Towards Sustainable Construction: Life Cycle Assessment of Railway Bridges

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Towards Sustainable Construction: Life Cycle Assessment of Railway Bridges

GUANGLI DU

Licentiate Thesis in

Structural Engineering and Bridges

Stockholm, Sweden 2012

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Towards Sustainable

Construction: Life Cycle

Assessment of Railway Bridges

Guangli Du

February 2012

TRITA-BKN. Bulletin 112, 2012 ISSN 1103-4270

ISRN KTH/BKN/B-112-SE

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KTH Royal Institute of Technology

Department of Civil and Architectural Engineering Division of Structural Engineering and Bridges Stockholm, Sweden, 2012

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Preface

This licentiate thesis was produced at the Division of Structural Engineering and Bridges, Department of Civil and Architectural Engineering, KTH Royal Institute of Technology. The project was co-operated and financed by the Swedish Transport Administration (Trafikverket), and the Nordic Project ETSI on Bridge LCC/LCA.

First, I would like to express my deep gratitude to my supervisor Professor Raid Karoumi and my assistant supervisor Professor Håkan Sundquist, who provided me with the opportunity to work on my favorite subject. This thesis would not complete without their professional guidance and substantial support. I appreciate their encouragement and fruitful discussions during my research.

Second, I especially would like to thank the LCA expert Otto During at the Swedish Cement and Concrete Research Institute, for his help and invaluable comments. I also owe my sincere appreciation to my colleagues at the Division of Structure Engineering and Bridges, who accompanied me with encouragement and joy during my research.

Finally, I heartily thank my parents and friends for their deepest love and support.

Stockholm, February 2012 Guangli Du

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Abstract

Since last few decades, the increased pressure from the environmental issues of natural resource depletion, global warming and air pollution have posed a great challenge worldwide. Among all the industrial fields, bridge infrastructures and their belonged construction sector contribute to a wide range of energy and raw materials consumptions, which is responsible for the most significant pollutions. However, current bridges are mainly designed by the criterion of economic, technique, and safety standards, while their correlated environmental burdens have unfortunately rarely been considered. The life cycle assessment (LCA) method has been verified as a systematic tool, which enables the fully assessment and complete comparison for the environmental impact among different bridge options through a life cycle manner. The study presented in this thesis is focused on railway bridges, as the LCA implementation is under great expectations to set a new design criterion, to optimize the structural design towards the environmental sustainability, and to assist the decision-making among design proposals.

This thesis consists of two parts: an extended summary and three appended papers.

Part one gives an overview introduction that serves as a supplementary description for this research work. It outlines the background theory, current development status, the LCA implementation into the railway bridges, as well as the developed excel-based LCA tool. Part two, includes three appended papers which provides a more detailed theoretical review of the current literatures and knowledge associated with bridge LCA, by highlighting the great challenging issues. A systematic flowchart is presented both in Paper I and Paper II for how to model and assess the bridge life cycle, together by coping with the structural components and associated emissions. This flowchart is further illustrated on a case study of the Banafjäl Bridge in Sweden, which has been extensively analyzed by two LCA methods: CML 2001 method and streamlined quantitative approach. The obtained results can be contributed as an analytical reference for other similar bridges.

Based on the theoretical review and analytical results from case studies, it has been found that the environmental profile of a bridge is dominated by the selected structural type, which affects the life cycle scenarios holistically and thus further influences the environmental performance. However, the environmental profile of the structure is though very case specific; one cannot draw a general conclusion for a certain type of bridge without performing the LCA study. The case study has found that the impact of material manufacture phase is mostly identified significant among the whole life cycle. The availability of the inventory data and project information are appeared as the major problem in the bridge LCA study. Moreover, lack of standardized guideline, criteria and input information is another key issue. A criterion is needed to illustrate what are the qualified limits of a bridge to fulfill the environmental requirements.

Therefore, the development of LCA for railway bridges still needs further collaborative efforts from government, industry and research institutes.

Keywords: Life cycle assessment, LCA, Environment, Railway Bridge, Sustainability

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List of publications

This thesis is based on the work contained in the following papers

Paper I: Du Guangli, Karoumi Raid, Life cycle assessment of bridges: a literature survey and critical issues, submitted to ASCE journal of Bridge Engineering.

Paper II: Du Guangli, Karoumi Raid, Life cycle assessment of a railway bridge:

comparison of two superstructure designs, accepted by the Journal of Structure and Infrastructure Engineering.

Paper III: Thiebault Vincent, Du Guangli, Karoumi Raid, Design of railway bridges considering LCA, accepted by the journal of ICE Bridge Engineering.

All the calculations and theoretical backgrounds study in those papers are carried out by the first author. In Paper III, the co-authors have participated in the work planning and idea proposals, with the contribution to the revision and answering to the reviewer’s comments.

Additional Conference papers produced by the author

Du G. L., A Literature review of life cycle assessment for bridge infrastructure, published in COST Action C25: Sustainability of Constructions: An Integrated Approach to Life-time Structural Engineering. Malta, 2010.

Du G. L., Life cycle assessment for railway bridge infrastructure: a case study of Bollstaån Bridge, published in COST Action C25: Proceedings of the international conference sustainability of constructions-towards a better built Environment.

Innsbruck, Austria, 2011.

Rossi, B., Lukic I., Iqbal N., Du G. L., Cregg D., Borg R. P., Haler P., Life cycle impacts assessment of steel, composite, concrete and wooden columns, published in COST Action C25: Proceedings of the international conference sustainability of constructions-towards a better built Environment. Innsbruck, Austria, 2011.

Du Guangli, Karoumi Raid, Life cycle assessment of the Banafjäl Bridge, submitted to fib Symposium: Concrete Structures for Sustainable Community. Stockholm, 2012.

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1 Introduction

1.1 Background

The environmental issues have become one of the most critical concerns confronting the society today. How to quantify the environmental impact from industrial sectors has been put on the top list of agenda. The European commission (2001) pointed that the built environment accounts for the largest single share of greenhouse gas emissions, which are equivalent to 40% in terms of energy usage.

