I've been following these composting toilet threads for a while now. My boat needs a toilet, and I'm convinced it will be a composting one. I'm just not about to spend almost a grand for a plastic bucket with a stirring stick. Just not gonna do it. So I guess I'll have to build one, can't be that hard. I have a few questions. In the picture above why is there a lid covering the collection chamber? If its to provide a seal why not put a gasket on the backside of the seat and the surface of the lid that mates with the seat? That would form an air seal. Second, why are these units taller than a porta-potty or a conventional water toilet? I understand the purpose of the stirring stick is to break up the solid material and mix it with the peat moss or coconut fiber.
Judging from pic's at C-Head's website, it looks like Sandy (the owner) tried attaching the sealing lid to the toilet lid at one time. I can think of a couple of reasons that might not have turned out to be practical, including the precision needed to make the lid fit properly. For example, just a small shift in the plastic bolts attaching the toilet lid and seat could have moved the sealing lid enough to keep it from doing its job.
Sometimes simple solutions are so practical there's no sense getting fancy.... it isn't exactly a hardship to grab the lid and set it out of the way, and I'd say it beats having to use a coffee filter every time you go.
And unlike the Air Head or Nature's Head, the C-Head does
happen to be the same height as a standard toilet.
You're right; it isn't really that hard to build your own - assuming you have a work space and the time, and are reasonably handy with tools. In fact, it sounds like a good idea. But in my life, time to fiddle around building stuff instead of buying it has been shrinking for years now. When I retire I'll theoretically have plenty of time, but I'm hoping to have my boat in the water by then. Taking on sub-projects along the way would just complicate things....