Old solar panels could become a valuable source of silver instead of ending up in landfill.
Australian researchers have successfully tested a recycling process that recovered nearly 100% of the silver from discarded solar panels at a much larger scale than previous experiments.
The team from the University of Newcastle used a technique called froth flotation, which has long been used by the mining industry to separate valuable minerals from other materials.
Their latest trial suggests the method could offer a cheaper and more practical way to recycle solar panels.
The researchers had previously shown in small laboratory experiments that flotation could recover silver without using acid. In the new study, they demonstrated that the process can operate continuously at pilot scale, an important step toward possible commercial use.
The trial processed 22 kilograms of solar-cell material obtained from about 460 kilograms of retired solar panels, roughly equivalent to 23 residential panels.
Almost all of the silver was recovered. Even more importantly, the process concentrated it into a much smaller amount of material. The final silver-rich product represented only 1.25% of the original solar-cell material but contained more than 80 times the original concentration of silver.
The findings have been released as a preprint on ChemRxiv.
Recovering silver could help solve one of the biggest problems facing solar-panel recycling: cost.
According to the researchers, recycling a solar panel currently costs around $10 to $15, while sending one to landfill costs only a few dollars. That makes recycling financially unattractive in many situations.
Silver could change the calculation because it is the most valuable material found in a solar cell. If recyclers can efficiently recover and sell it, recycling old panels could become much more economically appealing.
A preliminary economic assessment by the team suggests the flotation process could be three to five times cheaper than conventional methods based on acid leaching. Those methods can require large amounts of chemicals and also produce hazardous waste that must be carefully managed.
Froth flotation works differently. The Newcastle process uses water, air and small amounts of chemicals that encourage silver-containing particles to attach to air bubbles. These particles can then be separated from the remaining material.
The technology could become increasingly important as Australia’s huge number of installed solar panels eventually reach the end of their useful lives.
By 2050, Australia is expected to have more than one million metric tons of waste solar panels. The researchers estimate these panels could contain between 300 and 500 metric tons of silver.
Materials such as aluminum and glass can already be recovered relatively easily from old panels, but valuable silver is often more difficult to extract. Without effective recycling, much of it could simply be buried in landfill.
The researchers are now exploring whether the same approach could recover valuable materials from other electronic waste, including printed circuit boards from retired data-center equipment.
As renewable energy expands, technologies like this could help create a more circular system in which valuable materials from yesterday’s solar panels are recovered and reused rather than thrown away.
