Urban Metabolism Evaluation Methods: Life Cycle Assessment and Territorial Regeneration

Abstract

Urban Metabolism (UM) is a scientific phenomenon that comprises individual processes taking place in all cities at different spatial and temporal scales and that is based on the principle of conserving mass and energy. Analysing the metabolism of a city allows one to evaluate the impacts of urban functioning, taking into account the flows of energy, water, nutrients and waste and the materials in general that circulate within a city, and contributing to a multidimensional assessment of sustainability. Many authors have explored the phenomenon of UM and experimented with indices and evaluation methods, but there is still no consensus on the best assessment methods to use. The present paper presents an overview of UM assessment methods, particularly Life Cycle Assessment (LCA) and its possible uses for supporting territorial regeneration. A literature analysis is conducted of the evolution of this method in relation to scales that are different from the single product scale. LCA aims to assess the environmental impacts of the life cycles of single industrial products and services, but over the years it has gained increased attention in the urban planning field. Life cycle, in general, refers to all the phases that characterise the life of elements, comprising not only a single product, but extending this concept also to the wider territorial system. The concept of the life cycle of territorial systems is related to the evolution of the territory as a heritage and as a system of environmental, social and economic resources and services, whose transformation is linked to the different forms of governance. The territorial life cycle is formed by interconnected phases, referred to as the sub-systems of the resources and performance of a territory, that follow a predefined plan scenario. Consequently, the life cycle concept can be compared to that of change and it is closely linked to the analogy of ecosystems and the urban environment, which views the city as an entity in constant transformation. In the last few years, there has been an increase in activity in the LCA application field, with the introduction of scale variations and of the distinction between applications at the level of the single product and applications at the meso and macro levels. In other words, this approach is evolving and applications and hypotheses involving scales different from the micro scale are becoming popular. In this regard, extending the LCA tool to a meso perspective on a municipal scale or an individual urban district scale could prove to be a valid tool for assessing the sustainability of a territory with regard to the metabolic flows and the evolution of its life cycle.