Improving the composting toilet experience

We have been using a Nature’s Head composting toilet on Vida since September 2019. We liked it enough to add a second in November 2019. Our experience has ranged from them being abandoned (after use) for 6 months during lockdown through weekend use by two people and upto a couple of weeks by two people plus occasional guests.

During this time we haven’t had a 12 volt electrical supply and so we have not fitted the extraction fan or vent.

So what would improve things going forward?

Improving the user experience

This is going to be the shortest section. Whilst, I am wary of calling anything perfect we don’t have any suggestions for improving the usability of the Nature’s head. Perhaps a step would make it more comfortable for very short people. The integrated, solid seat works really well. It is easy to keep clean and perfectly comfortable enough. The instructions are very simple:

  • Always sit
  • Open the hatch for solids
  • Put paper down the hatch
  • Close hatch
  • Spin the handle a couple of times.

Improving the Emptying Process

Here we do have some changes that we are planning.

  • Fit the extractor fan. Not to prevent smells (we haven’t had any problems), but to help dry the solid waste by extracting the damp air above it. That will make emptying the solids easier.
  • Widen doors so the Nature’s head fits through them. The doors to both our heads compartments (and the door plus corridor from the aft cabin) are a very tight fit for the Nature’s Head and it takes a bit of wrestling to get it through. So as part of our refit they are all being made a bit wider (even if not for the full height) to make it much easier to carry the Nature’s Head out. It will also make the doors less cramped for my shoulders as the doors were really narrow. Taking the whole toilet outside to empty the solids avoids any possibility of mess inside the boat.
  • Have a set of solid boxes with vented lids (that can be closed) that the solids can be tipped into (more detail below)
  • See if we can fill some of the “ledges” in the top compartment that loose bits of compost get caught on when you are a bit enthusiastic with spinning the handle. It makes a bit of a mess (of the driest, coconut coir) when you remove the lid to empty the solids.

Dealing with the waste.

The liquid is no problem. Just take to a normal toilet and empty. If no toilet or emptying point available then pour into the sea (outside the 3 mile limit) or onto the ground eg a hedge (well away from water supplies, people, crops).

The most common solution for the solids seems to be to bag it and put it in a bin. That seems rather unpleasant for everyone, it creates more plastic waste and it wastes a really good resource – compost!

We plan to fully compost the solids so that they can either be put onto any appropriate bit of ground or used in gardening. If necessary, once fully composted they can be dumped at sea with no risks to anything/anyone. Ideally that means they need to be kept for about 12 months. This is no problem while we are not live-aboards – we simply take it home and put it into the normal compost bin. Out of caution and wishing to be sensitive to our neighbours, we use a big plastic compost bin with a lid and every so often we put some grass cuttings on top of the compost.

Once we live-aboard we plan to have a set of boxes, each sized for emptying the base a couple of times. These will be custom made to fit inside our lazarette locker. We will label each box with the date that the last solids were added. Once that is more than 12 months ago the box can be emptied (appropriately ashore or into the sea offshore) and restarted. We think this will work out a reasonable size so they are not too heavy to lift or too big to get in and out of the lazarette. Obviously if we find that we are filling the boxes too quickly we can add more boxes (subject to the size of the lazarette)

Each box will have a vent (that can be closed for transport). We will also have an extractor fan for the lazarrette. This will ensure the compost gradually dries (desiccates) which we understand is good for the composting and good for ensuring no smells.

Building the first box will allow us to test the size and will also provide a better way to get the compost from the boat to the compost bin at home. At the moment we either have to take the whole toilet home (very awkward to carry down the ladder) or tip the waste into a plastic bag (which we then put in another plastic bag for security). These bags then get thrown away after tipping the contents into the compost bin, this obviously creating unnecessary plastic waste.

We hope (I’ll try to remember to measure it this weekend) that our fixed lazarette hatch size is bigger than the dimensions of the opening in the toilet base. Then each box can have catches (for it’s lid) that are the same as the toilet top section and so a box can clip onto the toilet base. To empty the base, the toilet top is removed, a box latched on it it’s place and the whole thing turned over so all the waste falls into the box with no mess. If, however, our lazarette hatch is not large enough, I’ll create a “funnel” intermediary to connect the box to the base, adapting from one size to the other.

Whether we can fit a whole 12 months of solid waste into our lazarette locker remains to be seen. It is very hard to predict as the toilet takes less days to fill if in continuous use than if used only at weekends (it composts down significantly in between the weekends). it will depend on how many guests we have and how much time is spent where there are other toilets we use.

The 12 months is a very arbitrary length of time. It is generally expected to be completely safe to use on a garden after 6 month with a recommendation that it isn’t used for food crops for 12 months. Our understanding is that even after quite a short time there is no risk to marine life if you empty the compost at sea (beyond the 3 mile limit).

Supplies

At the moment we buy bulk recycled toilet paper from Who Gives a Crap. Obviously, when cruising we will need to buy whatever is available where we go, however, we will still bulk buy when we find recycled, plastic free products.

We also bulk buy Coir Briquettes at the moment. A years supply takes very little space but there are plenty of alternatives that can be used if these are not available.

We use vinegar in a little spray bottle for cleaning the toilet seat, hatch etc. Cheap and widely available.

Conclusion

Composting toilets are great. So the only improvements are to make them a bit simpler to empty and reduce the impact caused by the waste you create.

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