Figure 1.1 shows that the construction and the transportation sector generate considerable large amount of greenhouse gas emissions among all the industrial fields. While Figure 1.2, illustrates worldwide and European trends of the concrete and steel consumption. It shows that the production of concrete and steel, as the main material in the construction sector, has increased by 50% globally in the last decades. Moreover, in the U.S., at least 123 million metric tons of building related construction and demolition wastes are generated annually; that one billion tons of concrete are equivalent to 408000-847000 cars on American roads (Vieira and Horvath, 2008).

More specifically for the railway bridge infrastructures, they represent an important role among the entire transportation and construction sector. The rail transportation has showed greater environmental advantage when comparing with the road transportation. In Swedish railway bridge management system BaTMan, about 3700 railway bridges were found registered in 2009 (Janssen, 2009; John, 2010). The European white paper (2011) even addressed the ambitious sustainability strategy that, by 2050, the majority of medium-distance passenger transport, about 300km and beyond, should go by rail (Europa IP/11/372). This means, the number of railway infrastructures such as bridges will increase simultaneously.

Railway bridges are not environmental friendly structures. During its long life span, numerous amount of material and energy flows are involved through the material manufacture, construction, maintenance and end of life scenarios. However, it has been realized that the current decision-making process is mainly oriented on the technique, safety and economic perspectives, that the environmental assessment is not integrated and considered. In response to this awareness, the authorities try to construct ‘more sustainable’ railway bridge structures by encouraging the implementation of the environmental assessment.

Life cycle assessment (LCA) has proved to be a comprehensive tool for quantifying and assessing the environmental impacts of the products through its whole life cycle. It has the potential to provide the reliable environmental profile of the infrastructures, thus to assist the decision-maker for the future strategy formulation. However, although the LCA as a decision-supporting tool has been widely used in other industry and the building field, its applications are rarely implemented for the railway bridges; very limited research and literatures are

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available. A systematic and standardised guideline and criteria is still missing.

Therefore, the implementation of LCA in this field has a high investigation potential both practically and academically.

Figure 1.1: Total greenhouse gas emissions by sector (%) in EU-27, 2008 (EEA, 2011)

Figure 1.2: Trends of World and U.S. Steel and Cement consumption (Chaturvedi S., 2001)

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1.2 Aims and scope

The LCA implementation to railway bridges, may set a new design criterion, optimize the design towards environmental sustainability and assist the decision-making among different design proposals.

The main aim of this work is to evaluate and investigate the key operational issues of the LCA implementation for railway bridges, as well as to establish a generalized operational framework, thus to promote the application of LCA as a decision- supporting tool for railway bridges. However, it has been realized that considering LCA for railway bridges is still new, without standard guidelines and criterion available. A criterion is needed to illustrate what are the qualified limits of a bridge to fulfill the environmental requirements, how to identify a bridge is ‘sustainable’ base on the evaluation results. Based on those considerations, the first part of this thesis is to present a complete survey of the theoretical background, current development status and the critical issues emerged in this field. The second part, including three appended papers, is intended to present a holistic framework specified for LCA implementation of railway bridges, and a large number of detailed state of the art literatures regarding the environmental assessment of bridges are collected and illustrated. Furthermore, a case study of the Banafjäl Bridge in Sweden is selected to be extensively analyzed by two LCA methods with several life cycle inventory databases involved, mainly with the purpose to show the operational procedure of applying LCA in railway bridges.

This study is focused on railway bridges, by covering the whole life cycle from raw material extraction, through material manufacture phase, construction phase, maintenance and use phase till end of the life (EOL). However, due to the data limitation, the material processing and distribution in the manufacture phase are mainly modelled by the ready-made local LCI databases. The construction phase is constrained on the energy consumption of construction machines, while scaffoldings and labour work are omitted. The maintenance and EOL scenarios in the future life stages are performed based on a series of technical assumptions. The excel-based tool presented in this work is based on 12 types of emissions instead of a complete inventory data; the emissions are selected due to their relevance to the targeted mid-point impact category.

1.3 Research contribution

The contribution of the current work is:

• Based on the LCA framework, an excel-based LCA tool is developed for assessing railway bridges. The tool enables the simultaneous comparison between two railway bridges covering the whole life cycle. Several LCI databases are used for providing environmental inventory data of materials.

The analyzed results are presented on the characterization and normalization level, with the presentation of environmental allocation from each structural component.

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• The literature survey is carried out regarding the LCA methodology, LCI database, and the development status in the field of railway bridges, which lead to a general framework for implementing LCA into railway bridges. Several critical issues for the operational procedure are addressed.

• A general operational framework is developed for the LCA implementation into railway bridges. This framework is further applied in the case study of Banafjäl Bridge, by two different assessment methods. The case study is particularly focused on the environmental comparison of the superstructure designs.

1.4 Outline of thesis

This thesis is a combined work based on the results presented in the three appended papers. It contains an overview introduction (Chapter 1-5) as a supplementary description for this research project. The overview introduction addresses the background theory, current development status of LCA, the LCA implementation in the railway bridges, as well as the developed computer tools, relevant case studies and several unsolved issues. The brief description of each appended paper is listed below:

Paper I performed a detailed literature review of the current knowledge and developments associated with the LCA of bridges. Based on the survey, a systematic flowchart for guiding the implementation of the LCA for the railway bridge structure was presented. Several associated critical issues were highlighted in the final conclusion.

Paper II developed a Bridge LCA framework to implement the LCA methodology into the railway bridge structure. This model was further applied in a case study of the Banafjäl Bridge, as an environmental comparison between two design alternatives:

ballast track design and fixed-slab track design. The case study was performed with the software SimaPro, by implementing the LCA CML 2001 method and several LCI database. The parameter of traffic disturbance, weighting factors and recycling rate were investigated by the sensitivity analysis. The normalized results were presented for each structural component as well as the environmental allocation in the separated life cycle stage.

Paper III developed an excel-based tool for performing the LCA analysis of the railway bridges, based on the simplified quantitative LCA method. The open sourced LCI database and LCIA factors from literatures are applied in the tool. This tool is further implemented for analyzing the case study between the two alternative designs from the Banafjäl Bridge: ballast design and fixed slab design. The 10% variations of the inventory input have been modeled for the sensitivity analysis. The final result is presented in the format of total aggregated value for each design solution, as well as emission substances through each life cycle stage.

