The Lovable Loo is a primitive yet effective composting toilet. It uses ancient outhouse principles of composting waste material and if maintained conscientiously, is very effective. Here is an awesome website to humanure management and composting. www.humanurehandbook.com/
Here are some links to commercially available versions:
If aesthetics aren’t important, or if you just like the post-industrial used 5-gallon bucket look, there’s the Honey Bucket Emergency Toilet seat. It has all the functionality of a far more luxurious outhouse, but costs less than $20. And, you can disguise it as a bucket of drywall compound!
I am considering using one of these options on the construction site while I’m building and have no water. Check with your municipality to make certain that dry composting toilets are legal.