Excerpt from this article:
Replacing smartphones has become a yearly or bi-yearly activity for many of us. We upgrade from old and busted to the new hotness with regularity, but we don’t always know what to our old devices. I stash most of mine in a drawer in case of emergency, but whatever you do with your old phone, do not throw it away.
National recycling program Call2Recycle tells USA Today that the lithium-ion batteries in discarded cell phones were responsible for 65% of waste facility fires in California in 2017. Even worse, one exploded battery can set off a chain reaction, which can lead to massive, devastating fires that can do real damage and put people at risk.