Despite urban areas covering less than 1 of the world, they host over 50 of the world's population. As population and human activities expand they exert heavy environmental pressure through the resource requirement, their production and consumption. Hence, it is important to understand the resource flows into the city, the transformations that take place and the resulting products and wastes. One method of measuring resource use efficiency is through the analysis of urban metabolism. It provides a good analytical framework for accounting of urban stocks and throughputs and helps understand critical processes as well (increasing or decreasing ground water resources, long-term impacts of hazardous construction materials, etc.). We have considered Mumbai, a business and industrial city, with a population of about 18 million, as a case study. It highlights the economic, social and environmental conditions of the city. On the input side, water, energy, food and construction material use are taken into account, and on the output side, wastewater, air pollution and municipal solid waste are examined. From the methodological point of view, it is easier to examine the input side but there are some difficulties from the output end. Similar difficulties can be found in the identification of built-in material stock (buildings, roads, etc.). The material stock is limited to building stock and passenger vehicle fleet. The concept of urban metabolism is put forth as an organizing concept for data collection, analysis, and synthesis on urban systems. The main findings and recommendations of the case study underpin efficient resource urban policy and design, as well as enhance sustainable production and consumption.
