Jerry McIntire wrote:The most impressive composting toilet I've had the pleasure of using has much in common with Steve Heckeroth's progressive chamber design, which needs so little attention and involves no hauling or emptying of buckets of poo. I have a drawing of the design, which I'll share once I figure out how to do it. Meanwhile I'll describe it.
Like the Sunny John, it's a vault toilet technically. Under the bathroom in a building (house) is a large concrete vault-- but not as large as you'd think. The secret is a metal mesh with 1 - 2" square openings midway through the drop zone. At start-up, the mesh is covered with several layers of newspaper, then some fresh compostable material, and a heaping handful of worms.
Begin use. When I was using these toilets, they had been in operation for fourteen (14) years and they HAD YET TO BE EMPTIED. Not enough had piled up in the bottom of the chamber to need emptying. Worms are your friends! Amazing reduction in volume. The compost could be removed at any time and used on trees, etc. This is permaculture at its best, big return for a well-designed, inexpensive system that is so low maintenance it's hard to believe. The residential building code in my state will allow these because they are a vault toilet. Vault toilets need to be emptied-- if they ever get full!
These toilets use a urine diverter to keep the solids from getting too wet, and because urine is such an easily used source of fertilizer. Dilute it 2:1 or 5:1 or 10:1, water:urine, and apply it.