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Solar power is booming, with millions of metric tons of solar panels being produced each year. A panel has a projected lifespan of about 25 years, which means that today’s new solar farms will go out of service in the late 2040s. Most of the weight in a solar panel, about 75 percent, is glass, aluminum, with 10 percent; wiring in a junction box, at 5 percent; and silicon, with just 3.5 percent. Dedicated recyclers are needed, the authors write, to do a more thorough job of recycling all the components of a panel—including the crystalline silicon in the photovoltaic cells themselves. Silicon wafers account for about half the cost of a panel, as well as over half the energy and carbon footprint of manufacturing a panel. But silicon isn't currently being targeted for recycling much because the recovered silicon isn't pure enough to go straight back to a wafer manufacturer. Studies show that the impurity levels are an important issue during the recycling processes. The resulting