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Chapter 2. Life cycle assessment

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2 Life cycle assessment

2.1 Life cycle thinking

In order to keep the sustainability balance among the economy, environment and the society, a variety of life cycle thinking (LCT) based approaches are propagated, such as life cycle management (LCM), life cycle cost (LCC), and life cycle assessment (LCA). LCT is a systematic approach intends to consider the products from ‘cradle’ to

‘grave’, from the raw material extraction, through products manufacture, use and maintenance until the final disposal. Decisions are needed in each life stage of the product, the application of LCT can thus help connect all environmental and social issues in an integrated holistic system, therefore avoid the short term policy resulting in the long term unbalanced development, or transferring the burden from one stage to another, such as saving money/resource/environmental impact in the initial production phase but leading to the increase in the maintenance phase. The following list presents the definition of several common life cycle thinking terms:

i. Life cycle assessment (LCA) is an environmental related approach based on LCT, which quantifies the potential environmental impact of a product or service through the whole life cycle.

ii. Life cycle cost (LCC) is an economic concept based on LCT, which takes account of all the monetary cost of a product or service from ‘cradle’ to

‘grave’, that the equivalent monetary value of LCA can also be transformed and combined into LCC analysis.

iii. Life cycle management (LCM) is the application of life cycle thinking to modern business practice, with the aim to manage the total life cycle of an organization’s product and services toward more sustainable consumption and production (Jensen and Remmen 2004; SAIC 2006)

2.2 Brief history of LCA

Even though today’s LCA has been involved into a wide range of different industrial sectors, with various tools and methodologies formulated, the application of LCA is still new in history. In the 70s, the initiation of the LCA concept mainly comes from the oil crisis and energy shortage. According to the investigation of LCA history in the U.S. conducted by Hunt R. G. and Franklin W. E., (1996), it is believed that the first LCA study was performed by Harre E. Teasley at Coca-Cola Company in 1969, for the purpose of quantifying the energy, material and environmental burdens from the beverage packages. Since then, the LCA studies were steadily conducted under various names, such as historical term of resource and environmental profile analysis (REPA), integral environmental analysis, environmental profiles, etc. Based on Baumann H.

and Tillman A. M., (2004), the LCAs study between 1969 and 1972 were all limited to the packaging and waste management field, and the solid waste was the main concern other than the energy and emissions. In 1973, the first LCA computer program was

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developed in U.S. Meanwhile, the U.S. LCAs projects inspired the identical ideas in Britain and Germany, which later followed by Sweden. During 1975 until 1988 there were very few public documents about LCA. In 1990, the term ‘LCA’ was first created during the workshop organized by the Society of Environmental Toxicology and Chemistry (SETAC). Soon the first complete LCA methodology appeared in a peer reviewed scientific journal in 1992 (Hunt R., J. and Franklin W., 1992). Apart from the achievements established by SETAC, in 90s and continuing today, the International Organization for Standardization (ISO) have developed worldwide standards in an effort to streamline the international harmonizing LCA guidelines series from ISO14040 to ISO14044 (Fava J. A., 2011). Besides ISO and SETAC, various research, software tools and methodologies were developed in parallel after the 90s. Table 2.1 presented briefly the history of the LCA developments between the 70s and 90s.

Table 2.1 Brief history of LCA development

1969, original LCA study conducted by Coca-Cola Company. (Hunt & Franklin, 1996) 1970, steady study of REPA (early name of LCA). (Hunt & Franklin, 1996)

1972, Dr Boustead wrote teaching text on silica glass production in the UK (Baumann and Tillman, 2004)

1973 The first LCA computer program was funded. (Hunt & Franklin, 1996)

1974, first complete LCA report regarding data and methodology produced by EPA. (Hunt

& Franklin, 1974)

1979, the SETAC (society for Environmental Toxicology and Chemistry) was founded.

1980, public domain of a comprehensive peer reviewed LCA database by Solar Energy Research Institute (Bider et al., 1980; Hunt & Franklin, 1996)

1975-1988, low public interest in LCA.

1990, international forum of REPA in U.S. (Hunt & Franklin, 1996) 1990, SETAC workshop, the term of ‘LCA’ was created.

1992, the first complete LCA methodology appeared in a peer reviewed scientific journal.

(Hunt & Franklin, 1992)

2.3 What is LCA (Paper I)

Life cycle assessment (LCA) is a systematic method that quantifies the potential environmental impacts of a product or a service throughout its whole life cycle, from raw material acquisition phase, manufacture phase, use and maintenance phase till the end of the life. The potential environmental categories cover the resource depletion, human health, and ecological health (ISO14040, 2006). The LCA process can be used to determine the potential environmental impacts from any product, process, or service (SAIC, 2006). The application of LCA can provide scientific based results to the

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decision maker, thus help set the new design criterion for environmental design;

compare and choose the environmental competitive products; identify the environmental deficiencies of the product for further optimization.

As stated in the ISO LCA standards, the general LCA framework consists of four components, see Figure 2.1:

1) Goal and Scope definition phase defines the aims, product system, and expected result of the study;

2) Inventory analysis phase quantifies all the emissions related to the product system based on the functional unit of the product.

3) Impact assessment phase transforms the inventory result into the environmental impact categories.

4) Interpretation phase explains the results with the goal of the study through the whole analysis procedure.

Paper I (see Appedix A) has presented a detailed background theory in terms of LCA framework, LCIA methods survey, a number of LCI database and software descriptions. Therefore, this section mainly provides the supplementary knowledge based on Paper I.

Figure 2.1: LCA framework (ISO 14040, 2006)

2.3.1 Goal and scope definition phase

The framework of LCA starts with the goal and scope definition phase; it determines the object and scope of the study, the purpose and expected result, the functional unit and the relevant assumptions. All the analysis in the followed steps is carried out on the basis of those initial determinations. This step is the most important and mandatory part for every LCA study, not only because the statement will affect the course of the entire study but also to guarantee clear external communications following completion of the study (J. B. Guinée, 2002). In order to obtain a fair result, the relevant parameters and concerned perspectives need to be clarified here. The example of the goals might be given as: ‘identify the product component which cause

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the most environmental impact. If we change the design of one element, how would it affect the final environmental performance? How optimize the product could achieve the best environmental performance?’ Once the appropriate goals are identified, it is important to determine the types of information required to answer the questions (SAIC, 2006). For the scope definition, a well-defined flowchart always is helpful to cover all of the activities that may affect the whole system.

