[Digestion] Solar powered toilet

[Duncan Martin]

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> 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
>
> _______________________________________________
> Digestion mailing list
>
> to Send a Message to the list, use the email address
> Digestion at bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
>
> http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org
>
> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/digestion_lists.bioenergylists.org/attachments/20120907/15246568/attachment.html>