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Towards greener road infrastructure Life cycle assessment of case studies and recommendations for impact reductions and planning of road infrastructure
The increasingly serious environmental challenges of our time call for action and it is crucial that our efforts are efficient and aimed at the main sources of environmental impacts. Also, it should be ensured that the reductions of impacts to some environmental issues do not cause unwanted increase of others. Approaches for impact reduction should therefore not look at systems (e.g. goods, services) as being separated from the economy and society, but also account for the ripple effects caused by the system in focus, and include several environmental aspects to avoid problem-shifting. This thesis addresses the environmental aspects related to road infrastructure through a range of case studies from built Norwegian road projects, aiming at identifying characteristics of their environmental performance, potential measures for impact reduction and inclusion of environmental assessments in road planning. The environmental impacts are explored through Life cycle assessment (LCA), ensuring a holistic approach which embraces the whole life cycle and a wide range of environmental issues. The impact assessment method ReCiPe was applied, including 18 impact categories. This study also involves development of LCA tools and methods for application in research as well as in practical road planning, and discussions regarding potential strategies for implementation of LCA in the road planning process. The most comprehensive case study involves two highway projects in southern Norway. One project was construction of a new highway and the other an expansion of an existing highway. These cases were chosen to render evaluation of the importance of the variation in complexity and site characteristics of the constructions. It was found that the environmental impacts related to these case studies differ quite substantially, when compared on the basis of 1 m2 of effective surface area. The main aspects causing the variations are the shares of bridges, tunnels and open road sections within each road case, and different amounts of construction activities. For climate change, the expansion highway case gives about 60% of the impacts compared to the new highway, mainly due to differences in consumption of materials such as concrete, reinforcing and blasting in construction. For some categories the expanded highway causes only 40% of the impacts caused by the new highway. For both cases, the material production and operation and maintenance are the most important stages of the life cycle for most impact categories; material production contributing to slightly more impacts than operation and maintenance. However, blasting and mass transport related to tunnel construction contribute substantially. The overall most important impact parameters, considering all impact categories, are concrete, reinforcing, steel, blasting and asphalt in maintenance. This work also includes LCAs of 52 separate road elements (9 road sections, 10 tunnels and 33 bridges), which vary in size and design and are compared on the basis of 1 m2 of effective surface area. In most cases the road sections cause the lowest impacts and bridges most. There are, however, variations here as some of the road sections are more emission intensive than some of the cases in the other elements categories. For road sections the asphalt consumption, especially in maintenance, cause significant impacts to the majority of the impact categories; in many cases more than half of the totals. Other important parameters are blasting, masstransport and steel guardrails. For tunnels, concrete and reinforcing cause high shares of the overall impacts in several impact categories, and blasting cause 70 to 80% of the totals to some categories. Ventilation and lighting in the use phase are also important factors, accounting for 15 to 20% in more than half of the impact categories. Bridges are addressed separately according to what is the main material in the load-bearing system. For concrete bridges, concrete and reinforcing dominate the impacts even more than in the case of tunnels. Overall, reinforcing contributes between about 25 and 70% of the impacts and concrete causes about 30 to 50%. Other material inputs causing significant impacts are steel, asphalt (mainly in maintenance) and electricity for lighting during operation. Steel contributes the main share of the impacts in almost all categories for steel bridges, from about 40 to 90%. Concrete inputs also contribute significantly, from 20 to 40%, in the majority of categories. Other important parameters are electricity consumption for lighting and asphalt. For timber bridges, steel is the input parameter contributing the most to impacts in most categories, followed by concrete and laminated wood. Copper is also causing significant impacts to many of the categories. ReCiPe endpoint and normalised scores are calculated for the case studies. The results indicate that for road infrastructure, the most important environmental impact categories are human toxicity, particulate matter formation, fossil depletion and climate change. The second most important categories are agricultural land occupation, natural land transformation and metal depletion. This differs from what is found in previous literature and the Product Category Rule for road infrastructure. This work has contributed to the development of four LCA tools for road infrastructure; a) the SimaPro model developed for this study, b) BridgeLCA, c) the LCA module in EFFEKT, and d) the Process code LCA model. The SimaPro model on road infrastructure is fully developed by the author, for this particular research study. BridgeLCA is developed, with significant contributions from the author, as part of a joint Nordic research project (ETSI). This tool is meant for use in planning and design of road bridges in the Nordic countries. The LCA module in EFFEKT is developed by the author in collaboration with the Norwegian National Public Road Administration, for integration in the cost-benefit analysis that is part of the planning process of road infrastructure. Three bridges (steel, concrete and timber) are analysed with BridgeLCA and three alternatives for crossing of a fjord are assessed in EFFEKT. Through supervising of a master student, a first version of the Process code method is developed, for research purposes and for investigating whether such a method could be suitable for integration in road planning procedures. It is in the early planning stages of a road project one has the largest potentials for reducing environmental impacts, as it is here the big decisions are made, such as choosing the alignment of one new road corridor among several alternative ones. Hence, it is highly beneficial to have good methods for evaluating life cycle environmental impacts at early stages of planning. The LCA module included in the EFFEKT software is considered a good starting point for this, but this study shows that the method is too coarse to be able to provide the needed accuracy in LCA results, when compared to the use of more detailed methods. The challenge at early stages of road planning, however, is a lack of good estimates for the consumption of materials and energy and the amount of different activities in the construction and operation stage, hence such information is often limited and must be deducted from merely geometrical parameters of the road infrastructure. The inclusion of LCA in later planning stages, with a satisfactory level of accuracy, is a lot easier than is the case for the early planning stage. Information from such studies at later planning stages should preferably inform also the LCA tools at early stages of planning. However, if such a tool is to be an integrated part of the planning procedures for road infrastructures, the methodology, structure, accessibility and complexity of the tool must be thoroughly considered, to ensure comparability of the quality of the assessment regardless of level of LCA experience from the user.