[Digestion] Solar powered toilet

Fri Sep 7 06:06:48 CDT 2012

Snip-  Promoting low-tech reliable sanitation systems, which can be built operated and maintained by local labour, would be a good start - snip

I agree with you Duncan,  but this issue is now alive in the media and we are all capable of adding to the concept designs and even building a solution for ourselves that could be rolled out worldwide.  Now there is a challenge - photos??

Best Regards

Les Gornall
Process Consultant
PROjEN BioEnergy

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From: digestion-bounces at lists.bioenergylists.org [mailto:digestion-bounces at lists.bioenergylists.org] On Behalf Of Duncan Martin
Sent: 07 September 2012 11:54
To: eric roy; For Discussion of Anaerobic Digestion
Subject: Re: [Digestion] Solar powered toilet

Eric and all

Ingenious and no doubt workable - but it looks to me like the kind of silly research that so many academics waste time and money on. (I speak as a retired academic myself!)

Lets consider the practical barriers to its widespread use - bearing in mind that their video says that their aim is to provide an off-grid sanitation system for use in developing countries.

  1.  Cost - even with a minimal panel area, it wouldn't be cheap.
  2.  How many hours of sunshine - again with a minimal panel area - would be needed for sanitization after one use?
  3.  Their little 'holding tank' supposedly allows AD to break down faecal matter - but it would need to be very much bigger and more expensive to do so effectively.
  4.  That combination of concerns suggest that it would not be remotely affordable for individual households. Economies of scale would apply at community level - but the size and cost of the solar array would multiply on a more-or-less per capita basis (or maybe I should per backside!) so it would still be expensive
  5.  With frequent use (especially at community level) the system might need multiple treatment tanks operated on a timed sequence to ensure adequate treatment time - more cost, more complexity.
  6.  They've thought of batteries to cover night use but what about cloudy days - or weeks? There aren't many places in this world where the sun shines for hours every day, whereas using the toilet is a daily need. Back-up generators? More cost! Petrol to drive it? More cost! (Yes, AD stage would generate biogas - but it would be very costly to store enough gas to fuel the generator during a cloudy spell, which might last for weeks.)
  7.  All this complexity has to be maintained - and all systems would need to be backed-up because of the risk of breakdowns, (One of the first design rules for any kind of sewage treatment system is to keep it simple and very reliable -- because shit just keeps on coming, so you can't shut down for repairs!)
  8.  The overall  environmental impact of manufacturing all this kit would be substantial
  9.  Finally, several of the components are easily stolen (panels, batteries, generators) and easy to sell on. My experience in Africa suggests that this could be a major weakness.
  10. So if one of these superloos ever gets installed in a real-world application in a developing country, I wouldn't bet on it working for very long. We might see them sooner in the developed world at sensitive locations (eg national parks) - but even there the overall environmental benefit would be open to question, so they might be mere greenwash.
Bill and Melinda should spend their money on something more useful than feeding the egos of researchers!

Promoting low-tech reliable sanitation systems, which can be built operated and maintained by local labour, would be a good start.....

Duncan Martin
Cloughjordan Ecovillage
Ireland

On 7 September 2012 00:39, eric roy <mailericroy at yahoo.com<mailto:mailericroy at yahoo.com>> wrote:
Hi Everyone,

I was wondering if any of you have seen this system and can comment on it. I find it very interesting on how they're using some sort of electro-chemical cell to sanitize the supertenent outflow for water-reuse.

http://www.huffingtonpost.com/2012/08/16/toilet-of-the-future-caltech-solar-powered-toilet-video-photos_n_1791874.html

Do you think they're cycling salt water through out the system? or fresh water?
How expensive and reliable this type of fuel cell is? I thought it was pretty cool, and would love to learn a little bit more about it. If you know more about this system please let me know.

Cheers

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