A MuSIASEM And Emergy Based Study On Measuring Urban Metabolism In Megacities

Megacities consume a large amount of energy and materials,leading to associated environmental impacts.The main reason is that megacities are experiencing irrational urban metabolism.Urban metabolism is defined as the total sum of both technological and socioeconomic processes that occur in one city.Research methods such as material flow analysis,energy flow analysis,input-output analysis,ecological footprint,emergy analysis and multi-scale integrated analysis of societal and ecosystem metabolism(MuSIASEM),are the main methods in this research field.This paper chose MuSIASEM as the main method.MuSIASEM is a synthetic and effective tool for analyzing the metabolic pathway of a system.By extending the MuSIASEM to the N-3 level(detailed industrial sectors)and combining this method with emergy analysis,this study provides a unique analysis framework on urban metabolism and can better identify the resource consumption process occurred during the urban metabolism.A case study of Shanghai and Tokyo is conducted.The results show that Shanghai had a higher exosomatic energy metabolic rate(EMR)but a lower economic labor productivity(ELP)for its metabolism.At the level of N-1(paid work sector and household sector),biological and economic pressure(BEP),societal overhead of human activities(SOHA)and societal overhead of exosomatic energy throughput(SOET)of the two cities are analyzed,indicating that Shanghai is facing a higher environmental and resource pressure.At the level of N-2(the primary,secondary and tertiary sectors),the structures of the paid work sector in both cities are analyzed,in which the ELP of the tertiary sector is the most important determinant for the high ELP of the urban system.At the level of N-3(detailed industrial sectors),the structures of the secondary and tertiary sectors in both cities are analyzed.The results show that manufacturing is largely attributed for the high EMR in Shanghai.Finally,an analysis on manufacturing,retail and transportation industries in both cities based on emergy and MuSIASEM is conducted.The results show that Shanghai has consumed a large amount of ecological resources for its urban metabolism.Based on the research results in this study,several policy recommendations are raised to support the city to move toward sustainable development.