Abstract
Multi-tier sustainable supply chain management (MT-SSCM) recently emerged to reach out towards raw material suppliers and to address the suppliers' often severe sustainability impacts. Current applications and approaches focus on short supply chains (SC) such as food chains and enable focal firms to reach out to sub-suppliers or lower-tier suppliers as far as tier-4. However, the existing theory can hardly be applied to longer SCs as the visible horizon limits the actions of a focal firm. Mineral SCs consist of a commodity chain upstream and an end-product chain downstream. In total, they comprise up to nine tiers. Current sustainability challenges like the debate concerning conflict minerals reveal the limited reach of downstream actors into the upstream SC and call for an extension of the given MT-SSCM approaches. In this study, global authors on sustainability in mineral SCs contributed their professional knowledge in a three-round Delphi approach. A total of 44 experts systematically contrasted and evaluated the sustainability challenges in mineral SCs as well as a generic mineral SC structure. As a result, a cascaded MT-SSCM approach is proposed with multiple focal firms, representing the top level in each the upstream and downstream SC and their SC members representing the lower level. Furthermore, the study defines the required top level actions to enable tailored responses to the sustainability issues at the lower level. This cascaded design represents a novel approach in MT-SSCM which multiplies existing approaches to extend their reach to the most critical suppliers in terms of sustainability.