Environmental assessment of Smart City Solutions using a coupled urban metabolism—life cycle impact assessment approach

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The purpose of the study is to quantify the environmental performance of Smart City Solutions at urban system level and thus evaluate their contribution to develop environmentally sustainable urban systems. Further, the study illustrates how this quantification is conducted. The case city chosen in our modeling is Copenhagen, where seven Smart City Solutions are introduced: Green Roofs, Smart Windows, Pneumatic Waste Collection, Sensorized Waste Collection, Smart Water Meters, Greywater Recycling, and Smart Energy Grid. The assessment is conducted using a fused urban metabolism (UM)-life cycle assessment (LCA) approach, referred to as UM-LCA. The UM-LCA uses metabolic flows across an urban system as inputs and outputs in an LCA. All life cycle stages of the metabolic flows can be accounted for by using this approach and burden shifting from one stage to another is made quantifiable and hence transparent. The impact assessment is conducted using the ReCiPe method. The results obtained for the midpoint indicator, global warming potential (GWP), show reduced environmental performance effect at 75% relative to a business as usual reference scenario by introducing Smart Windows. Furthermore, the GWP indicator shows an environmental improvement of 10% for a Smart Energy Grid solution. Introduction of Pneumatic Waste Collection or Greywater Recycling reveals a minor negative performance effect of 0.76 and 0.70%, respectively, for GWP. The performance changes in terms of GWP for the remaining solutions are so small that these are expected to be within the uncertainty of the calculations. To obtain endpoint indicators (damages), the entire palette of ReCiPe indicators is included. The results of the endpoint indicator assessment yield a tendency similar to the one observed for climate change. It is found that the implementation of Smart City Solutions generally has a negative influence on the environmental sustainability performance of an urban system. The limited positive influence from the Smart City Solutions is due to burden shifting from the direct impacts of the urban system to embedded impacts which are out of sight for most policy makers. The influence of the Solutions on Copenhagen is generally small, due to a focus on reducing in areas that are not a large environmental burden in Copenhagen. The results are not sufficient to discard the idea of using Smart City Solutions to reduce environmental impacts, but highlight the importance of choosing solutions with the right focus and optimizing the design to best fit the intensions.