Mineral resources in life cycle impact assessment: part II
– recommendations on application-dependent use of existing methods and on future
method development needs
Authors: Berger Markus , Sonderegger Thomas , Alvarenga Rodrigo , Bach Vanessa , Cimprich Alexander , Dewulf Jo , Frischknecht Rolf , Guinée Jeroen , Helbig Christoph , Huppertz Tom , Jolliet Olivier , Motoshita Masaharu , Northey Stephen , Peña Claudia A. , Rugani Benedetto , Sahnoune Abdelhadi , Schrijvers Dieuwertje , Schulze Rita , Sonnemann Guido , Valero Alicia , Weidema Bo P. , Young Steven B. 
Published: February 2020

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.