Published in the journal Science of the Total Environment, the results of the study contribute to the consideration of life cycle perspective to help decision making.

Researchers at the UNESCO Chair in Life Cycle and Climate Change ESCI-UPF, Barcelona, the University of Medellin, Colombia, and the École des Mines de Saint-Étienne (EMSE), France, have analysed the existing Life Cycle Assessment (LCA) and sustainability methods used in the assessment of an urban region. Published in the journal Science of the Total Environment, the study “Towards life cycle sustainability assessment of cities. A review of background knowledge” concludes that currently sustainability assessment tools not include a life cycle perspectives on the sustainability of an entire city.

Sustainable cities

“Cities are one of the top priorities of international organizations, when it comes to setting sustainable development strategies, both in the economic, social and environmental areas,” says Jaume Albertí, leader of the Sustainable Construction and Energy Research line at the Chair. According to the United Nations Human Settlements Programme (UN-HABITAT), cities consume 78 per cent of the world’s energy and produce more than 60% of all carbon dioxide and significant amounts of other greenhouse gas emissions.

“Cities are gaining relevance to combat environmental impacts such as climate change, but decision-makers generally lack a life cycle perspective,” explains Albertí. An example of how cities are becoming key actors for global efforts reduce global greenhouse gas emissions are “The Guiding Principles for City Climate Action Planning”, presented by UN-Habitat during the United Nations Climate Change Conference, COP 21, held in 2015 in Paris. Parties and participants at the Cop21 highlighted “the role of cities as the place where the struggle to mitigate climate change will be either won or lost”, as stated by UN-HABITAT.

This study is aimed at policy makers, administrators and managers interested in the field of sustainability applied to cities and, especially, to environmental scientists dedicated to investigate whether existing methods are sufficient for a satisfactory sustainability assessment for cities, or developing new methods or evaluation tools in this field.

Life Cycle Assessment as a Tool

The researchers have analysed the existing methods based on Life Cycle Assessment (LCA), in the construction sector, ranging from constructive materials to urban regions. Aimed at analysing the effectiveness of existing standards, indexes and guides for the evaluation of the sustainability of urban cities or regions, the study shows that there is a lack of consensus in the definition of the city and its limits, which hinders the development of sustainability standards.

The study identifies the need for a definition of the city Function, the Functional Unit to allow the comparison between the cities, and the Reference Flow of neighbourhoods, cities, and urban region, to quantify impacts. It also demonstrates the need for a definition of the city boundaries. These are the criteria necessary for evaluating the sustainability of the life cycle of cities, according to existing international standards.

There are examples with evaluations in which the life cycle perspective is applied in complex systems such as neighbourhoods, but not beyond them. “For these systems there is no consensus on the definition of the Functional Unit and, therefore, it is not possible to make comparative assessments between cities or regions,” says Albertí.

Life cycle assessment in the construction sector, ranging from products to urban regions. Credits: Own elaboration.

The analysis concludes that currently sustainability assessment tools not include a complete life cycle perspective. In most cases, only environmental sustainability is evaluated, ignoring the economic and social aspects, necessary for a complete evaluation of the sustainability of a process or product. In many cases, is performed a simplified evaluation considering one of the environmental impacts, such as global warming (CO2 emissions). In all cases, without a common definition of the system used, there is no possibility of comparing the results between different cities or urban regions.

In this context, the research efforts of the Chair are been addressed on developing and using life cycle sustainability assessments to cities, “which implies defining the criteria for evaluating the sustainability of the life cycle of cities, from a life cycle perspective: the city Function, the Functional Unit and the Reference Flow,” concludes Albertí.

This review article is part of the Sustainable Construction and Energy Research line and Energy of the Chair, within the TyLCA Project, which includes Albertí’s PhD Thesis.

Reference article:
Albertí J., Balaguera A., Brodhag C., Fullana-i-Palmer P., 2017. Towards life cycle sustainability assessment of cities. A review of background knowledge. Science of the Total Environment. 609, 1049-1063. doi: 10.1016/j.scitotenv.2017.07.179

Total Environment. 609, 1049-1063. doi: 10.1016/j.scitotenv.2017.07.179 For more information or collaborations:

Jaume Albertí. jaume.alberti@esci.upf.edu