast concrete manufacturing unit process is a small contributor to the overall LCI profile of precast concrete products. The study includes a unit process contribution analysis to determine the significance of precast manufacturing, observations have been made as to the adequacy of this primary data, and where warranted recommendations for future data collection efforts have been made. 9

18 Table 2a. Concrete Mix Designs and Properties (U.S. Customary Units) Mix constituent and property, unit per yd 3 Belowground precast (unless noted otherwise) infrastructure products Portland cement, lb 564 Fly ash, lb 118 Fine aggregate, lb 1450 Coarse aggregate. Lb 1470 Mix water, lb 270 Water-reducing admixture, lb 2.0 Total (density), lb 3874 Total (density), lb/cu ft 143 Reinforcing steel bars (rebar), reinforcing wire (mesh), strands, lb 56 Mix property Water cementitious materials ratio 0.40 Cement substitution with SCM, % 17 Nominal compressive strength, psi 5000 Note: SCM = supplementary cementitious material. Table 2b. Concrete Mix Designs and Properties (SI Units) Mix constituents and property, unit per m 3 Belowground precast (unless noted otherwise) infrastructure products Portland cement, kg 335 Fly ash, kg 70 Fine aggregate, kg 860 Coarse aggregate. kg 872 Mix water, kg 160 Water-reducing admixture, kg 1.2 Total (density), kg 2298 Total (density), kg/cu ft 85 Reinforcing steel bars (rebar), reinforcing wire (mesh), strands, kg 33.5 Mix property Water cementitious materials ratio 0.40 Cement substitution with SCM, % 17 Nominal compressive strength, MPa 35 Note: SCM = supplementary cementitious material Steel LCI data. Steel is an integral component of both precast and cast-in-place concrete products (reinforcing bar, wire strand, and welded wire reinforcing). Steel is a widely traded commodity containing varying levels of recycled content. For this study, the study team has adopted the latest international LCI steel data. The World Steel Association (WSA) maintains LCI databases for steel construction products. The WSA subscribes to a system expansion method for handling primary (virgin) and secondary (recycled) content production based on closed-loop recycling methodology. This system expansion methodology is ISO-compliant 6. The methodology essentially starts with primary 10

19 production and accounts for net recycled content and end-of-life recovered metal to provide an overall primary and secondary mixed product profile for each product. The specific origin of input material (whether primary or recycled) is not relevant because it is the net conservation of material that typically minimizes total environmental impacts. Under this framework, consistent with ISO , it is acknowledged that material not recycled needs to be replaced by primary material feedstock Product transportation. Whenever possible primary transportation data (based on average industry data) are applied in this LCA study. A number of the raw material and all final product transportation data have been averaged for the construction site using commodity flow data from national sources of transportation statistics (see Appendix K for details) On-site construction effects. Since the early 1990s the Athena Institute has been developing its Impact Estimator for Buildings software. The software enables users to model various building materials and assemblies within the context of a whole building over its expected life cycle in various North American cities. The software includes LCI data for the construction of various commercial structural systems (precast concrete, cast-in-place concrete, and structural steel). The on-site construction effects include materials and equipment transportation, on-site equipment energy use, and on-site solid waste generation. These on-site construction LCI data have been used to model the requisite on-site construction effects for each product. The placement and backfilling of belowground precast concrete product is estimated using Athena Institute data for heavy machinery use as machine hours necessary fuel consumption per machine-hour Waste treatment and end-of-life management. Waste treatment (recycling or landfill) of waste generated (at the plant level or on-site construction) is included. The Athena Institute maintains an LCI database for concrete crushing, disposal, and reuse. Removal of these precast products, crushing, and disposal and reuse as aggregate is also included as follows: Septic tank: excavate, crush product, recycle all post-consumer steel scrap, landfill concrete. Manhole structure: excavate, crush product, recycle all post-consumer steel and iron scrap, landfill concrete. Utility structure: excavate, crush product, recycle all post-consumer steel and iron scrap, recycle all concrete. Pipe: excavate, crush product, recycle all post-consumer steel scrap, recycle 50% of concrete and landfill remaining 50%. New structures will be placed in the excavated holes but this process is not included in the system boundary Primary Data Collection from Precast Concrete Plants Precast concrete participating plants. The primary data on production of precast concrete have been collected from three plants in the US producing a variety of underground infrastructure products. Production weighted average data from the following plants is included 11

