I've wondered the same, Far North, especially with the larger stuff. There's such a lot of it that I wonder how all of it can be recycled. I'd like to think it could, but I'm not sure. I especially think of old cars/vehicles and aircraft. There's somewhere (in America , I think), where there's an aircraft "graveyard" - somewhere in the desert if memory serves me right, where there are hundreds of defunct aircraft just left to deteriorate.
The ideas discussed in the posts here though, are excellent.
I try, whenever possible, to pass on things I no longer need if they still have a good life in them. Other things, I'll try to repair, if I can, but that is not always possible, sadly.