Life Cycle Assessment of a Norwegian Bridge
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Life cycle assessment (LCA) methodology aims at evaluating the environmental impacts of a product or system from a holistic approach. In this methodology, all life cycle phases of the product are identified and assessed, from the raw material acquisition to the end-of-life phase. This master thesis is dealing with the LCA of a Norwegian bridge. First, a literature review is realized by going through 14 bridge LCA references. Then, a detailed description of bridge LCA methodology is performed. Finally, an LCA study is applied on Tverlandsbrua, a Norwegian bridge project, in order to assess the overall global warming impact of the bridge life cycle. The conclusions of the literature review are very different according to the goals and scopes of the studies. Concrete and timber bridges are often more environmentally performing than steel or composite concrete-steel bridges. Material production is generally the life cycle phase leading to most impacts, followed by the maintenance & repair phase. Improvements in material design and use of recycled materials are important to bring down the overall emissions. The LCA methodology description has been through all elements specified in the ISO standards. The methodology has been adapted to the needs of the case study but the goal and scope definition has been kept wide enough to allow comparisons with future bridge assessments. Input data (energy, material flows, etc.) are as much as possible gathered from the client and subcontractors of the project, but sometimes assumed. Output data (greenhouse gases emissions) are either directly collected from environmental reports or calculated by an LCA software. The overall global warming impact of Tverlandsbrua is 6665 kgCO2-eq per functional unit (FU), all life cycle phases considered. The FU, i.e. the unit to which the emissions are referred, is defined as 1 square meter effective bridge deck area through a lifetime of 100 years. When the operation phase (mainly consisting of traffic-related emissions) is not considered, the emissions are brought down to 1358 kgCO2-eq per FU. Concrete, steel and asphalt life cycles are identified as the main component contributors. Uncertainty and sensitivity analyses, discussions and recommendations for further studies are performed in order to give clues for more environmentally performing solutions.