We have two types of composting toilets on the quinta: dry toilets and vermicomposting flush toilets.
We have built composting toilets according to the system popularised by Joe Jenkins, author of The Humanure Handbook (now in its 3rd edition and purchasable for download online). I like this system the most of all the dry toilets I’ve looked at so far because it doesn’t require the construction of a separate building (or allocating sufficient space) to accommodate a twin-chamber toilet and its composting bins below. There is no requirement to separate urine from faeces, and the composting system is efficient and designed for optimum thermophilic decomposition. It’s also beautifully simple and easy to construct and maintain, and it’s convenient and portable.
People became so enthusiastic about this system and their home-made units that Jenkins’ toilets got dubbed "Loveable Loos" – not surprising when you consider he’s employing the KISS principle – and he’s now been persuaded to manufacture them for people who don’t want to build their own.
Here’s a video about them …
The only disadvantage to this system is that it’s necessary to empty the collecting bins and wash them out on a regular basis, but the modern squeamishness about human waste products seems a bit odd to me. This isn’t really any different to cleaning out the chicken coop.
Jenkins’ composting method has been developed over nearly 30 years of use. He uses bins rather than heaps as the efficiency of the composting process relies on keeping the waste well contained in the centre of the material, surrounded by other organic matter and with a substantial ‘sponge’ of material below. This prevents smells and the likelihood of the waste leaching into the soil or watercourses in a raw state. The human waste is also well mixed with other organic material, vegetable peelings, cooking scaps, etc, which results in a more nutrititive compost than human waste + woodshavings alone (which Jenkins doesn’t recommend using).
More videos from Joe Jenkins here.
Vermicomposting flush toilets
In spring 2013, I came across a different system for dealing with human waste based on an ordinary flush toilet. This system, pioneered by Anna Edey in the 1990s, uses worms and their associated ecosystem to deal with the waste and plants to manage the treated liquid residues.
I saw that I could substantially simplify Anna Edey’s system using components from the industrial waste stream and decided to experiment with it for the wee house, and we built it during the summer of 2013. It was finally commissioned in early 2014 once we finished connecting a water supply to this side of the quinta and the worms are currently doing an excellent job.
So good, in fact, that when a problem arose locally with a village septic tank discharging untreated sewage into a protected landscape, I went to the local municipality with a Portuguese architect friend to suggest they adopt a vermicomposting solution to our design. The municipality agreed to the idea, subject to permission from the national conservation organisation with overall jurisdiction over the protected landscape. Unfortunately this was not forthcoming owing (we think) to us not being ‘corporate’ enough, but the municipality were keen to take the idea further regardless.
The domestic-scale vermicomposting sewerage system installed here at Quinta do Vale is now approved for use in this area under the provisions for ‘septic tank with drainage’ and is being adopted by a growing number of people. We’ve overseen the installation of a system for the local junta de freguesia to replace a defective septic tank and more are in the pipeline.
I’ve also given a number of workshops both locally and further afield on installing the system. It’s all open-sourced and there’s now a website dedicated to the system with case studies and a forum for the user community to ask questions and iron out any difficulties.
I’m currently planning a crowdfunding campaign to take this further, not just in Portugal but globally. I want to run a series of tests on the output from several installed systems and run experiments on various different organic materials used so solid data is available on performance. I also want to produce a series of videos on installing and operating the system. Watch this space!