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December 06, 2008

City Eco Lab: dry loo solutions

Many people ask, "What has design got to do with sustainable development?".

Well, take toilets.

In the South, 40% of the global population lives without toilets. In most places, scarcity of water renders sewer systems impossible, while ad hoc human waste disposal spreads waterborne illnesses that prey upon millions, and cripple developing economies.

In the North, roughly 20% of our already profligate daily water use is to flush toilets with drinking water. City dwellers have simply got to reduce this appalling waste - but how?

Hardened eco-warriors take pride in using hand-made dry toilets like the ones in the caravan below, and it is not hard to obtain worthy but grim solutions.

toilette-seche-caravane.jpg

But rickety utilities like these are not a solution for retrofitting millions of urban homes - especially if squeamish people like me are to be expected to use them.

Sustainable urban waste water management moves away from the disposal-based linear system that most of us know now - flushing - to a recovery-based, closed-loop system that encourages the conservation of water and nutrient resources without compromising public health.

And these new closed-loop systems have to be retrofittable to millions of existing homes.

According to Dena Fam an Australian researcher, "the knowledge and technology already exist for this change to take place. There is a gap, however, between the current availability of innovative technology and the cultural acceptance of waterless toilets".

Fam discovered that it is important to maintain a sense of ‘normality’ for the user in the design of new toilet systems. Only a small minority of citizens will opt for sustainable toilet behaviour because it is the right thing to do.

Part of the problem is a lack of system design that makes it easy to maintain,use and manage new waterless systems optimally. "If waterless toilets are to be accepted by the user" says Fam, "the design must take into consideration not only the technical aspects of the hardware but also the introduction and management of the waterless system in order to fit the prevailing socio-cultural context".

The Dry Flush system (below), now being developed in Australia, takes these cultural issues explicitly into account.

dry-flush.png

For industrial designer Virginia Gardiner, the key is to exploit the economic potential of waste. She has develped a waterless toilet, the G/CH4 (see below) that creates an urban infrastructure in which people trade their waste for biofuel.

ToiletPhoto_gwg.png

Gardiner explains:"many NGOs are hard at work installing composting eco-toilets for those in need - but a continual challenge is to motivate communities to look after their new toilets. By turning human waste into a high-value commodity, energy, the Gardiner CH4 offers plenty of incentive to sustain itself".

The G/CH4 is a low-cost mechanical toilet that is sold alongside a simple biodigestor unit. In the toilet, a biodegradable lining material transfers and contains excrement in a sealed container which the user empties into the biodigestor, sited at an outdoor location, in exchange for methane gas: free cooking fuel.

"We are now preparing to build the techincal rig including a full-scale biodigestor, and test it in London" says Gardiner. "We are gathering funds for this critical phase of the project. Upon its completion, field tests will begin in Lagos, Nigeria, where we have already conducted extensive market research".

My conclusion, after seeing her prototype in City Eco Lab, is that Gardiner should do some trials in London, now, and not wait to get to Lagos.

The contexts may differ, but the need for closed-loop waste systems is shared by both northern and developing cities.

For example, systems to capture rainwater, that can be retrofitted to existing houses, are taking off in a big way because an architect, Sally Dominguez, designed them to be modular, work well, and be easy to instal:

HOGBB houses SPARK3.jpg

Someone needs to develop hog loos, pronto.

Posted by John Thackara at December 6, 2008 08:45 PM

Comments

Here's the thing: Methane is a tricky process. It likes warmth, it prefers a certain carbon-to-nitrogen ratio and it needs tending. Handing a paper carton of shit do deposit into a methane digester is going to encounter way more taboos and tech transfer issues than composting the excreta and using it to grow larger papayas or bamboo or pig feed or something of value that could even be used for energy. Also, excreta-derived methane is already in place. (Hog loos have been created, BTW!)

Posted by: Carol at December 27, 2008 04:34 AM

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