Ecological Indicators 85 (2018) 276–284

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Ecological Indicators

journal homepage: www.elsevier.com/locate/ecolind

Research paper Efficiency estimation of urban metabolism via Emergy, DEA of time-series MARK ⁎ Yi Wua,b, Wei Quec, , Yun-guo Liua,b, Jiang Lia,b, Li Caod, Shao-bo Liue, Guang-ming Zenga,b, Jing Zhangf a College of Environmental Science and Engineering, University, 410082, PR b Key Laboratory of Environmental Biology and Pollution Control (), Ministry of Education, Changsha 410082, PR China c School of Economy and Trade, Hunan University, Changsha 410082, PR China d School of Business Administration, Hunan University, Changsha 410082, PR China e School of Metallurgy and Environment, , Changsha 410083, PR China f College of Chemistry, University, Xiangtan 411105, PR China

ARTICLE INFO ABSTRACT

Keywords: Evaluating the efficiency of urban metabolism is an effective tool to quantitatively analyze the relationship Efficiency of urban metabolism between social, environmental and economic input and output in an urban ecosystem. In this paper, there are the Emergy combination Emergy synthesis, Principal Component Analysis (PCA) and Date Envelopment Analysis (DEA) of DEA of time series time-series approach to comprehensive assessment urban metabolism for the first time. DEA of time-series has Changsha the advantage of fully considering the technology changes every year, it can reflect clearly the overall situation of urban metabolism, including the use of various resources and the development of environmental sustainability cycle. The results show that, with the overall efficiency of metabolism ensured a generally steady rise in Changsha, the trend of urban environmental load rate is increased obviously, there is facing the huge pressure of ecosystem in Changsha. This paper suggests that government and enterprises should take measures to promote the con- struction of the eco industrial park, gradually realize industrial symbiosis, upgrade through the adjustment of energy structure and industrial structure.

1. Introduction compares the urban to an ecosystem or an organism, having inputs, transformation and outputs of material and energy, i.e., a metabolism With the advancement of urbanization in the world, urban systems (Conke and Ferreira, 2015). The concept of urban metabolism is an are increasingly becoming the center of human habitation, commercial application of biological metabolism to elaborate urban development activities and engines of economic growth in a globalized world. Since issues (Pincetl et al., 2012). In 1965, Wolman first time introduced the 2007 more than half of the global population lives in cities, a propor- concept of urban metabolism, the concept used to describe the meta- tion that is expected to increase to 60 per cent by 2050, mega-cities bolism of matter and energy exchange between nature and society with more than 10 million people are increasing in number (Facchini (Wolman, 1965). Urban metabolism urban complex ecosystem re- et al., 2016). The influx of large population into the urban indicates that garded as a living organism, material circulation and energy flow the city's human activities will be more frequent, the consumption of analysis between the city and the surrounding environment, it is a urban resources and the deterioration of the ecological environment multi-level, integrated approach to energy consumption and use pattern will increase, so continue to build and maintain the sustainable devel- of multi-scale analysis of urban systems (Rosado et al., 2016). There- opment of the urban is particularly important (Kennedy et al., 2012). fore, the city should be regarded as part of the global eco-system, its For many countries and regions around the world, in or der to realize natural ecosystem and artificial ecosystem metabolism of organisms are sustainable economic growth and reduce the pressure on ecosystems, it in line mode. Urban metabolism is modeled as a metabolic process to is imperative that the urban need a set of mature management tools and describe the process of urban development. An analysis of urban me- assessment systems. tabolism involves quantification of a city’s inputs, outputs and storage Urban sustainability research can be conducted from different per- of energy, materials, nutrients, water, and wastes (Kennedy et al., spectives. One that has been recognized as adequate and consistent 2007). Then the urban metabolic approach represents a comprehensive

⁎ Corresponding author. E-mail address: [email protected] (W. Que). http://dx.doi.org/10.1016/j.ecolind.2017.10.043 Received 7 August 2017; Accepted 19 October 2017 1470-160X/ © 2017 Elsevier Ltd. All rights reserved. Y. Wu et al. Ecological Indicators 85 (2018) 276–284

Fig. 1. Emergy synthesis diagram for Changsha. framework that helps monitor the conversion that happen in the city advantages of this method are that it can explain the input flow and their contribution to sustainable development (Holmes and Pincetl, quantity and quality, tracking the interaction between system compo- 2012). Fig. 1 shows an urban system boundary including broadly de- nents (Geng et al., 2013). Compared to the traditional DEA model, DEA fined inflows, outflows, internal flows, storage and production of bio- of time-series model takes full account of the factors of technological mass, minerals, water, and energy. change in each year (Lynde and Richmond, 1999), and this advantage is When urban growth is obtained through increased resource the ability to accurately reflect changes in urban metabolic efficiency throughput, environmental problems and economic costs depend on the between different years. management of the inputs and outputs of material and energy that The remainder of the paper is structured as follows. Section 2 in- happing in urban space (Newman, 1999); simply put, it depends on the troduces the emergy and the research area, describing the integration of city's metabolic efficiency. Evaluating the efficiency of urban metabo- PCA and DEA. Section 3 provides the emergy results of each index, lism is an effective tool to quantitatively analyze the relationship be- which lays the foundation for the empirical part behind. Our results and tween social, environmental and economic input and output in an discussion are described in Section 4. Section 5 presents our conclusion. urban ecosystem. A growing body of research is engaged in the in- fl vestigation of matter and energy ow of each city, and through the 2. Material and methods linear process modeling of urban ecological system efficiency, and fl usually focuses on the city of the production energy ow or other 2.1. Comprehensive emergy material (Schulz, 2007; Song et al., 2016; Yang et al., 2012). With the proceeding reform and opening-up in recent decades, Emergy analysis by the American ecologist H.T. Odum first pro- China achieves an unsurpassed economic growth. However, the in- posed (Odum, 1971), which is widely used in different types of eva- creasingly deterioration of environmental pollution and urban sus- luation of the sustainable development of ecosystem (Paoli et al., 2008). tainable development still concerns many scholars. They begin to study Since the theory introduced into China since the 1990s, many re- fl the urban metabolism from the aspects of material ow and energy. searchers have been based on emergy theory from multiple perspectives Changsha which also become to the national circular economy pilot is for the research of the urban system (Jiang et al., 2007; Liu et al., 2010; “ ” called Resource-economical and Environment-friendly Society in Wang et al., 2005). Energy is defined as a kind of energy available to 2007. Therefore, we elect Changsha in China as a case study. This paper directly or indirectly to make a product or service, emergy synthesis fl aims to obtain a relatively complete picture of emergy ows in urban method connects ecological system and economic system by a common ffi fl development; as well as compare the e ciency of emergy ows from unit of measurement, which makes up for the traditional analysis 2000 to 2014 in Changsha city, for improving the evaluation of urban methods of economic statistics and energy, because it can't compare ffi e ciency. In this paper, there are combination Emergy synthesis, PCA different kinds of energy on the same scale. to compress and derive key variables, and DEA of time-series approach When emergy is used to study the economic ecosystem of Changsha, to evaluate resources used with both concerns of economic cost and the boundary of research is established initially, then we draw a value fi environmental bene ts. Emergy synthesis connects social economic system graph to understand the operation within the survey system, this system with ecological system through a common unit of measure, the will facilitate the identification of the sources and major operating fi solar emergy joule (sej) (Liu et al., 2014), it is bene t for DEA of time- processes of different material flow and emergy flow through the fi series model to data uni ed processing; In addition, the main system, and their interactions (Fig. 1). All the emergy input can be

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