They either clean the phones and give them to charities (my parents have been donating phones to a battered womens' shelter for years) or they dismantle them and sell the parts, so the phones aren't ending up at the dump and trying to keep some of the bad elements in the phones that leach into the soil.
Yeah, that would be a great site for me because I change phones quite often, about every year, and need to find something to do with the old ones rather than throw them away. I hate wasting.
AGAIN, even if the phone or DPA is dead, they sell the lead, mercury, cadium, etc. that are in the phone. Since we make money destroying the planet, let's try to do a little to help save it.