Life cycle assessment of end-of-life crystalline silicon photovoltaic module recycling : influence of substitution assumptions and regional background systems on climate performance

Abstract

This thesis examines and assesses the global warming potential of end-of-life crystalline silicon photovoltaic (PV) module recycling, using scenario-based life cycle assessment of the Full Recovery End of Life Photovoltaic (FRELP) process. An avoided-burden approach was applied to study the impact of material-specific substitution assumptions and regional background systems on climate impact results in German and Chinese conditions. Three substitution scenarios, optimistic, moderate, and conservative, were simulated in order to evaluate the sensitivity of avoided global warming potential (GWP) to the recovered material quality and the displacement assumptions. The results demonstrate that avoided primary production dominates the overall climate performance of the recycling system while the direct recycling process burden is relatively small. Climate benefits can vary significantly according to the substitutability of recovered materials and the carbon intensity of the regional background systems that are displaced. It was identified that aluminium as the largest contributor to avoided GWP due to its significant recovered mass and the high carbon intensity of its virgin counterpart. Glass also contributed substantially to avoided impacts but was the most sensitive to substitution assumptions arising from differences in recovered-material quality and end-use equivalence. Silicon and silver contributed less to overall avoided GWP despite having vital roles for high-value recovery and broader circularity objectives. The study further exhibits that localized background systems can potentially influence avoided climate burdens as much as, and sometimes more so than, substitution assumptions within one region. That suggests that a climate-based assessment of PV recycling should move beyond recovery-rate focused evaluations and involve explicitly identifying the impact of material quality and substitution realism, the regional context of PV production, and the conditional character of climate-related benefits in avoided-burden modeling.