I know, I am sorry, it has been a while, but on this cold, dreich morning, I am finally sitting down to write a new blog post. I am not sure how, but I appear to have made it through three seasons now without writing about the compost loos.
Of all our experiments the compost loos are the things that have just worked, without fuss or the need for me to tear my hair out. They have their moments, don’t get me wrong, but essentially they are a beautifully simple system with little intervention needed.
I can’t claim credit for this.
When we first thought about using composting loos we did some internet searching for units to buy (we don’t always do things the hard way!). But, there was a limited choice and they were either too small, too basic, needed a power supply, or if they ticked all the boxes, just too expensive. Then we discovered Milkwood and all became clear. This amazing group of permaculture teachers in Australia provided a guide to building your own composting loos based on their own experiments. So we used their basic model and decided to build our own.
Now I will admit I am stronger on aesthetics than I am on technology, so Neel did the actual building with me holding weatherboard, hammering in a few nails, taking them out again and then re-hammering them (I have learnt a lot since then and might only have to nail up boards once now). I was determined that we would have beautiful loos with plenty of space and proper wash basins, because quite frankly there is no excuse not to. We wanted our campers to see that compost loos can be a normal, practical part of everyday life. We are big fans of sustainable, natural materials so wooden structures seemed to make sense. The huts ended up looking a bit like beehives and I absolutely love them.
To quote the Sustainability Centre, “a composting toilet is a ventilated container that provides the optimum conditions for decomposition under controlled aerobic (with oxygen) conditions. In the composting process, organic matter is broken down by naturally occurring bacteria and fungi into a dry, non-smelly humus”. Having dealt with the easy bit of how to make the loos look pretty, this is what we were now aiming for.
Some compost loos, for example tree bogs, successfully cope with combined liquids and solids and create fantastic compost heaps that become a source of food for willow, or other fast growing trees, planted around them. In order to use these, however, it is best to be a good way away from watercourses and ponds as human waste can soak into the water system before it is properly dealt with. We are surrounded by watercourses and a farm pond, and also sit on heavy clay which is not great for soak away systems, so we needed our compost to be contained. More importantly our very supportive local environmental health department wanted our compost to be contained. When urine and poo is kept together an anaerobic (without oxygen) process is started and creates the smell that everyone expects when they come across a composting loo. The composting process also takes a lot longer if the waste is too wet. So the system used by Milkwood, which contained the compost and separated liquids from solids was perfect for us.
At the centre of the system is a wheelie bin. This provides a receptacle for the compost and also has the benefit of being easily removed and wheeled away to a quiet corner of the farm when it is full. Our local council provides the necessary supply of secondhand bins. When the bins are full it is easy to seal them up for storage and label them with a number so that we know when the compost, or humanure, was first created. Left in a nice sunny spot the waste will happily compost inside the bin in warm, dry conditions for a couple of years before it is ready to reuse. We just put a new bin in under the loo seat and start the process all over the again. Adding a handful of soak material a couple of times a day helps to keep the waste dry and also creates air gaps where the aerobic bacteria can get to work on breaking down the waste. It also covers up the evidence! We used cocoa shell until it became impossible to get a hold of last year. It worked brilliantly, and made good use of a waste product, but it did mean buying in from abroad and all the air miles that this involves. We are now experimenting with dried grass cuttings from the meadow, which if they work, will create a lovely circular process. When the humanure has been created we will empty the bins into the farm copse where the trees can make use of it. We will also be using it this year as a mulch for our new hedge. We do have to be very careful to follow the Safe Sludge Matrix and make sure that we are not spreading the humanure on areas that are accessible to the public or are used to grow food crops.
So that’s the solids dealt with, what about the liquids? The Milkwood team allow urine to go into the wheelie bin and out again through a grill at the bottom. It then soaks away into the ground. This works well in a hotter country where the compost dries out in the bin more quickly. We have to divert the urine away from the bin and so we borrowed another great idea. Free Range Designs have created a very handy urine separator that sits just underneath the loo seat. It collects liquid and diverts it away into another receptacle. In our case this is a caravan wastemaster. The wastemaster is then emptied into our own septic tack system as necessary. The urine separator does occasionally create its own problems, as parents that have stayed with us will know only too well. Sometimes solids don’t always end up where they should and children in particular can find the loos more challenging to use until they get the hang of them. However, we are working on this and have plans for a urinal and a version of the loo that works better for children. I would much prefer to use the urine to help boost our household compost bins or feed the garden plants, but we just have too much of it. Urine provides a very good source of nutrients for plants and I have seen it referred to as ‘liquid gold’. The next project is to find a way to use the urine more effectively, or let it safely soak away into the natural environment without polluting the watercourse system.
The other key to creating great humanure is air flow. This has the combined effect of taking any smells away, keeping waste material dry and providing the oxygen for the composting process. The Milkwood design includes a chimney that connects to the back of the wheelie bin and creates airflow through the bin and away from the loo cubicle. The black chimney pipe heats up in the Australian sunshine and the air heated inside it rises out of the top of the pipe. This drags cool air into the pipe from the wheelie bins and so the process continues. Sadly we can’t compete with Australian summers here in sunny Suffolk so this process is not as effective on our loos. We have raised the height of the pipe above the huts to catch the sun but this isn’t really enough. After a couple of months of seeing the loos in use we borrowed yet another idea and added small computer fans to the pipes to draw air through. This works really well and has helped to keep the bin contents smell free and dry.
Finally, I know that there are concerns over flies and yes, very occasionally I do have to deal with them in the loos. But, we are on a meadow and the loos are not airtight structures, so the odd insect in the loos is inevitable, and frankly quite useful in the composting process. The loo seats that we use are now of the wrap over type and if you are planning to build your own compost loos I would recommend this for peace of mind. It does help to keep everything ‘sealed’ but you do have to be careful not to cut off the airflow into the wheelie bins.
We hope that we are continuously updating and improving all of the facilities on site as we discover new ideas and learn from our visitors. The loos are no exception and I am sure that their design will adapt some more over time. So far they have coped with a wedding, a mini festival and over 800 campers and glampers with ease. They are also saving gallons of water and are providing us with a source of nutrients to give back to the soil. As more and more large organisations, such as Glastonbury Festival, start to use them as standard perhaps they will get the recognition that they deserve?
We are always happy to chat about our on site experiments so do let us know if we can be of any help with your own project to build a compost loo. You are also very welcome to come and have a look at how the process works in practice here.
