I have not yet come across a reasonable way of recycling shoes and heels, but you can donate and re-sell what you no longer wear.
If your shoes need care do not hesitate to take them to your cobbler. Please explain that the heels come off, but the shoes can be cared for. You will find more specific information on shoe care here.
We have also created some fun videos for people who would like to create their own heel finishes on an existing pair of heels. This is a great way of up-cycling something that might have been scuffed or breathing new-life into something you don’t wear as much.
Thank you client extraordinaire @mpastinelli for sharing your expertise.