I much prefer composting toilets as ashes and lime in pit outhouses keep the smell down, but don’t help compost the excrement. Sawdust from non-kiln dried lumber, chipper shredded stuff, leaf mould, dirt, etc all work well. The crap composts within a few months or less and the entire sysmtem is normally without any odor at all. All you need are a number of five gallon buckets and the composting materials, and a place to dump the buckets to compost completely. When we did it we had about 8 buckets and they partially composted in them before being dumped. It was quite non-offensive, relatively speaking, and much less offensive that a regular pit outhouse.
Link to Humanure online:
Instructions:
http://humanurehandbook.com/instructions.html
Yeah, I’m planning on a composting toilet system myself, but I wanted to throw the ashes thing out there for anybody who was planning to use lime.