New Internationalist

My dirty secret

Weird as it seems, this summer’s scary news stories about drought and global water crisis took a load off my shoulders – and allowed me to come clean with a dirty secret I’ve kept from neighbours and friends for almost 20 years.

It goes back to an article I wrote during the early 1990s about composting toilet manufacturer Abby Rockefeller, who taught me that water could be put to higher uses than moving human sewage – black water, it’s sometimes called – through pipes to be flung into the nearest river or lake. Rockefeller was equally passionate about the ‘grey water’ from sinks and bathtubs. Her idea was to separate out grey water to irrigate gardens, from black water that could be converted to fertilizer, thereby keeping both out of the sewage pipes and lakes. As with regular garbage, resources only get wasted as garbage when they’re commingled – whence Rockefeller’s slogan that ‘waste is a verb, not a noun’.

Ever since that interview, I’ve been sneaking down early in the morning or late at night to pour rinse water from cleaning cans and pots on my three-by-four-metre front garden. ‘It’s a scientific experiment,’ I’d explain whenever neighbours caught me in the act.

Actually, my 20-year experiment shows that a wild garden with two bushes and one fast-growing oak can thrive on the combination of rain and grey water, with no need for a garden hose. The water is poured directly over plant roots, so there’s no loss to evaporation. And the film of cleaning liquid and food particles – harmful as sewage because they feed algae in lakes and consume oxygen that fish need – break down as nutrients in the soil. Plus, avoiding water from the hose is appreciated by plants, which like their water soft and free of municipal chlorine and fluoride.

To get back to this season’s water crisis, it’s the rich opportunities for reuse and recycling – not the scarcity – that should focus municipal debate about water. Actually, conserving or cutting back on water use is only a drop in the bucket of the water cycle-based strategy that’s needed.

Most cities have plenty of water to go around, when the water goes through a full water cycle. Indeed, including plant watering as part of the water cycle is one reason why agriculture in cities is such a natural, and why, in some cases, city gardens are better than rural farms for growing water-intensive crops such as fruits and vegetables. After all, the reason cities have so much waste is that they have no valuable place to put their under-appreciated resources.

Beyond conservation are a series of opportunities to wring benefits from the priority uses of household and workplace water, and then return them to the water cycle in as good shape as possible.  

A case study of bio-mimicry
To expand on my little experiment, we could start by capturing rain water on the roof and using it for dishwater – a nice trick because rain water is soft and needs less soap. Once used as dishwater, the grey water could be piped to the garden, where the piping hot water would not only fertilize plants but carry the heat from the dishwater to warm the soil and add some season extension to the garden in early spring and late fall – thereby creating a hospitable environment for a wide range of fruits and vegetables valued in a multicultural city. Some of the water that formerly would have been used for  the dishwashing machine or garden hose could be diverted to aquaculture – small neighbourhood fisheries for tilapia and other species that tolerate still waters – which supplies lean protein for humans and nutrient-rich water for yet more garden plants. Filtered clean by plants and soil, that water would fall to the water table and then be returned to the water cycle.

Urban agriculture and aquaculture help the water cycle work the same way they do in nature. It’s a case study of bio-mimicry.

Cities have many other ways to use water, and the heat or cool it carries at different stages, resourcefully. Toronto, for example, keeps many of its downtown office towers cool with ‘deepwater cooling’, cold water from deep in Lake Ontario piped through office buildings to keep them cool, thereby providing a low-cost form of solar air-conditioning.

Alternatively, green roofs, as mandated for large buildings in Toronto, capture rain water, keeping it out of the sewers and saving it for plants that evaporate the water on hot summer days, thereby cooling the city, again thanks to low-cost solar power. A lot better than letting rain fall aimlessly into sewers, usually ending up as swill, full of the flotsam and jetsam of city streets, which is often dumped untreated in lakes and rivers.

Sometimes green infrastructure comes as cheap as a law protecting near-city green belts, rich with swamp and other all-natural soil and earth filters and regulators of water. Economists Sara Wilson and Michelle Molnar, reporting on Toronto’s green belt for the David Suzuki Foundation last May, estimated that regional marshes and forests save typical households over $380 a year in residential water treatment bills.  

Problem or opportunity?
In all likelihood, advancing global warming will bring drought more often to areas that have seldom faced it over the last few thousand years. Such droughts will more frequently afflict dryland areas that have long served as ‘breadbaskets’ of the world, at the very moment in history when expanding human populations most require the staple crops that they have produced. Anxiety about this has led many, such as Inter Press Service food analyst Stephen Leahy, to worry about what will happen to a world that requires the equivalent irrigation of 20 Nile or 100 Colorado Rivers a year.

I do not want to minimize the need to conserve water. At the same time, it’s still possible, especially in cities, to see the problem of water shortage as a series of opportunities disguised as a problem, as the old saying goes.

The real problem is more of our own making than that of the climate. We have governments that treat water and food in separate ministries and departments, though neither can exist without the other. Food cannot grow without water. Likewise, the water cycle cannot exist without plants and animals that use both its liquid asset and the heat or cool it carries.

Cities offer the most visible opportunities for bringing those two essential resources – the food cycle and the water cycle – together for their own mutual benefit and ours. That is the context in which reuse and recycling of water will thrive. 

Wayne Roberts is the author of the No-Nonsense Guide to World Food.

Photo (top): Amelia Wells under a CC Licence


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  1. #1 Jane Giffould 02 Oct 12

    I cannot see the problem with putting washing water on the garden, is nothing new. Back in 1972/3 I lived in Kenya and was lucky to have a flush toilet, flushed by the shower water. This went into a septic tank which had a habit of liquid overflow from which grew delicious tomatoes that I had not planted! Kitchen water went directly on the garden. Move on to the drought of 1976 when I was in England. I diverted shower, washbasin and kitchen water onto the garden to enable plants to thrive. Move on again to the 90's to now when I am again in England. Being in the East of England there is lower rainfall than some parts. So a fairly regular throw out of washing up water. A faulty washing machine that had to be manually emptied ensured that a willow cutting grew into an enormous tree as well as strawberries and other fruits benefitting. This year I have been trying to divert all washing water onto the garden and so it rained! I see nothing weird in using water twice and when looking for suitable piping have been commended for it. One of my wheelie bins was filled with snow during the winter to provide a supply of water for the summer. It keeps re-filling with rain water. I do not see why Wayne Roberts finds something shameful in what I have been doing on and off for 40 years as a matter of course.

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Wayne Roberts a New Internationalist contributor

Wayne Roberts is the author of the No-Nonsense Guide to World Food. Follow Wayne at @wrobertsfood or on Facebook.

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