I collect a few carrier bags full and load them into my panniers.
Then I cycle up to the Pennines and find a great big hill. There are plenty of big hills in the Pennines, but you want one where you can see for a very long way. It's better of there are lots of sheep.
Then I like to see how far I can roll them down the hill. When I get bored of that, I aim at the sheep. I always try to ring a sheep with an old tyre.
It's not very green, I admit. But good fun nonetheless and gets ride of my old tyres.
Just chuck 'em in the bin.