recycle an old Mac

Check you local Office Max or Staples retailers. You can drop off old tech for recycling there.

Apple will arrange shipping for recycling if you are trading in an old computer when you buy a new one.

Before you recycle, you should follow the guidance Apple provides here: What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

In the case of recycling, you don't have to reinstall the macOS, but you should reformat the drive to wipe your data.

+1 on using Office Max or Staples. We are two hours of two-lane highway from the nearest Apple Store, and our municipal recycling center is part of the landfill on the edge of town. As a result all our stuff goes to the the local Staples, less than 10 minutes from us. I've not used Office Max but Staples' list of accepted items is more generous than the municipal drop-off:

https://www.staples.com/stores/recycling

I see they have added new acceptable items since I visited that page last month, even luggage!

Also, please ensure you are using the appropriate recycling program for your area:

Apple Recycling Programs