20 in this LCA: plant A Farmingdale, New Jersey; plant B Dunn, North Carolina; and plant C Bristol, Virginia. The data represent 12 consecutive months of operation in The results production volume-weighted results are presented in Appendix C. The study team followed a generic procedure for primary data collection as described in Section After carrying out the initial LCI calculations, the results were sent to CPCI, NPCA, and PCI for a pre-check in order that extreme values, revealed by the analysis, could be checked, verified, and corrected if necessary. The resulting data set consists of the LCI flows and it has been input into the LCA modeling software (SimaPro, referenced below) Primary data collection system for the precast concrete plants. This section describes the data collection system (DCS), the data averaging approaches, and the treatment of data gaps for the precast concrete production. We have followed these generic DCS procedures: 1. Identification of the data that needs to be collected; 2. Planning when, where, and how data are to be collected and by whom; 3. Identification and treatment of data gaps (see below); 4. The actual data collection (measurement or retrieval from book, experience, expert, etc.); 5. Documentation of the resulting data, together with possible sources of error, bias or lack of knowledge; 6. Averaging the data across the plants; 7. Validation of the data collection system, the collected data and its documentation was validated by PCI and verifiers; and 8. Communication of the data and its documentation, As per ISO 14044:2006, Section , the treatment of missing data shall be documented. For each unit process and for each reporting location where missing data are identified, the treatment of the missing data and data gaps should result in: (a) a non-zero data value that is explained, (b) a zero data value if explained, or (c) a calculated value based on the reported values from unit processes employing similar technology. We have followed c). Further: (1) if only one plant has reported data on an "input/output parameter", this cannot be used as average for the industry; (2) if only two plants have provided data on an "input/ output parameter" (excluding fuels), the mean value will be used as average for the industry; (3) if three or more plants have provided data on an "input/ output parameter", weighted average value will be used as average for the industry; and (4) for alternative fuels (such as, liquefied petroleum gas, gasoline or diesel) the weighted average value will be used as average for the industry. For example, if forklift(s) run on LPG in plant 1, on gasoline in Plant 2, and diesel on Plant 3 and the following amount of fuel is consumed: Plant 1 (WF 1 = 20%): 100 liters LPG; 0 liters gasoline; 0 liters diesel, Plant 2 (WF 2 = 30%): 0 liters LPG; 100 liters gasoline; 0 liters diesel, Plant 3 (WF 3 = 50%): 0 liters LPG; 0 liters gasoline; 100 liters diesel, 12

21 then the weighted average profile per cu yd cement is calculated as follows: LPG = = 20 liters; Gasoline = = 30 liters; Diesel = = 50 liters. There are two methods available for integrating LCI data across an industry sample: vertical and horizontal. Vertical integration implies averaging the data across each unit or system process and then integrating through the supply or product chain. Horizontal integration implies first integrating the data through the supply chain and then using a weighting factor, based on annual production data, to horizontally integrate the primary data. Based on the data availability, the vertical approach is applied in this LCA study. Averaging weighting factors per plant are calculated respectively as follows: WF 1 = y 1 / (y 1 + y 2 + y 3 ) = y 1 / Y total and WF 1 % = (y 1 / Y total ) 100 where Y total = total annual production of three US Plants (in cu yd basis); y 1 = annual production of US plant 1 (in cu yd basis); y 2 = annual production of US plant 2 (in cu yd basis); y3 = annual production of US plant 3 (in cu yd basis). For example, if the annual production of plant 1, 2, and 3 are respectively 100, 400, and 500 cu yd, the averaging weighting factors will be respectively WF 1 = 0.1, WF 2 = 0.4, and WF 3 = LCI MODEL OF THE UNDERGROUND INFRASTRUCTURE PRODUCTS The LCA modeling software used in the project is SimaPro version Each product is modeled independently from cradle-to-grave. The modeling consists of assembling the constituent products and processes so called unit processes into a complete assembly. The manhole consists of the following constituent products: precast concrete, steel rungs, zinc coating on steel rungs, cast iron lid and frame, butyl rubber joint sealant, reinforcing steel and aggregate for the base. The septic tank consists of precast concrete, butyl rubber joint sealant, reinforcing steel, and aggregate for the base. The utility structure consists of precast concrete, cast iron lid and frame, reinforcing steel and aggregate for the base. The pipe consists of precast concrete, reinforcing steel and aggregate for the base. Further detail including material quantities are provided in Appendix D. 13

