How do I recycle pounds of LEGOs, or donate them if I don't want to bother selling them?

Goodwill and other thrift shops I talked to said they only resell complete sets, but I have a box of mixed up pieces. I don't have time or a need to resell them, but don't want them to go to the landfill. They don't have the recycle symbol on them. I'm in the US.