Group Model-Building to identify potential sources of environmental impacts outside the scope of LCA studies

Specific methodologies that consider a more comprehensive/diverse set of parameters must be explored by the LCA community. This study utilises the Group Model-Building (GMB) method to identify, and Causal Loop Diagram (CLD) technique to make explicit, variables which are not typically considered in LCA studies, but may have significant influence upon environmental impacts through cause-effect links and feedback loops in product systems. A literature review on LCAs concerning household washing machines and conventional passenger cars product systems is performed to investigate what are the commonly used functional unit, life cycle stages and system boundaries. Two parallel GMB sessions were organised to elicit relevant variables and relations in the product systems and build in a first version of CLDs. Individual interviews with the participants were undertaken to refine and validate the system models. Final versions of the system models were built. GMB and CLD can serve as a basis for (i) delimitating appropriated system boundaries for LCA and (ii) identifying variables/areas to be included in sensitivity and scenario analysis. Sensitivity and scenario analysis examine the influence that those variables/areas have on the environmental impacts of the product and describe both different contexts and profiles of users. GMB and CLD have the potential to bridge the divide between quantitative and qualitative variables, for more robust understanding of the causes and mechanisms of environmental impacts and improving conclusions and recommendations in LCA.