Almost all the economic value in a crystalline silicon solar module is concentrated in one material. Silver accounts for just 0.03% of a panel’s mass, but, according to data presented by Dr. Andreas Obst, head of recycling at Fraunhofer CSP, a German solar research institute, it can be worth more than the glass, aluminum and silicon combined.
A standard crystalline silicon solar module weighs approximately 11.6 kg. Obst said glass accounts for 67.5% of that weight but yields only around EUR 34 ($39) per module at current prices. The aluminum frame – 12.7% by weight – yields around EUR 229. The silicon cells, at 2.7% of module weight, generate roughly EUR 38. The silver contacts, representing just 0.03% of module mass, are worth approximately EUR 600 per module at the material prices cited by Obst.
“When you’re talking about recycling of solar modules, you should talk about silver recovery,” said Obst. “The silicon from the solar cells just accounts for roughly 2.7% of the weight of an individual module – it’s really not that much money which would come out of the solar cells itself.”
Modules installed during Europe’s subsidy-driven buildout in the late 2000s are approaching the end of their 20-year support periods. Drawing on German installation and subsidy data, Obst estimated that Germany alone could face approximately 600,000 metric tons (MT) of PV waste per year at the peak of that wave in the early 2030s.
A 2016 joint projection by the International Renewable Energy Agency (IRENA) and the IEA Photovoltaic Power Systems Programme (IEA-PVPS) put cumulative end-of-life PV volumes at between 1.7 million MT and 8 million MT globally by 2030.
Prof. Yansong Shen, director of the ARC Research Hub for Photovoltaic Reliability and Sustainability at the University of New South Wales, estimated that Australia alone would face approximately 1 million MT of cumulative end-of-life panels by 2035. In Australia, by Shen’s account, recycling infrastructure is nowhere near that scale, with current capacity largely focused on aluminum frames and glass. A credible national system, he said, could begin emerging within three to five years.
Silver value
Shen cited spot silver prices of around $68 to $69 per troy ounce at press time, up from roughly $20 two years earlier. Obst said part of that rise reflects growing PV industry demand and the absence of recycling infrastructure. He said the global PV industry consumed approximately 6,000 metric tons of silver in 2023, against world annual mine production of roughly 30,000 metric tons, citing data from the Silver Institute.
Specific silver consumption per unit of installed capacity has fallen from roughly 200 MT per gigawatt-peak in 2006 to under 30 MT per gigawatt-peak today, but total industry demand has risen with deployment volumes.
“Silver reserve is being used up in PV manufacturing sectors,” Shen told pv magazine. Without continued silver-thrifting, copper substitution, and large-scale recycling, he said, most currently known silver reserves could be consumed within 25 years.
Obst drew a comparison with the photographic industry, which at its peak consumed roughly 35% of global annual silver production but recovered more than 70% of what it used. “The PV industry is nowhere near that,” he said.
Silver in a PV module is not straightforwardly recoverable – it is finely dispersed through the cell metallization and encapsulated in the laminate. Recovering it requires either a hydrometallurgical or pyrometallurgical process, said Obst. “To recover the silver you need more advanced techniques. It’s not that easy to recover as for example the aluminium frame, which you can just separate mechanically.”
No commercial hydrometallurgical recyclers responded to requests for comment. Obst’s assessment, based on Fraunhofer CSP’s process development work, was that a dedicated hydrometallurgical line requires throughput of several thousand metric tons of solar cells per year to justify its capital cost – a view that could not be independently tested against commercial operators.
Mechanical separation
The most common approach in current commercial PV recycling facilities is mechanical separation. The method carries lower operating costs but Ko said it contaminates high-value material streams when it relies primarily on crushing and shredding.
“Once glass, silicon, metals, and polymers are reduced into mixed particles, contamination becomes a significant challenge regardless of the subsequent separation technology employed,” said Terry Ko, chief operating officer of California-based PV Circonomy.
Ko said PV Circonomy’s PV Circulator performs sequential layer-by-layer separation, preventing glass from being crushed into the silicon stream, and has achieved a 99.3% mass recovery rate by weight according to SGS certification cited by the company. Ko acknowledged that no industry-wide purity specifications for recycled PV silicon feedstocks currently exist, with downstream refiners developing their own acceptance criteria.
Obst agreed that mechanical processes face inherent limitations on silver recovery specifically – a view that could not be independently tested against commercial hydrometallurgical operators, none of which responded to requests for comment.
Thermal processing
Obst assessed thermal pyrolysis – an oxygen-limited thermal treatment that decomposes encapsulants – positively, drawing on a visit to a facility operated by Shinryo Corp., a Mitsubishi Chemical Group subsidiary that operates PV recycling plants in Japan. The Kitakyushu-based company’s process uses high-temperature treatment to break down encapsulants, enabling the recovery of glass and metals from end-of-life modules.
“After a pyrolysis process it simplifies subsequent separation of glass and silicon because the grain sizes of the material are very different,” he said.
At around $1,000/MT of PV waste, according to Obst, the process carries a significant cost premium over mechanical alternatives. French company ROSI Solar, which operates a commercial pyrolysis line in France and is scaling internationally, did not respond to requests for comment.
Recovering silicon at PV-grade purity faces two structural constraints, Obst said. Purification requires removing the phosphorus-doped emitter layer with hydrofluoric acid, a process that demands large quantities of the chemical and is costly at scale. The second constraint is the industry’s shift from p-type to n-type base material. “As the base dopant remains in the material, you would end up in materials that nobody wants today.”
A 2022 collaboration between Fraunhofer CSP and Fraunhofer ISE produced a passivated emitter and rear cell (PERC) with 19.7% efficiency from 100% recycled silicon, against 22% on virgin material in the same run. The project has not been publicly reported to have moved beyond the demonstration stage.
Missing modules
One anomaly remains unexplained. Despite subsidy-era installations approaching decommissioning age, Obst said PV waste volumes arriving at German recycling facilities have declined in recent years. Fraunhofer CSP attempted to trace the discrepancy through customs statistics but could not close the gap. “Where are those modules?” Obst said. “I have no idea.”
That uncertainty is the central problem for anyone planning recycling investment. Facilities will need to scale for a 2030s peak whose timing and magnitude remain unclear, then absorb years of lower throughput before volumes recover in the 2040s – a cycle that Obst said makes the business case difficult to model, let alone finance.
Obst suggested physical storage of incoming modules as one option to maintain stable processing throughput. Ko said PV Circonomy is developing a hardware-as-a-service model to deploy processing capacity closer to where modules are generated, and had held active discussions in Australia.
What the missing-modules anomaly ultimately underscores is a mismatch the IEA-PVPS noted as recently as May: solar recycling technology is advancing, but the economic infrastructure to deploy it at scale – and the waste volumes needed to make it viable – have not yet arrived together.
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