Annie Hill wrote:I should like to have an effective composting toilet, but the space where my sea-toilet is presently located is tiny. … More than anything, however, I want something that doesn't smell. i suspect it would need to be vented.
Hi Annie,
Sorry this reply took so long!
As far as smells, and having no vent, on my boat it's only an issue when the cover over the solids side is opened. I find the smell far less than that from "Porta potties" when their door is opened for use. Other people have reported to me that they are surprised that there is "no odor" (their words) inside the boat. When the weather is hot, it's helpful to empty the bucket about once a week; three weeks of use in hot weather gets more noticeable when you open the cover. The interior of the cabinet developed some odor over long use; I think that the plastic parts probably need to be swapped out every couple of months, to air and then be swapped back with the other set.
Actual composting doesn't happen much in the container – the expectation of a boat-size composting head is that the solids will be transferred to a larger arrangement on shore for complete composting (or dumped elsewhere). But the beginning of a composting environment makes it much less smelly than non-composting head versions.
You could use any size bucket that would fit your space, to do this. Tall but narrow seems like it might be helpful? The key is the separation from urine, and cellulose-type material in the bucket and to cover the poo. A smaller container would just mean that you would have to empty it more often. A number of years ago, on a different boat, I used the "sea kayaker method," involving separation from pee, and a 2 L plastic food storage container with a tight fitting press-on cover. This was not smelly when sealed, but nasty when opened – it has since occurred to me that the same system with a slightly larger container and proper dry materials would be much better, even on a kayak. I'm not really suggesting this system for a larger boat – it's pesky, in practice, if it's not needed – but a small rather than a large bucket, and a funnel for diverting urine, could be done pretty compactly. It's the snug cover over the bucket, however that's arranged, that means you can get away without a vent.
That's great that New Zealand is friendly toward composting heads! As for dumping the pee in the enclosed ponds, it's probably true that one gallon would not matter. It's partly the principal – if every one of every boat that came in there did the same, in those crowded places it probably would be noticeable. But also, when I pour out those jugs in regular, open water, there's a big cloud that goes into the water, and chunks of salts. God knows what that means about my kidneys… but at any rate, it does feel better to refrain while in those tight places with such beautiful clear water.
Cheers,
Shemaya