Extending the geopolitical supply risk method: material “substitutability” indicators applied to electric vehicles and dental X-ray equipment

Purpose While environmental LCA is relatively well developed, impact assessment methods for the “natural resources” AoP are weak. In particular, resource “criticality” is not addressed in conventional environmental impact assessment methods, though it could be captured within life cycle sustainability assessment. In that regard, the present article extends the previously developed geopolitical supply risk (GPSR) method by demonstrating the connection of criticality to a functional unit while incorporating measures of material substitutability to reflect the “vulnerability” dimension of criticality. Methods The GPSR method developed by Gemechu et al. (J Ind Ecol 20:154–165, 2015a ) and subsequently extended by Helbig et al. (J Clean Prod 137:1170–1178, 2016a ), and Cimprich et al. (J Clean Prod, 2017 ) is integrated into an LCIA characterization model. Further, semi-quantitative material substitutability indicator values based on a study by Graedel et al. (PNAS 112:6295–6300, 2015 ) are incorporated to represent the vulnerability dimension of criticality. The method is demonstrated with an update of a previously published case study of a European-manufactured electric vehicle by Gemechu et al. (Int J Life Cycle Assess 22:31–39, 2015b ), along with a new case study of dental X-ray equipment. Due to novel aspects of the GPSR method, the latter case involves constructing an unusually comprehensive bill of materials by tracing unit processes to input commodities with identification codes for collecting commodity trade data. Results and discussion Supply risk “hotspots” are often associated with “minor” commodities such as neodymium in an electric vehicle and cesium iodide in a dental X-ray system. Though difficult to measure, material substitutability can mitigate supply risk. Environmental loads of a dental X-ray system are dominated by production of relatively small specialized functional components like capacitors and printed circuit boards, which are far more environmentally intensive per unit of mass than common structural and mechanical components. Thus, small components comprised of minor materials can “pack a punch” from a supply risk and environmental perspective. Conclusions The GPSR method presented in the present article brings resource criticality assessment to a product-level while addressing a gap in conventional LCIA methods regarding short-run, socioeconomic availability of natural resources. Further, the case studies illustrate the significanc