Building a compost toilet

Getting permission to build a smallholding and house under the One Planet Development (OPD) scheme in Wales is going to be a very detailed and long process involving a lot of hard work and spreadsheets which is exciting and terrifying at the same time. However, there are a few things we can get on with now in terms of clearing the rubbish that is there (abandoned caravans) and clearing some bracken to encourage more wild flower growth. We are also allowed to camp there for a total 56 days of the year. So basically, we need a toilet.

Compost toilet WalesUnder the OPD we won't be on mains water or have a septic tank or use the "usual" methods for getting rid of our toilet waste. When you think about it, as clean water becomes more and more precious and scarce, it seems a bit bonkers that we use so much of it to flush our toilets. Our waste then contributes to damage and pollution further down the chain through chemical processing, and then on the other hand, hazardous chemicals are used to grow our crops in poor soil lacking in nutrients, when our human waste can be used in such a useful and productive way.

Increasingly, looking at closed loop systems are a significant way we move forward more sustainably and on a smallholding it makes sense. We eat the food we grow, we excrete waste, that waste breaks down over two years (by which point it resembles a lovely crumbly soil) to make an organic compost full of nutrients that can be used to enrich the soil and grow our food, beginning the cycle again. If we benefit from the nutrients and energy in our food we should return the benefits back to the soil. What you take out, you should put back in. 

After a lot of research and sketching, Eric designed the mechanics of the toilet, deciding to use a wee separator from Free Range Designs. The wee being syphoned into an old 5 litre bottle which was probably full of bulk bought washing liquid or white vinegar. The pipes and plumbing bits and pieces were left over from old jobs. The poo goes straight into an old camping toilet, basically a tall bucket with a toilet seat, the seat broke a while ago and the whole thing was replaced but we kept the bucket. I ask for people's empty buckets of bird feed fat balls as they are really useful so next to the toilet there is a hole cut into the top where one of these sits to hold the sawdust that you scatter into the bucket once you are finished. Using sawdust removes any pongy odours, absorbs excess moisture and helps the composting process. We will then empty the bucket when it's full into a sealed compost bin. Wheelie bins are often used but are not rat proof so we are still working this bit out, Eric is thinking of making a special tumbling compost bin using an old steel oil drum, although preferably one previously used for transporting friut juice rather than oil. The wee will be either poured onto compost heaps or watered down and used to water some plants - not leafy plants! - such as potatoes. Keeping the poo and wee separate means the wee can be used for different things and it keeps the poo side of things dryer and less leaky. 

Compost toilet Wales

Everything we make and do on our smallholding will be done as much as possible with recycled materials which are almost zero carbon and also save us money as we are on an extremely tight budget. We were going to use a shower tent we have for privacy but Eric found a small shed on Ebay which was a perfect size for the toilet, and it can then double as a hide for watching the wildlife near to the river and a store for a few tools. It was also only 40 minutes from us so easy to strap to the car roof and get home. I have loads of emulsion paint leftover from work in bright colours. We won't be able to use this in Wales as washing our brushes would mean the waste water might end up peculating down to the river which is a SSSI (Site of Special Scientific Interest). Although these paints have low VOC (Volatile Organic Compounds) they are still not safe enough to use. So rather than chuck them out I decided to use them up on the inside of the shed after brushing it down and cleaning it up. The wood for the main structure was all left over from jobs so the other main costs were new hinges, wood varnish to make the structure more durable and fence paint for the outside of the shed. Compost toilet Wales

I made a curtain from some lovely hand embroidered tableware I got from Freecycle, curtain tape I had leftover from work, the rings were free from a friend and the rail Eric had coppiced recently. The shed had no glass so I bought a pane from a local glass business. 

Compost toilet Wales

So overall a very satisfyingly thrifty project using stuff we mainly already had. 💚

Here are the costings:



Paint - free, left over from work


Curtain rail and rings


Curtain and curtain tape


Toilet - old camping toilet


Wee seperator


Foundation - Freecycle fence posts


Fence paint


Lock - free from neighbours door


Wood for seat and lid - free from old project




Wood Varnish - small amount


Pane of glass 


New Shed Floor


Fixings (Screws, glue, roofing tacks, etc. Mostly leftovers)


Metpost post holders from Ebay




Total cost



A few years ago Eric did a one day compost toilet course at the Centre for Alternative Technology in Wales which was excellent. You can find loads of great information on their website.

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