The 'Easy Empty' Composting Toilet Project: Part 1 - Ground Works

Ever since the invention of the flushing toilet in 1596, the human race has been recklessly wasting a hugely important resource and contaminating our oceans with the same. Now, at last, the technology is available for each and everyone of us to compost our faeces and get them transported to our local organic farm for recycling into valuable fertiliser and soil improver. Now is the time for us all to 'close the loop' and build composting toilets - knock down your garage and build a toilet instead. Don't feed the crabs - return the minerals and nutrients back to the land!

We ourselves have been defecating in an outside toilet here for 5 years and, yes ...... there have been problems!

The original design was really simple - a garden shed perched over the top of a 1,000 litre IBC, which worked really well except it filled up too quickly and was then extremely awkward to move from beneath the shed.

Version V1.02 is a significant upgrade from the previous design and needs to cater for 5 permanent residents and dozens of summertime visitors, so the system of removing the IBCs must be improved. In this design the IBCs can be easily removed without damaging/demolishing the shed.

Composting toilets are a really great idea as long as they can be emptied easily without getting oneself covered in human faeces during the process. Whatever container the faeces end up in, that container needs to be able to keep the waste from contaminating the environment and be able to be easily transported. The great beauty about IBCs is that they are almost purposely designed for exactly this kind of job - they are water tight, easy to transport and once away from the dwelling can be left in the corner of a field to 'mature' into useable compost.

Version 1.02 will have the same 'shed above a tank' principle, but will have a large, flat and smooth concrete pad at ground level on which the IBCs will be made to slide backwards and forwards. If this sounds a bit wacko, then read on:

When the IBCs are empty, they are fairly light weight and can be rolled and pushed around on smooth concrete by one person alone. When they are full, they can still be slid around, but require a tractor to do so. If, for example, there is a full IBC at the back of the structure, it should, in theory, be able to slide forwards by means of chains attached to the tractor as long as the concrete slab is built properly.

Everything is dependant on the slab: It must be smooth, flat, slippery and strong. Slippery? How do we make concrete slippery? Answer: oil.

You may think that this design is a bit risky, being dependant on a full IBC slip sliding along a concrete slab, but, in a previous lifetime I worked in places where full IBCs were actually deliberately pushed along slippery, oily, concrete floors by fork lift trucks - so I know for a fact that it can be done.

• Concrete mixer
• Shovel
• Spirit level
• 4" x 2" timber x 20m
• 4" x 4" Metal post holders
• 15 bags of cement
• 3 large ton bags of 12mm chippings and dust
• Duck boards
• Large soft bristled brush

Essentially, this is just a concrete slab with 6 metal post holders positioned around the outside, but there are a few key points to remember, especially on how to get a nice flat smooth finish in one go without having to put on a second layer:

1. Remove the excess soil and dump it somewhere appropriate. The slab needs to be slightly bigger than 2 x IBCs positioned side by side. I made the slab 2,200 mm wide and 3" thick.
2. Get the plot roughly level, mark out the holes, dig the holes and put marker sticks in the holes for the metal post holders. Use a mini digger to dig the holes and level the plot and don't do it when the ground is too water logged.
3. Check the levels once more, check that the diagonals are equal and, using a piece of 3" x 3" timber, gently knock in the 6 metal post holders. Don't put the holders in too far as the timber needs to be kept nice and dry above ground level.
4. Pour in concrete around the posts and allow 12 hours to cure.
5. Build a wooden frame from 4" x 2" and screw it together. Don't use nails as it needs to be disassembled without disturbing the concrete.
6. Uses pieces of scrap wood to shutter off any gaps where the concrete would escape the frame.
7. Pour in the concrete from the back and start tamping it with a 2m length of 4" x 2" .Tamping the concrete is a 2 person job. Tamping is performed by jiggling the 4" x 2" up and down just at the surface of the concrete and simultaneously moving from side to side.
8. When the frame is full, finish the tamping and leave the concrete until it starts to cure. Remove the 4" x 2" before the concrete is 100 % cured or it may not release.
9. To get a smooth finish, use a soft bristle broom to brush out any imperfections on the surface before the concrete is fully cured. Test a small section first as if the concrete is too soft, the broom will do more harm than good.

So that's the ground works finished. The concrete needs to be left to cure for at least 5 days before IBCs can go onto it. Small children and dogs are OK though.

The next task is to start building the wooden part of the structure ..... Part 2 is here:

https://www.instructables.com/id/The-Easy-Empty-Composting-Toilet-Project-Part-2-Su/