A Loo with a View - Build your own Treebog

Tim Green
Wednesday, 18th May 2011

Down on the farm with no mains water supply, going to the loo in the spring drought can prove rather tricky so Tim and Rebecca decided to build a compost toilet that the trees could look after. The only problem is, once you've been in the best bogs of the world, one's own construction has a lot to live up to...

In my life I've been lucky enough to use some of the most beautiful toilets in the world. In an open-fronted affair in South India there was nothing between me and the Indian Ocean sunset but a vast empty white sand beach and in Nepal the vista from the smallest room (or shack) was the snow-capped peaks of the tallest mountains on Earth. Nothing compared, however, to a 200ft long-drop perched on the top of the Mara escarpment in Kenya. As I sat, behind me was a simple woven screen and before me were eagles and vultures wheeling above vast herds of migrating wildebeest hundreds of feet below.

Clearly the bar had been set rather high when it came to constructing a toilet of our own. Unfortunately, although not entirely ignored, lavatorial aesthetics had to play second fiddle to some practical considerations. The early drought last year highlighted an urgent need for a composting loo of some kind on the farm. The old adage of "if it's yellow let it mellow; if it's brown flush it down" is all very well if you have at least some flushing potential. We have no mains water supply and last May the spring that supplies our domestic water had ceased to spring forth.

Quick and simple to build: Planting the willows

So the design brief Mother Nature had set was to build a waterless closet that could be up and functioning within a couple of days. To that I added "and requires no maintenance". It's not that I'm overtly squeamish about poo (hard to be a livestock farmer if you are!) but given a choice of emptying toilets or not, I'd always choose the latter. To my mind the only answer was a treebog.

Desperate for the looThe treebog is a breathtakingly simple idea. It's a shack on stilts surrounded by hungry plants – of which willow trees seem to be considered the favourite. As the human deposits accumulate they begin to compost and the hope is that the willows turn that compost into more trees at a similar rate. The only maintenance required is coppicing the trees and an occasional "peak-knocking" (I'll let you work out what that is!)

Starting a treebog often entails planting a good dense ring of willows just outside where the building will be. Providing you do it in winter, planting willows is as easy as tree planting gets – just push the green willow wands into the ground and make sure they don't dry out. In our case planting trees wasn't necessary as the ideal spot for the treebog at the bottom of the garden just happened to be an unmanaged mass of willows. All that was needed was to hack a big enough hole in them to make space for the building.

I'm sure there are innumerable ways to build a shed on stilts but I went for the easiest – four thick fence posts hammered into the ground and a liberal usage of diagonal bracers. The platform was made from old scaffold planks and the shed frame from whatever bits of wood I had lying around. The only hard and fast rules with the platform are to have it at least a metre off the ground and to remember to put a hole in it!

Sitting in the lap of luxury

The essential suffolk latchHerds of wildebeest sweeping majestically across the plainOnce you have a platform you actually have a usable, if exposed, treebog. Everything after that is luxury, although I would recommend a chicken wire screen around the stilts to keep out those foraging mammals with particularly broad tastes. I have seen people use a double layer of chicken wire with loose straw stuffed between them to double up as a visual screen. Not really a privacy screen as piles of poo tend not to worry about who sees them, more the other way round.

I felt our treebog required a few luxuries so up went the cladding, corrugated roof and guttering which leads into a water butt which will eventually be plumbed into a sink for hand-washing. As far as I'm concerned, no outside toilet is complete without a Suffolk latch and a window - all loos must have views. There aren't so many wildebeest in the West Country but a nest box for a robin should fill the void. Also in a fit of nature-love I put up a nesting platform inside with the hope of tempting in some swallows but in the time it took me to recharge my cordless drill a blackbird had moved in. Poobelle, as she came to be known, went on to raise a successful family of four with her husband, Dunny.

Poobelle gathering nesting material

Balancing the waste product

As with using all composting toilets it pays to add some high carbon matter to balance out the naturally nitrogenous waste we produce. We have used sawdust, straw, woodchip and ash but the best so far is a microbially impregnated bran. If you've ever tried bokashi composting you will probably be familiar with this. I mix up a 20kg bag of bran (the stuff for horses) with a purchased "Effective Micro-organism" innoculant and that lasts us a year with just a handful used with each deposit. This EM bran has pretty much made the loo aroma free. The only time we have any odour issues is when a bit too much urine has entered the system. We think urine is far too valuable on the compost heap to waste but some of our guests are quite understandably less comfortable with this. Maybe a separate straw bale pissoir will be one of this year's constructions.

From left to right - Plopsy, Number 2, Stinkerbell and Stool

So far, one year on, the humanure layer is still only 6 inches deep so the willows seem to be doing their job. If things do start to mount up then I have plans to experiment with tiger worms to create a tree-worm hybrid bog.

Needless to say, using purified drinking water to flush away poo now strikes me as a thoroughly old-fashioned and bizarre idea.

A new visitor, Poobelle 2, on lookout 

Rebecca Hosking and Tim Green made the BBC2 film, 'A Farm For a Future' which explored peak oil and climate change in relation to farming. Whilst researching, they discovered permaculture and decided to return to the small mixed farm that Rebecca grew up on in Devon, help with day to day tasks and experiment with some cutting edge ideas and techniques. They regularly report the results for Permaculture online.


Alice Griffin |
Fri, 27/05/2011 - 17:07
Although I can appreciate the bar was set quite high (who else gets to do their business in such breathtaking places?), I think your tree bog is rather lovely indeed!
Dionysos |
Thu, 02/06/2011 - 07:12
Just what I was looking for! But now to adapt it for a rather steep Greek olive grove . . . I'll try the willows but wonder if the old-fashioned rush we use in the grey water recycling tubs would work just as well. Obviously something to be established in the Autumn, before the winter rains. Did I miss the bit about the access door? Or does it all just lift up at the end of the year and move to the next view, sedan-chair style?
bamboochik |
Tue, 07/06/2011 - 16:15
I really like this idea. Hmmmm, and I have tons of wild willows here! Let's see, where did I put my hammer? ;-)
Karen Maskall |
Mon, 21/11/2011 - 21:48
oh that is amazing. I wonder how it would be received in my elevated tiered garden overlooking the communal playing fields. Friends could come and watch the footie matches on a Sunday afternoon and partake of a bit of light relief at the same time without missing a single goal. I could even charge spectators to sit at the best seat in the house ... All good stuff ha ha
Markus 'Giles' Koehorst |
Wed, 18/07/2012 - 16:02
I have been experimenting with a camping loo I got from Ebay. Works really well but you do have to empty the bucket. I changed it so I could use a bigger bucket, but still, that is the uncomfortable part. Is there any way to use your design for a loo in a yurt? It would be near the outside wall, with a platform underneath it, but it would be difficult to plant willows under it.
bamboochik |
Mon, 18/02/2013 - 14:59
Aren't you afraid the willows will infiltrate the screened in poo area? I have willow here and I know it definitely goes where the most fertile, damp, areas are. (I live on a wetland here in the deep south, USA.)
Bogman |
Tue, 19/02/2013 - 19:26
This may cure your problem with urine... I've seen a camping toilet ( before I got the chance to invent it myself ) which is basically a frame with a toilet seat much like you have in the treebog but it has a bag to catch the solids which can be discarded but more importantly it has a type of funnel at the front connected to a hose which lets the urine run off into the ground. I think something like this would stop you having too much build up in your fabulous loo.