22 The production systems unit processes (single operation or black box ) that constitute each completed underground product assembly including end-of-life (EOL) processes are shown in Table 3. On-site installation includes the construction activities on-site to install the structures. It includes material and equipment transportation, and on-site heavy machinery and crane energy use. Worker transportation to the construction site has been excluded from the on-site construction effects as per the previously reviewed goal and scope document. Table 3. Constitute Elements of the Underground Infrastructure Product Assembly Life Cycle Stages Primary products manufacturing Out-bound transportation On-site installation materials and processes EOL processes Note: EOL means end-of-life. Underground Infrastructure Product Assemblies Manhole Septic tank Utility structure Pipe Precast concrete (reinforced) production Precast concrete, (reinforced) production Precast concrete, (reinforced) production Precast concrete, (reinforced) production Steel rungs production Zinc coating (galvanizing) on steel rungs process Cast iron lid and frame Cast iron lid and production frame production Joint sealant butyl rubber Joint sealant butyl production rubber production of all of all of all of all utility structure concrete pipe manhole products to the septic tank products products to the products to the installation site to the installation site installation site installation site Sand base extraction Sand base extraction Sand base extraction Sand base extraction Sand base transportation Sand base Sand base Sand base transportation transportation transportation Gravel base Gravel base extraction extraction Gravel base Gravel base transportation transportation On-site installation On-site installation On-site installation On-site installation EOL excavation EOL excavation EOL excavation EOL excavation EOL crushing EOL crushing EOL crushing EOL crushing EOL transportation EOL transportation EOL transportation and recycling steel and recycling steel and recycling steel and iron and iron EOL transportation and recycling steel and iron EOL transportation and landfilling of concrete EOL transportation and landfilling of concrete EOL transportation and recycling of concrete EOL transportation and landfilling of concrete (50%) and recycling of concrete (50%). Unit process (single operation) is defined as a unit process that cannot be further sub-divided into included processes; and unit process (black box) is defined as a unit process that includes more than one single-operation unit processes. 14

23 4. LIFE CYCLE IMPACT ASSESSMENT INDICATORS AND METHODOLOGIES Life-cycle impact assessment (LCIA) is the phase in which the set of results of the inventory analysis mainly the inventory table is further processed and interpreted in terms of environmental impacts. According to LCA-based ISO Standards, the mandatory elements of LCIA are: Selection of impact categories, category indicators, and characterization models; Assignment of LCI results (classification) to the impact categories; Calculation of category indicator results (characterization). For this LCA study, the impact categories and assessment methods are the mid-point indicators from the U.S. EPA Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI). The methodologies underlying TRACI reflect state-of-the-art developments and best available practice for life-cycle impact assessment (LCIA) in the United States 10. They include primary energy (fossil fuel depletion), global warming, ozone depletion, photochemical oxidants (smog), eutrophication, and acidification potential. Table 4 sets out the impact categories supported by TRACI and their inherent impact potential. Table 4. Impact Categories in Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) Impact category Natural environment Human health Resources Global warming (climate change)* Acidification Ozone depletion Eutrophication Photochemical Smog Ecotoxicity Human health: PM-2.5 Human health: criteria air pollutants Human health: cancer Human health: non-cancer Fossil fuel Water use Land use *Please note that TRACI uses the term global warming impact category as a synonym to the ISO term climate change impact category. It should be noted that while LCI enjoys a fairly consistent methodology, the life cycle impact assessment (LCIA) phase is very much a work in progress and there is no overall agreement on which LCIA categories should be included in a LCA or a single accepted methodology for calculating all of the impact categories to be included. Clause , ISO 14044:2000 states: The selection of impact categories, category indicators and characterization models shall be both justified and consistent with the goal and scope of the LCA. Typically, LCIA is completed in isolation of the LCI, that is, the LCI requests a complete mass and energy balance for each 15

