Mineral resources in life cycle impact assessment: part II – recommendations on application-dependent use of existing methods and on future method development needs

Abstract

Purpose Assessing impacts of abiotic resource use has been a topic of persistent debate among life cycle impact assessment (LCIA) method developers and a source of confusion for life cycle assessment (LCA) practitioners considering the different interpretations of the safeguard subject for mineral resources and the resulting variety of LCIA methods to choose from. Based on the review and assessment of 27 existing LCIA methods, accomplished in the first part of this paper series (Sonderegger et al. 2020), this paper provides recommendations regarding the application-dependent use of existing methods and areas for future method development. Method Within the “global guidance for LCIA indicators and methods” project of the Life Cycle Initiative hosted by UN Environment, 62 members of the “task force mineral resources” representing different stakeholders discussed the strengths and limitations of existing LCIA methods and developed initial conclusions. These were used by a subgroup of eight members at the Pellston Workshop® held in Valencia, Spain, to derive recommendations on the application-dependent use and future development of impact assessment methods. Results and discussion First, the safeguard subject for mineral resources within the area of protection (AoP) natural resources was defined. Subsequently, seven key questions regarding the consequences of mineral resource use were formulated, grouped into “inside-out” related questions (i.e., current resource use leading to changes in opportunities for future users to use resources) and “outside-in” related questions (i.e., potential restrictions of resource availability for current resource users). Existing LCIA methods were assigned to these questions, and seven methods (ADPultimate reserves, SOPURR, LIME2endpoint, CEENE, ADPeconomic reserves, ESSENZ, and GeoPolRisk) are recommended for use in current LCA studies at different levels of recommendation. All 27 identified LCIA methods were tested on an LCA case study of an electric vehicle, and yielded divergent results due to their modeling of impact mechanisms that address different questions related to mineral resource use. Besides method-specific recommendations, we recommend that all methods increase the number of minerals covered, regularly update their characterization factors, and consider the inclusion of secondary resources and anthropogenic stocks. Furthermore, the concept of dissipative resource use should be defined and integrated in future method developments. Conclusion In an international consensus-finding process, the current challenges of assessing impacts of resource use in LCA have been addressed by defining the safeguard subject for mineral resources, formulating key questions related to this safeguard subject, recommending existing LCIA methods in relation to these questions, and highlighting areas for future method development.

A Review of Life Cycle Assessment Studies of Electric Vehicles with a Focus on Resource Use

“…Future LCA studies should properly choose a suitable impact assessment method based on the chosen problem statement (see guidance of Sonderegger et al (2020) [23] and Berger et al (2020) [22]) also bearing in mind that not all methods contain CFs for all assessed elements. Further, the importance of criticality assessment into LCA studies to achieve additional results and identify further hotspots is underlined.…”

“…Over the past decade, many publications have analyzed the environmental impacts of alternative drivetrain technologies compared to conventional vehicles powered by internal combustion engines. Multiple methods to assess resource efficiency of product systems have been developed and integrated into LCA [22].…”

“…As shown by Berger et al (2020) [22] and Sonderegger et al (2020) [23], for the assessment of resource use several methods exist addressing a variety of aspects including the depletion of resources, future efforts of mining resources, thermodynamic accounting, and supply risks. Depending on the research question, one or more methods could be chosen.…”

A crustal scarcity indicator for long-term global elemental resource assessment in LCA

“…The third criterion is practical applicability in terms of providing CFs for as many relevant elements as possible. This is a general merit for a mineral impact assessment method (Berger et al 2020), but particularly so from a long-term perspective since it is difficult to a priori establish which elements are of future interest and which are not.…”

“…The variant based on ultimate reserves is recommended by the Life Cycle Initiative's task force on mineral resources for assessing the "contribution of a product system to the depletion of mineral resources" (Berger et al 2020). The variant based on economic reserves is suggested by the same task force for assessing the "potential availability issues for a product system related to mid-term physico-economic scarcity of minerals" (Berger et al 2020). However, only the variant based on ultimate reserves is included in the comparison because it has the most long-term perspective of the variants due to the consideration of ultimate reserves.…”