The functional unit is another important concept, which provides an equivalent basis that all the material and energy flows would refer to. The functional unit must represent the function of the compared options in a reasonably fair way (Baumann H.

and Tillman A. M., 2004). Since all of the associated material and energy flow will be calculated consistently from it. One proper functional unit of a steel girder bridge might be ‘during a 120 years life span with annual traffic volume of 20312 tkm train freight.’ The functional unit becomes more important when a comparison between two products is carried out, for instance we cannot directly compare a 20 meters long steel bridge with a 50 meters long concrete bridge. One way to deal with such qualitative differences between compared alternatives is to describe them in words out of the LCA calculations (Baumann H. and Tillman A. M., 2004).

2.3.2 Inventory analysis phase

The life cycle inventory (LCI) takes account of the inputs and outputs inventories related with the product, which requires the collection of numerous data both regionally and globally. The aim of the LCI is to assist the calculation for the quantities of resources, emissions and waste generated per functional unit (Rebitzer et al., 2004). This process considers the energy and raw material as input into the model, and the products, environmental releases as output in the form of pollutants (CO2, NH3, CO, P, NO2) into air, water, soil. The inventory data of the energy, transportation, material consumption and waste treatment covers a wide range of sources, including manufacture factory, government, company, and scientific journals.

However, it has been noticed that the LCI data are largely affected by the regional and processed technologies, that the data from different sources may affect the quality of the final result. Table 2.2 shows the CO2 emissions of concrete varied from three different LCI databases, the difference mainly raised from the technological differences and concrete strength. Moreover, a number of current available LCI databases are listed in Table 1 in Paper I. The LCI data of specific material is usually presented on a unit basis, thus easy to be implemented for the selected material.

SAIC (2006) provides the framework of performing life cycle inventory analysis, listed as:

1. Based on the goal and scope definition, develop a flow chart of the processes that under evaluation. The flow chart diagram is established by covering all of the activities and steps considered in the whole system, with the allocation of the interlinking relations between activities. The more complex and detail the flowchart is, the more accurate the result may obtain.

2. Develop a data collection plan based on the goal definition, data sources availability, and data quality indicators. The level of the

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accuracy and the potential user of the data can largely affect this process. A variety of sources can be extracted, which should come over the issue of geographical, time horizon, technological differences.

The site-specific data is always preferable than the average data, but hard to obtain.

3. Collect data: The data collection and compilation is one of the most work intensive steps through LCA. The information and data collected during this stage assures the data quality and final result, thus it is important to keep the procedure transparent and clear.

4. Evaluate and report results: The result of LCI is usually a long list contains a numerous emissions in terms of water, air and solid. The final environmental profile of the product highly related with the quality of the LCI data. Thus the report should clearly document the data in terms of the methodology, system boundary and assumptions.

Table 2.2 LCI of CO2 emissions from concrete (kg/m³)

4.3×10⁵ Ecoinvent v2.1

3.3 ×10⁵ Stripple (2001)

8.7×10⁵ Bouhaya et al., (2009)

2.3.3 Impact assessment phase

The life cycle impact assessment (LCIA) is the evaluation process of the potential human health and environmental impacts, from the environmental resources and releases identified during the LCI (SAIC 2006). The LCIA process follows the guideline of ISO standards, transforms the emission flows from the life cycle inventory level into the intuitive impact categories, by focusing at either the problem-oriented level (midpoint) or the damage-oriented level (endpoint). The midpoint level aimed to interpret the complex emission list into the easier and more common accepted group of impact categories (Global warming, Acidification, Abiotic depletion); while the endpoint level, which is a further step than the midpoint, cast the emphasis into the consequence damages of human health, ecosystem quality or resource depletions.

Figure 2.3 presents an example of the overall scheme of IMPACT 2002+ method.

Unlike the endpoint method of Eco-indicator 99’ or EPS, it combines the midpoint and endpoint approach, with the elementary emissions assigning into 14 types of environmental categories (Climate change, Ozone layer depletion, Acidification, Photochemical ozone creation, Eutrophication, etc), which eventually categorized into 4 damage categories.

LCIA is deemed as the most time-consuming stage within the LCA. Paper I listed numerous LCIA methods which have been developed by different research institutes and organizations, such as CML 2001, Eco-indicator 99, EDIP 97, EDIP 2003, EPS 2000, Impact 2002+ , JEPIX, LIME, TRACI, IPCC (for global warming). The specific

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instruction for how to implement each LCIA method is illustrated in several literatures, such as Hischier et al., (2009) and Bare, J. C., & Gloria, T. P. (2006). They pointed that each method is actually a collection of impact assessment methods for the individual impact categories (e.g., stratospheric ozone protection, human health, etc.).

However, lack of a standard LCIA method is still one of the obstacles encountered by the LCA practitioners. Although those LCIA methods are developed by following the same principles and frameworks from ISO standards, they still differ from the aspects of category groups, orientation levels (midpoint or endpoint), elementary LCI emissions and the covered LCIA steps (normalization and weighting). It has been discussed in several literatures that different LCIA methods may lead to different results. For instance, Amy E. L. and Thomas L. T. (2008) compared several LCIA methods regarding the bio-fuels, they pointed out that there are no exactly ‘one right LCIA method’, since each of them has been peer reviewed and evaluated for accuracy and internal consistency. The selection of LCIA method is largely depending on the individual study goal and scope.

SAIC (2006) and Gunée (2001) gave a general instruction of performing LCIA process, which consist of the following steps:

Select the impact categories

Impact category selection is one of the most important steps in the impact assessment.

