As part of the preparations for the UCLoo Festival 2013 (19 Nov. – 3 Dec.), the project team spent an afternoon at the Centre for Alternative Technology (CAT) near Machynlleth, Wales (please donate to UCLoo Festival – just £5 or less will help to make sure the conversation on ecological urban sanitation continues: http://spacehive.com/ucloofestival2013 But hurry – we must reach our fundraising total by 17th October!)
The centre is a “living laboratory” for past and present green technologies, exhibiting lower-environmental-impact alternatives for energy, building and plant cultivation.
The centre is also known for its forward-thinking research on ecological sanitation, and we were introduced to four functioning ecological toilets:
1. A low-flush, tiger-worm model developed for Tanzania by Claire Furlong and Walter Gibson at Sanitation Ventures filters toilet liquids through layers of soil and gravel. Worms living in the top layer digest the solid matter, replicating the filtration system of a forest floor.
- Pros: it’s an odourless, attractive, self-contained unit.
- Cons: because the toilet was developed for a warmer climate, it needs lots of insulation to keep the worms warm enough to do their job.
2. The Aquatron, from Sweden, uses a water-efficient (2/4L) system, flushing toilet contents down a pipe into an hourglass-shaped plastic basin that separates the liquids from the poo through gravity-propelled spinning. The solids then fall through a flap into a composting chamber beneath.
- Pros: it’s water-efficient, odourless and looks like a standard toilet.
- Cons: the composting chambers (there are two, allowing each to “rest” for two years before the compost is used) are accessed on an angle and require someone to enter the chamber in order to empty it.
3. NatSol‘s version is a double-chambered composting toilet with a ride-on bench seat, that separates the urine from the faeces, whisking it away down a pipe while the solids fall into the pit below.
- Pros: no water is used, and urine can easily be collected for re-use with a urine-diverting plate.
- Cons: because waste is contained and there is no flush removal system, the toilet smells if it’s not regularly treated with “soak” material (sawdust, straw etc.) to keep it dry.
- Undecided: only sitting is allowed.
4. The Australian-made DOWMUS (Domestic Organic Waste Management Utilisation System), another composting system (installed with an enamel pedestal), is designed to accept all household waste water. However at CAT, a urinal is also provided, to reduce the level of liquid entering the compost pit.
- Pros: smells are removed through a pipe-and-fan system.
- Cons: because the mixture remains wet through the mixing of urine with feces, the toilet container does not compost the matter in the cold Welsh climate, so it fills with raw sewage which must be emptied periodically.
At CAT, faecal waste is composted and used as garden fertilizer once it reaches a safe level of decomposition. Although regulations do not prevent certain uses of nutrient-rich urine in farming, pee at CAT is not currently harvested for use but instead is processed through soak beds, using reeds with nitrogen-rich roots to purify the liquid, which eventually reaches bathing quality.
Our tour guide, Grace Crabb, was very knowledgeable and well-informed, and we hope she’ll visit and perhaps even give a talk at the upcoming UCLoo Festival!