Home handymen (and women) accumulate a lot of stuff over the years. One of the biggest collections is frequently all those used screws, nuts and bolts gathered during repairs or disassembly of broken things. Look in the average handyman's workshop and you'll find overflowing containers of threaded things everywhere. There's no chance that all of it will ever be used, so periodic reduction of the cache is recommended.
Load it all in the trunk of your car and take it to a scrap metal yard. They will weigh it and pay you a few cents per pound.
Give it to your young neighbor. He probably hasn't been overrun by his collection yet and will welcome them and offer thanks.
Post on Craigslist or Freecycle and give your collection to a stranger.
Do not throw those old nuts and bolts in the trash. It isn't likely that any environmental harm will result, but it will take many years for them to rust away once buried in a landfill.