In every LCA it is necessary to consider which environmental impacts to take into account. The ISO standard only gives general headlines for impact categories of resource use, ecological consequences and human health (ISO 14040 1997). However, they must be interpreted in terms of more operational impact categories such as global warming, acidification and resource depletion, etc. (Baumann and Tillman 2004). The selection of the impact categories is largely affected by the relevance from the goal and scope phase and the determined LCIA methodology. While the availability of the inventory data is another key factor. In some cases, the collected information and inventory data is very limited and incomplete.

Classification

Classification sorts and assigns the LCI result parameters into a various commonly acknowledged impact categories (Baumann and Tillman 2004). According to SAIC (2006) there are generally two ways of assigning LCI results into the multiple impact categories: partition LCI results into the impact categories to avoid the ‘double counting’ when they affect each other; or assign all LCI results to all impact categories when the effect are independent of each other. For example: NOx can be fully assigned into the category of Acidification as well as another category of Eutrophication (Baumann and Tillman 2004).

Characterization

Characterization quantifies a number of chemicals into an equal scale to determine the amount of impact each one has on the target category. This process transfers all of the relevant emissions into one equivalent category, for instance, Ammonia, Hydrogen chloride, Nitrogen oxides are summed up into the acidification impact category based

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on their characterization factors. An example of commonly used impact category indicators (SAIC, 2006) is presented in Table 2.3. Impact indicators can be characterized by following the equations in below (Hammervold J. et al., 2009):

e_ij= x_i∙ f_ij

d_k = � (e_ij∙ c_jk)

i=0,j=p

i=0,J=0

eij = emission of the LCI item j for total consumption of input parameter i;

xi = consumption of the input parameter i;

fij = emission of LCI item j per unit input parameter i;

dk = total potential impacts in impact category k, expressed in equivalents cjk = the characterization factor for LCI item j to impact category k

Normalization

The normalization, grouping and weighting are three optional steps proposed through the LCA framework by ISO standards. The idea of normalization is to analyze the respective share of each impact to the overall damage by applying normalization factors to midpoint or damage oriented impact categories for the further interpretation. This process enables the comparison of the impact category result with a selected reference value (SAIC, 2006). The operational documentation of the CML method recommends the use of normalization data based on one geographically and temporally well-defined reference system, preferably the world for one year (Guinée, 2001). Table 2.4 presents a list of normalization factors based on the reference from Western Europe (Jolliet, 2003). The equations below express the normalization procedure (Hammervold J. et al., 2009):

m_k = d_k× n_k mk = normalized potential impacts for category k nk = normalization factor for category k

Grouping

Grouping sorts the characterization results into one or more sets for ease the interpretation of the results (Tillman, 2004). ISO standards addressed two ways of grouping: 1) sort indicators by characteristics such as air, water, solid emissions or local, regional or global locations. 2) sort indicators by ranking, such as high, low or medium.

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As described in Baumann and Tillman (2004); SAIC (2006); Guneè (2001), weighting is a qualitative or quantitative procedure where the relative importance of an environmental impact is weighted against all the other, the relative importance are expressed by their weighting factors. The importance can be oriented based on several principles, such as monetarisation, authorized targets, authoritative panels, proxies, technology abatement. However, ISO standards has addressed that the weighted impacts cannot be used for the product comparison due to the biased results.

2.3.4 Interpretation

Interpretation refines the numerous LCA results into specific concerns with meaningful conclusions. ISO 14040 (1997) defines that the interpretation phase of life cycle assessment in which the findings of either the inventory analysis or the impact assessment, or both, are combined consistent with the defined goal and scope in order to reach conclusions and recommendations. During this stage, the limitations, drawbacks, issues of uncertainties should be revealed clearly.

Figure 2.3: IMPACT 2002+ Midpoint and Endpoint impact assessment (Jolliet et al.

2003)

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Table 2.3 Commonly used life cycle impact categories (SAIC, 2006)

Impact

category Scale Examplese of LCI data Common possible characterization

factor

Description of characterization

factor

Global

Warming Global

Carbon dioxide (CO2) Nitrogen Dioxide (NO2)

Methane (CH4) Chlorofluorocarbons

(CFCs)

Hydrochlorofluorocarbons (HCFCs)

Methyl Bromide (CH3Br)

Global Warming Potential

Concerts LCI data to carbon

dioxide (CO2) equivalents Note: global

warming potentials can be

50, 100, or 500 year potentials.

Stratospheric Ozone

Depletion Global

Chlorofluorocarbons (CFCs)

Hydrochlorofluorocarbons (HCFCs)

Halons

Methy Bromide (CH3Br)

Ozone Depletion Potential

Concerts LCI data to trichlorofluorome

thane (CFC-11) equivalents

Acidification Regional Local

Sulfur Oxides (SOx) Nitrogen Oxides (NOx) Hydrochloric Acid (HCL)

Hydroflouric Acid (HF) Ammonia (NH4)

Acidification Potential

Concerts LCI data to hydrogen

(H⁺) equivalents

Eutrophication Local

Phosphate (PO4) Nitrogen Oxide (NO) Nitrogen Dioxide (NO2)

Nitrates Ammonia (NH4)

Eutrophication Potential

Concerts LCI data to phosphate (PO4)

equivalents

Photochemical

Smog Local Non-methane hydrocarbon (NMHC)

Photochemical Oxidant Creation Potential

Concerts LCI data to ethane

(C2H6) equivalents

Terrestrial

Toxicity Local Toxic chemicals with a reported lethal

concentration to rodents LC50

Concerts LC50

data to equivalents: use

multi-media modelling

exposure pathways

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Toxicity Local Toxic chemicals with a reported lethal

concentration to fish LC50

Concerts LC50

exposure pathways

Human Health Global Regional

Local

Total releases to air, water

and soil LC50

Concerts LC50

exposure pathways

Resource Depletion

Global Regional

Local

Quantity of minerals used Quantity of fossil fuels

used

Resource Depletion

Potential

Concerts LCI data to a ratio of

quantity of resource used versus quantity of

resource left in reserve.

Land use Global Regional

Local

Quantity disposed of in a landfill or other land

modifications

Land Availability

Converts mass of solid waste into volume using an

estimated density.

Water use Regional

Local Water used or consumed Water Shortage Potential

Concerts LCI data to a ratio of quantity of water

used versus quantity of resource left in

reserve.

