Assessing Mineral Resource Scarcity in a Circular Economy Context

Detta är en avhandling från Gothenburg : Chalmers tekniska högskola

Sammanfattning: Due to humanity’s dependence on metal resources there are growing concerns regarding impacts related to their potential scarcity, both for current and future generations. The vision of a more circular economy suggests that extending the functional use of metals through measures aiming for resource-efficiency (RE) such as increasing technical lifetime, repairing and recycling could reduce mineral resource scarcity. However, evidence of this is limited. In addition, there is limited understanding regarding on what principles metals can be prioritized when assessing mineral resource scarcity. The aim of this thesis is to provide knowledge on mineral resource scarcity impacts of RE measures applied to metal-diverse products and on which conditions they depend. This is achieved by: 1) studying RE measures from a life cycle perspective; 2) comparing principles of prioritization between metals on which mineral resource scarcity impacts are assessed and 3) analysing how such principles (of prioritization) can affect conclusions regarding RE measures applied to metal-diverse products. The research is conducted through case studies, syntheses of literature and method development within the methodologies of life cycle assessment, material flow analysis and criticality assessment.   Results indicate that effects of RE measures depend on a number of product characteristics and real-world conditions. RE measures can both increase and decrease mineral resource scarcity impacts compared to business as usual and effects vary greatly between metals. RE measures based on use extension e.g. reuse of laptops, repair of smartphones, and increasing technical lifetimes of LED lighting, have been indicated to reduce impacts through two principal features: use extension, and, increased functional recycling. However, there are risks of increasing mineral resource scarcity impacts if RE measures require additional metal use, product use extensions are short and if functional recycling is lacking. For example, repair of smartphones risks to increase the use of metals in commonly replaced components such as screens. Because of the varying effects on different metals, implementation of RE measures requires prioritizing some metals over others. The principles of prioritization give diverging results, and, are sometimes unclear and methodologically inconsistent. The thesis clarifies how they relate to concepts such as depletion, criticality, rarity and scarcity. Further it suggests that, although mineral resources are fundamentally stock resources, they can pose stock, fund and flow problems. Distinguishing between these different problems in distinct methodologies is conducive to purposive and complementary assessment by resolving methodological inconsistencies and providing accurate terminology. In the long term, scarcity is most purposively addressed by focusing on depletion of ecospheric stocks. Accordingly, the Crustal Scarcity Indicator is proposed to assess potential long term scarcity in life cycle assessment, alongside other environmental impacts. In the near term, potential scarcity for nations, industries and companies, as commonly assessed in criticality assessment, is most purposively addressed by focusing on technospheric circumstances, such as geopolitics, which can disrupt technospheric resource flows. In medium term, secondary resources in technospheric funds could be relevant, especially, with the advent of a more circular economy. Altogether, it is recommended that implementation of RE measures to metal-diverse products are based on analysis of product characteristics and real-world conditions and that effects of RE measures are assessed by methodologies which distinguish between mineral resource flows, funds and stocks so that well-informed prioritizations between metals can be made.