The successful installation of a vermicomposting flush toilet at Quinta do Vale in 2014 was the project which started the whole thing off. This was the initial modification of Anna Edey’s design by Wendy Howard which eventually led to the open sourcing of the design and the development of this website.
Quinta do Vale is an off-grid permaculture project of 2ha in the mountains of Central Portugal. It’s an evolving demonstration site for many aspects of sustainable living, with a particular emphasis on off-grid infrastructure. It’s run by Wendy Howard.
When I first started planning the infrastructure here, I intended to use Joe Jenkins‘ dry ‘humanure’ composting toilet system throughout. It’s simple, easy to construct and maintain, portable even, and doesn’t require separation of urine from faeces. And it’s an efficient thermophilic composting process with a well-balanced output. It’s no wonder Jenkins’ toilets have been dubbed ‘Loveable Loos’. What’s not to like?
Many people though dislike dry toilets. If there’s to be a mass movement towards better ways to deal with our sewerage, then this can’t be ignored.
In 2013, we were converting an old hen coop into an outhouse toilet. Coincidently, at the same time I came across Anna Edey’s experiments with vermicomposting flush toilets in Massachusetts two decades ago. It’s described on the website promoting her book. Edey’s website didn’t give full details, but there was enough information for me to work the rest out for myself. As it happened, the situation of the outhouse was ideal for installing a similar system, so that’s what I did.
The nature of the mountainous region where I live with its steep slopes (averaging 30-45°) and thin soils makes it a particularly challenging environment for conventional septic tanks which rely on soil biota to treat tank effluent. Slopes are too steep and soils too thin to fall within recommended ranges for successful treatment. It’s also common here for there to be almost no rain during the summer months and soils lacking in organic material soon bake dry. There is little evidence of soil life. As a result, most of the waterways of the region evidence septic tank pollution. In the absence of any other conventional solution for rural sewage treatment, I was keen to see how well a vermicomposting system would perform.
From a conventional flush toilet, flushings drain through a waste pipe into an insulated plastic container. The container holds a large quantity of worms who inhabit the surface layers of a mass of carbon-rich organic material (wood shavings, bracken, leaf litter, etc. topped with a starter layer of half-processed compost).
When the flushings enter the container, the solids remain on the surface to be processed by the worms and the liquids drain through the organic filter material and exit the container. They then pass through another waste pipe to a growing bed, also full of carbon-rich material, where they’re taken up by plants or further processed by soil bacteria.
I used a second-hand 1,000-litre plastic IBC to form the basis of the system. We made an access hatch by cutting half of the tank’s top out. It slots back into place neatly, held by the screw-top lid to the central opening (through which the waste pipe empties into the tank) and an aluminium bar which clips onto the frame each side. Once the tank was sited, we connected 110mm plastic waste pipe to the outlet and dug it into a trench leading to the growing bed.
The tank is sited immediately below the toilet in a dry-stone schist enclosure. As the walls were built, insulation was added to keep the worms within their optimum temperature range of 13-27°C, winter and summer. Closest to the tank, we used sheets of polystyrene insulation, and filled the gap between the insulation and the stone wall with Leca (lightweight expanded clay aggregate). A relatively lightweight galvanised corrugated metal hinged roof makes access to the tank simple. More polystyrene insulation was fixed to the underside of the roof and the top of the tank.
The growing bed, about 1.5m³ in volume, contains ½m depth of wood shavings, leaves, etc. to act as an organic sponge and carbon reserve. The vermifiltered water is piped into the bed and flows through a branched system of perforated 40mm waste pipes laid in the upper layers of organic material. The pipes were wrapped in horticultural fleece before covering with more organic material and then topsoil. This one bed has proved sufficient to deal with the comparatively small volume of liquid generated by the toilet (greywater goes elsewhere). The bed is unlined – there’s no possibility of contamination of groundwater or neighbouring properties. There has been no evidence of any seepage through the filter, even after large amounts of rain.
Once the water supply was connected to allow for flushing, the system was ready to go. The original plan was to start things off with worm-rich horse manure, but a cold wet February was the wrong time to find worms in the manure heaps. Instead I obtained a kilo of worms – about 5,000 Eisenia fetida or tigerworms – from ebay and added them to the tank along with some recent additions to the humanure compost heap and some kitchen scraps. We then started using the toilet. The green filter bed was backfilled with topsoil and planted with a lemon tree.
During the initial settling-in period, there was a slight smell from the container, but it disappeared within a week and the system has been working well for over 2 years now. It needs topping up with more organic material every 4-6 months and has dealt effortlessly with regular usage by between 1 and 6 people. The lemon tree showed signs of nitrogen deficiency by the summer of the second year (indicating the worm tank is working so well that almost no nutrient is escaping) and had to be fertilised.
I had a small incident in December 2016 when the tank started to fill with water. I unknowingly knocked the filter mesh out of place when scooping out some worms to start another tank going and some organic material got past it and blocked the outlet. I realised something was wrong when I could hear water falling on water in the tank after flushing. Fortunately some drainage was still happening so the worms were OK, if a little stressed. I cleared the blockage, resited the filter mesh, added some fresh organic material and all is well again.
The vermicomposting toilet system at Quinta do Vale can be viewed, along with other off-grid infrastructure and permaculture design implementations, by arrangement. For further details, see the project’s website.
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