Table 2.4 Normalization factors (Jolliet, 2003) Damage categories Normalization

factors Unit

Human health 0.0077 DALT/pers/yr

Ecosystem Quality 4650 PDF·m²·yr/pers/yr

Climate Change 9950 Kg CO2/pers/yr

Resources 152000 MJ/pers/yr

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15

2.4 Critical issues

Increased researches have contributed to the LCA development since the 70’. Although we witness a steady development of LCA, several key issues have appeared to hinder its implementations. The operational processing to implement LCA is still far more from accomplishment. Therefore, this section addresses the limitations and drawbacks of LCA.

Lack of proper data

As highlighted in Paper I, the lack of proper LCI data is one main obstacle hindering LCA implementation. The development of a consistent and international-level based database remains as a short-term goal to achieve for LCA practitioners. Due to the differed manufacturing technologies, there emerged numerous commercial LCI databases across diverse industry sectors. Each LCI database consists of a long complex list of inventory emissions, which takes account of the uncertainty influence from technology process, regional condition, and assumption variations. Thus, a controversial analysis result may be obtained when using different LCI databases. In practical cases, the realistic LCI data provided by the manufacture is always preferable than the global average data. However, the real production process of the selected material is usually unknown for LCA practitioners. The current LCI databases still cannot cover all the needed material and processes, thus a wider collection and development of the LCI databases is required.

Involvement of uncertainties

There is an on-going debate over the uncertainty issues of LCA, which has been discussed in several literatures such as Björklund (2002), Heijungs R, Huijbregts M (2004), Baker, J.W. and M. Lepech (2009). The LCA covers a wide broad of parameters and scenarios, which associated with a number of uncertainties and assumptions. These should be handled carefully for the further decision making purpose. The obtained LCA result is not objective, but decisive by the goal and scope definition and various input parameters. It is pointed by several literatures that the uncertainties can arise from LCI database, methodology, modelling construction, choice of parameters, measurement of inputs, scenarios etc. The LCA results may lack of reliability without interpreting those uncertainties transparently. One may obtain a controversial and inconsistent result by applying different LCI data, methodology or functional unit. No criterion is available to explain the significance of the analyzed result, or in what sense option A is better than option B. Moreover, the standardized guidelines for implementing LCA other than the ISO standards are highly needed.

Various methodologies

Currently, a number of LCIA methods have been developed by different research institutes with the emphasis on several specific impact categories, see Table 2.5. For instance, category of carcinogens and non-carcinogens are included in the method of Impact 2002+ and TRACI, but treated distinctly as human toxicity in the method of CML 2007. However, the LCA results are largely limited to the selected method, while a standardized guideline is still missing regarding the method selection. Moreover,

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several impacts (acidification, photochemical ozone depletion and eutrophication) are more refereed to the regional area other than global. Table 2.6 presents the impact treatment factors for global, EU-15, and Denmark within the method of EDIP97. More efforts are required for the establishment of localized impact factors for different geographical areas.

Table 2.5: Impact categories included in different methodologies (Nebel B. et al., 2009)

CML 2007 Impact 2002+ TRACI Eco-indicator 99’ EPS 2000

Abiotic depletion Carcinogens Global warming (GWP 100)

Carcinogens Life expectancy

Acidification Non-carcinogens Acidification Resp.inorganics Severe morbidity

Eutrophication Respiratory inorganics

Carcinogens Climate change Morbidity

Global warming (GWP 100)

Ionising radiation Non-carcinogens Radiation Severe nuisance

Ozone layer depletion

Respiratoty effects

Ozone layer Nuisance

Human toxicity Respiratory organics

Eutrophication Ecotoxicity Crop growth capacity

Fresh water aquatic ecotox.

Aquatic ecotoxicity Ozone depletion Acidification /Eutrophication

Wood growth capacity

Marine aquatic ecotoxicity

Terrestrial ecotoxicity

Ecotoxicity Land use Fish and meat production

Terrestrial ecotoxicity

Terrestrial acid/nutri

Smog Minerals Soil Acidification

Photochemical oxidation

Land occupation Fossil fuels Prod. Cap.

Irrigation water

Global warming Prod. Cap.

Drinking water

Non-renewable energy

Depletion of reserves

Mineral extraction Species extinction

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17 Arbitrary results from weighting

Weighting is an optional stage within the LCIA procedures, which relies on the viewpoints from political, monetary, ethical and cultural sensations. Since there is no societal consensus on these fundamental values, there is no reason to expect consensus either on weighting factors, or on the weighting method or even on the choice of using a weighting method at all (Finnveden G., 1999). Therefore, the weighting results are greatly objective and arbitrary, which should not be used for the environmental clarification or comparison of products.

Table 2.6: Comparison of weighting factors (Stranddorf H. K. et al., 2003)

Normalization reference Weighting factors

Impact Categories

Orig.

EDIP 97

Global EU- 15

Den- mark

Orig.

EDIP 97

Global EU-15 Den- mark

Abiotic depletion

kg Sb

eq./capita/year

N/A N/A N/A N/A N/A N/A N/A N/A

Acidification Kg SO2

eq./capita/year

124 59 74 101 1.3 N/A 1.27 1.34

Eutrophication Kg NO3- eq./capita/year

298 95 119 260 1.2 N/A 1.22 1.34

Global warming

Ton CO2- eq./capita/year

8.7 8.7 8.7 8.7 1.3 1.12 1.05 1.11

Ozone layer depletion

Kg CFC-11 eq./capita/year

0.2 0.103 0.103 0.103 23 4.4 2.46 ∞

Photochemical oxidation

Kg C2H4- eq./capita/year

20 22 25 20

1.2 1.0 1.33 1.26

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Chapter 3. LCA implementation for Railway Bridges

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3 LCA implementation for Railway Bridges

3.1 Current status (Paper I)

Railway bridges have become one of the most important infrastructures in the European transportation system. The European white paper 2011 addressed the strategy that the majority of medium-distance passenger transport should go by rail by 2050 (Europa, MEMO/11/197). Moreover, the European Commission strategized to triple the length of the current high-speed rail network by 2030, which will simultaneously require the increase of the rail infrastructures (Europa, IP/11/372).

