By 2050, the International Renewable Energy Agency projects that up to 78 million metric tons of solar panels will have reached the end of their life, and that the world will be generating about 6 million metric tons of new solar e-waste annually. While the latter number is a small fraction of the total e-waste humanity produces each year, standard electronics recycling methods don’t cut it for solar panels. Recovering the most valuable materials from one, including silver and silicon, requires bespoke recycling solutions. And if we fail to develop those solutions along with policies that support their widespread adoption, we already know what will happen.
“If we don’t mandate recycling, many of the modules will go to landfill,” said Arizona State University solar researcher Meng Tao, who recently authored a review paper on recycling silicon solar panels, which comprise 95 percent of the solar market.
Solar panels are composed of photovoltaic (PV) cells that convert sunlight to electricity. When these panels enter landfills, valuable resources go to waste. And because solar panels contain toxic materials like lead that can leach out as they break down, landfilling also creates new environmental hazards.
Under EU law, producers are required to ensure their solar panels are recycled properly. In Japan, India, and Australia, recycling requirements are in the works. In the United States, it’s the Wild West: With the exception of a state law in Washington, the US has no solar recycling mandates whatsoever. Voluntary, industry-led recycling efforts are limited in scope. “Right now, we’re pretty confident the number is around 10 percent of solar panels recycled,” said Sam Vanderhoof, the CEO of Recycle PV Solar, one of the only US companies dedicated to PV recycling. The rest, he says, go to landfills or are exported overseas for reuse in developing countries with weak environmental protections.
Recyclers often take off the panel’s frame and its junction box to recover the aluminum and copper, then shred the rest of the module, including the glass, polymers, and silicon cells, which get coated in a silver electrode and soldered using tin and lead. (Because the vast majority of that mixture by weight is glass, the resultant product is considered an impure, crushed glass.) Tao and his colleagues estimate that a recycler taking apart a standard 60-cell silicon panel can get about $3 for the recovered aluminum, copper, and glass. Vanderhoof, meanwhile, says that the cost of recycling that panel in the US is between $12 and $25—after transportation costs, which “oftentimes equal the cost to recycle.” At the same time, in states that allow it, it typically costs less than a dollar to dump a solar panel in a solid-waste landfill.
“We believe the big blind spot in the US for recycling is that the cost far exceeds the revenue,” Meng said. “It’s on the order of a 10-to-1 ratio.”
If a solar panel’s more valuable components—namely, the silicon and silver—could be separated and purified efficiently, that could improve that cost-to-revenue ratio. A small number of dedicated solar PV recyclers are trying to do this. Veolia, which runs the world’s only commercial-scale silicon PV recycling plant in France, shreds and grinds up panels and then uses an optical technique to recover low-purity silicon. According to Vanderhoof, Recycle PV Solar initially used a “heat process and a ball mill process” that could recapture more than 90 percent of the materials present in a panel, including low-purity silver and silicon. But the company recently received some new equipment from its European partners that can do “95 plus percent recapture,” he said, while separating the recaptured materials much better.
In addition to developing better recycling methods, the solar industry should be thinking about how to repurpose panels whenever possible, since used solar panels are likely to fetch a higher price than the metals and minerals inside them (and since reuse generally requires less energy than recycling). As is the case with recycling, the EU is out in front on this: Through its Circular Business Models for the Solar Power Industry program, the European Commission is funding a range of demonstration projects showing how solar panels from rooftops and solar farms can be repurposed, including for powering ebike charging stations in Berlin and housing complexes in Belgium.