What happens to solar panels when they stop working?

For all of the idyllic visions of solar blanketing the globe, sun glinting off the glass-like modernist amber waves, there’s comparatively little consideration of the final resting place of those same panels lying in landfills, their power sapped. 

The most environmentally friendly solution, of course, is recycling them instead. But opportunities are currently expensive, limited and dependent on geography. Thus far, the repercussions of that minimal market are narrow; panels are designed to last two or three decades, and most large solar installations haven’t hit that age yet. By 2030, however, the mass of panels reaching the end of their useful lives will hit 8 million metric tons, according to the International Energy Agency.    

That means the solar industry will need an economically viable solution to deal with the equipment  if it’s to live up to its sustainable bona fides. As time ticks toward 2050 (a year when several countries, utilities and US states have said they’ll hit net-zero emissions) solar is slated to become an increasingly large portion of the electricity mix; and the challenge of what to do with all the defunct panels will only grow.  

“Recycling is a must,” said Meng Tao, a professor of engineering and a senior sustainability scientist at Arizona State University. “Otherwise, the green technology is not that green.” 

In the next decade, solar recycling could evolve from the purview of scrappy start-ups into a streamlined market. Without policy and significant funding, however, recycling and solar experts say it will be almost impossible to build a wide-reaching market.  

Prepping for 2030 

Arizona-based First Solar, which is the largest solar manufacturer in the Western Hemisphere, started recycling its own thin-film cadmium-telluride panels in 2005. Because the majority of the company’s panels are still operating, though, First Solar mostly deals with panels damaged during manufacturing or soon after installation. That means the volumes First Solar currently recycles are small, less than 0.5% of what it’s produced.  

Last year the company recovered about 30,000t and recycled more than 90% of the materials. The great majority of that mass is glass, which accounts for approximately 96% of a First Solar panel’s weight.  

The process requires pulverising the panels using a shredder and a hammer mill and then washing the semiconductor off the glass with a chemical solution of sulfuric acid and hydrogen peroxide. The crushed glass, known as “cullet” in the recycling world, is transported to a glass recycling facility. First Solar returns the semiconductor solution back to its suppliers for refinement and reuse.  

Recycling adds resiliency to the supply chain, said Andreas Wade, First Solar's global sustainability director, allowing the company to be less tied to fluctuations in commodity markets for its semiconductor materials. Recycling the cadmium telluride is also cheaper than extracting that material from mines, according to Wade.  

But First Solar’s techniques are not fully transferable to silicon solar technology, which makes up about 90% of the current market. Costs to recycle those panels still far outstrip profits.  

The European Union, which has required solar recycling since 2012, has engineered one way to address that gulf. The Waste Electrical and Electronic Equipment Directive charges member nations with establishing federal laws governing recycling. Several countries require producers to pay an upfront fee per panel sold, which is then used to fund recycling. Because more panels are being installed than are currently being recycled, the funds are enough to cover the relatively small amount of recycling required today.  

Those types of mandates are largely absent in many other parts of the globe, however. In the US, only Washington state currently requires solar recycling, and manufacturers aren’t mandated to comply until 2023. Japan, India, and Australia are in the process of considering recycling schemes.  

That largely leaves the responsibility to the market. And because recycling costs more than it yields in proceeds, it remains unclear who will pay to dispose of the millions of tons of panels that will be decommissioned in the coming decades.     

“Someone needs to foot the bill,” said Chris Davis, business development manager at Arizona-based We Recycle Solar.  

For now, companies in the US that recycle silicon solar panels largely rely on other revenue streams, Davis said. He wouldn’t comment on whether We Recycle Solar’s PV recycling business is profitable or how much it charges customers for recycling. But he did say the company also makes money through business lines such as plant decommissioning, consulting, and product refurbishing.   

New York’s Sunnking, an electronics recycler, said solar panels only account for about 5% of the volume the business currently recycles, though it expects a significant increase as more panels reach their end-of-life stage.  