The construction activities are not environmental friendly process, that the authorities have realized the importance of evaluating the environmental impact from the construction sector. However, the research on railway bridges has for long time only focused on the technique, economic and safety perspectives; that the implementation of environmental assessment is rarely done. It is a new trend to integrate the environmental assessment approach with the traditional design criteria to achieve the goal of sustainability.

LCA as one of the most systematic methods, has been used in the decision making process regarding the environmental evaluation. It has been widely used in a various sectors, such as agriculture, food, production, building etc., but its application in railway bridges remains almost blank. As mentioned in Paper I, very rare research and literatures can be found on the LCA implementation into railway bridges. Although a number of LCA commercial software are available, they can hardly be applied into railway bridges directly. Mainly because, the railway bridges are complex structures, with the involvement of a large amount of material and energy consumptions through long life span. Bridge engineering knowledge is thus required to make fair assumptions to handle the complicate scenarios in each life stage. Based on those considerations and the similarities between road bridges and railway bridges, Paper I performs a review of the current literatures and knowledge of LCA on road bridges, with highlighting several key challenging issues in this field. Furthermore, a systematic flowchart is introduced as a guideline to demonstrate the LCA implementation into railway bridges.

This section aims to outline the necessary parameters that should be considered for the railway bridge LCA implementation. And an excel-based LCA tool for railway bridges is also developed and presented based on the literature survey.

3.2 A systematic Railway Bridge LCA model

The implementation of LCA into railway bridges requires adequate knowledge of the construction material and the subsequent bridge life cycle scenarios. As the main

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construction material for railway bridges, both of concrete and steel consume large quantities of energy and raw materials during the manufacture stage. Designing a bridge with the optimal environmental performance demands a systematic environmental life cycle assessment. The absence of a systematic LCA model is one of the obstacles hindering the LCA application into railway bridges. Both Paper I and Paper II present a detailed life cycle assessment model for railway bridges; see Figure 1 in Paper I. The material and energy flow in each stage are modeled by the LCI data linked with the specific unit processes. The life cycle stages, bridge structural components and the associated material processing are all important parameters which should be highlighted in the model.

3.2.1 Considered life cycle stages (Paper I, Paper II and Paper III)

All three appended papers illustrated the considered life cycle stages of the railway bridges, either in a general manner (Paper II) or for a specific case (Paper II and Paper III), which reveals that the LCA can be carried out on different levels of details; vary from simplified flowchart to an expanded system in detail. The availability of information regarding the life cycle scenarios always plays an important role through the analysis. With inadequate data, the considered scenarios and structural components cannot be fully included into the analysis. For example, in Paper II, the assessment of temporary support structures, labor work transportation through the construction stage are omitted due to lack of information. The recommendations of a broad set of life cycle stages are listed below:

a) Material manufacture phase takes accounts of the environmental burden from the raw material mining until obtaining the final products at the factory gate.

Through a bridge life cycle, large amount of construction materials are in need, such as concrete, steel, reinforcement, rubber, aggregates etc. The realistic data is usually unavailable from the local supplier, thus the material and energy flows are mostly extracted from the commercial LCI database.

b) Construction phase encompass the environmental burden from the energy consumption of the construction machines, related traffic disturbances, establishment of the temporary structures. Currently there are several methods widely used for the construction of bridges, such as 1) full span supporting method; 2) precast segmental method; 3) balanced cantilever form-traveller cast method; 4) incremental launching method (Guangzhou University, 2009).

Different construction approaches may lead to different energy efficiency in the construction machines, which should be fully considered in the analysis if the relevant information is available.

c) Maintenance and use phase is the longest and an important phase through a bridge life cycle. Table 1 in Paper II presents a series of maintenance activities for railway bridges recommended by H. Tirus, et al., (2010). The maintenance activities and application intervals are important parameters for predicting the extra material and energy consumption. However, this stage involves a large amount of future scenarios; the relevant maintenance schedules vary in each project, thus the modelling is mainly assumed based on today’s knowledge. In

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the maintenance stage, the machinery operation, related traffic disturbances and extra material consumption will all result into extra environmental burdens. The traffic shift during maintenance from train freight and passengers to the road transportation should be counted. The plan of maintenance scenarios can significantly affect final environmental performance.

d) End of life phase concrete, reinforcement and steel are the most commonly used material in bridges, within which steel is 100% recyclable and the scrap can be converted into the same (or higher or lower) quality steels (Doll et al. 2005), the concrete can be crushed into aggregates for road foundations or construction filling. This phase covers several end of life (EOL) scenarios and further waste treatment. The activities include the demolition work, waste sorting and transportation. Waste treatment scenarios take account of material reuse or recycling, incineration and final landfills. The optimization of EOL strategies is important for the environmental performance.

3.2.2 Considered Bridge structural components

Most railway bridges in Sweden are designed for the service life between 80 to 120 years. In order to achieve the lowest life cycle environmental performance, the decision for selecting the optimal bridge design should orient on the selection of material type, construction technology, maintenance schedules and EOL waste treatment scenarios.

Table 3.1 listed a minimum set of structural components that should be considered for the LCA of railway bridges. The main associated materials are mostly concrete, timber, steel, reinforcement. The corresponding inventory data can be found from various sources as described in Chapter 2. A detailed LCI database list can also be found in Table 1 in the appended Paper I.

Table 3.1: Example of structural components to be considered for LCA of the railway bridges

Structure Structural element

Foundation Piles, embankment, abutment

Load bearing structure slab, beam, truss, arch, cable, bracing, steel girder, frame, painting

Railway track Rails, sleepers, fixed slab track, ballast track, rail fasteners, rail pads

Bridge equipment Dehumidification machine, railing, parapet, bearing, joints

Earthwork Drainage, excavation, landfill

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3.2.3 A simplified LCA tool for railway bridges

Currently there are many LCA tools with embedded LCI database developed and available on the market, for instance the tool of ATHENA, BEES 3.0, ECO-it, and Envest are developed for the LCA of building design, the tool of SimaPro, Gabi, LCAiT, and Spin are capable to perform the LCA for a general product. However, among those tools none is specific for railway bridges. Implementing LCA for railway bridges is deemed to be a complex and time-consuming work that requires good knowledge of bridge structures. The reason is mainly because that the bridges have long life span, with the involvement of large amount of material flows and different life scenarios. All those require the adjustment of general LCA framework for the railway bridges. This section presents a simplified excel-based LCA tool developed for assessing railway bridges, by implementing IMPACT 2002+ assessment method and several inventory databases from Ecoinvent v2.1, ELCD, worldsteel and U.S. LCI. Figure 3.1 presents the general structure of this tool, that each step is established in a separate excel spreadsheet.

