Exploratory: Sustainable Cities for Citizens

In recent decades, the relationship between urban development and sustainability has become increasingly evident and important. The expansion of the urban environments, while doubtless bringing advantages and merits, is linked also to global challenges of sustainability, particularly in regions where the process of urbanization is still unfolding. In urbanized regions such as Europe, where more than 70% of people are urban dwellers, sustainability is one of the most important challenges, especially regarding the use of energy, energy efficiency, and de-carbonization of infrastructures and cities (European Commission and European Investment Bank, 2016).

Cities and urban communities can play a crucial role in the global work of improving sustainability [4]. The urban population in 2016 was 54% of the total global population and the proportion is expected to grow to 70% by 2050 [3]. While cities are prized for being drivers of innovation, social experimentation, and economic growth, rapid urbanization has brought major social and environmental challenges. With increasing density and complexity of all elements of the energy system, e.g., energy generation and distribution systems, transportation, consumption of food, goods, and services, waste handling, supply of fresh water, and other ecosystem services, cities are responsible for more than 60% of energy consumption and generate an estimated 70% of human-induced greenhouse gas emissions, contributing strongly to climate change [5]. As urbanization increases, cities will need to become more sustainable and the growing urban population will require new and innovative ways to manage urban living. This will require identification of new solutions to overcome problems such as overcrowding, social exclusion, declining human wellbeing, high energy consumption, inefficient resource management, and environmental degradation.

Within this vision, the European Union advocates improving sustainable development, contributing to a reduction in greenhouse gas emissions in line with the EU’s 2020 Climate & Energy Package [6], which defines targets for 2020 (20% domestic reduction in greenhouse gas emissions; 20% increase in renewable energy; 20% reduction in energy use). The new Climate & Energy Package [7] recently defined further stricter targets for 2030 (at least 27% improvement in energy efficiency; at least 27% renewable in energy consumed; 40% domestic reduction in greenhouse gas emissions).

To meet these targets, the European Union is developing policies to improve the sustainability of EU cities. However, despite the fact that “sustainable cities” are considered a game changer for the future of European urbanization, a standard method for assessing the environmental performance of cities and their infrastructures is not specified. In general, the methods used to evaluate the sustainability of cities focuses on assessing the single points of view (e.g. transport, energy, policies, etc.) with the aim to build a set of measures able to provide the user with a wide view.

This post is based on a paper by Maranghi et al. [1], in which the authors propose an approach to analyse urban sustainability by integrating urban metabolism (UM) and life cycle assessment (LCA) in a complex systems perspective. By means of a multiscale view of the city, they advocate a synergy between UM and LCA to cope with urban sustainability both from the macroscale point of view (UM, requiring large-scale data) and the microscale point of view (LCA, requiring more detailed data). They propose a survey aimed at reducing the dichotomy between the macro and the micro scale and find an appropriate set of measures to realize a trade-off between the granularity of the data that needs to be collected for the two scales.

As a guiding principle to decide to which granularity should be selected to appropriately develop both UM and LCA studies, they refer to the theory of complex systems and design a model based on urban subdimensions, following the approach based on ecological networks proposed by Zhang and colleagues [8,9] for urban energy systems. They also consider that the sustainability of a city – a complex, dissipative system – should be assessed considering energy, material, and information flows at scales that offer an overall view (as in the UM approach), while at the same time giving insights into processes going on in the city, i.e., how flows are transformed and efficiently used (as in the LCA approach). The combined approach involves implementation of UM and LCA at an urban scale that is suitable for both approaches.

The authors also formulated an appropriate data collection approach that considers the main dimensions of a city and its transformation processes. Such transformations include flows of material, energy and information, as well as the role that utilities, policy and decision makers play. These two aspects are further combined by the resulting quality of life for citizens. Urban metabolism is suitable for studying the city at a wider scale, without entering into spatial or temporal details, while LCA can be applied on smaller spatial and temporal scales and is usually applied to smaller subsystems.

In the figure below is possible to see the integrated approach proposed in the paper and its follow-up suggesting a non linear model for the urban environment based on the multiplex network theory.

The paper [1] describing this research has been recently published and it is available here: https://doi.org/10.1016/j.ecolind.2020.106074.

[1] Simone Maranghi, Maria Laura Parisi, Angelo Facchini, Alessandro Rubino, Olga Kordas, Riccardo Basosi, “Integrating urban metabolism and life cycle assessment to analyse urban sustainability”,Ecological Indicators,Volume 112,2020,106074,ISSN 1470-160X,

https://doi.org/10.1016/j.ecolind.2020.106074.

[2] Fath, B.D., Scharler, U.M., Ulanowicz, R.E., Hannon, B., 2007. Ecological network ana-

lysis: network construction. Ecol. Model. 208 (1), 49–55. https://doi.org/10.1016/j.

ecolmodel.2007.04.029.

[3] European Commission and European Investment Bank, 2016. “Smart Cities & Sustainable Development” Program in Europe.

[4] Wolfram, M., Frantzeskaki, N., Maschmeyer, S., 2016. Cities, systems and sustainability:

status and perspectives of research on urban transformations. Curr. Opin. Environ.

Sustain. 22, 18–25. https://doi.org/10.1016/j.cosust.2017.01.014.

[5] UN-Habitat, 2011. Cities and Climate Change: Global Report on Human Settlements.

Earthscan, London ISBN 978-1-84971-370-2.

[6] European Commission, 2008. Package of Implementation measures for the EU’s objectives on climate change and renewable energy for 2020, Brussels.

[7] European Commission, 2014. A policy framework for climate and energy in the period from 2020 to 2030. COM (2014) 15 final, Brussels.

[8] Zhang, Y., Lu, H., Fath, B.D., Zheng, H., 2016. Modelling urban nitrogen metabolic

processes based on ecological network analysis: a case of study in Beijing, China.

Ecol. Model. 337, 29–38. https://doi.org/10.1016/j.ecolmodel.2016.06.001.

[9] Zhang, Y., Zheng, H., Fath, B.D., 2015. Ecological network analysis of an industrial

symbiosis system: a case study of the Shandong Lubei eco-industrial park. Ecol.

Model. 306, 174–184. https://doi.org/10.1016/j.ecolmodel.2014.05.005.

Written by: Agnese Bonavita

Revised by: Luca Pappalardo