First Solar’s Wade expects progress in Europe to lead the industry. Ultimately, he said, the solar industry will have to confront its waste if it wants to keep growing. Otherwise, it could run up against scarcity of materials or pressure to fully decarbonise its supply chain.    

“As this sector professionalises, and we see the first indications for that in Europe…I think these learning curves will also accelerate, and we’ll see more efficient processes,” said Wade. “If the industry wants to maintain the terawatt-scale of growth trajectory, obviously, circularity is a critical prerequisite.”  

Making recycling viable 

Cost is the biggest barrier to expanding solar recycling’s reach. Currently, it costs more to ship and recycle panels than a recycler can earn from reselling solar materials and components. In the US, Sunnking said the average solar panel costs about $16 to recycle. We Recycle Solar quoted between $15 and $25 per panel. ASU’s Tao, the lead author on a 2020 paper on PV recycling, puts the figure even higher, around $30 per module.  

“Recycling, in general, is a money-losing business,” said Tao. “So, we need to figure out a way to pay for it.”  

Breaking out the components of silicon solar panels is more difficult than First Solar’s process of separating its semiconductor from glass. Silicon cells are sandwiched between glass. After separating the two, the glass has to be crushed and cleaned. The extracted silicon is usually of a lower purity than can be reused in solar cells, according to Tao. The resale value of the metals extracted from the process, including silver, copper, gold, and tin, is also not enough to offset the cost of the process.  

“In order to operate standalone, or high-volume recycling facilities, you need sufficient throughput,” said Wade. “And you need the certainty that the stuff you recover has a market.” 

Determining a use for the lower-grade silicon recycling produces will help the market, Tao said. But manufacturing efficiencies for solar panels equates to another life-cycle hurdle since panels are increasingly being made with ever-smaller amounts of the most costly and valuable materials.  

The varying sizes of today’s solar modules could also complicate the process. 

“It’s not very cost-effective to try to process a First Solar Series 4 right now and then a minute later try to process a Jinko module, based on form factor,” said Davis at We Recycle Solar. 

In his paper, Tao floated “module standardisation” as a way to streamline recycling, but he acknowledges that “that’s very unlikely to happen because it’s competition that drives differentiation.” In the coming years, modules are expected to get bigger and more efficient, and producers are unlikely to settle on a single standard.  

Davis said recyclers can adapt to the differences, but he expects processing costs to increase over time due to labour, shipping and changing commodity prices.  

Others forecast greater efficiency and lower costs as a higher volume of panels streams through the system in the coming years.    

“The key is quantity. We need quantity. The solar industry works in gigawatts; the PV [recycling] industry works in tonnes. We need tonnes and tonnes, and tonnes,” said Bertrand Lempkowicz, head of public affairs at PV Cycle, a non-profit member organisation based in Europe that helps coordinate recycling in conjunction with the EU’s requirements. “To have the quantity, the key point is legislation.”  

Because many recyclers and recycling advocates don’t expect the process to be cost-effective on its own in the near future — if ever — policy can compel recycling and help pay for it. 

Both Lempkowicz and Tao expressed hopes that the incoming Biden administration will take up the issue of solar recycling. A 100% clean electricity standard was a marquee policy of the president-elect’s campaign platform.  

The Solar Energy Industries Association, which has built a US-based network of partner recyclers, would like to see PV-specific recycling pilots and research from the national labs, said Evelyn Butler, SEIA's senior director of codes and standards.  

But if US standards for electronics recycling — often considered to be a close analog to solar recycling — are any indication of how the nation will respond to the challenge, the solutions will likely be uneven and disparate. Only about half of US states have e-waste recycling laws, according to a recently published paper from researchers at the University of Delaware.  

For solar to play the role that advocates and policymakers, including President-elect Biden, hope for in the coming decades, Tao said, the industry must reframe its priorities around the product’s entire footprint.  

“We really need to look at the whole life cycle to decide what is the best module structure to make, not what is the highest-efficiency or lowest-cost module to make,” he said.