Solar panels might be the energy source of the future, but they also create a problem without an easy solution: what do we do with millions of panels when they stop working?

In November 2016, the Environment Ministry of Japan warned that the country will produce 800,000 tons of solar waste by 2040, and it can’t yet handle those volumes. That same year, the International Renewable Energy Agency estimated that there were already 250,000 metric tons of solar panel waste worldwide and that this number would grow to 78 million by 2050. “That’s an amazing amount of growth,” says Mary Hutzler, a senior fellow at the Institute for Energy Research. “It’s going to be a major problem.”

Usually, panels are warrantied for 25 to 30 years and can last even longer. But as the solar industry has grown, the market has been flooded with cheaply made Chinese panels that can break down in as few as five years, according to Solar Power World editor-in-chief Kelly Pickerel.

To understand the challenges of solar waste, it’s helpful to understand how the panels are built. There are different types of solar panels, but most of them contain aluminum, glass, silver, and an elastic material called ethylene-vinyl acetate. The problem is that they can also contain more dangerous and sometimes cancer-causing, materials such as lead, chromium, and cadmium. Functional panels are sealed off with glass and are very safe. But when the glass breaks or the panels are damaged, those substances can leak.

Recycling isn’t economically viable right now for solar panels

This risk is especially high with poorly made solar panels installed in areas that experience extreme weather, like hurricanes and hail. Winds and rain can break the glass, allowing chemicals to leach into the soil and then into the water system, according to Hutzler. Pickerel points out that though solar power helped Puerto Rico recover after Hurricane Maria, there were a couple areas on the island where panels were damaged. “In those situations, we have to make sure that we collect the damaged panels,” she says.

To be clear, damaged solar panels leaching toxic materials isn’t an enormous risk, given how much solar panels help address the near-term dangers of global warming and how many other dangers are present during hurricanes. But it’s one we need to keep in mind since climate change experts suggest that these extreme weather events are here to stay.

Solar panels are just one part of the problem of old electronics, which is now the fastest-growing category of waste. China once accepted about 70 percent of the world’s e-waste, but it started refusing to take recycling a couple of years ago. Since then, Western countries have started shipping their waste to Southeast Asian countries, but it’s not a long-term solution. For example, companies sometimes sell old (but not dead) panels to other countries that want them for cheap, but, again, that just moves the waste around.

While it’s far from the only industry struggling to dispose of old devices, there’s an extra challenge with solar panels: recycling isn’t economically viable right now. Solar panels do contain some valuable materials, including silver and copper, but not as much as cellphones and other gadgets. And they definitely don’t contain enough to make up for the high costs of safely breaking down a panel into its constituent parts. As a result, the Electric Power Research Institute has suggested that storing old panels long-term, like in a landfill, might be the most practical option until the recycling situation is figured out. Similarly, Pickerel adds that people sometimes collect damaged panels and put them in shipping containers so they’re all at least in one area.

Still, the Solar Energy Industries Association, the major industry group, is working with recycling centers in hopes of addressing this problem early, according to Justin Baca, SEIA’s vice president of markets and research. Two years ago, SEIA established a national recycling program, reaching out to US-based recyclers to vet their processes and make deals.

Right now, they’re working with five recycling centers. “The volumes are really low right now, which is both a blessing and a curse,” says Baca. “It’s a blessing in that it’s good not to have a lot of waste. But not having a lot of waste means traditional recyclers aren’t very interested, since it only becomes economical to do at certain waste volumes.” At the same time, he adds, that makes it difficult to know what recycling costs could be in the future. If the volume goes up, maybe it will be worth it to recycling companies.

Pickerel says that this is a problem that will need a legislative solution. “I don’t think different materials is going to do anything,” she says. “Things are changing where we’re using no frames, and that makes it even harder to recycle because there’s no aluminum [in the frames to reuse].” A policy change, she thinks, will really make a difference.

There are signs that policies are changing. Hutzler mentions that one solution energy policymakers are considering is adding a fee onto the cost of the solar panels that would make it easier for them to be removed and recycled. Washington state is taking an even more proactive approach: last year, it passed legislation that requires solar panel manufacturers to have a recycling plan for their products. In June, Europe opened its first solar panel recycling plant. These are all small steps in the right direction, but we still need a comprehensive plan in place before the panels shut down. It’s all well and good to be excited about a promising technology, but we still need to think about what happens after.