Can we recycle human urine to close the nutrient cycle?

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  • AndyWarren
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  • I'm the Managing Director of NatSol Ltd, Composting and Remote Toilet Specialists. We operate almost exclusively in the UK and design and manufacture our own products. These are supplied to sites such as allotments, rural churches, public parks and campsites.
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Re: Can we recycle human urine to close the nutrient cycle?

Thanks Kris,

Nice video. Encouraging.

One of the issues which doesn't get touched enough is that liquid fertilisers don't address the need for humus. Ideally, the urine would be mixed with high carbon waste streams such as cardboard, straw etc and go through a composting process to humify the nutrients.

Not that I'm not an expert on the biology of that, just fine with the practice of on a garden sized scale.

Andy

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  • JKMakowka
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Re: Can we recycle human urine to close the nutrient cycle?

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  • AndyWarren
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  • I'm the Managing Director of NatSol Ltd, Composting and Remote Toilet Specialists. We operate almost exclusively in the UK and design and manufacture our own products. These are supplied to sites such as allotments, rural churches, public parks and campsites.
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Re: Can we recycle human urine to close the nutrient cycle?

Well, that's a very good question. It's a long time ago and he no longer lives there. I will see what he remembers, but it wasn't a filter in the sense of a gauze or similar. That would have blocked far too easily. It was more like a settlement area. I recall a vertical piece of 110mm pipe with the incoming waste being sent to the bottom and the overflow being at the top. The bottom would have had a removable cap for cleaning.  Perhaps it was bigger diameter than 110mm so as to slow down flow and get more settlement.

Will see if I can update.

Regards, Andy
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Re: Can we recycle human urine to close the nutrient cycle?

An interesting story you are telling, Andy!  It would be nice to see that garden...

Would you mind telling us more about the filter?  What material is it made of and what size is it?

Cheers, H-A
Hanns-Andre Pitot
M.Eng. Environmental Pollution Control
presently in Seesen, Germany

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Re: Can we recycle human urine to close the nutrient cycle?

Hi Hanns-Andre,

Thanks for your two posts. A friend of mine who was Head of Research and Innovation at the Centre for Alternative Technology, Mid Wales, set up a system of this sort at his home in Machynlleth. He had a urine separating flush toilet upstairs and the urine was combined with waste water from the bathroom. We devised a hair filter to prevent hair blocking the irrigation pipes.

The mixed grey water and urine was fed to these small bore irrigation pipes which went to his soft fruit bushes. They did very well as I remember things, though he no longer lives there.

Best regards, Andy
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Re: Can we recycle human urine to close the nutrient cycle?

Dear lead author,

There actually is another way of making use of urine; that would be via the irrigation of treated waste water. This approach makes sense since urine needs to be diluted anyway, usually 5 to 10 times, when applied to soil. So the traditional approach of the sewage system is maintained but in order to reduce the investment costs and the load on the treatment plant, the solids (feces) would ideally be kept out of the sewage system.

Such an approach allows to reduce the costs of the sewage system by allowing small bore technology. If people use flush toilets, that approach requires so called withholding tanks on site, which are like small septic tanks which discharge into the sewage system and are emptied on a
regular basis. Alternatively, the small bore sewer could be implemented in conjunction with urine diverting dry toilets, where the urine is going together with the gray water into the sewer, whereas the solids are processed on site. Ideally, the processed solids could be picked up as ‘bio-waste’ in conjunction with the collection of organic waste (which is usually required anyway) and composted together.
 
Irrigation of treated waste water is quite common in the US and other parts of the world. I remember when I was a student in State College, PA, there was such a system for the irrigation of treated waste water. In the US, these are, however, usually implemented in conjunction with a regular sewage system. Apparently, small bore systems are used in Australia. I think for the irrigation of the waste water, you’d need in the order of 100 to 200 m² per person, depending on the climate.
 
I once suggested such a system – a combination of urine diverting dry toilets (as a choice, or alternatively, WC in combination with a withholding tank), small bore sewer system, treatment ponds, and waste water irrigation for Moroto, a municipality of about 20000 people in North-East Uganda. A local farmer on whose land the treatment and irrigation were supposed to happen, was very interested, but unfortunately, the plan didn’t go through. Of course, for such a system to work, you need enough land and the active participation of farmers.

A word about treatment ponds : Of course, these can be replaced by another technology (with the aim of reducing odors and eliminating pathogens), but treatment ponds are cheap in terms of construction and astonishingly effective. Due to the high level of UV radiation in tropical countries, pathogen counts are strongly reduced in such an arrangement.

Would something like that be something for Bolivia ?

Kind regards, H-A
Hanns-Andre Pitot
M.Eng. Environmental Pollution Control
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Re: Can we recycle human urine to close the nutrient cycle?

