The fourth is an amazing piece of art. With some really smart engineering.
It seems that the secret to having no odor is to have a large pit and to vent the pit. It also helps to separate the pee. In all four, folks were encouraged to pee outside - way from the outhouses.
Sawdust is used in case there is any smell. A properly built outhouse can be better for the environment than a septic tank or a sewage treatment plant. I like these three designs much better than any of the humanure systems or composting toilets.
The Loveable Loo is demonstrated by loveable Lulu, who shows us the compost toilet and the garden that it can produce.
Build one yourself: Humanure Toilet