wrote on Oct 7^th, 2012 at 9:56am:

Hydraulic log splitter on a tractor is probably the best way then. Bruixot

This sounds like the most appropriate answer to me. A log splitter should make short work of them and you shouldn't have the danger of embedded stones fracturing and causing you an injury.

They would probably still need cutting into smaller lengths for  your fire though. Maybe a saw mill could cut them for you?