Most boats have a holding tank system which keeps your poo in a smelly soup. We keep our poo in dirt!
When I bought Wisdom, it had the standard marine head with septic hoses running everywhere. The hoses were old and reeked of toilet wastes. It seemed that no matter how much I cleaned them, they always smelled. The head was rather old and after rebuilding it a few times, I decided to ditch the traditional method and convert over to a composting toilet.
The way it works is the solids and the liquids are kept in separate areas. The liquid tank fills up rather quickly and needs to be dumped weekly. The solids tank actually lasts a very long time. With two people using it, we choose to dump it every 6 months. It is not full, nor in need of being dumped at 6 months; we simply feel that it has been long enough. When we dump the solids tank, it doesn't look like a pile of poo. Instead, it looks like dark dirt (though I wouldn't put this on the vegetable garden)!
The composting toilet we chose is very comfortable to sit on and use, and it fits well in the boat. I did drill a weep hole in the section that holds the pee bucket so that shower water would drain out.
Installation was also very straight forward. Remove the old head and all associated plumbing, then attach the compost toilet to the sole. The kit includes fans and hoses and all sorts of attachments to the toilet, but we decided to try it out as it is first, then install the rest of it if we felt the need.
Two years later, we still haven't felt the need to install the other parts. The head sits in our head/shower and quietly serves its purpose without much intervention.
But what about bugs and flies? Well, that is where the dirt comes into play. We found that using pure peat moss and poo was a wonderful breeding ground for gnats and flies. By mixing in a fair amount of diatomaceous earth with the peat moss, nothing would spawn. We mix the diatomaceous earth in until the lot of it takes on a grey color, that seems to do the trick!
If the pee bin ever begins to smell, we simply pour in a cap full of white vinegar. That will neutralize any smells instantly, once again restoring peace to our floating home.
The boat began to smell much better once the heads were switched. Removing the old smelly poo hoses and replacing them with the compost made a huge impact on the quality of life below deck!
Since these composting toilets work as standalone devices, they would also work great in cabins, RVs, and other boats.