Emergy analysis of Chinese agriculture G.Q. Chen a,b, * , M.M. Jiang a , B. Chen a , Z.F. Yang b , C. Lin c a National Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, Peking University, Beijing 100871, China b National Laboratory for Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China c Key Laboratory of Agricultural Bio-Environment Engineering Ministry of Agriculture, China Agriculture University, Beijing 100083, China Received 10 June 2005; received in revised form 10 January 2006; accepted 13 January 2006 Available online 17 February 2006 Abstract This study presents an ecological analysis of Chinese agriculture for the period from 1980 to 2000, on the basis of Odum’s well-known concept of emergy in ecological economy. Emergy analysis methods are explained, illustrated and used to diagram the agro-ecosystem, to evaluate environmental and economic inputs and harvested yield, and to assess the sustainability of the Chinese agriculture as a whole. Detailed structure of the input/output and system indicators are examined from a historical perspective for the contemporary Chinese agriculture in the latest two decades after China’s Reform and Open in the late 1980s. Temporal variation of indices such as increasing environmental load ratio (ELR), decreasing emergy self-support ratio (ESR) and decreasing emergy yield ratio (EYR) illustrate a weakening sustainability of the Chinese agro-ecosystem characteristic of profound transition from a self-supporting tradition to a modern industry based on non-renewable resource consumption. # 2006 Elsevier B.V. All rights reserved. Keywords: Emergy analysis; Chinese agriculture; Agro-ecosystem; Resource accounting; Sustainable development 1. Introduction For the world with a soaring population, there has been a great challenge to reconcile food production and natural conservation in the modern agriculture, which embodies a human-controlled agro-ecosystem dependent on both the environmental inputs, such as sunlight, wind, water and soil, and the purchased economic inputs, such as fertilizers, pesticides, fuels, electricity, mechanical equipment and some other industrial products. Systems ecological evalua- tion and assessment would be essential for a sound resource relocation for and sustainable development of the agriculture industry. To integrate the value of free environment investment, goods, services and information in a common unit, an ecological evaluation approach based on a novel concept of emergy in terms of embodied energy was first presented in 1983 by Odum, out of a creative combination of energetics (Lotka, 1945) and systems ecology (Odum and Brown, 1975; Odum, 1994, 1988, 1996). Emergy (spelled with an ‘‘m’’) was used by Odum to evaluate the work previously done to make a product or service, which was described as the available energy (exergy) of one kind previously required to be used up directly and indirectly to make the product or service (Odum, 1988; Scienceman, 1987). It represents all the work given by the environment to sustain a certain system and produce a certain level of output. As a measure of energy used in the past, emergy (with unit emjoule) analysis is totally different from conventional energy (with unit joule) analysis which merely accounts for the remaining available energy at present, therefore proved a more feasible approach to evaluate the status and position of different energy carriers in universal energy hierarchy. Till now, various systems have been evaluated by emergy analysis on regional and www.elsevier.com/locate/agee Agriculture, Ecosystems and Environment 115 (2006) 161–173 * Corresponding author. Tel.: +86 10 62767167; fax: +86 10 62750416. E-mail address: gqchen@pku.edu.cn (G.Q. Chen). 0167-8809/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2006.01.005