PV module recycling critical as ‘we will use all the silver in the world in five years’, warns UNSW professor

“If we maintain this solar panel production rate, we will use all the silver in the world, from the real world, in five years. So, after five years, we have no silver to produce a single piece of new solar panels,” Shen warns.

The professor, who leads the world’s largest research organisation dedicated to solar module recycling in Australia, as noted by Dr Garvin Heath, NREL, argues that recycling end-of-life solar modules is not a reverse manufacturing process but an urban mining challenge that requires metallurgical engineering expertise.

Shen highlights that the industry’s early approach to the problem was fundamentally not efficient.

“In the very beginning, many of the people working in this area were from PV manufacturing research,” he explains. “They see this problem as a reverse process of PV manufacturing. That’s why it did not work well in the past, because they did it the wrong way.”

The professor’s background in extractive metallurgy, specifically pyrometallurgy and hydrometallurgy processes used to extract metals from natural silicon-based ores, positioned him to recognise solar module recycling as an urban mining process.

“For solar panel recycling, we hope to extract metals like silver and copper from the man-made silicon-based material,” Shen explains. “And even better than the natural resources, those are very complex in composition and morphology, and are very different from one location to another. But for the solar panels, they are very consistent.”

The scale of the challenge is substantial. Shen cites global projections showing cumulative PV capacity reaching 1,600GW by 2030, generating approximately 8 million tons of waste. By 2050, those figures are expected to reach 4,500GW and 78 million tons, respectively. Australia, he notes, represents one of the highest per-capita solar installations globally.

These projections align with data from Australian module manufacturer Tindo Solar. Its CEO, Richard Petterson, told PV Tech Premium that if Australia installed around 1TW of solar modules over 25 years, the nation would need to recycle around 40GW of modules each year; if the country installed 500GW, 20GW of modules would still need recycling annually.

It is worth noting that the Australian government has begun addressing the issue, committing AU$24.7 million (US$17.86 million) to a national solar module recycling pilot programme.

Five-step process remains incomplete globally

Shen outlines a five-step recycling process, noting that most commercial operators worldwide have only reached the second step. The process begins with the removal of the aluminium frame, which he characterises as “a zero-step, very easy part.”

Step one involves delamination, separating the front glass and back sheet to access the middle layer – solar cells, which contain silver and silicon.

“The ‘troublemaker’ is PV manufacturers. They are doing such a very good job, and [the modules] can last 24-30 years, which is good, but that’s also the challenge for recyclers to delaminate,” he notes.

Step two involves sorting the separated materials: glass, silver-silicon powders, back sheet, and other residues. Step three, which Shen identifies as “the most challenging part”, requires extracting silver and silicon from the middle-layer solar cells.

“Now, worldwide, we have some solar panel recycling companies. They basically stopped at step two, the sorting step. They did not do much in step three, extracting the silicon as well as the metal recovery,” he says.

Steps four and five address environmental closure and material recovery. Step four treats off-gas and waste liquid from the delamination and leaching processes to create a closed-loop system, while step five extracts metals from the liquid and converts them into reusable materials.

Shen notes that recovered silver need not meet the purity standards required for new solar modules. “We are working with the fashion industry, the industry they don’t care about, like, 99.999 silver,” he explains. “They just need to design something for the people as decoration.”

The professor emphasises that around 94% of material from end-of-life solar modules can be recycled, but notes that “all these processes, since step three, step four and step five, are all challenging. They are not all yet available in the commercial operations.”

Tackling Australia’s end-of-life module issue

When asked about state-level landfill bans, such as Victoria’s prohibition on solar modules in landfills, Shen argues that a national ban is necessary primarily for environmental protection rather than as an industry development tool.

“We need to ban this for our next generation, otherwise the environment will be very, very damaged, like all these heavy metals and all these waste gas, waste materials, waste liquid, will damage Australia’s soil, and that may not be easily recovered,” he argues.

Shen proposes a dual-infrastructure approach to handle Australia’s recycling needs. The first generation involves ground-based plants located near major cities like Sydney, Melbourne, Brisbane, and Perth, though “definitely, not the inner-city centre.”

These facilities would process modules transported from rooftops and utility-scale solar PV power plants, though he acknowledges that the “logistics are very expensive.”

The second generation involves mobile processing units.

“We developed a mobile unit to the best of our abilities. This unit will re-design and transform various chemical reactors for processes such as determination, sorting, leaching, etc. Our goal is to adapt these chemical reactors from large-scale systems to a more ‘portable’, small-scale design,” explains Shen.

These containerised units would be transported to regional solar PV power plant locations for on-site processing, though with lower throughput than stationary facilities.

“Some of them will be near cities, and some of them will be mobile-based. By combining the two, I hope that we can solve the problem,” Shen says.

Shen identifies a structural challenge in Australian research funding that he believes hinders commercialisation.

“Technology invention may be limited at the materials discovery stage or process design stage. The current bottleneck for PV recycling is that we put a lot of funding and resources into materials research. They are very important, but they are confined to a laboratory scale. This did not solve the industry-scale problem. It’s just a beginning,” he argues.

As a result, Shen advocates for greater emphasis on process engineering alongside materials science.

“We need to promote Australia’s process engineering,” he says, noting that its academic mass has declined over the past 20 years.

“We may need at least 30% process engineers for the real-world technology development.”

The professor warns that without this shift, Australian research funding risks being converted “to some papers” that are then commercialised elsewhere.

Shen’s research hub at UNSW is the world’s largest and “most comprehensive and systematic research organisation” focused on solar module recycling, as noted by Dr Garvin Heath, a global PV recycling researcher, with comparable groups operating in Europe, Japan and America.

The challenge now, Shen says, is translating that research capability into Australian industrial practice to service the country’s numerous solar PV power plants and rooftop installations as modules reach end-of-life across Australia’s grids.