Some thoughts on composting heads.
We have the Nature's Head. Interesting side note when we bought it we used it for a little bit then loaned to our friends boat. They used it, for maybe a couple of months, and then installed their own Natuer's Head. Ours came back to our boat, which was in the yard at that time.
Years ago I lived with an outhouse wherein we first peed outside. The container was a 55 gallon clamp top steel
drum. The dry stuff was chain sawdust from the summer's firewood work. The significant thing, as already pointed out, is the separation of urine from faeces. Second to that is aeration of the faeces which is where the AirHead and others make progress.
It is important to note that not much "composting" happens if the head is used daily because in maybe 4 weeks (2 people) the head container has to be emptied and recharged with dry stuff. We use coir from coconuts bought as cellophane wrapped bricks as it is renewable, while peat moss is not. So I prefer to describe our head to guests and visitors as a desiccating head. The dry stuff and the 24x7 fan pulling cabin
air into the chamber and exhausting it out on deck
dries out the faeces. When the 4 weeks are up that mixture is not offensive to my nose. But if you want olfactory offence don't tend to the urine container. By the second day it's beginning to smell; by the third day strong; by a week gagging.
Since the solids have not composted, at least for full time liveaboards, the solids should, in my opinion, be use as a fertilizer _only_ in certain conditions: under tree crops and covered with some earth or a thick layer of leaves. Never put the solids on a place where root or leaf crops are grown. Never covers a lot of territory, but consider that if you are not in control of those solids for a time of 6 -12 months, when you leave them they are not ready for your plate. The fruits and nuts of trees are mostly above contamination. However, low to the ground tree produce can be contaminated by up-splash from rain.
As a last thought, my understanding of the no-discharge rules are that if our urine and faeces are deposited into _any_ container that container becomes a Marine Sanitation Device and the contents are subject to the no-discharge rule
. Here's another however, if we go over the side directly into the waters ours is not subject to the no-discharge rule
So... I sold a new electra-san device at a loss, before installation
, to make the choice of a "desiccating" head. We don't like traditional head smell and we don't mind the upkeep of our new head. The old holding tank space was converted to a freshwater tank. The holes for plumbing
, 4, (2 heads) were glassed closed.