Distribution of emergy indices and its application

Emergy analysis of both industrial and ecological processes can make process system engineering decisions that are ecologically conscious. However, the traditional emergy analysis usually focuses on the analysis of the entire industrial system or comparison between different systems. In order to find out the rules of each member industry's influence on the entire system so as to work out the most effective measures to improve the sustainability of the industrial system, in this paper, a new emergy-based conceptdistribution of emergy indices (DEI)is proposed. The emergy indices of the entire system can be expressed as the sum of the DEI of each member industry, and the DEI is equal to the product of the weighing coefficient and corresponding emergy indices. The weighing coefficient indicates the degree to which the member industry affects the system. Thus, the best way to improve one attribute of a system is to modify the member industry that has the biggest weighting coefficient in all members. Polyvinyl chloride (PVC) production from natural gas and crude salt is used as a case study to illustrate the theory of distribution of emergy indices, and the result proves the theory correct and effective.