24 unit process or product system under consideration and once completed the LCI is sifted (classified and characterized) through various LCIA indicator categories to determine possible impacts. For this study, we have relied on ISO to select the various impact categories to be included in the LCIA and TRACI as the LCIA methodology. ISO 21930:2007 provides an internationally accepted scope for decisions as to which LCIA categories should be supported for building sustainability metric analysis, while the TRACI LCIA methodology provides a North American context for the actual measures to be supported. ISO 21930:2007 stipulates a number of mid-point LCIA characterization measures to be supported and while not opposing end-point measures, dissuades their use until they are more internationally accepted. The measures advocated by ISO 21930:2007 include: 1. Use of resources and energy a. Depletion of non-renewable material resources b. Use of renewable resource c. Depletion of non-renewable primary energy d. Use of renewable primary energy 2. Climate change 3. Depletion of the stratospheric ozone layer 4. Formation of photochemical oxidants 5. Acidification of land and water sources 6. Eutrophication Optional end-point LCIA measures listed in ISO include human toxicity and ecotoxicity; however, the uncertainty increases with movement from mid-point to end-point measures. Therefore we do not recommend using or reporting end-point measures. Absent from the TRACI list is any impact category dealing with solid waste. While TRACI supports fossil fuel depletion (on a global scale), it does not readily report primary energy use as an impact category. It is the study team s recommendation that solid waste, water use, and total primary energy use be tabulated and summarized as an impact category directly from the LCI results. Further, we adopted the cumulative energy demand method (CML 2001) to organize and report primary energy resource use. 12 Total primary energy is the sum of all energy sources drawn directly from the earth, such as natural gas, oil, coal, biomass, and hydropower energy. The total primary energy can be further broken down into categories. For this reason, we have elected to provide a measure of total primary energy derived from LCI flows broken down into renewable and non-renewable and feedstock energy sources (Table 5). Higher heating value (HHV) of primary energy carriers is used to calculate the primary energy values used in the study. Higher heating value, gross heating value, or total heating value includes the latent heat of vaporization and is determined when water vapor in the fuel combustion products is condensed. Conversely, lower heating value or net heating value does not include latent heat of vaporization. In the US, when the heating value of a fuel is specified without designating higher or lower, it generally means the higher heating value

25 Table 5. Selected Impact Indicators Impact category Unit equivalence basis (indicator result) Source of the characterization method Level of site specificity selected Global warming kg CO 2 - equivalents TRACI Global Acidification kg H+ TRACI North America Ozone depletion kg CFC-11 TRACI Global Eutrophication kg N water TRACI North America Particulate matter kg PM2.5 TRACI North America Photochemical smog kg ethylene TRACI North America Solid waste kg Sum of LCI flows North America Water use kg Sum of LCI flows North America Abiotic resource depletion, excluding energy kg antimony/yr CML 2001 Global Total primary energy * MJ Non-renewable, fossil MJ Non-renewable, nuclear MJ Renewable (solar, wind, hydro, geothermal) MJ CED adapted Global Renewable (biomass) MJ Feedstock, fossil MJ Feedstock, biomass MJ * Both the site-specific and the upstream waste related to electricity production; fossil fuels pre-combustion; and oil, grease, and lubricants production are accounted for in the LCA study. Sub-set of primary energy. With respect to the other LCIA measures, we recommend the inclusion of the following TRACI impact categories (IC) and characterization factors (CF). A characterization factor is a factor derived from a characterization model which is applied to convert an assigned life cycle inventory analysis result to the common unit of the category indicator. The common unit allows calculation of the category indicator result. 1 a. Global warming (IC) TRACI uses global warming potentials (CF), a midpoint metric proposed by the International Panel on Climate Change (IPCC), for the calculation of the potency of greenhouse gases relative to CO 2. The 100-year time horizons recommended by the IPCC and used by the US for policy making and reporting are adopted within TRACI. The methodology and science behind the global warming potential (GWP) calculation can be considered one of the most accepted LCIA categories. GWP 100 is expressed on equivalency basis relative to CO 2, that is, equivalent CO 2 mass basis. b. Acidification (IC) As per TRACI, acidification comprises processes that increase the acidity (hydrogen ion concentration, [H+]) of water and soil systems. Acidification is a more regional rather than global impact effecting fresh water and forests as well as human health when high concentrations of SO 2 are attained. The acidification potential (CF) of an air emission is calculated on the basis of the number of H+ ions which can be produced and therefore is expressed as potential H+ equivalents on a mass basis. 17

