[karka91]

hi, european here. Never heard about composting here.

Those are not vaults. Those are just holes in ground with a cover on top. It's mostly decorative and there so that you don't walk on top of the coffin.

We don't usually own these also. Usually city where you live has a cemetery that must provide a place for the coffin.

[wielebny]

In Poland municipality provides a place in ground, but for at most 20 years. After that the place is recycled for another burial. You're free to buy it though to prolong that term and in my opinion it's quite common among the elder ones.

[pndy]

> In Poland municipality provides a place in ground

That would apply to municipal graveyard while church owned ones are managed separately. In either case, if grave spot fee isn't paid on time, space goes back to the pool while remains of previous "occupant" are transferred to the ossuarium - IIRC.