Environmental Life Cycle Assessment of Bridges

This paper presents a detailed comparative environmental life cycle assessment (LCA) case study of three built bridges in Norway. To encompass a wide scale of bridge designs, the analysis dealt with a steel box girder bridge, a concrete box girder bridge, and a wooden arch bridge. This study presents the first LCA of road bridges using a standardized bridge classification. The LCA includes a wide range of pollutants and a high level of detail in life cycle material and energy consumption. Findings here and from earlier LCAs on bridges are together used as bases for general recommendations on conducting LCAs on bridges. The study shows that it is the production of materials for the main load-carrying systems (i.e., the bridge superstructure) and the abutments that accounts for the main share of the environmental impacts, as these parts require large quantities of materials, with a limited number of materials being the important ones. The construction phase accounts for relatively fewer impacts. The use phase contributes more significantly, mainly because of resurfacing with asphalt. Use of building equipment and transport of personnel in all the life cycle phases are of minor importance, as are the use of formwork, mastic, blasting, and the end-of-life incineration of wood. The environmental issues of global warming, abiotic depletion, and acidification are found to be the most important given the assumptions made in this study. A comparison of the three bridges shows that the concrete bridge alternative performs best environmentally on the whole, but when it comes to global warming, the wooden bridge is better than the other two. The results support the idea that it is possible to decide upon environmentally effective design alternatives, at a fair level of accuracy, at different stages of the bridge design process, a target that is now becoming more and more emphasized in the bridge-engineering sector.