I carried mementos of a dear friend who passed away suddenly just months before we were to walk the CF together. I gave it a lot of thought because there is quite a bit of ”litter” along the Camino that began as someone’s cherished memento but after time and weather have become (sorry) nothing but bits of garbage to the hundreds of thousands of other people who pass by. Some of the plastics and so forth left behind will be despoiling the landscape for centuries.
I decided on feathers. My friend loved birds. I collected them before I left while I was doing practice hikes. I sanitized them so I wouldn’t bring any nasties into Spain. They were extremely easy to carry and completely biodegradable. I didn’t plan it, but I ended up dropping most of them from bridges. We often paused to look at the view when crossing bridges, and I liked dropping them and watching them land in the water and float away.
I did another long walk (not a Camino) just weeks after my brother passed away. I had a lot of the same concerns about leaving a residue. For him, I carried a tiny bottle of bubbles, and when I took a break, I blew some bubbles for him and watched them float away. It usually left me in tears, but at the same time it was soothing.