Integrated emergy and economic evaluation of Huzhou Mulberry-Dyke and fish-pond systems

Abstract

The Huzhou mulberry-dyke and fish-pond system (HMFS) is a compound structure of agriculture with interaction among several subsystems, and it is an effective example of a circular economy by exogenous input and waste reduction to maintain a harmonious relationship between humans and nature. As increases in rural urbanization and transition of peasants occur, the traditional systems remain in a constant state of change, along with different kinds of adaptation models. In this study, two main existing models are examined by field investigation and extensive literature analysis. Emergy theory and methods are adopted to make a further quantitative analysis from emergy structure and indices synthetically and systemically. In this process, the models of HMFS are split into several subsystems, including mulberry dyke, fish pond, rape dyke, and silkworm, in terms of a modularization approach. The proportion of combinations among different subsystems is calculated by the average production level of local peasants. The empirical results of emergy analysis indicate that the two existent patterns of HMFS are themselves superior in terms of environmental capacity and commercial efficiency. The mulberry-silkworm-fish model possesses more sustainable characteristics than the rape-fish model by the mass flow and energy flux. In addition, the rape-fish model may obtain considerably better economic returns by more inorganic resources, and thus achieve higher economic benefits. Therefore, the rape-fish model may be an evolutionary model to make directions for further research and protection, while other adaptive units are introduced to form multiple systems.