User Input

The user input spreadsheet requires entering the quantity of material and energy consumption of each structural component considered through the life cycle stages.

The description of the considered life cycle stages and structural components is mentioned in the former section. The input data of the material manufacture phase mainly depends on the selected structure components, the level of detail can vary from considering only few main structural components to covering all of the structural elements with sub-type components in detail. The construction phase consists of the labor work, energy consumptions from the construction machines and the temporary supporting structures. In the maintenance phase, extra environmental burdens are generated from the maintenance scenarios and the related traffic disturbances. The prediction of maintenance activities and the related intervals are the main parameters.

The quantity of consumed material and energy are mostly estimated from the realistic maintenance information. The EOL stage intends to model the future waste treatment scenarios based on today’s technology, which mostly cover the scenarios of bridge demolition, waste sorting, material reuse or recycling, incineration and final landfill.

LCI database

The life cycle inventory results are listed in the tool, which link with all of the input material types. The quality of LCI data is usually dependent on the involved processing activities, that the same type of material may have different LCI profile due to regional and technological differences. A wide range of LCI database for the construction sector is discussed in Paper I. In this railway bridge LCA tool, the LCI data of material, energy and processes are collected from several databases, including Ecoinvent v2.1, ELCD, Worldsteel and U.S. LCI. Table 3.2 presents a list of material type and selected LCI database involved in the tool. Those databases provide transparent data with detailed illustration of each processing procedure. However, in this excel tool, only the final aggregated emission data is used, that 12 types emissions are extracted and presented: Ammonia, Benzene, Carbon monoxide, Nitrogen oxides, Sulphur oxides, Hydrogen chloride, Hydrogen fluoride, Hydrogen sulphide, Carbon

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dioxide, Dinitrogen monoxide, Methane, NMVOC. Those emissions were selected due to their relevance to the contributed mid-point impact category.

Figure 3.1 Structure of the LCA tool

Life cycle impact assessment

In previous chapter, it was mentioned that although a numerous LCIA methods are currently available, there is no ‘exactly one right’ method. That different impact category lists are suggested in different methods, as in Table 2.5. The selection of LCIA method and categories should be compatible on the guidance of initial goal and scope definition. The excel tool implemented the IMPACT 2002+ method, which is a combination of midpoint and endpoint approaches. The output LCI emissions are grouped into seven mid-point categories as listed in Table 3.3, oriented to the damage categories of human health, ecological health, and resource depletion. The assessment is performed on the characterization level and normalization level, that the characterization factors of IMPACT 2002+ method and the normalisation factors from Western Europe 95 are applied. The tool also enables the replacement of the assessment factors from other methods.

User input Material and

energy quantities

LCI result Life cycle impact

assessment Results and Graphs

LCI database unit process and emissions

data

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24 Results and Graphs

The results from the excel tool are illustrated in two levels: 12 types of emissions from the inventory level and 7 types of mid-point impact categories. The results table presents the allocation of environmental burden of each structural component, the quantity of emissions for each material by each life cycle stages; the environmental impact of each life cycle stage; and the total environmental impact of the whole bridge.

Figure 3.2 presents example of characterized and normalized result graphs based on a conceptual input data.

Table 3.2 The material type and related LCI database

Material type LCI database

Welded steel plates World steel

Paint - top coat, per m² U.S. LCI Database hot rolled steel section ELCD v2.0 Crushed stone 16/32, open pit

mining, production mix ELCD v2.0 Hot rolled stainless steel, grade

304 RER S ELCD v2.0

Steel, converter, chromium steel 18/8, at plant

Rubber, normal

Concrete, normal, at plant Reinforcing steel, at plant Zinc coating

Passenger car

Ecoinvent v2.1

Truck transportation Steel recycling

Electricity

Reinforcing steel, at plant

Concrete, sole plate and foundations, at plant

Concrete, high quality Concrete, low quality

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Table 3.3 Selected impact categories and emissions Mid-point impact

categories Unit Considered emissions

Human toxicity kg eq. of chloroethylene in air/kg Ammonia, Benzene, Hydrogen sulphide

Respiratory kg eq. of PM2.5 into air/kg Ammonia, Carbon monoxide, Nitrogen oxides, Sulphur oxides

Photochemical

oxidation kg eq. of ethylene into air/kg Benzene, Methane, NMVOC

Aquatic ecotoxicity kg eq. of triethylene glyco in

water/kg Ammonia, Benzene

Terrestrial

ecotoxicity kg eq. of SO2 into air/kg Ammonia, Nitrogen oxides, Sulphur oxides

Aquatic

acidification kg eq. SO2 into air /kg Ammonia, Hydrogen

chloride, Hydrogen fluoride, Hydrogen sulphide, Nitrogen oxides, Sulphur oxides

Global warming kg eq. CO2 into air/kg Carbon monoxide, Carbon

dioxide, Dinitrogen monoxide, Methane

Towards Sustainable Construction: Life Cycle Assessment of Railway Bridges

Towards Sustainable Construction: Life Cycle Assessment of Railway Bridges

GUANGLI DU

Licentiate Thesis in

Structural Engineering and Bridges

Stockholm, Sweden 2012

Towards Sustainable

Construction: Life Cycle

Assessment of Railway Bridges

Guangli Du

Preface

Abstract

List of publications

Contents

1 Introduction

1.1 Background

1.2 Aims and scope

1.3 Research contribution

1.4 Outline of thesis

2 Life cycle assessment

2.1 Life cycle thinking

2.2 Brief history of LCA

2.3 What is LCA (Paper I)

2.4 Critical issues

3 LCA implementation for Railway Bridges

3.1 Current status (Paper I)

3.2 A systematic Railway Bridge LCA model