Mineral resources in life cycle impact assessment: part II\u2013 recommendations on application-dependent use of existing methods and on futuremethod development needs

Abstract

PurposeAssessing impacts of abiotic resource use has been a topic ofpersistent debate among life cycle impact assessment (LCIA) method developersand a source of confusion for life cycle assessment (LCA) practitionersconsidering the different interpretations of the safeguard subject for mineralresources and the resulting variety of LCIA methods to choose from. Based on thereview and assessment of 27 existing LCIA methods, accomplished in the firstpart of this paper series (Sonderegger et al. 2020), this paper provides recommendations regarding theapplication-dependent use of existing methods and areas for future methoddevelopment.MethodWithin the “global guidance for LCIA indicators andmethods” project of the Life Cycle Initiative hosted by UN Environment,62 members of the “task force mineral resources” representingdifferent stakeholders discussed the strengths and limitations of existing LCIAmethods and developed initial conclusions. These were used by a subgroup ofeight members at the Pellston Workshop® held in Valencia, Spain, toderive recommendations on the application-dependent use and future developmentof impact assessment methods.Results and discussionFirst, the safeguard subject for mineral resources within the areaof protection (AoP) natural resources was defined. Subsequently, seven keyquestions regarding the consequences of mineral resource use were formulated,grouped into “inside-out” related questions (i.e., currentresource use leading to changes in opportunities for future users to useresources) and “outside-in” related questions (i.e., potentialrestrictions of resource availability for current resource users). Existing LCIAmethods were assigned to these questions, and seven methods(ADPultimate reserves, SOPURR,LIME2endpoint, CEENE, ADPeconomic reserves, ESSENZ, and GeoPolRisk) are recommended for use incurrent LCA studies at different levels of recommendation. All 27 identifiedLCIA methods were tested on an LCA case study of an electric vehicle, andyielded divergent results due to their modeling of impact mechanisms thataddress different questions related to mineral resource use. Besidesmethod-specific recommendations, we recommend that all methods increase thenumber of minerals covered, regularly update their characterization factors, andconsider the inclusion of secondary resources and anthropogenic stocks.Furthermore, the concept of dissipative resource use should be defined andintegrated in future method developments.ConclusionIn an international consensus-finding process, the currentchallenges of assessing impacts of resource use in LCA have been addressed bydefining the safeguard subject for mineral resources, formulating key questionsrelated to this safeguard subject, recommending existing LCIA methods inrelation to these questions, and highlighting areas for future methoddevelopment.