Emergy analysis of urban metabolism in Beijing

Urban metabolism is a self- organizing system within materials,energy,money and human labor flows,which is a hot topic in the area of urban sustainable development research. Based on the emergy theory,we analyzed the urban metabolic emergy system's structure,intensities,environmental pressures and output efficiencies. The conclusions are drawn that since 2001 to 2010,the import and export emergy growth contributed mostly to the emergy consumptions of Beijing metabolic system. Emergy use intensities of Beijing had increased with the rapid rise in the non- renewable resource emergy and import emergy,which resulted in the increasing environmental pressures and gradually declining of output efficiency and sustainability. Facing the growing resource and energy shortage,Beijing should encourage the exploitation and utilization of renewable resources and energy,increase the consumption efficiency of non- renewable resources and energy,establish the mechanism to re- use wastes of resources and energy to promote the urban metabolism in Beijing.