METHODS, TOOLS, AND SOFTWARE Methodological Aspects of Applying Life Cycle Assessment to Industrial Symbioses

circular economy consequential life cycle assessment (LCA) decision making environmental impact industrial ecology industrial symbiosis Summary In view of recent studies of the historical development and current status of industrial symbiosis (IS), life cycle assessment (LCA) is proposed as a general framework for quanti-fying the environmental performance of by-product exchange. Recent guidelines for LCA (International Reference Life Cycle Data System [ILCD] guidelines) are applied to answer the main research questions in the IS literature reviewed. A typology of five main research questions is proposed: (1) analysis, (2) improvement, and (3) expansion of existing systems; (4) design of new eco-industrial parks, and (5) restructuring of circular economies. The LCA guidelines were found useful in framing the question and choosing an appropriate reference case for comparison. The selection of a correct reference case reduces the risk of overestimating the benefits of by-product exchange. In the analysis of existing systems, environmentally extended input-output analysis (EEIOA) can be used to streamline the anal-ysis and provide an industry average baseline for comparison. However, when large-scale changes are applied to the system, more sophisticated tools are necessary for assessment of the consequences, from market analysis to general equilibrium modeling and future sce-nario work. Such a rigorous application of systems analysis was not found in the current IS literature, but would benefit the field substantially, especially when the environmental impact of large-scale economic changes is analyzed