Hi! I'm looking to build an outdoor (enclosed in its own small shed/shelter) compost toilet on my small farm in Montana (Zone 3/4...cold & arid climate) primarily for summer use full-time by one person and also occasional event usage by 10-40 people. So, far I've been recommended both the 'Sunny John" and barrel type systems. Looking for any advice on one versus the other? And, any recommended resources on construction? Thanks in advance!
I would say an outdoor system is better for Montana. The freezing weather can cause some extreme difficulties for composting in barrels if you are not using a urine diverter. If you don't have a copy of Jo Jenkins book, the Humanure Handbook, get one. I have used an outdoor sawdust toilet pile for 3 years and even have had the DEQ admit that it is a viable legal system in Montana, as long as it is not a nuisance to the neighbors. As for construction, just make a normal compost pile that animals cannot get into and give nature her crap back. Best of luck.
p.s. my household of two produces roughly 10-15 gallons of compostable wastes a week. We fill up a 4x4x8 compost bin in a year with added cover materials.
If you have plenty of space, you could even consider a double chambered system, rather than buckets, since you're planning to build a separate structure anyway. You use one chamber for a year or longer, then cover the openings above it and let it compost while using the other chamber for a year or more. That way when you open it, everything is already decomposed.
We have a double chamber system for our composting toilets. Every user is supposed to throw a shovel full of cover material down after use. The material varies seasonally, including sawdust, wood shavings, autumn leaves, and dry soil. We have an average of 10 to 15 people using each toilet and that's a bit too much, but with fewer people using it, I think any of those cover materials would be fine, though wood shavings don't break down fully, and dry soil covers the smell best but is heavy to bring and to empty.
We made our chambers as wide and tall as normal doors so it's not cramped to get inside. They are 8 feet long so you really have to go all the way inside to empty them. But with fewer people you could make it only 4 feet long, in which case you could empty it without going inside, so it wouldn't have to be so tall. We happened to be building on a hillside, so the entry for the users is at ground level uphill, and the manure removal doors are at ground level downhill.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.