26 c. Ozone depletion (IC) Stratospheric ozone depletion is the reduction of the protective ozone within the stratosphere caused by emissions of ozone-depleting substances. International consensus exists on the use of ozone depletion potentials (CF), a metric proposed by the World Meteorological Organization for calculating the relative importance of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HFCs), and halons expected to contribute significantly to the breakdown of the ozone layer. TRACI is using the ozone depletion potentials published in the Handbook for the International Treaties for the Protection of the Ozone Layer (UNEP-SETAC 2000), where chemicals are characterized relative to CFC-11. d. Eutrophication (IC) In TRACI, eutrophication is defined as the fertilization of surface waters by nutrients that were previously scarce. This measure encompasses the release of mineral salts and their nutrient enrichment effects on waters typically made up of nitrogen (N) and phosphorous (P) compounds and organic matter flowing into waterways. The result is expressed on an equivalent mass of nitrogen basis. The characterization factors estimate the eutrophication potential of a release of chemicals containing N or P to air or water, per kilogram of chemical released, relative to 1 kg N discharged directly to surface freshwater. e. Photochemical smog (IC) Photochemical ozone formation potential (CF) Under certain climatic conditions, air emissions from industry and transportation can be trapped at ground level where, in the presence of sunlight, they produce photochemical smog, a symptom of photochemical ozone creation potential (POCP). While ozone is not emitted directly, it is a product of interactions of volatile organic compounds (VOCs) and nitrogen oxides (NO x ). The smog indicator is expressed on a mass of equivalent ethylene basis. f. Solid waste (IC) summarizes the cradle-to-gate LCI solid waste flows, and it is expressed in kg. g. Water use (IC) summarizes the cradle-to-gate LCI water usage flows, and it is expressed in kg. h. Abiotic resource depletion As per CML 2001 method, the abiotic depletion potential (ADP) baseline factors for characterizing abiotic resources are based on ultimate reserves and extraction rates. According to Guinee & Heijungs (1995) a method based on ultimate reserves and rates of extraction is the best option, as these parameters best indicate the seriousness of resource depletion. As the notion of economic reserves involves a variety of economic considerations not directly related to the environmental problem of resource depletion, ultimate reserves appears to be a more appropriate yardstick. The indicator is expressed in kg of the reference resource antimony. For the full list of the natural resources included, please see the referenced link to Leiden University s Guide on Environmental Life Cycle Assessment. 14 Fossil fuels are excluded because they will be reported under a separate category (total primary energy). i. Total primary energy (IC) Total primary energy is the sum of all energy sources which are drawn directly from the earth, such as natural gas, oil, coal, biomass or 18

27 hydropower energy. The total primary energy contains further categories namely nonrenewable and renewable energy, and fuel and feedstock energy. Non-renewable energy includes all fossil and mineral primary energy sources, such as natural gas, oil, coal and nuclear energy. Renewable energy includes all other primary energy sources, such as hydropower and biomass. Feedstock energy is that part of the primary energy entering the system which is not consumed and/or is available as fuel energy and for use outside the system boundary. Total Primary Energy is expressed in MJ. j. Human health: criteria air pollutants The midpoint level selected by TRACI will be used based on exposure to elevated particulate matter (PM) less than 2.5 micrometers in diameter. Particulate matter is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Emissions of SO 2 and NO x lead to formation of the secondary particulates sulphate and nitrate. Particles can be suspended in the air for long periods of time. Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope. Many manmade and natural sources emit PM directly or emit other pollutants that react in the atmosphere to form PM. These solid and liquid particles come in a wide range of sizes. Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system. Particles less than 2.5 micrometers in diameter (PM2.5) are referred to as "fine" particles and are believed to pose the greatest health risks. Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs. The impact method and characterization factors for land use are still in development. Although it can have a significant impact, most North American LCI data do not include measures of land use; therefore land use is excluded at this time. 5. CO-PRODUCT ALLOCATION 5.1. Co-Product Allocation Rules in General The multi-functionality of many processes has been identified as a significant methodological LCA issue. The general situation is that most processes that constitute part of a product system are multi-functional: (1) they produce more than one product (co-production), (2) treat two or more waste inputs (combined waste treatment), (3) treat one waste input and produce one valuable output (open- or close-loop recycling) or (4) serve three or more valuable functions from both input and output perspective. 15 In such cases the materials and energy flows, as well as associated environmental releases, shall be allocated to the different products according to clearly stated procedures (ISO 14044, Section 4.3.4). As per ISO 14044, allocation means partitioning the input or output flows of a process or a product system between the product system under study and one or more other product systems. The guidance provided by (ISO) recognizes the variety of approaches that can be used to deal with multifunctional processes. ISO suggests a generic step-wise framework in LCA. 2 19

