I lived in Yosemite National Park for over eight years. I climbed a lot, backpacked a lot, but I was also able to pursue many projects that I thought up.
One of these ideas was a bear-proof composter for myself and other residents. I didn't have much support from NPS or the concessionaire, the company that runs the lodging and dining in the park, so I had to be creative. I couldn't find mention of a composter like this having been made before, so I didn't have much of a reference. I looked over the web and talked to a bunch of people, but nothing really materialized until I went to the dump one day. A bunch of old bear proof trash can pieces were being thrown away. My solution began to solidify.
I wanted a bear-proof composter that residents could use but that couldn't be easily accessed by guests or unauthorized persons. The result was a modified double-can composter that used a magnetic key.
Being an electrician, I work with welders and other trades, so I asked the welder and the laborers for help in this project. The laborers were able to provide the manpower and resources to move the heavy material around, while the weld shop did custom welding for me.
I ground off the door handle and shaved and spread the door opening so that neither bears nor humans could get a fingerhold.
I needed to provide the composter with a lot of air movement, but couldn't allow holes on the outside where a bear could put a claw in and tear it open. So the composter needed an inner layer and an outer layer.
I eventually found two steel trashcans that would fit together when a little bit of space was set between them. I took the outer can and drilled 1/2" holes along the bottom and 1/4" holes along the perimeter of the bottom. An old piece of 1/2" EMT made for a nice spacer.