Sorting out your poop

Note

This is where we get really opinionated!

Just switch to a compost toilet (note that following the The Humanure Handbook we are not using the name Composting Toilet to recognise that the Composting process doesn't happen inside the toilet but afterwards). It is by far the best option for minimising your impact on the world around you. There is no alternative that combines

  • safety (no holes in the boat)
  • lowest maintenance (no smelly hoses or tanks or pumps)
  • least pollution into the sea of any toilet
  • cheap
  • nice to use
  • can be used in boatyards
  • can be used in all harbours, coastlines, protected areas
  • simplest to fit
  • adaptable (use it in the middle of the saloon when refitting the heads compartment)
  • can be left for months without any problems
  • never gets blocked
  • easy for visitors (although they won't be expecting that and might see it as weird or a big issue).

Alternatively there are hundreds of videos you can watch on YouTube of

  • people having to unblock traditional marine toilets
  • empty sewage out of holding tanks
  • use a bucket in a boatyard or walk to the boatyard toilets in the dark and rain
  • not be able to cruise the Jamaican coast because their older boat does not have a holding tank.
  • come back to the boat after a few months to find the marine toilet is disgusting and not working

Then get yourself a compost toilet.

Note that a PortaPotti (or chemical toilet) is a very different thing to a compost toilet. The solids and liquids get mixed together with chemicals and no "composting medium" (such as coconut coir or peat moss) which means you have raw, smelly sewage to empty. That means finding somewhere to empty it (often a messy business). The capacity isn't very large (which you will be glad of when you have to carry it ashore) but that means you will end up running out of capacity on even a short passage or after a few days at anchor in a remote place. PortaPotti's are not suitable for cruising boats, as our summer holiday with 5 of us on a Hirondelle Mk1 23 ft catamaran proved!

Which one?

Natures Head

We have two Natures Heads on Vida. They are great. We really like them. At one point during the Covid pandemic we left one of the toilets fairly full of solids and then were not allowed to visit the boat for 6 months. When we came back there was no smell, no problem and we just carried on using it. If it were not for price and availability in the UK after Brexit we would choose them again.

The only things to be aware of are:

  • you need quite wide doors as you need to carry full base unit to somewhere you can empty it. Our original heads compartment doors were too narrow (but that was for our shoulders as well as the Natures Head toilet).
  • the stirrer isn't brilliant, quite a lot of the starter compost never gets mixed in which is a bit wasteful.
  • the solids capacity is a lot, and if you only use it at weekends (such as when doing a refit) it will last for ages as it "composts" down when you are not there for a few days.
  • there is no warning when the urine bottle gets full. Don't let it overflow as it isn't very nice to have to clean up. We empty it about once every 48 hours with two of us not using any other toilets.
  • we buy dried out coconut coir bricks. Approx 1 brick needs to be moistened and then put into the base before it is used (approximately level with the stirrer when it is flat).
  • we have made a wood box exactly the same size as the base unit opening. We line this with a black rubbish bag and then strap it onto the base unit. We can then turn it over and all the septage (the solids from a urine diverting compost toilet) drops into the bag that is inside the box with no mess. We find that is more reliable and easier than just using a bag. Unless your bags are very strong you will need to double bag the septage. We currently take the septage home where we put it in Composting bins along with grass cuttings etc for at least 12 months.

DIY

Before buying our first Natures Head we built a really basic DIY compost toilet to try at home. It worked well but we decided that we wanted a toilet with a stirrer rather than needing to sprinkle something over the solids after use.

All you need is to build a box with a standard toilet seat (ideally it wants to have a reasonable seal to the box - a wood seat with a flat base that can be fixed to the box lid is ideal). Under the seat will be a diverter (or separator) and under that a container for solids and another for liquids.

We would recommend buying a urine diverter as a separating dry toilet produces much less compost (important if you don't have space for multiple large compost bins in a garden). Note that the Humanure Handbook does not recommend Urine Diverting Toilets as the urine can help the composting process - however, that does require a lot more space for extra cover material, creates more volume of compost and requires a couple of large compost bins - that isn't going to be possible on a boat.

Our preference would be to buy a container designed for the liquids as you want it to be reasonably sturdy and it is nicer to carry to a toilet ashore if it isn't transparent. About 5 litres is a good capacity.

You can use almost any container for the solids (a bucket will do), but you will need to add some compost or sawdust or coconut coir on top after each use to avoid smells.

You might want to add an extractor fan to the box, it will avoid any smells and will will speed up the composting process (it helps dry the solids more quickly).

Some useful suppliers:

Compoost Toilets

These are a UK company with a fairly new product Compoost Toilets. As Natures Head are now difficult to get and very much more expensive in the UK these look like a good option.

They look very much better with a really clean shape.

Boats will want the "Deluxe Compost toilet 12v self stirring with bottle" model.

They do need 12volt power for the stirrer and the solids capacity is much smaller than the Natures Head. However, the solids container lifts out and will be much easier to empty.

Compo Closet

Their compost toilet is called the "Cuddy", and are new to me (June 2023) Compo Closet. They look really tidy and compact, plus they are available in the UK (and the price is competitive in the UK despite being made in the US).

The solids container is removable and has a stirrer. The stir handle retracts into the front face so no side access is needed to the (very neatly cube shaped) toilet. The capacities look good with custom shaped containers to make the most use of the space. It has a warning light for a full urine container.

Compared to the Compoost they look as clean (although less curvy) but they don't need a 12volt supply for the stirrer and the capacity of both containers is larger. Plus they have a built-in "modesty cover" for the solids. They are quite a bit cheaper.

Compared to the Natures Head they have a removable solids container, more compact footprint, a urine full indicator light, they claim to be more available in the UK and are cheaper. However, the capacity of both containers is smaller than the Natures Head and so will need to be emptied more frequently.

Dealing with the waste

If you can find a way to not handle the solids until they have been "resting" for about 48 hours your life will be nicer. With two Natures Heads and two of us we are able to stop using one for solids when it gets full and leave it for a couple of days before emptying it.

If you have access to a composting bin then this is going to be the best option. After the 48 hour waiting period just empty the septage into the compost bin, it helps if you are able to cover it with something like grass cuttings and the bin should have a secure lid.

You will need to let the waste compost for 12 months before it can be used where anything is grown for food. After that it will be unrecognisable and can be used as compost anywhere.

We have been able to do this since September 2019, so far we have one 220 litre composting bin than we have "filled" (probably 50% poop and 50% grass). We started filling a second bin in Summer 2022. We will make sure that when we leave this house there won't be any poop in the compost bins that has not been fully composted ie for at least 12 months.

When cruising you are probably not going to be able to find a proper composting bin very often. So here are some links to further advice:

The liquids are not dangerous and can be poured down a toilet or somewhere on the ground well clear of people and food. When offshore they can be emptied into the sea (regulations vary by country as to when this is ok). You might need extra containers if coastal cruising.

When cruising we are planning to have several storage containers (initially 3) and accept that there will be a certain amount of active waste management to achieve best composting. That will include stirring and moving between containers. The composting will work better in warmer climates. We plan to use our aft lazarette locker with an extractor fan and vented containers. Fortunately, boxes that fit onto the Natures Head base for easy emptying, will also fit through the lazarette locker hatch. These plans are being updated at the moment. See Our Compost Toilet deadline