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End-of-life crystalline-silicon photovoltaic modules secondary resource

Discarded crystalline-silicon photovoltaic modules and their separated cell fractions are a composite secondary resource generated by photovoltaic equipment use and dismantling. Their silicon wafers, metal contacts, glass and encapsulants remain distinct from elemental silicon, silicon-metal commodity, silver and mineral species. This record excludes CdTe and CIGS thin-film modules, manufacturing scrap of unspecified origin and generic electronic waste. The curated experiment used a chemical extract from end-of-life Hyundai m-Si units, not intact modules in direct contact with microorganisms. Criticality designations of constituent elements are not inherited by this waste feed.

Microbial & Biochemical Mechanisms (1)

Silver-bearing cathode deposition during sludge-inoculated microbial fuel-cell treatment of panel leachate

recovery Microbial

A living anaerobic-sludge-derived bioanode supplied current in a laboratory dual-chamber microbial fuel cell treating a prepared photovoltaic-panel leachate at a separate graphite cathode. Dissolved silver decreased and silver-rich deposits appeared on the cathode. This follows thermal processing and chemical leaching; it is not direct microbial dissolution of the modules. The experiment does not establish an isolated-product yield for the original module inventory or identify a causally responsible microbial species.

Experimental Context & Analytical Limits:
Kanellos et al. (online 2023, volume 2024), Materials and Methods, pp. 77–78: end-of-life Hyundai m-Si modules were dismantled, fragmented, heated at 550 degrees C for 15 minutes, screened and their recovered cells ground. A 5 M nitric-acid extraction at a reported solid/liquid ratio of 30%, ambient temperature and one-hour contact preceded NaOH pretreatment and tenfold dilution. The resulting R4 catholyte started at pH 1.5 with approximately 200 ppm Ag, 50 ppm Cu and 900 ppm Al. A 70 mL anode chamber and 140 mL cathode chamber were separated by Nafion; operation was at 30 degrees C across a 100-ohm external resistance. Startup inoculum was 10% v/v anaerobic sludge from the municipal wastewater treatment plant of Attica, Greece, with glucose supplied at 1.5 g COD/L in buffered anolyte. Taxonomic composition and strains were not resolved. After oxygen-based acclimation, the cathode was changed from Pt-coated cloth to 3-by-3 cm graphite paper; catholyte was nitrogen-sparged for one minute. R4 comprised two consecutive approximately seven-hour batch cycles with fresh cathode paper per cycle, rather than two independent reactor replicates. Dissolved metals were measured by atomic absorption and electrode deposits by SEM-EDS and XRD. The biological compartment and the metal-deposition compartment are separate.
Curated Evidence Points:
The R4 results on pp. 82–84 and Figures 7, 9 and 10 support decreasing dissolved Ag and Ag-bearing deposits from an actual panel-derived extract during operation of the inoculated cell. The authors report complete aqueous Ag removal within seven hours and mean removal rates of 31.4–33.6 micromol Ag/h. AAS detection limits, harvested deposit mass and a closed whole-module balance are not reported, so the stated complete recovery is retained as the authors' solution-based interpretation, not verified 100% recovery of panel silver.
Methods and Figures 1–8 compare real mixed leachate R4 with separate synthetic single-metal solutions R1–R3. R4 silver removal was slower than the synthetic silver case, with a reported 61% lower mean rate. The solutions differed in co-solutes and conductivity, so this comparison does not isolate a single inhibitory mechanism. No matched uninoculated, killed-biomass or open-circuit R4 time course is reported; microbial necessity and the abiotic share of removal remain unresolved.
Figure 9 and pp. 83–84 report local EDS Ag fractions of 68–96% w/w at different electrode positions. The separate 86% estimate is derived from solution analyses and is not a bulk assay of an isolated product. Figure 5 is assigned to fcc silver by the authors, but the displayed trace labelled carbon paper contains peaks at the same labelled positions; without raw diffraction or a resolved blank comparison, unequivocal phase identification from that figure is not assumed. Elemental EDS signals do not independently establish the proposed Cu, Al or Pb oxide phases.
R4 retains most dissolved Cu and Al after seven hours: the text reports approximately 10% and 4% removal respectively. Co-deposition, electrode passivation and oxygen reactions are proposed explanations, not independently isolated causes. The starting Table 1 is labelled chemical-extract composition yet is silicon-dominated on a percentage basis that is not reconciled with the aqueous R4 concentrations; it is not used as a whole-feed recovery denominator. No purified reusable silver product, completed continuous process or industrial deployment is demonstrated.

Sources & References

  1. kanellos2023: Kanellos, G., Tremouli, A., Tsakiridis, P., Remoundaki, E. and Lyberatos, G. Silver Recovery from End-of-Life Photovoltaic Panels Based on Microbial Fuel Cell Technology. Waste and Biomass Valorization 15:75–86 (2024); published online 11 April 2023. DOI 10.1007/s12649-023-02128-1. Full 12-page publisher PDF and HTML inspected, including Methods pp. 77–78, R4 results pp. 82–84 and Figures 5–10.
    https://doi.org/10.1007/s12649-023-02128-1 (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T13:12:16.612882+00:00 codex (GPT-6; codex) CREATE Created a distinct crystalline-silicon photovoltaic waste identity and a laboratory panel-leachate bioelectrochemical recovery mechanism, preserving chemical pretreatment, unresolved microbial attribution, mixed-product and diffraction-blank limitations.

Record source: data/records/end-of-life-crystalline-silicon-photovoltaic-modules.yaml