Application and problems of emergy evaluation: A systemic review based on bibliometric and content analysis methods

The emergy evaluation method (EME) is an effective tool to analyze the sustainability of a system because the method links economic and environmental considerations. This study systematically analyzes the latest development and problems of EME based on the joint use of bibliometric and content analysis methods. By quantitatively and visually reviewing 886 emergy-related papers from 1996 to 2018, this study indicates that the EME method has been undergoing a rapid development over the past decades, including a growing number of publications and citations, widespread application in various regions and categories, and higher acceptance rates by mainstream academic journals. EME has been primarily applied to evaluate the sustainability of complex systems, accounting for 86% of the published papers. At the same time, the improvement of the emergy evaluation methodology has been a main concern for emergy-related studies since the 1990s. Specifically, doubts about emergy conservation have been reduced, while the problems of the emergy accounting of negative outputs, co-products, splits, recycling, uncertainty, indicators and integration with other tools have achieved more attention. There have been a few solutions proposed by different authors to deal with the problems, but the ideas and approaches have not been in agreement so far. Therefore, an advanced methodology will be required for the increasing operational level of EME in different fields, including a more standardized accounting framework, improved emergy algebras, and clearer illustrations of the emergy conservation logic. This study contributes to an understanding of the current application of EME by quantitative and visual graphs. Meanwhile, the systematic and classified review of the latest problems and proposed solutions in the EME methodology will provide some specific guidance for future EME research. The improvement of the EME method will make it a readily accessible scientific and operational tool for sustainability management in various fields.