In nature, there is no such thing as waste. Whatever is excreted by one organism is recycled by another. One creature’s waste is another’s food.
To humans, on the other hand, waste, by definition, is an unpleasant nuisance: something we would rather not think about, and would prefer to get rid of by the quickest and easiest method available. So the fundamental issue with waste is not technical, but psychological: getting people to think about waste as a potential resource.
The waste we generate at Abrazo House is mostly dealt with on-site:
We also treat onsite all the grey water from our sinks, showers, washing machines, etc., as well as the human waste from our toilets.
Many people have the impression that grey water treatment is a horribly technical subject that you need an engineering degree to deal with. This is a complete fallacy. Provided you use biodegradable soaps (which can be bought or made at home using natural ingredients), there is nothing in grey water that cannot be used directly on the garden. The soil itself does a magnificent job of recycling all the nutrients in grey water into forms that can be used by plants.
In fact, the amazing thing about dealing with your grey water is how exceptionally simple it can be. The only engineering issue (which is really just a question of plumbing) is how to get the water to the soil as quickly and reliably as possible. For this you need a free-draining pit or trench covered with a mulch of bark chips or the like. During the first few years in Snail Cabin, the plant that grew best was a grape vine that we planted on top of the mulch pit that treated the water from our kitchen sink.
Since the beginning of the project we have composted the human waste (urine and feces) from both residents and visitors. Our toilets have gradually become more sophisticated and comfortable — but we still use only simple, cheap and reliable systems, with no complex parts to go wrong.
During the first couple of years at the land, we had the simplest possible toilet: a pit in the ground with a seat over the top. By covering the waste with earth or wood shavings we ensured there was no smell or health hazard from flies. Once the pit filled up we would simply dig a new one.
After we got tired of going outside in all weathers, we built a dual chamber dry (composting) toilet for Snail Cabin, consisting of two concrete chambers each with a wooden seat. After each visit we simply cover the waste with a layer of wood shavings. Excess moisture has sometimes led to smells, which we have dealt with by adding more wood shavings.
As one chamber fills up with waste and wood shavings, the other one is composting down with the help of earthworms and other beneficial organisms. After six months to a year, we shovel out the finished compost (which doesn’t smell) and use it on the garden.
In the main house, however, we decided to go with conventional flush toilets. One reason was public perception: the vast majority of people are unprepared to accept that anything other than a flush toilet can be a hygienic way of getting rid of your waste. Even if I managed to persuade the other members of the family to accept dry toilets, there would still be the problem of all the relatives, in-laws, visitors, friends of friends, and so on, who are simply not going to be happy to visit us and use a dry toilet. Also, there are practical benefits to using flush toilets — the principal one being that water is good at moving waste around, which allows us to have the toilets inside the house and the treatment system outside.
The Abrazo House waste water treatment system (see diagram) has no moving parts, uses no electricity, requires no direct contact with uncomposted human waste (except for covering it up with wood shavings once every few days) and cost less than €500 in materials.
Black water (from the toilets) first passes through a dual-chamber composting system like the one in Snail Cabin, with a biofilter (make of branches) which traps the solids and lets the liquids pass through. The liquids then join the grey water ( from sinks, showers and washing machine) and pass through a trench filled with mulch which filters out the nutrients and allows the clean water to flow down the slope into a pond, where the final stage of cleaning takes place.