All things environmental

Musings about the environment and all it touches, from education to city planning

Flintenbreite: the original vacuum toilets

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Flintenbreite eco-village in Lubeck

Last week when I described my visit to Jenfelder Au, I mentioned that Flintenbreite served as the inspiration.  Time to find out more about Flintenbreite.

Compared to Jenfelder Au, it’s a smaller development: 117 units in a mix of low-rise townhouses and duplexes over a 5.6-hectare site, in Lübeck, near Hamburg.  It is also older: it was built as one of the ecological complexes for the 2000 World Fair centered in Hanover, and permanent residents have lived in since 2002.

The World Fair was based on environmental concepts that became subsequently known as the Hannover principles.  Among these are:

  • the right of humanity and nature to co-exist in a healthy, supportive, diverse and sustainable condition.
  • the elimination of the concept of waste.
  • reliance on natural energy flows.

In Flintenbreite, this meant trying to use self-sustaining, integrated energy and wastewater concepts, as well as implementing innovative energy saving technologies, with an eye to minimizing interference with nature.  Yes, but how?  Remember, this is happening in the 90s, and some of things we now take for granted, such as cheap solar panels, don’t exist yet.

By all accounts an ordinary suburb -except for the toilets

This is where Dr Otterpohl came in.  He proposed to apply his conviction that human wastes are a resource. The core principle is simple: keep the wastes separated.  Much is the wastewater generated by a household: bath water, wash water, etc, is fairly clean and easy to treat. Toilet water is another story.  Otterpohl’s flash of insight was to use vacuum instead of flush water to dispose of these wastes – and then, ferment them, undiluted, into biogas.

None of the components of the system were new ideas.  Greywater separation was practiced in California. There were vacuum systems here and there, conveying ordinary sewage where large sewage pipes couldn’t be installed.  Methane digesters to produce biogas were already common in sewage treatment plants (but they fermented only sludge, not sewage, which is too dilute).

In Flintenbreite, the system designed by Dr Otterpohl uses an artificial wetland to treat greywater.  Urine, feces, and a small amount of water are conveyed to a central biogas digester which produces methane for the community; it is delivered to a cogeneration engine that supplies electricity and heat to the community. From what I could gather, the small volume of residual liquid produced by the digester is also treated in the wetland. (Originally the system was meant to digest kitchen wastes also; this part was never implemented, and biowastes are collected as part of the now-common municipal green wastes collection system.)

A bird’s eye view

A video, linked here, shows the site, with Dr Otterpohl explaining how the system works.  It is only available in German, and can’t be found in YouTUbe, but you still get an idea of what the place looks like.  It’s under ten minutes long; at 1:30, Otterpohl shows how silly it is to mix the large volume of greywater with the small concentrate of blackwater, using a shot glass and a Bavarian beer stein for comparison. Three minutes in you see the artificial wetland and how it was constructed: requires little energy, it looks good, it produces clear water.  According to a resident, the system never smells, and the kids adjusted quickly to the toilet (which, despite using vacuum, isn’t particularly noisy).  The guts of the system: collection tank, biogas digester, biogas collection tank, and cogen system (engine and generator), are shown from the 8th minute.

The water flows in Flintenbreite

If you’d like more details, you can listen to a podcast – in English, this time – narrated by Dr Otterpohl, here, or take a look at a set of presentation slides, here, or a summary, here.

With all this, you would think Dr Otterpohl is proud of his pioneering system at Flintenbreite, prouder yet that the system is now scaled up at a larger scale at Jenfelder Au.  But when I interviewed him, he was somewhat bitter about Jenfelder Au.  He has been elbowed aside, now that the design has been shown to work. I can imagine why, though – ha may not be an easy person to work with.  Ever the perfectionist, and the visionary, he says that the system should not be copied unless it incorporates one final separation: feces and urine should not be collected together.  Feces are the source of biogas, are semi-solid, and may contain pathogens.  Urine is a liquid that contains fertilizing elements.  It is foolish to blend them, he says.

I’ll be profiling Dr Otterpohl’s new research on separating toilets and management system in another post, because it is also quite remarkable.  But for now, I’d like to give him his due: if the vacuum toilets of Flintenbreite was the only system he ever designed, there would still be a lot to be thankful for.  I’m a bit awe-struck, myself.


Written by enviropaul

July 21, 2019 at 1:20 pm

One Response

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  1. […] So I’ll have to wait longer yet before I can find someone who can discuss whether the system has lived up to expectations.  Or maybe next time I’ll go visit Flintenbreite, a similar complex a few kilometers away in Lubeck.  Flintenbreite was the inspiration for Jenfelder Au: it is much smaller, but it has been operating, trouble free, for nearly twenty years.  That’ll be my next post, I hope. […]

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