I too have struggled with what to do with olive prunings.
Yes there are ways of chopping (small bits) up, but then they do not rot very quickly, it is often too dry for the fungi. We use a trituradora on a tractor as well as goats and burning anything worth it in the house woodburner.

Mulch is used for paths etc as it stops growth (it takes Nitrogen in before it releases any goodness).

The municipal compost place near Camarles will take them in and will make them into compost, but charge 23€ a tonne  to accept them. You pay about 10€ a tonne for the compost which is good value.