Hello Andy,

I completely agree with your thinking.  Medicines are a concern in the aquatic environment, since they can pass through waste water treatment plants.  But in case of an application on land, these should be quickly degraded by the soil microbes.  Most medicines are organic in nature, so they should be relatively easily degradable by microorganisms.

Regards, H-A
Hanns-Andre Pitot
M.Eng. Environmental Pollution Control
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  • AndyWarren
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Re: Can we recycle human urine to close the nutrient cycle?

Hi Everybody,

I haven't been following posts for a while but have just spotted this one. I'm managing director of NatSol Ltd ( natsol.co.uk ). We supply toilets for remote locations (i.e. remote from mains sewage which can sometimes be on inner city allotments where it is more expensive to connect to mains than to install a stand alone toilet). Most of our toilets are urine separating composting toilets where the compost is likely to get used on site - though not for crops where the edible part is in contact with the ground. We also have a non-urine separating pump out toilet for busy public sites.

A number of our composting toilet customers have wanted to collect and use the urine rather than send it to a soakaway. This is easily done but in every case so far the Soil Association has said no. The customers who want to do this are almost always seeking organic certification as well. I think there is currently one customer we know of who is not seeking SA approval and is planning on doing this.

The Soil Association is concerned about medications present in urine (including the contraceptive pill), GM chemicals (apparently) and possibly other un-natural constituents of human urine.

My own view (though I am not a biologist) is that these are small risks in comparision to the benefits of on-site use of urine as a fertisliser. Maybe they feel that if they allow that kind of use it may be the thin end of the wedge.

Kind regards, Andy
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  • ProdriguezAT
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Re: Can we recycle human urine to close the nutrient cycle?

Hello Professor Ajit Seshadri

I appreciate your comment. It is true that to work on these issues, we must first overcome several cultural barriers. For this it would help us to remember that ancient cultures had different management of our own waste. In this part of the world, that is, in Latin America, we have a very interesting experience called “terra preta” specifically in the Amazon region. I share with you a document that, if you don't already know it, might be of interest to you.

I also found this video that I would like to share with you: 
 

Greetings!

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Re: Can we recycle human urine to close the nutrient cycle?

Hi Tore!

Thanks for your comment. 

We invite you to review this short systematization of a project for the differentiated collection of urine and feces to convert them into compost and solid fertilizer.

Greetings!
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Re: Can we recycle human urine to close the nutrient cycle?

Hi Dave,

Thank you for the document you shared and your reflections on it. Vuna's document is really interesting and has very useful information to understand the technical, service management, social and economic dimensions related to this line of sanitation with a circular approach. Thanks for sharing this information.
 
Aguatuya,the organization where I work, has an interesting experience with the company EPSAS, the water and sanitation service provider for the city of La Paz, in Bolivia. This company provides the urine and feces collection service (separately) from houses that have dry toilets. Obviously, this is a pilot project and the service has not become economically sustainable by itself, but it is one more way in which the service provider serves a population that is not connected to the sewer network. To learn more about this experience, you can watch this video with automatically generated English subtitles.

Thinking about this, I was left with doubts about the viability of this type of large-scale venture and I searched the web a little to see if there was any company that could be self-sustainable with the provision of the service and I didn't find anything conclusive... Perhaps the closest thing is this experience that I share in the following link.
 
While this startup is just starting out and running on external funding, let's keep our fingers crossed that it does well! In this way, these experiences that can be extremely beneficial for humanity will discover the means by which to be sustainable and attractive as an enterprise.
 
Kind regards, 
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  • Dave
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Re: Can we recycle human urine to close the nutrient cycle?

Vuna's Valorisation of Urine Nutrients,  Promoting Sanitation & Nutrient Recovery through Urine Separation, Final Project Report 2015 is attached.

Pages 33 to 35 deal with the business case for urine valorisation (as opposed to the technical and health aspects).  At the time it was concluded that the cost of transport and treatment of urine was 10 to 40 times greater than the retail value of the NPK in the urine.  The report does note, however, that niche markets for organic fertilisers do realise much higher values for NPK than the going rate for mass produced fertilisers.

Barring some revolutionary breakthrough in transport and treatment, the logical conclusion is that the only practical way to realise the value in urine is at the point of generation, where the labour cost for collection,  treatment and application may be free or close to free.  In other words, if you practice urine separation and use that urine to fertilise your own crops or garden using your own labour in your spare time, that makes sense.  If you have to use time that can more productively be used doing something else, then the case is marginal.  If you have to transport the urine somewhere else for treatment, and then the product has to be further transported, stored and marketed, the whole process is unlikely to be economically viable.

If anyone knows of any large scale (i.e. beyond household scale) urine valorisation undertaking anywhere in the world which has proven economically sustainable (i.e. truly "circular" or "closed loop") without external funding, please share the details.
Regards

Dave

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