Developing an integrated framework to quantify sustainability indicators in the context of urban systems

Urban systems can be considered living organisms driven by flows of matter and energy (biophysical approach). In addition, the fact of concentrating many people in a small space also implies socioeconomic aspects of coexistence. Currently 60% of the world's population is concentrated in cities. This makes cities great consumers of natural resources, generating a large amount of greenhouse gas emissions, as well as waste. Therefore, this thesis aims to apply and to develop methodologies to determine and quantify the degree of sustainability that Spanish cities have and thus identify their weaknesses. Therefore, this thesis is intended to serve as support for political leaders when making decisions and to create lines of action to improve and achieve the goal of a sustainable city

Assessing the sustainability dimension at local scale: Case study of Spanish cities

Nowadays, cities host most of the world population. As a result of human activities within their boundaries, most greenhouse gases emissions, natural resources consumption and waste generation are concentrated in urban areas. For these reasons, studies focusing on assessing the sustainability of cities have increased in recent decades. Bearing in mind the three pillars of sustainability (social, economic and environmental), this study aims to evaluate the level of sustainability of 31 representative Spanish cities through multiple sustainability indicators, which have been aggregated into a composite sustainability indicator that is reported by a three-letter code. Thus, each pillar of sustainability is represented by a letter A, B or C in the three-letter code, so that the letter A corresponds to the best rate and C to the worst. Within the geographical and socio-demographic framework of Spain, the results show considerable differences between the cities in the south and the north of the country. Accordingly, most of the cities with the best sustainability scores according to the award of at least two A in the three-letters code are located in the north of the country. Examples of this category are Pamplona and L’Hospitalet de Llobregat (both ranked as AAA). Cities such as Murcia, Gijon, Badajoz and Huelva obtained the worst ranking with the CCC rating. For this group of cities, actions for the improvement of sustainability have been identifiedThis research was supported by a project granted by the Spanish Government and FEDER/Ministry of Science and Innovation – Spanish National Research Agency (CTQ2016-75136-P) and by a project granted by Xunta de Galicia (project ref. ED431F 2016/001). Dr. S.G.-G. would like to express her gratitude to the Spanish Ministry of Economy and Competitiveness for financial support (Grant reference RYC-2014-14984). The authors belong to the Galician Competitive Research Group GRC ED431C 2017/29 and to the CRETUS Strategic Partnership (ED431E2018/01). All these programs are co-funded by FEDER (UE)S

Environmental analysis of servicing centralised and decentralised wastewater treatment for population living in neighbourhoods

The planning and construction of large-scale wastewater infrastructure, such as sewerage networks and wastewater treatment plants, is undertaken by the public sector or by publicly regulated monopolies. Only on smaller scales can infrastructure be managed by private companies or through local collective initiatives. Within this framework of water cycle management, there is an increasing movement of the population towards cities where economic activity is concentrated. This scenario is particularly pronounced in certain regions of the world and makes it necessary to rethink whether decentralised treatment offers a way of ensuring the servicing of wastewater treatment in new urban developments, alleviating pressure on facilities that are at the limit of their capacity. In this study four systems were evaluated: two centralised and two decentralised configurations, from an environmental and economic perspective, posing as working hypothesis how different wastewater treatment schemes influence the carbon footprint of the population living in a neighbourhood. The analysis of the results identifies that the decentralised systems present a reduction in the carbon footprint of residents of around 20–23 % depending on the technology considered. In addition, reclaimed water can meet the water quality requirements for irrigation of the green areas in the neighbourhood. Although decentralised systems have higher construction costs, they can be amortised due to lower energy consumption, so the payback time is estimated to be 8–9 years, lower than that of centralised systems. Considering the problems associated with changing and replacing existing networks, decentralised wastewater treatment systems is especially recommended for new dwelling developments, based on its environmental and economic indicatorsThis research was supported by the EU project: Run4Life (GA no 730285-1). The authors belong to the Galician Competitive Research Group GRC ED431C 2017/29) and to the CRETUS Strategic Partnership (ED431E 2018/01). Dr. S. González-Garcia would like to express her gratitude to the Spanish Ministry of Economy and Competitiveness for financial support (Grant reference RYC-2014-14984). All these programs are co-funded by FEDER (EU)2022-06-28S