Working on strategies towards urban sustainability

Global sustainability is an issue of urban sustainability since cities have become the primary human habitat. Urban settlements represent only 2.7% of the world's land area. However, the world's cities use over 75% of the world's resources, and they are responsible for 80% of greenhouse gas emissions. For this reason, it is necessary to define concepts and strategies in order to reduce the city's use of natural resources and production of wastes while simultaneously improving its livability, so it can better fit within the capacities of the local, regional and global ecosystems in a framework of social equity and welfare. This dissertation is based on the application of several tools and approaches, many of them derived from the discipline of industrial ecology, to the urban environment and, in particular, to neighbourhoods. Industrial ecology is based on the analogy between natural and industrial systems, and consists of a systematic and integrated way by which an industrial system (i.e. a city, a region) is viewed not in isolation from its surrounding systems, but in concert with them. Ecodesign presents itself as one of the key tools in the move towards more sustainable settlements. Its application in a new neighbourhood in Barcelona has presented the opportunity to discuss and implement several concepts essential to urban sustainability (i.e. urban metabolism, self-sufficiency of resources, land use mixticity, multifunctionality, compactness). Besides, several opportunities and constraints in the process of urban ecodesign have been identified. Then, the concepts of urban metabolism and self-sufficiency are explored in more detail in the following chapters. Thus, an assessment of the energy and water flows in two commercial neighbourhoods (retail parks) is presented. From this, a set of environmental indicators for monitoring is obtained. Besides, the role of urban form in energy consumption and in the urban water cycle is discussed. The research on urban water flows arises two specific questions regarding rainwater harvesting strategies, which are dealt with in two specific chapters. The first one is about the potential of rainwater harvesting of different kind of roofs (both in quality and quantity terms); and the second one is about the economic performance of rainwater harvesting systems in dense neighbourhoods. In addition, several practical examples of the application of some of the concepts, strategies and tools arisen along the research are presented. This results in a set of key methodological ideas that are expected to facilitate a transition towards urban sustainability. These ideas are the importance of acting at an early stage of the design, the need to monitor and assess the performance of the neighbourhood along its life cycle, the requirement of an interdisciplinary team with sufficient understanding of the local context, the incorporation of several essential concepts in the design of neighbourhoods and cities in general (land use mixticity, high-density of the built-up area, urban metabolism and self-sufficiency) and access to information and criteria for urban ecodesign. The consideration of this set of ideas will be useful in the move towards urban sustainability.