Game Theory-Informed Blockchain Framework for Social Life Cycle Assessment: Enhancing Sustainability in Germanium Extraction from PV Scrap

by Mehzabeen Mannan, Sami G. Al-Ghamdi, Kazi Khoda

Conference Year: 2024

Abstract

Social Life Cycle Assessment (SLCA) is crucial for ensuring responsible and ethical practices throughout the supply chain of critical earth minerals, by evaluating factors such as working conditions, community impacts, and overall social sustainability (1). As the demand for these minerals escalates, understanding their social footprint becomes increasingly imperative (2). SLCA goes beyond traditional technoeconomic analysis (TEA) or life cycle assessment (LCA) by encompassing the societal implications and ethical considerations associated with mineral extraction, thereby providing a comprehensive evaluation of the mineral's overall sustainability. One major challenge associated with Social Life Cycle Assessment (SLCA) is the lack of transparency and verifiability throughout the mineral supply chain, hindering efforts to ensure responsible practices. Another challenge involves gathering data reliably and securely, which is crucial for conducting accurate assessments and fostering stakeholder trust. The integration of a game theory-informed blockchain framework, along with detailed simulation of the mineral extraction process, offers a promising solution by enhancing traceability, accountability, and trust among stakeholders, effectively addressing these challenges. The blockchain framework also enables the secure and anonymous gathering of data from stakeholders, encouraging their participation in economically stable solutions based on game theory. This not only increases the visibility of the supply chain but also enhances interaction for competitive and cooperative scopes, fostering improved social sustainability and conflict resolution within the supply chain Game theory provides strategic insights into stakeholder interactions, facilitating optimal decision-making to improve social sustainability and resolve conflicts within the supply chain (3). Germanium (Ge) stands as a critical mineral in the U.S. due to its pivotal role in various high-tech applications, including infrared systems, fiber optics, electronics, PET plastics, and solar cells (4). With the burgeoning demand propelled by the expansion of solar energy and 5G networks, coupled with limited substitutes, the imperative for germanium extraction has intensified. While global production is scattered across China, Russia, the USA, Finland, Japan, Ukraine, and Canada, the United States heavily depends on imports, maintaining a reserve of approximately 2,500 tons, primarily extracted as a byproduct from zinc refineries and coal fly ash (4,5). However, a significant and illustrative source for secondary germanium lies in photovoltaic (PV) production scrap, offering a promising opportunity. This avenue gains prominence, especially in light of the projected generation of solar waste, estimated to range from 54 to 160 million tonnes between 2016 and 2050 (6,7). Environmental assessments underscore the stark differences: coal ash and zinc ore extraction emit 5771 kg CO2-eq/kg Ge crystals and 852 kg CO2-eq/kg Ge crystals, respectively, while PV scrap extraction emits only 280 kg CO2-eq/kg Ge crystals (6,8). Leveraging PV scrap for germanium extraction not only addresses the pressing need for domestic supply but also presents a sustainable solution with significantly reduced environmental impact, thus aligning with broader sustainability goals and energy transition initiatives. Utilizing selective catechol complexation, membrane adsorption, elution, and solvent extraction, germanium can be recovered from waste solar panels by advanced hydrometallurgical techniques, with high selectivity against silicate ions being essential due to the panels' elevated germanium concentration; the process involved using 0.1 M hydrochloric acid for eluting the germanium ions (9). However, SLCA is crucial for germanium production from PV scrap as it evaluates the social implications and impacts associated with the entire lifecycle of the extraction process. It also provides insights into potential social risks and opportunities, enabling stakeholders to make informed decisions and implement measures to mitigate negative impacts while maximizing social benefits. Hence, this study proposes a novel approach to address the overall sustainability challenges associated with Ge extraction, focusing on recycling from PV production scrap through introducing a novel game theory-informed blockchain framework designed to facilitate SLCA within a sustainable circular chemical economy. In this work, a game theory-informed blockchain framework is introduced to enhance transparency, sustainability, and equity in the germanium supply chain, enabling stakeholders to verify ethical standards throughout the process. Leveraging a combination of robust software platforms and frameworks is essential for the comprehensive implementation of game theory-informed blockchain solutions for SLCA in Ge extraction from PV scrap. Ethereum, with its Ethereum Virtual Machine (EVM), serves as a foundational platform for executing smart contracts and decentralized applications (DApps), ensuring secure and transparent transactions within SLCA networks. IPFS (InterPlanetary File System) offers decentralized storage solutions, enabling data storage in a distributed manner, ensuring resilience and accessibility for SLCA datasets, including data on Ge extraction processes and environmental impacts. Polkadot's interoperability protocol enhances connectivity between diverse blockchain networks, facilitating seamless data exchange and collaboration among stakeholders involved in the Ge supply chain. GAMS MINLP solver provides sophisticated optimization capabilities for game theory-based bi-level optimization tasks, allowing stakeholders to optimize decision-making processes within SLCA frameworks, optimizing extraction processes and resource allocation. Furthermore, the SLCA was performed using the openLCA software, harnessing the power of the esteemed PSILCA database known for its up-to-date data sources, thorough data quality pedigree matrix, and meticulously documented data sources, each accompanied by their respective risk levels. Developing APIs to connect these elements fosters integration and interoperability, streamlining data exchange and analysis within SLCA networks, enhancing transparency, accountability, and trust within the Ge supply chain and addressing social sustainability challenges effectively. TEA confirmed the economic viability, while LCA focused on reducing waste and emissions. Preliminary results indicate the potential of the proposed framework to significantly improve transparency, efficiency, and equity in Ge extraction from PV scrap. By setting a new standard for sustainability in the circular chemical economy, this study paves the way for responsible and equitable critical mineral processing and recycling practices.