Conclusions

LCA literature has dealt with the environmental impacts of multiple elements of the urban fabric. However, studies only showed the individual performance of certain elements. This study compiled LCA data in an attempt to quantify the environmental burdens of an entire street profile as a whole, thereby combining the impacts of the elements that constitute the urban fabric: the paved skins and the subterranean networks. The best and worst practices were identified.

The best practices in the design of streets accounted for a carbon footprint of

1.1 t of CO2 eq. This design consisted of concrete sidewalks, asphalt pavements, HDPE gas pipes, PVC water pipes, and concrete sewer pipe with CP1 trench. When considering this configuration in urban planning, the global warming potential of streets can be reduced by 23 %. The most impacting scenario included the following practices: granite in sidewalks, LDPE in water supply pipes and HDPE in the sewer system with PP2 trenches. Pavements and sidewalks are the most contributing elements to the overall environmental burdens of streets, mainly because their exposition intensifies their maintenance.

Proper urban fabric design must consider three key aspects: the material selection, lifespan and, in the case of subterranean networks, the installation procedures. First, promoting cleaner production in the construction materials sector (e.g., granite production, Mendoza et al. 2014b) is essential to reduce the environmental burdens of constructive assets and achieve major environmental improvements at city level. Second, lifespan must be included in the design parameters of long-term urban planning. Third, the installation of subterranean networks has a relevant contribution to the total impacts and must be adapted to the technical and environmental requirements of the construction site.

Studies that quantify the environmental burdens of urban elements provide basic information for the decision-making process when environment is considered in urban planning. Thus, the application of life cycle thinking implies the inclusion of environmental criteria during the conception of cities. Towards a sustainable design of cities, urban planning studies might also integrate the social and economic dimensions in the decision-making process. From a life cycle perspective, Social Life Cycle Assessment (S-LCA) (UNEP/SETAC 2009) and Life Cycle Costing (LCC) (ISO 2008) methods may provide a standard quantitative way to assess urban elements.

 
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