The growing urbanization of the planet, visible in the fact that by the middle of this century some 70% percent of the population will live in cities, situates the urban question as a key issue for global sustainability. Many of the causes generating the huge environmental crises, climate change for instance, have their rationale in the metabolic inefficiency of our cities. Greater metabolic efficiency contributes to the energy rationalization of urban system and also contributes to greater urban competitiveness. Urban metabolic analysis demonstrates efficiency that small and medium-sized cities can have in the new neo-tertiary context, and could be used as a test to previously evaluate the functional and ecological consequences of future urban transformations.
