If you sell or give away your bike
to the "scrap" guy, he will take it apart
and sell the remains for scrap metal.
The metal will be melted down to make
a new toaster or something while
the numerous plastic parts will be buried
in landfill. Therefore, the most eco-friendly
thing to do is to sell it to someone who
will USE it.
The giant factories can crank out still
someone could ride your old bike.
It's up to you.