Emergy Assessment for Urban Sustainable Development

This paper is a study of the use of emergy indices for the evaluation of sustainable urban development. The Emergy Exchange Ratio (EER) and Emergy Waste Index (EWI) were introduced into the Emergy Sustainability Index (ESI) to establish a new index that reflects the emergy benefit per unit cost of environmental impact, which includes the market exchange and pollution/waste flow in the measurement of the system’s sustainability. The new index was named the Emergy Index for Sustainable Development (EISD). Furthermore, the new EISD has been employed to conduct a case study to evaluate the development of three typical urban ecosystems in China from 1996 to 2000. The general EISD of the city of Zhongshan is 8.4 times higher than that of Beijing and 1.2 times higher than that of Guangzhou. Although the degree of urbanization of Guangzhou is similar to Beijing, the general EISD of Guangzhou is 3.2 times higher than that of Beijing, partly due to the superior environment bearing capacity of the natural subtropical ecosystem. The EISD of these three urban ecosystems generally declined following initial increased urbanization at the beginning of the period. The EISD of Beijing and Guangzhou rose again from 1999 to 2000 as a result of environment protection and industry reorganization. All of the three cities, especially Beijing, need further reorganization of their industrial structure to improve the Emergy Exchange Ratio (EER) of their products and decrease environmental impacts, and finally, to improve their ability for sustainable development. The case study shows that EISD can assess the sustainable development ability for different sites, considering environmental impact and social-economic effects at the same time.