Environment and Complexity of the Urban System of Rome (Italy): An Emergy Synthesis

A preliminary assessment of the direct and indirect environmental support to the stability and sustainability of the urban system of Rome, Italy, was performed by means of the emergy synthesis approach. A raw inventory of mass and energy flows is firstly provided. Then raw data are converted into emergy flows driving the urban system. Finally, performance indicators are calculated. Emergy synthesis provides a way of assessing the interplay of human-dominated systems, and their surrounding environment, by quantifying the renewable and nonrenewable, local and imported resources, environmental services, and driving forces at the larger scale of the biosphere. The population of the city of Rome is 4.4 percent of the total Italian population and its emergy use is about 4.0 percent of total Italian emergy use. Emergy use per capita is 5.50E+16 seJ/yr, compared to an average value for Italy of 3.60E+16 seJ/yr. An empower density of 1.09E+14 seJ/m/yr was calculated for Rome, much higher than for average Italy, 6.86E+12 seJ/m/yr. Finally, the emergy/GDP, an indirect measure of economic performance of the system, is 2.43E+12 seJ/€ for Rome compared to 1.64E+12 seJ/€ for Italy, suggesting that in an urban system (generally characterized by a larger fraction of tertiary activities) the required environmental support for the generation of economic results is much higher than for the whole economic system. Results for Rome are compared with similar studies published by other authors for the cities of Taipei, San Juan and Macao.