Sustainable Urban Metabolism

Abstract

Abstract Cities’ performance is key to a more sustainable society. The complexity of urban sustainability seeks forstrong methodologies in assessing production and consumption activities of cities. In view of a bioinspiredmetaphor “metabolism”, a city can be seen as an organism that intakes, digests, and releases materials andsimultaneously exchanges energy with the external environment. Urban metabolism (UM) has become amethodological framework in which the analyses of all the energy and material flows associated with theproduction and consumption activities in cities are encapsulated. A range of approaches of measuring theintensity and structure of UM are evaluated for their applications and insights for urban sustainability. Urbanmetabolicdataandcasestudiesarealsooverviewed.Last,butnottheleast,futureprospectsregardingresearchdevelopment of UM are discussed for their potential application in urban energy and infrastructure planning. INTRODUCTION The majority of population now resides in cities. Oururban reality can be defined as the gathering of largeamountofmaterials,highdensityofcommercialbuildingsand residence, and intensive disposal of emissions, efflu-ent, and solid waste. Although cities themselves are not anew phenomenon, they are growing and expanding at apace that we could not foresee in the past. In fact, metro-politan area has become a more appropriate term for someof complex urban systems. Living in a city or a metropol-itan area is without doubt a great promotion for humanwell-being, given its convenient mode of life and efficientwayofworking.However,adeepconcernhasbeensharedby public and scientists that the unprecedented develop-ment of cities has caused a range of environmental pro-blems and exerts huge pressure on natural ecosystems thatwe rely on. Essentially, cities change the social organiza-tion of energy and materials with their intense consump-tion and production activities. The sustainability of thehuman society can be greatly improved, given betterdesign and management of these urban activities.The concept of urban metabolism (UM) is proposed toanalyze the energy and material flows of cities in quest of abetter understanding of sustainable urban system. The pur-pose of this entry is to provide an overview of the coreconcepts of UM and how they can be applied to assessingsystemsustainability.Itmayguidebothsciencecommunityand the public to build resource-efficient and knowledge-driven urban environment. In this entry, the fundamentalconcepts of UM and other related terms are defined andexplained. Following that, major methodologies and indi-cators for UM study are briefly discussed and comparedfor their merits and limitations. Next, the case studies con-cerning energy andmaterial flows of cities are reviewed forvarious metabolic flows that were investigated, and thesources of existing database for UM study are explored.The relationship between the application of UM and theassessmentof sustainability is alsodiscussedfrom differentperspectives, suggesting the need of applying the knowl-edge of UM for a more sustainable urban planning andmanagement.