Thanks for your reply, Rune-mo! There won't be access to large amounts of sawdust, just what is created from occasional wood cutting... there will be topsoil, leaf-litter,, etc. as well as wood -ash from the fire. I was thinking of a trench or several smaller trenches to compost the dog waste - not sure how deep / how many layers before moving on to a new trench... will check out the book, thanks!!