Composting Toilet

When you live aboard, there are primarily two options for dealing with human waste/sewage:

The first option is a holding tank. This means a tank where human waste sits until it gets full and needs to be pumped out. There are great benefits to a holding tank. They give you the most “home” like experience, marinas typically have pump out facilities, and you don’t really have to deal with your waste up close. There are some downsides though too. The waste sitting in your holding tank will most definitely emit smells, if there are problems with the tank it’s a nasty job, and you need to move the boat to empty them. Most sailboats come with a holding tank though, so often times it’s worth it to just keep what works.

The second option is a composting toilet. This means liquid waste gets automatically separated into a liquids container, and you (for lack of a better word) aim your solid waste into its own solids container that is filled with some kind of composting material (like peat moss or coco coir). After expelling solids from your body into that solids container, you stir up the solids with the composting material, and over time your waste turns into essentially kitty litter than can be safely disposed of. The benefits of a composting toilet are there are a lot less sewage smells you have to deal with, there are a lot less things that can go wrong, and you don’t need to rely on a marina’s facilities to be able to use your toilet. Our marine once had the pump out station down for over a month, so this is a real concern.

For the downsides of a composting toilet, you need to dispose of your waste (particularly the liquids) more frequently. This means you need to get a lot more familiar and hands-on with your waste that you’d probably like to. It’s also more inconvenient day to day. There will be times where it’s the middle of the night and all your liquid containers are full. This means a late night walk/ dinghy ride to the marina, or finding a bottle that someone can piss in.

Paperwing came installed with a Nature’s Head composting toilet, and has no holding tank. This document will walk you through our thoughts and tips of living with a Nature’s Head as liveaboards.

General Thoughts

First of all, the commercial options like Nature’s Head are wildly expensive for what is a jug that your liquids get funnelled into, and a trap door so you can dump into a bucket. However, our boat never smells like sewage and it works quite well. The solids dry up as expected, though it depends on the composting material. Many boat neighbors constantly struggle with the sewage smell from a holding tank. Even if you can effectively vent overboard, if your orientation to the wind is wrong that air can get vented right back into the boat and bring the smells back. The ability to empty the toilet without moving the boat is also a major advantage. The boat is most stressful when there are tasks that cannot wait, and often the wind and tides will not be in your favor to move the boat. This is a quick way to have an existential crisis as a liveaboard. When you realize your life is so difficult you can’t even even use the bathroom in your home, it’s hard to find it enjoyable.

Having said that, frequently dumping liquids is an annoying low level chore, and you will need to spend a lot of time dumping jugs in public toilets. The ideal solution is likely diverting the liquids to a holding tank, and still keeping solids in the composting toilet. Sewage smells come from the mixing of solids and liquids, so you would get the benefits of no sewage smells + move the boat less frequently to pump out + still get to pee in your home freely. This is something we may investigate in the future.

Composting Tips

In our experience, the hardest parts of living with a composting toilet is 1) determining where to dump the waste and 2) how to keep the solids waste from molding.

Dumping Liquids

If two people are living aboard, the liquids will need to be emptied almost every day. With that, we recommend buying at least 1 extra liquids containers, and plan to swap it frequently. Liquids can be dumped in pump out stations if possible, or you can do what we do — find a very gross public restroom and pour the liquids into the toilet and flush it down Unfortunately, it does take a bit of practice to learn to aim the jug so the liquids don’t splash out. The liquids container will also get gross with calcified urine in it. You can effectively clean these with a mixture of citric acid and water.

Dumping Solids

Solids are weirdly less gross to dispose of than liquids, as long as you wait for the waste to fully compost (we take ours out every 4 - 6 weeks). Our strategy is to wear gloves and a mask, put a trash bag over the solids container, then flip it over and spin the “agitator” handle. This still doesn’t remove everything, so we often need to used a gloved hand to free the compost. This sounds gross, but isn’t too bad as you can’t see any solids by this point.

We then dump the compost in the “pit style restrooms” that are common at local parks. Technically you can put the trash bags with compost directly in the dumpers and that’s what most people do. However for us the chore is infrequent enough, that we use it to justify a small hike and dump only the compost (not the trash bag) in the pit.

Preventing mold in solids

Most documentation for composting toilets recommend using peat moss as composting material. In our experience, peat moss leads to lots of mold in the compost.

We’ve had the best experience with coco coir bricks instead of peat moss. They are much easier to store and transport, and we went from constant mold problems to none after switching. In order to soften the bricks, make many holes into the brick with a screwdriver, put it in a plastic bag with 1/2 cup of water. Then, allow the bag to bake in the sun all day. Do two bricks and two bags, every time after dumping the solids.

The other critical part of the composting toilet is the exhaust fan. The Nature’s Head fans fail frequently, but they are cheap and can be replaced with regular PC fans in a pinch. Obviously, always keep this fan running and have an exhaust outlet.