28 The following three steps are required: 1. Wherever possible allocation should be avoided by (1) dividing the unit process to be allocated into two or more sub-processes and collecting the input and output data related to these sub-processes, or (2) expanding the product system to include additional functions related to the co-products, taking into account the requirements of ISO Where allocation cannot be avoided, the inputs and outputs of the system should be partitioned between its different products and functions in a way that reflects the underlying physical relations between them; that is, they should reflect that inputs and outputs are changed by quantitative changes in the products or functions delivered by the system. 3. Where physical relationships alone cannot be established or used as the basis for allocation, the inputs should be allocated between the products and functions in a way that reflects other relationships between them. For example, input and output data might be allocated between co-products in relation the economic value of the products. ISO requirements and recommendations have been followed in this LCA study for allocation procedures in general (Section ) and allocation procedures for reuse and recycling (Section ). We have also followed the recommendations of the UNEP-SETAC life cycle initiative, Life Cycle Inventory Program, Task Force 3: Methodological Consistency, Inventory Methods in LCA: Towards Consistency and Improvement Background data (energy, electricity and transportation): U.S. LCI Database. Physical properties (mass and energy content) are used as basis of allocation for the energy data included in the U.S. LCI Database; for example, refined energy data (diesel, gasoline, fuel oil and propane) are allocated by mass in relation to the refinery emissions. Energy demands are allocated by energy content (HHV) in relation to crude oil consumption. These LCI datasets are used in this project without further adjustment Precast concrete products No allocation has been deemed necessary as the plants only manufacture precast concrete products. System expansion has been used to avoid allocation to address the concrete waste generated on-site, which is assumed to be 100% crushed and to avoid the coarse aggregate extraction and transportation at the plant gate. The environmental load of the precast concrete products is calculated by applying the following formula : P = A + I D where, P = environmental load of the precast concrete products; A = environmental load of the precast concrete manufacturing process; As per equation in Section 2.4.2, see 20

29 I = environmental load of the crushing process for the concrete waste; D = environmental load of the coarse aggregate extraction and transportation Ecoinvent dataset adjusted to North America. Cut-off rules for by-products and recycling are applied in the Ecoinvent database 12 By-products which contribute nothing or only very little to the total proceeds of an economic activity but which are used in a subsequent process (re- or down-cycling) will not be reported in the list of inputs and outputs of the database. Neither are credits granted, nor are a part of the inputs and outputs of the respective process allocated to these by-products. Ecoinvent datasets are adjusted to North American conditions but no further adjustments are made for the allocation rules Co-Product Allocation Rules for Comparative Commodities Steel Steel products are important commodities used in construction, and steel is an integral component of precast concrete products. Hence, special attention is paid to apply the current peer-reviewed LCI data according to ISO series for steel and recycling methodologies, which are accepted and recognized by World Steel Association (WSA). It is important that the results of this LCA study be recognized by the WSA, which represents the interests of the steel industry. The World Steel Association and other metal industry associations are applying the "closed loop" approach, which follows the "end-of life" philosophy. In the Declaration by the Metals Industry on Recycling Principles endorsed by 17 international industry associations in 2007 and published at the International Journal of LCA it is claimed: For purposes of environmental modeling, decision-making, and policy discussions involving recycling of metals, the metals industry strongly supports the end-of-life recycling approach over the recycled content approach. This project is using peer-reviewed LCI data on primary and secondary steel production provided by the WSA. To aid LCA practitioners to carry out full cradle-to-grave life cycle assessments involving steel products, the WSA has developed an LCI database of steel products, which accounts for the end of life recycling of steel products, in other words the cradle-to-grave LCI data. Fig. 4 shows a simplification of the WSA LCA process. 21

30 Figure 4. Simplification of the LCA process by aggregating manufacturing and end of life information on scrap. Source: World Steel Association Application of the World Steel LCI Data to Recycling Scenarios. Updated October Page 3. The general life cycle equation 18 for the closed material loop recycling methodology is applied as shown by the equation below: LCI for 1 kg of metal including end of life = Xpr RR Y (Xpr Xre) = Xpr RR VS where Xpr = The LCI for 100% primary metal production; Xre = The LCI for 100% secondary metal production from scrap; RR = Recovery rate of steel products used in North American construction sector (86.9%). 18 The overall recycling rate indicates the efficiency with which pre-consumer scrap and post-consumer scrap are collected and recycled; Y = Process yield (95.3%); VS = Value of scrap: VS = Y (Xpr Xre). The equation indicates that the system LCI depends not upon the source of the material (primary or secondary) but on the recycling ratio (RR) of the metal at end of life and upon the process yield (Y) associated with the recycling process. 22